Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: SleepLess on October 10, 2012, 07:20:10 am
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Yep... One more!
This 5F4 was done back in April and has just returned to me because of very low volume. When I mean low I mean that even on 12 it sounds like a church mouse compared to a Champ... The power tubes are brand new from the store, I also swapped each preamp tube with a known-to-work one and the rectifier (normally a 5U4GB) was replaced by a GZ34 just for the test: still low volume whatever the tube. I have also reflowed most of the solder joints.
Here's my voltage chart. I have a very loud noise on V3 pin 7 as soon as I touch the pin with my red MM probe...:
Tube
Pin V1 V2 V3 V4 V5 V6
1 141 179 218 0 0 0
2 0 0 0 3.38AC 3.38AC 426
3 2.2 1.47 1.7 414 414 0
4 3.38AC 3.38AC 3.38AC 417 417 352AC
5 3.38AC 3.38AC 3.38AC -41 -41 0
6 136 285 276 -41 -41 351AC
7 0 178 23 3.38AC 3.38AC 0
8 2.2 178 73 0 0 424
Two pics:
(http://imageshack.us/a/img829/9105/mg1802d.jpg)
(http://imageshack.us/a/img189/7158/mg1803q.jpg)
Thanks for letting me know what you think about all this!!!
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Check the coupling cap between pin 1 and pin 7 on valve 3. There should be no DC voltage on pin 7
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I have changed it (the 0.02uF cap you mentioned, the one that is between pin 1 and pin 7 of V3) for another one that's known to work. I still get 23V on pin 7 and 74V on pin 8 of V3. I don't know if that's normal.
The amp now works (had a missing underboard connection that I found with my MM continuity tester). The only thing now is that each time I hit a true bypass pedal (such as my reverb) the amp emits a loud pop, whether I turn it ON or OFF. This pop doesn't occur with non true-bypass pedals such as my fuzz or treble booster or clean boost... I have never experienced such a loud pop with an amp, and I have built and played tens of other tweed amps. Is there something I can do to prevent this loud pop??? The guy who owns it only has true-bypass pedals in his rig and that will make the amp hardly usable with all those pops he's gonna have...
Thanks!
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This 5F4 was done back in April and has just returned to me because of very low volume. When I mean low I mean that even on 12 it sounds like a church mouse compared to a Champ...
I was gonna bet he had the speakers plugged into the wrong speaker jack. If you plug into the extension speaker jack with nothing plugged into the regular speaker jack, it will exhibit the same type of problem. That's because the stock wiring is to have a shorting jack for the main speaker jack, and that tends to short the signal away from your speakers (in the wrong, extension speaker jack), and give low volume.
But it sounds like you had a different issue.Check the coupling cap between pin 1 and pin 7 on valve 3. There should be no DC voltage on pin 7
With stock wiring, pin 7 is the grid of the split-load inverter. It will be some voltage less than the cathode, but you won't get an accurate reading with most meters because of the load they present. So I'd call SleepLess' readings believable for proper voltages.
I have a very loud noise on V3 pin 7 as soon as I touch the pin with my red MM probe...
Normal. You should get a pop when you touch your meter lead to the output tube plates. You'll get a louder pop when you touch the output tube grids, and louder still for every successive stage as you work back towards the input jack. The d.c. voltage disturbance that you meter momentarily causes is being amplified more and more by the amp as you get further from the speaker.
The only thing now is that each time I hit a true bypass pedal (such as my reverb) the amp emits a loud pop, whether I turn it ON or OFF. This pop doesn't occur with non true-bypass pedals such as my fuzz or treble booster or clean boost...
That is also probably typical.
I get the same kind of pop sometimes with my Fulltone pedals. They actually have a sticker inside the box (maybe on the bottom of the pedal too) that says the pops are due to static discharge from the switch. The cure, according to Fulltone, is to activate the switch several times, then use the pedal. Usually does the trick for me.
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The only thing now is that each time I hit a true bypass pedal (such as my reverb) the amp emits a loud pop, whether I turn it ON or OFF. This pop doesn't occur with non true-bypass pedals such as my fuzz or treble booster or clean boost...
That is also probably typical.
I get the same kind of pop sometimes with my Fulltone pedals. They actually have a sticker inside the box (maybe on the bottom of the pedal too) that says the pops are due to static discharge from the switch. The cure, according to Fulltone, is to activate the switch several times, then use the pedal. Usually does the trick for me.
OK... So can I safely send the amp back and say "if the amp emits a loud pop when you engage or disengage your pedals, the problem comes from your pedals and not the amp!"??? Which is something I'd told him already but he answered back that his pedals only pop when he plays through this 5F4 and not through his other 5 amps...
Engaging and disengaging my Neunaber Wet Reverb several times doesn't change a thing for me, the pop is as loud each time... But I believe what you say and I read from R.G.Keen that pedals are the source of these pops, not the amps. I actually didn't think I HAD to test my amps with pedals before sending them out, although I occasionally do...
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Same happens with my 5F4 copy, and less-so with my 5E3 copy. And only does it with my Fulltone pedals; as you say, non-true-bypass doesn't make the click.
And it doesn't always do it either.
Take a look at this (http://www.geofex.com/Article_Folders/box_pop.htm). R.G. Keen now designs pedals for Visual Sound. I can take a picture of the old labels on my Fulltone stuff (from ~2000), but I noticed they now claim a "proprietary anti-pop circuit" in their pedals, meaning they took steps to fix the problem in the pedals. Alternately, Jack Orman suggests it might be a problem with the LED power circuit, and offers a fix (http://www.muzique.com/lab/led.htm).
So why is it more obvious with your Super than with his other amps? Most likely, if his other amps have gain channels (and he uses them), it's because the Super has a wider dynamic range because the output tubes will be the first thing to distort. Because of that, the pops do not get squashed the way they would in a distortion channel as the rest of the guitar signal is being clipped.
Once I played my 5F4 copy alongside a guy with a 50w half-stack. His amp was pretty well cranked, and I had a Full-Drive and my amp turned up to ~4-1/2. I sounded like I was blowing him out of the room. The reason was my sound wasn't getting compressed (amp wasn't loud enough for output tube distortion, and the pedal was set in "Comp Cut" mode). By comparison, he was playing with a preamp gain control set very high and the master down, and had a lot of distortion, but also a lot of compression and sounded muted.
He could've stomped, clicked popped, etc and you'd barely notice it through that setup, but a clean and dynamic amp would make it obvious.
I still say the problem is your buddy's/customer's pedal. Have him bring it along and demonstrate the problem. 85% chance he won't replicate it in person with you. If he does, look to see if Keen's suggestions were already followed in the pedal. If not, mod the pedal. Stay towards the high end with your added resistors (4.7M @ 1/8w-1/4w sounds good).
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Thanks a lot!
If I understand everything correctly the pedals are at stake in these pops and not the amp... So I'm good to go...
I noticed one thing though: I took out the Neunaber WET Reverb (true-bypass) from my pedalboard to check if the pop would disappear, and then every single pedal popped. Even non true-bypass ones such as my treble booster or fuzz. When I put it back in no pedal popped except the WET but this pop was maybe three times bigger than the pops from all the other pedals before I put the WET back in. The conclusion is that the WET seems to collect all the remaining voltage of the other pedals (it's the last pedal in the signal chain) and of course emits a loud pop when it's engaged or disengaged. When I say loud, I mean it's totally audible even with the amp on 9/12... When the WET's out, then every single pedal seems to keep its own voltage and releases it when it's engaged/disengaged.
ONE thing is still puzzling to me though: these pops do NOT reduce in volume the more I engage or disengage the pedals, it stays as loud as on the first click... Really strange because I built another 5F4 before and it never popped and I had the same pedals...
To put it in a nutshell, are you absolutely, 100% percent sure that I can't do or check anything that might be wrong in the amp???
Thanks again!
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Think of it this way:
If you remove all pedals, and play the guitar through the amp, are there any issues? If no, your work is done. The problem almost certainly has to be in the pedals.
The answer might be different if you used guitars with active electronics, or a transistor amp; those might have issues which place d.c. on the interconnecting cables. But passive guitar electronics, and the circuitry of the 5F4 is such that you shouldn't be able to create this phenomenon.
Caveat: If you want to be 100% sure, double-check your input jack wiring/grounding, including the value of the resistor running from hot/switched contact to the ground lug. If you're confident that 1M is the proper value, and that all jacks have proper grounds, you're all set.
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Crap, I removed all the pedals and put it up on 10. I get some noise and scratches and my guitar pots scratch when I turn them between 6 and 10, on all my guitars (tried 3 different, they usually never make a noise when I plug them into my other amps).
Something is difinitely wrong with the amp, I gotta find what it is... :BangHead:
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Then check input jack wiring.
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After searching and searching, measuring and rewiring, I now only have a pop in the bright input 1.
I had a 6.8KΩ resistor going to the diode instead of the 470Ω 1W required when you have the bias mod installed (10KL with 33K resistor mounted)... That was the biggest mistake (though I don't really notice much difference in the amp's tone and response...?) What was that change supposed to do?
The three remaining inputs are noise-free with the pedals now. I changed the 68K resistors going to V1 pin 7 and got the same result. I changed the 1M resistor on that input jack and had the same results. Do you guys think it could be a bad or shorted input jack? Does this ever happen? If it's not this then I absolutely don't know what it can be...
Thanks!
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Hi.
I thought I had found the solution but I haven't. Bright channel input 1 is definitely noisy. It is the only input that provides the loud pop with the pedals. The other three are quiet. It is also the only input that makes a noise when I plug or unplug a jack into it.
So far I have:
- Changed V1
- Changed the input jack
- Changed the 1M resistor that is soldered on it.
- Changed the two 68K resistors that are on the board and linked to the jack. So now I don't have anything else to change because I have changed every component from the jack to the socket...
- Changed the two 0.02uF caps that are at the beginning of the board.
- Changed the 100pF cap across the Volume I pot.
I'm stumped and need you guys...
Thanks!
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I'm sure you already did this, but double-check the ground on that jack? Maybe run a wire from the ground lug to ground?
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Yeah I did... It is well grounded...
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This amp is driving me crazy... I have pops from pedals with a cable connected to each of the 4 inputs. Of course the pops coming from inputs 1 are louder than the ones from inputs 2 because of the 1M resistors.
The inputs that make noise when I plug and unplug a jack are inputs 1. That seems to point to the 1M resistors but I have already changed them...
What the hell...? :cussing:
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Hi.
OK so now the amp is emitting a loud siren when I unplug a guitar cord from whatever input and sometimes when I plug one in.
Bright channel input 1 is the noisiest: I get a pop as soon as the cord touches the inside connector. The other inputs do not do that.
What do you recommend? I have alrady changed that jack and I have already changed its 1M resistor and the two 68K resistors that are linked to it...
I really need your insight. It's been more ten days since I started debugging this amp and I haven't made any progress...
Thanks!
Do you guys think it could be a bad V1 socket? I pulled V1 out and I don't have the noise anymore when I plug the cord in Bright channel 1...
Is there a way of knowing without having to replace the whole socket?
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I have tested the V1, V2 and V3 sockets with my MM and continuity tester with the tubes pulled out. All is good, each pin has continuity to its corresponding place on the board or pots.
Another test: I have hit the chassis with a chopstick all over and it is noisy... I mean, it scratches and booms. It makes the same noise the guitar cord makes when I plug it in...
This seems to point to a grounding problem, am I wrong? But if so, I absolutely don't know where to look. Here's what I have:
- Power cord grounded to a PT screw, by itself.
- Other PT screw is the ground for the HT CT and the stdby switch cap.
- 6V6s are grounded to a single ground point which is one of V5's screws.
- All the rest (HV CT through the first filter cap, board grounds, input jacks) go to the floating buss bar which is itself grounded to the side of the chassis, near the input jacks.
All my connections look good. I pulled on all of the grounded stuff and everything is safely soldered. Nothing moves.
I'm stumped... :BangHead:
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Probably a wiring error somewhere.
It's gonna be hard for you to spot. You'll have to methodically check every wire.
For example, I think I see an error on your speakers jacks. On the main speaker jack, the switched lug appears to be connected to the hot (tip) lug; it should be connected to the ground lug so the tip is shorted to ground if nothing is plugged in.
I don't think this is necessarily related to your problem, but rather an example that simple wiring errors are normal. When I built my Standel, it was an oscillator instead of an amp. Took an hour or so to find the simple wiring error I made, and it took a lot of careful comparison to the schematic and layout I drew.
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Have you tried some isolation washers on the problem input jack? also, have you done a thorough wood chopstick tapin' her to see where she squawks? :dontknow:
good luck, Jacko D
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Someone brought in a Victoria amp a year or two ago that had this same problem. It ended up being DC leaking across the phenolic board onto the input jacks. Try hanging the 68Ks an 1M resistors directly off of the jacks--then wire straight to the grid.
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Thanks a lot guys! I was totally stumped and you're giving me new leads that I'll try this weekend.
The chassis is noisy everywhere when I hit it with a wooden chopstick. But it is noisier on the preamp side of the chassis, not as much on the PT side...
I'll keep you posted and if in the meantime you have some new ideas please feel free. At this point everything is good to try...
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Probably a wiring error somewhere.
It's gonna be hard for you to spot. You'll have to methodically check every wire.
For example, I think I see an error on your speakers jacks. On the main speaker jack, the switched lug appears to be connected to the hot (tip) lug; it should be connected to the ground lug so the tip is shorted to ground if nothing is plugged in.
I don't think this is necessarily related to your problem, but rather an example that simple wiring errors are normal. When I built my Standel, it was an oscillator instead of an amp. Took an hour or so to find the simple wiring error I made, and it took a lot of careful comparison to the schematic and layout I drew.
I didn't know that the switched lug had to be connected to ground... :dontknow: I have fixed this but the amp is still not working properly. But at least I have saved a future problem... :l2:
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It's a minor point.
The idea was if the internal speaker was unplugged, the hot is shorted to ground and saves the output transformer. But this arrangement is also why a properly wired amp will have almost no output if you accidentally plug into the external speaker jack and not the main speaker jack.
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Damn... I have finished checking every wire and they all test good with my MM continuity tester and they go where they should...
I have also measured DC voltage on the input jacks and I don't have any leak...
:w2: :cry:
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I have just finshed another voltage chart and everything looks good BUT I have some loud crepitation on V2 pin 1 when I touch it my my red MM probe and pins 2 of V2 and V3 are noisy. The rest is good. Yet on the pot side I have 1.5VDC on the Treble and Presence pots and a litlle less on the Bass pot.
The thing is that these pots are not directly linked to any cap except the ones that are soldered to them i.e.
Any idea about where I could look for the culprit? The 8uF 475V cap maybe? How can I test it without changing it for another one?
Thanks!
EDIT: I have changed the .1uF cap soldered to the presence cap and also the .1uF cap that goes to pin 8 of V3... I still have 1.57VDC on the presence pot tabs... Where else could it be coming from?
Thanks!
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I have changed the .1uF cap soldered to the presence cap and also the .1uF cap that goes to pin 8 of V3... I still have 1.57VDC on the presence pot tabs... Where else could it be coming from?
V3-8 is part of the phase inverter. That .1µF cap feeds one grid of the output tubes. It has nothing to do with dc on any pot.
The presence pot is connected directly to the cathode of a gain stage (V3-3). There should be dc on it. Schematic shows 1.7vdc.
The only way to get dc on the treble pot (assuming no wiring errors) would be from V2-8 thru a leaky 250pF cap or leaky .1µF cap. If the .1µF is leaky, you should be able to turn the Bass pot all the way down and kill the dc voltage on the treble pot.
Does the amp sound OK?
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OK. It was the 250pf cap... I put a new one and now I only have 2mV on the treble pot and I don't have any noise or crepitation anymore when I touch the V2 pins 1 and 2. One proble solved, thanks a lot sluckey!
BUT the main problem is still here: the amp emits pops when I hit it with a chopstick and Bright input 1 is noisy as hell as soon as the guitar jack touches the switch...
I think I'm gonna shoot a video and post it here if you wish, via a youtube link. You will see these pops are absolutely not normal... And I checked every ground point, everything goes as it should and the ground connections are tight, they won't move...
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BUT the main problem is still here: the amp emits pops when I hit it with a chopstick and Bright input 1 is noisy as hell as soon as the guitar jack touches the switch...
You didn't wire the #1 input like the speaker jack, did you? The #1 jack should have the switch terminal tied to the ground lug. And the jack should be fastened tightly with a star washer between the jack body and chassis. Actually, I prefer a dedicated ground wire rather than rely on the jack nut.
This type problem usually indicates a loose/bad connection somewhere. Could be a loose wire, nut, bad solder, tube socket, etc. I recently had a similar problem that turned out to be dirty tube socket pins. I was able to track it to the actual offensive socket pin by using a very light touch of the chop stick.
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BUT the main problem is still here: the amp emits pops when I hit it with a chopstick and Bright input 1 is noisy as hell as soon as the guitar jack touches the switch...
You didn't wire the #1 input like the speaker jack, did you? The #1 jack should have the switch terminal tied to the ground lug. And the jack should be fastened tightly with a star washer between the jack body and chassis. Actually, I prefer a dedicated ground wire rather than rely on the jack nut.
This type problem usually indicates a loose/bad connection somewhere. Could be a loose wire, nut, bad solder, tube socket, etc. I recently had a similar problem that turned out to be dirty tube socket pins. I was able to track it to the actual offensive socket pin by using a very light touch of the chop stick.
So here's the video:
http://youtu.be/RI0u3pQdUqs (http://youtu.be/RI0u3pQdUqs)
And my input jacks are wired as such, nothing fancy here. They are tightly fastened to the chassis and a ground wire links normal channel to bright channel ground and then another wire extends to the ground buss bar. The blue wires are the input wires that go to their respective 68K resistors:
(http://img28.imageshack.us/img28/4593/inputjacks.jpg)
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That's very likely a loose/poor connection, maybe even more than one since it happens at both ends of the chassis. Revisit all your ground connections with your soldering iron. In fact, retouch all your solder connections. Check all chassis connections. Check tube sockets. Check B+ wiring. Really, it could be anything. Use a very light touch with the chopstick to try to localize a problem area.
And my input jacks are wired as such, nothing fancy here. They are tightly fastened to the chassis and a ground wire links normal channel to bright channel ground and then another wire extends to the ground buss bar. The blue wires are the input wires that go to their respective 68K resistors:
Is that pic actually your input jacks??? I ask because I see white wires inside your chassis???
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That's very likely a loose/poor connection, maybe even more than one since it happens at both ends of the chassis. Revisit all your ground connections with your soldering iron. In fact, retouch all your solder connections. Check all chassis connections. Check tube sockets. Check B+ wiring. Really, it could be anything. Use a very light touch with the chopstick to try to localize a problem area.
And my input jacks are wired as such, nothing fancy here. They are tightly fastened to the chassis and a ground wire links normal channel to bright channel ground and then another wire extends to the ground buss bar. The blue wires are the input wires that go to their respective 68K resistors:
Is that pic actually your input jacks??? I ask because I see white wires inside your chassis???
OK... Looks like some more hours to find this bug... :cry:
No this is not my input jack pic. It's just a pic of how it should be done and how I did it. My wires are white indeed...
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Shouldn't be hours to find that. And it'll only take about 30 minutes to retouch every solder joint. You may actually find the problem while retouching all the joints.
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It looks like you created some sort of ground buss, rather than use Fender's method of connecting underboard wires between the ground eyelets.
Was any of that buss soldered to the chassis? I couldn't quite tell from the video. And how was the ground connection to the chassis made at the power supply end? How about the green wire of your power cord?
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It looks like you created some sort of ground buss, rather than use Fender's method of connecting underboard wires between the ground eyelets.
Was any of that buss soldered to the chassis? I couldn't quite tell from the video. And how was the ground connection to the chassis made at the power supply end? How about the green wire of your power cord?
Hi Hotblue!
Like I said earlier on:
This seems to point to a grounding problem, am I wrong? But if so, I absolutely don't know where to look. Here's what I have:
- Power cord grounded to a PT screw, by itself.
- Other PT screw is the ground for the HT CT and the stdby switch cap.
- 6V6s are grounded to a single ground point which is one of V5's screws.
- All the rest (HV CT through the first filter cap, board grounds, input jacks) go to the floating buss bar which is itself grounded to the side of the chassis, near the input jacks.
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Have you tried taking a small, thin "ignition points" file and touching up between the hot tip on the input jack and the shorting tip? Check and make sure when your guitar cable jack is plugged in the shorting tip is not still touching the hot tip?
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Allrighty guys:
So far I have reflowed all my solder joints on the sockets side (except on the board) and the chopstick test is now perfect, no more resonance, it's quiet everywhere!
BUT I still have noisy input jacks, though not as much. But the boat's siren came back once when I unplugged the guitar jack from input 1 of bright channel. I said to myself "I have to record this and post it up on Youtube to show the guys" but even though I repeated the move about twenty times, no more siren, just the cracking pop you heard in the video...
When I mean siren I mean a really loud siren! My baby was asleep in another far away room in my apartment and he woke up crying because of that crap... It IS loud, but I couldn't make it happen again to show you guys...
Now I'm gonna reflow everything on the pot side...
Thanks!
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- Power cord grounded to a PT screw, by itself.
- Other PT screw is the ground for the HT CT and the stdby switch cap.
- 6V6s are grounded to a single ground point which is one of V5's screws.
- All the rest (HV CT through the first filter cap, board grounds, input jacks) go to the floating buss bar which is itself grounded to the side of the chassis, near the input jacks.
All of these use a Keps nut, or a nut & star washer, right? The buss isn't grounded to the chassis by soldering, but with a screw/nut of its own, right?
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So far I have reflowed all my solder joints on the sockets side (except on the board) and the chopstick test is now perfect, no more resonance, it's quiet everywhere!
OK, now do the control side, especially the input jacks.
BUT I still have noisy input jacks, though not as much. But the boat's siren came back once when I unplugged the guitar jack from input 1 of bright channel.
Properly wired jacks that have a good ground will not behave like that. The siren sounds a lot like the tube grid is losing it's ground connection occasionally. That ground connection is thru the input jacks and the 1MΩ resistor on the jacks.
It's easy to prove/disprove the jacks as a problem. Just use a gator clip lead, one end connected to chassis and the other end connected directly to pins 2 or 7 of the 12AY7 socket, while plugging/unplugging from the input jacks. There are still other possible culprits but this is so easy to eliminate that you really should do so before pulling any more hair.
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- Power cord grounded to a PT screw, by itself.
- Other PT screw is the ground for the HT CT and the stdby switch cap.
- 6V6s are grounded to a single ground point which is one of V5's screws.
- All the rest (HV CT through the first filter cap, board grounds, input jacks) go to the floating buss bar which is itself grounded to the side of the chassis, near the input jacks.
All of these use a Keps nut, or a nut & star washer, right? The buss isn't grounded to the chassis by soldering, but with a screw/nut of its own, right?
Absolutely HotBlue! Screw/Star washer/Nut!
I have found one more problem that I solved: I noticed that pins 8 and 3 of V1 were noisy when I hit them with a chopstick. So I unsoldered the 820Ω that is on the far right of the board and I actually didn't remember that it was barely long enough to reach its two eyelets. So I bent its legs and soldered them directly to the 25uF/50V cap's legs. And bingo, no more noise when I hit the 8 and 3 pins and the amp is a little more silent!
But it is still noisy at the inputs and I'm wondering if I don't have the exact same problem with another short-legged resistor. I'm talking about this one and I'd like you to tell me if I can bend its legs and solder them there without any problem (either the lower leg to the .1uF cap's leg or the higher leg to the 8uf/475V cap's leg, or possibly both?):
(http://img41.imageshack.us/img41/1103/mg1798.jpg)
Sluckey, I'll try what you say about the input jacks but honestly I think I can rule them out... I have changed the Bright channel input 1 jack 3 times with three different 1M resistors and the problem remains the same... But I'll try.
Thanks guys!
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.... it was barely long enough to reach its two eyelets. So I bent its legs and soldered them directly to the 25uF/50V cap's legs. And bingo, no more noise when I hit the 8 and 3 pins and the amp is a little more silent! ...
I think you may have it solved with that observation!
The leads were much longer on old carbon comp resistors. But these aren't readily available, so now the modern carbon comp resistors are a little too short for the original Fender eyelet board.
It's just one of those problems that crop up. Good reason to use a Hoffman-style turret board, or make your own eyelet boards to allow the use of the new, shorter resistors.
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OK HotBlue, but can you tell me if I can solder the circled resistor as on the pic I posted above?
Thanks!
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...can you tell me if I can solder the circled resistor as on the pic I posted above?
Thanks!
yes
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OK.
I have resoldered everything and I have moved the resistor circled above and soldered its legs to the circled spots. The amp is quieter but I still get those huge pops when I insert a jack in Bright Channel input 1 (not into the other inputs). Sluckey I'm doing your alligator clips test tomorrow since it makes noise and everybody's sleeping here... What would it mean if the pop remained? If it disappeared?
Thanks!
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You clip one end of the alligator to ground, and the other to a point that should be grounded.
If the pops stop, you found where the poor ground is.
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You clip one end of the alligator to ground, and the other to a point that should be grounded.
If the pops stop, you found where the poor ground is.
Yeah, I'll do this too, but I have already checked my grounds with my MM continuity tester and they're all good. The only ones I couldn't test were the three pots grounds that go through a cap first. All the rest show continuity...
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Sluckey I'm doing your alligator clips test tomorrow since it makes noise and everybody's sleeping here... What would it mean if the pop remained? If it disappeared?
It's been over 48hrs since I suggested that! If the pop remains, then you have a bad clip lead or you grounded the wrong grid pin. If it dissappears, the problem is ahead of the grid, ie, wire, resistors, jack, or wiring error.
Back to the chopstick video... Did you have the volume pots turned up during that video? Was there a guitar connected to that instrument cable when you were demonstrating the input jack popping noise?
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Sluckey I'm doing your alligator clips test tomorrow since it makes noise and everybody's sleeping here... What would it mean if the pop remained? If it disappeared?
It's been over 48hrs since I suggested that! If the pop remains, then you have a bad clip lead or you grounded the wrong grid pin. If it dissappears, the problem is ahead of the grid, ie, wire, resistors, jack, or wiring error.
Back to the chopstick video... Did you have the volume pots turned up during that video? Was there a guitar connected to that instrument cable when you were demonstrating the input jack popping noise?
I know Sluckey, but I had to go away for work...
As for the chopstick yes all the pots were set on 6/12. No guitar connected, just the cable...
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It's easy to prove/disprove the jacks as a problem. Just use a gator clip lead, one end connected to chassis and the other end connected directly to pins 2 or 7 of the 12AY7 socket, while plugging/unplugging from the input jacks. There are still other possible culprits but this is so easy to eliminate that you really should do so before pulling any more hair.
Right, I've done it Sluckey! Here are the results, all controls on 6.5 and a strat plugged in with all controls on 10, neck/middle pickups:
- Alligator clip to chassis and pin 2 of V1: pops still occur in Bright channel, amp can be played.
- Alligator clip to chassis and pin 7 of V1: no pop at all but NO SOUND from the amp, can't be played! Not getting any sound anymore is a third option I hadn't even thought of...
What's that supposed to mean? Bad pin 7?
Thanks!
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- Alligator clip to chassis and pin 2 of V1: pops still occur in Bright channel, amp can be played.
And that's how it should be. The normal inputs feed into V1-2. Grounding pin 2 will kill any pops (or guitar signal) coming from the normal inputs. But bright inputs will still function.
- Alligator clip to chassis and pin 7 of V1: no pop at all but NO SOUND from the amp, can't be played! Not getting any sound anymore is a third option I hadn't even thought of...
What's that supposed to mean? Bad pin 7?
And that's how it should be. The bright inputs feed into V1-7. Grounding pin 7 will kill any pops (or guitar signal) coming from the bright inputs. But the normal inputs will still function.
However, based on this statememt...As for the chopstick yes all the pots were set on 6/12. No guitar connected, just the cable...
... I'd say you don't have a problem. It's pretty normal to get a loud pop from any amp when you plug in just a cable with no guitar attached AND the volume is turned up. If the amp sounds OK I'd say you're done.
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However, based on this statememt...As for the chopstick yes all the pots were set on 6/12. No guitar connected, just the cable...
... I'd say you don't have a problem. It's pretty normal to get a loud pop from any amp when you plug in just a cable with no guitar attached AND the volume is turned up. If the amp sounds OK I'd say you're done.
The amp is noisy and there's a mixture of windy noise, high hiss and I get pops whether I have a guitar in or not when I touch Bright input 1...
Gonna shoot another video and post it here so you can see. Something is wrong and Bright channel input 1 has something to do with it... I haven't plugged in any pedals yet but I'm sure they will pop if I do. Give me some minutes to shoot it and post it on Youtube (that's the longest part, that's long to upload) and you'll see there definitely is still something wrong...
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There you go: you'll also notice a high-pitched noise at one point (about when I show the ground buss bar)...
http://youtu.be/UJcfSiKNZ8A (http://youtu.be/UJcfSiKNZ8A)
Thanks!
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I think that is normal behavior. How does the amp sound musically?
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I think that is normal behavior. How does the amp sound musically?
Oh my... really??? What about that squeal at 0:51 which sounds like a high-pitched beep???
I tapped the Bright channel input 1 only because it's the only one that pops, the other three are quiet when I do the same test...
I get the same kind of pop when I switch ON/OFF the pedals... Which indicates it's not the pedals, right?
Why is this freakin' jack popping like this while the others are silent?
The amp sounds good, but it is too noisy I think and I can't use any pedals with it...
I know I'm a newbee compared to you sluckey and to you HotBlue, but I have built about twenty-five amps including 12 tweeds (Champ, Super, 5E3, 5F6A) and it's the ONLY one that is this noisy and that has these pops at the input jack...
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OK, so how's it sounds (no pedals, just straight into the amp!)
Fender Tweed Super 5F4 Replica (http://www.youtube.com/watch?v=rtcjvd4mxYg#ws)
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I did hear the single beep at 51 seconds, but it was so short that I just dismissed it.
As for the background noise, that sounds like what I'd expect to hear with an amp set on 10 of 12 with fluorescent lighting. If you have any fluorescent lights on in that room, turn them off and see if the background noise decreases.
And the chopstick tapping on the bright #1 jack tip should produce a pop when you tap hard enough to open the switch contact. If you plug your guitar into the bright #1 jack, I don't expect tapping on that jack would cause any pops. But if you now tap on the emply normal #1 jack, I would expect popping.
Try this. Turn the amp off with nothing plugged into any of the input jacks. Connect one lead of your ohm meter to chassis. Connect the other lead to V1-7. What resistance do you measure? Now, with the meter still connected to V1-7, plug a cable (no guitar) into the bright #1 jack. What resistance do you measure?
The only suspects I have at this point would be a missing/faulty 1meg resistor on the #1 jack, bad wire between the jack and board, bad wire between board ond V1-7, bad/dirty V1 socket, or bad V1 tube.
BTW, I'm not an expert. I'm just a hobbyist. I've only had my hands on 13 amps in the last 30 years.
Do the resistance measurments and give us the numbers.
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Try this. Turn the amp off with nothing plugged into any of the input jacks. Connect one lead of your ohm meter to chassis. Connect the other lead to V1-7. What resistance do you measure? Now, with the meter still connected to V1-7, plug a cable (no guitar) into the bright #1 jack. What resistance do you measure?
Done. MM set on 200K range:
No cable plugged in: 34.7K
Cable plugged in Bright 1: 37.5K
BTW, I'm not an expert. I'm just a hobbyist. I've only had my hands on 13 amps in the last 30 years.
Do the resistance measurments and give us the numbers.
If you're not an expert you're pretty darn close to one to me! You have saved me in several occasions and you always know what to do and check. I am about three decades in amp knowledge behind you. And I'm still billion of years behind thinking about creating my own amp with my own schematic...
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No cable plugged in: 34.7K
Cable plugged in Bright 1: 37.5K
The reading with no cable is good, but the reading with cable plugged into Bright 1 is bad. It should be 1meg ohm.
Please check again.
And also repeat the test for the normal channel, but checking V1-2 and plugging into normal #1 jack.
BTW, nice playing. I noticed you also had the volume turned up on the normal channel. I would keep the unused channel volume on zero to minimize noise. Or, I'd jumper the channels.
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Thanks sluckey.
NORMAL channel (MM ground/pin2 of V1)
NO cable: 34.4K Ω
With cable in Input 1: 37.1K Ω
BRIGHT channel (MM ground/Pin7 of V1)
NO cable: 34.7K Ω
With cable in Input 1: 37.5K Ω
So I confirm my first readings... I do get 37.K with the cable in... That's a long way from 1M Ω!!!
Oh and I have changed my 1M resistor on the Bright channel twice already, so unless I'm really unlucky and I used three bad 1M Ω resistors... (and they test 1M Ω when I measure them once they're out of the circuit!)
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So I confirm my first readings... I do get 37.K with the cable in... That's a long way from 1M Ω!!!
You don't have a guitar connected to that cable, right?
I don't suspect the 1meg resistor, but the jacks cannot be wired correctly.
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So I confirm my first readings... I do get 37.K with the cable in... That's a long way from 1M Ω!!!
You don't have a guitar connected to that cable, right?
I don't suspect the 1meg resistor, but the jacks cannot be wired correctly.
Oh my... I had the guitar at the other end of the cable :BangHead:... So here are the readings without the guitar:
NORMAL:
NO cable: 34.4KΩ
With cable: 1.17MΩ
BRIGHT:
NO cable: 34.8KΩ
With cable: 1.12MΩ
Sorry sluckey...
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That's more like it. All readings look good. Try another tube in the V1 socket. 12AX7 will work if you don't have another 12AY7. Plug/unplug several times to wipe the socket pins clean. Use some contact cleaner if you have it. DON'T USE WD40!
I still believe that tapping on that empty Bright #1 jack with a chopstick while the amp volume is set on 10 should produce a loud pop sound. Maybe some of the experienced guys that do this professionally will ring in with their opinions.
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That's more like it. All readings look good. Try another tube in the V1 socket. 12AX7 will work if you don't have another 12AY7. Plug/unplug several times to wipe the socket pins clean. Use some contact cleaner if you have it. DON'T USE WD40!
I still believe that tapping on that empty Bright #1 jack with a chopstick while the amp volume is set on 10 should produce a loud pop sound. Maybe some of the experienced guys that do this professionally will ring in with their opinions.
Yep. So I have changed V1 (have some spare 12AY7s that I know work well) and nothing got better. I noticed that V2 pin 2 is a little bit noisy when I touch it with my chopstick. The rest of the amp is silent, save for that stupid hiss and those high-pitched squeals/interferences that occur from time to time (as heard in the second video at 0:51).
Next thing was to do my pedalboard test and the results are as bad as when I got the amp. Whatever input I plug the guitar in I get some really loud pops when I switch ON/OFF the pedals. Of course they're barely hearable with the guitar in either inputs 2, but they're huge in inputs 1. I know about the static discharge thing but this can't be IT because the pop remains as loud as it is on the first switching ON or the twentieth (yes, I tried 20 times to see if the pop volume would decrease!).
What a frikkin' amp... Can't debug this one... Crap. I think that I'm gonna try another 9 pins socket in V1 and see if I still get those sounds. Maybe it's just a dirty or bad V1 socket (or V2?).
I'll shoot another video tomorrow morning to show you the pedals pop. You'll see they're not normal. I mean, you could hear these pops during a concert with the amp on 9... That's totally unbearable...
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There you go:
http://youtu.be/0talvPolcIc (http://youtu.be/0talvPolcIc)
If you have any suggestions, please feel free. I can't return the amp the way it behaves with pedals (notwithstanding the extraterraneous noise that comes from time to time...)
I plugged the guitar in Bright 1 but the pops are the same in Normal 1. It's just not as loud in inputs 2 but I guess that's normal. The 1MΩ resistor on inputs 1 seem toi boost those damn pops...
Thanks.
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OK, I agree. That's not right. My gut tells me the problem is with the input jacks and/or V1. But since the pops occur on either channel the problem should be something common to both channels. Get a good set of voltage readings for the amp. And don't omit zero volt readings. They're important too.
Did you just build this amp? Has it ever worked right? Is this a customer's amp? What's the story?
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OK, I agree. That's not right. My gut tells me the problem is with the input jacks and/or V1. But since the pops occur on either channel the problem should be something common to both channels. Get a good set of voltage readings for the amp. And don't omit zero volt readings. They're important too.
Thanks sluckey. I know it's not right, I have built about ten tweeds including another 5F4 and it's the only one that does this. But I must admit, I had a hard time convincing you this one has something wrong... :laugh:
Here's the voltage chart. I went for the most accurate readings possible. B+ is 390V and tubes are 6L6 (30w max dissipation). 70% of that max dissipation gives 21w. So I did 21/390 which gives 56mA. Tubes are biased 10mA below that at 46mA. I can't go above, I'm already up full on the bias pot (33K resistor soldered across it) and my B+ is already quite low I think since the original fender schematic shows a 410V B+... When I say (200mV) it means that the readings were taken with the MM set on the 200mV range.
Tube
Pin V1 V2 V3 V4 V5 V6
1 134 176 194.9 00.2(200mV) 0 125.2(200mV)
2 00.8(200mV) 5.6(200mV) 8.1(200mV) 3.38AC 3.38AC 405
3 2.1 1.25 1.53 388 387 00.5(200mV)
4 3.38AC 3.38AC 3.38AC 393 393 350AC
5 3.38AC 3.38AC 3.38AC -34.3 -34.5 0
6 130.4 270 260 -34.4 -34.5 350AC
7 3.3(200mV) 176 22.2 3.38AC 3.38AC 0
8 2.1 177.3 70.2 00.2(200mV) 0 406
9 3.38AC 3.38AC 3.38AC
Did you just build this amp? Has it ever worked right? Is this a customer's amp? What's the story?
Yes, I built this amp back in April. It worked well. I don't remember trying it with pedals though, but I think I did and obviously it didn't pop or I wouldn't have sent it. Its owner lives 400 miles away from me so I shipped it over to him and it worked well. Then I think about two months later he had to change the power tubes (NOS 5881s) because one of them failed. He also stated that the amp was making noise (probably the same kind of noise it makes today) and that pedals popped. He also told me that he inserted a preamp tube the wrong way and lit the amp with it...
That's when I told him to stop doing anything to it and to take it to a local tech. He did and the amp was actually returned to him with more noise and more pedal pops than before, which is when I asked him to return it to me...
He doesn't remember which preamp tube he mis-inserted...
I don't know more than this...
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I've just had an email from its owner. He said the amp worked well upon arrival up until June (I shipped it in April). Then in June the pedals started popping. That's when he misinserted the power tubes and then took it to his tech.
I need your help.
Thanks.
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OK, here's what I suggest. We have to eliminate the input jacks/wiring. So, totally remove all 4 input jacks. And unsolder the two white wires on V1 socket, pins 2 and 7. Now install a single input jack. Use shielded cable and connect the jack directly to V1 as shown. Don't forget the jumper between pins 2 and 7.
Does this solve the popping? This is just a test but leave it like this until the popping is fixed.
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Done.
Doesn't solve the popping...
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OK, now we know it's not the jacks. That's progress. Next, replace the onboard 820Ω and 25µF cap that's connected to V1 pins 3 and 8. Does that fix it?
If not, replace V1 tube socket. Fixed now?
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OK, now we know it's not the jacks. That's progress. Next, replace the onboard 820Ω and 25µF cap that's connected to V1 pins 3 and 8. Does that fix it?
Nope... Pops remain...
If not, replace V1 tube socket. Fixed now?
Good Lord... Nope, they're still here... Looks like V1 is not the problem... :cry:
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I wonder if the eyelet board has gone bad? Fenderitis?
Doug has brought this up before as have others.
Did the client live in a high humidity area?
Brad :w2:
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I wonder if the eyelet board has gone bad? Fenderitis?
Doug has brought this up before as have others.
Did the client live in a high humidity area?
Brad :w2:
No, common average humidity...
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Describe your grounding system, especially concerning the board, power transformer high voltage center tap, and filter caps. Pics will help.
I still think its a bad connection. May not be a solder joint. May be a mechanical connection to the chassis. Could even be a component lead that is fractured inside a resistor or cap. Keep banging the chopstick.
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- Power cord grounded to a PT screw, by itself.
- Other PT screw is the ground for the HT CT and the stdby switch cap.
- 6L6s are grounded to a single ground point which is one of V5's screws.
- All the rest (HV CT through the first filter cap, board grounds, input jacks) go to the floating buss bar which is itself grounded to the side of the chassis, near the input jacks.
The pics:
(http://imageshack.us/a/img713/2779/img3329n.jpg)
(http://imageshack.us/a/img560/9112/img3330c.jpg)
(http://imageshack.us/a/img195/4364/img3331mq.jpg)
(http://imageshack.us/a/img22/8669/img3332nx.jpg)
Now I'm off for some more banging... Jeez this amp is the hardest debug I've had yet to do... I have already spent more time debugging it (and to no avail!) than building it! Crazy!
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I have just finished a 20-minute chopstick banging session (sounds cool huh?). I have changed a couple of resistors (the 270KΩ) and one 100KΩ that connects to V1 pin 1 because they were making some noise when tapping on them. But the pedals still pop even with the new ones.
I turned the amp full up, everything on 12, while doing this. This amp is sick let me tell you. It's like wind blowing through the speakers, but wind with some trees cracking in the distance. Definitely not healthy.
But nothing makes noise when tapping on the components, and I banged for 20 minutes... The customer says it worked flawlessly for two months, then his pedals started popping... :think1:
I'm stumped...
No one wrote about my latest voltage chart, so I guess everything is fine...?
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Hi.
I thought I had made significant progress with this test but apparently not:
- I pulled V3 out and lit the amp up, everything on 9. No pedals pop!!!!!
But then I put V3 back in and pulled V2, and then V2 back in and pulled V1, and no pops either...
The only thing I know is that whatever preamp tube I pull out, the pedals stop popping. Is this significant? Whan can it mean? Does it point to a certain area in the amp?
Thanks!
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Pulling any little tube will break the signal path, killing any sound from the amp, including pops. That's normal.
Your tube voltages did not reveal anything to me.
You seem to have two 100Ω resistors connected as an artificial center tap for the filaments but you also have the PT filament center tap lead grounded. Use one or the other but not both. I suggest removing the 100Ω resistors.
Your ground scheme needs to be totally redone. Study the grounding scheme at this link then make yours look like it.
http://www.el34world.com/charts/grounds.htm (http://www.el34world.com/charts/grounds.htm)
More on grounding... Your power cord ground is fine. Basically you want both PT centertaps, power tube cathodes, first and second filter caps, and bias cap ALL CONNECTED TOGETHER NEAR THE PT. It's fine to use a PT bolt but use a star washer or kep nut. Use at least an AWG18 size buss wire.
There are many successful grounding schemes out there. Mine differs slightly from Doug's, but Doug's scheme is very good. Rather than add confusion, just go by his scheme. I know it's a lot of work, but it needs to be done. And it will probably cure this amp. I still believe there's a bad connection involved, but hopefully it will get fixed during your ground overhaul.
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Pulling any little tube will break the signal path, killing any sound from the amp, including pops. That's normal.
OK. I should have guessed that...
Your tube voltages did not reveal anything to me.
Fine. At least it means that everything works properly...
You seem to have two 100Ω resistors connected as an artificial center tap for the filaments but you also have the PT filament center tap lead grounded. Use one or the other but not both. I suggest removing the 100Ω resistors.
OMG. How could I skip that all that time? :BangHead: I have removed the 100Ω resistors from the lamp and ground. Only the HT CT remains grounded, but that didn't solve anything... The amp actually seems to be even noisier without the 100Ω resistors...
Your ground scheme needs to be totally redone. Study the grounding scheme at this link then make yours look like it.
http://www.el34world.com/charts/grounds.htm (http://www.el34world.com/charts/grounds.htm)
More on grounding... Your power cord ground is fine. Basically you want both PT centertaps, power tube cathodes, first and second filter caps, and bias cap ALL CONNECTED TOGETHER NEAR THE PT. It's fine to use a PT bolt but use a star washer or kep nut. Use at least an AWG18 size buss wire.
There are many successful grounding schemes out there. Mine differs slightly from Doug's, but Doug's scheme is very good. Rather than add confusion, just go by his scheme. I know it's a lot of work, but it needs to be done. And it will probably cure this amp. I still believe there's a bad connection involved, but hopefully it will get fixed during your ground overhaul.
OK, I'm almost done with that... But one more thing before I continue:
I have a bias mod done in that amp:
- 56KΩ resistor removed from the board (but the ground wire between the 100uF/100V cap and the missing 56KΩ remains)
- The 6.8KΩ resistor has been removed and replaced by a 2w 470Ω.
- Bias pot is a 10KL with a 33KΩ resistor across it. The right lug receives the diode, the middle lug receives a cable that goes to the board where the other leg of the diode should have gone.
Is anything wrong with that?
(http://img809.imageshack.us/img809/8355/5f4biasmod1260x787.jpg)
Thanks!
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I want to see a pic that clearly shows every component in the bias circuit.
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I want to see a pic that clearly shows every component in the bias circuit.
(http://imageshack.us/a/img138/5692/img3334bz.jpg)
(http://imageshack.us/a/img850/307/img3333r.jpg)
Tell me if you need more Steve. I just followed Marsh Amps' 5F4 Bias Mod. I didn't invent anything. But if their mod contains a flaw, then I implemented that flaw for sure...
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Bias mod is OK. I just needed to see it (especially the diode) to understand what you were describing.
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Bias mod is OK. I just needed to see it (especially the diode) to understand what you were describing.
That's a good thing.
I have redone the grounding as per your instructions except for one thing: I left the floating ground buss bar and used it for the pots, input jacks and caps #3, #4 and #5. The rest is:
PT bolt: - power ground cord.
Other PT bolt: - HV CT + Bias cap and 1st Filter Cap + 6L6s cathodes + Stdby switch Cap.
Needless to say it hasn't changed a damn thing...
I'm about to send back this damn amp the way it is... It frikkin' upsets me.
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I left the floating ground buss bar and used it for the pots, input jacks and caps #3, #4 and #5.
I was hoping you would rip that buss out completely and totally redo it. Doing so may reveal/cure a bad connection.
Let's get in sync on the cap numbers... Starting with the left end of the board on the layout, call the bias cap #1, the next cap (plate) is #2, the next cap (screens) is #3, the next cap (PI) is #4, and finally, the next cap (preamp) is #5. My point is that caps 1, 2, and 3 need to connect directly to the power ground. Take cap 3 (screens) off the buss. This will involve moving an underboard jumper (sorry).
I feel your frustration with this amp, but I know it's fixable. At this point, if it were my personal amp I'd probably pull the board and start all over. Of course, doing so, you may never know what the exact problem is, if that's important. I hate working inside a narrow tweed chassis.
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Relfow all heater wire connections at the tubes, lamp , etc. It sounds like a weak heater joint.If you've done it already.. do it again.
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Relfow all heater wire connections at the tubes, lamp , etc. It sounds like a weak heater joint.If you've done it already.. do it again.
I will do this again, before removing the board (a second time...). I had the buss bar across the pots first but I figured I'd use a floating buss bar instead as I don't much like soldering across pots: first they can get damaged with the iron's heat and second if they get too noisy and need to be replaced one day it's a lot easier to remove them and replace them if the bar is not running across them...
Anyway, sluckey I didn't remove cap #3 from the buss bar because the link you provided has it grounded to the buss bar... Only #1 and #2 go to the PT bolt. But if you say #3 has to go to the PT bolt as well, then I will remove that board again...
I'll never thank you all enough! I would have sent it back and told the guy "well just don't play it with pedals dude!" if you hadn't been here... :think1:
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I didn't remove cap #3 from the buss bar because the link you provided has it grounded to the buss bar... Only #1 and #2 go to the PT bolt.
Don't confuse the cap #s for your specific board with the cap #s of Doug's generic drawing. Doug's #1 cap is really your #2 cap and his #2 cap is really your #3 cap. Doug's filter caps aren't even on the board in his drawing.
I don't like the buss bar attached to the pots either. That's one minor difference between the method I use versus Doug's method.
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I didn't remove cap #3 from the buss bar because the link you provided has it grounded to the buss bar... Only #1 and #2 go to the PT bolt.
Don't confuse the cap #s for your specific board with the cap #s of Doug's generic drawing. Doug's #1 cap is really your #2 cap and his #2 cap is really your #3 cap. Doug's filter caps aren't even on the board in his drawing.
I don't like the buss bar attached to the pots either. That's one minor difference between the method I use versus Doug's method.
OK, I was going to make a mistake... So basically:
- 100uF/100V cap is my #1
- First 16uF/475V cap is my #2
- Second 16uF/475V cap is my #3
And all these three caps need to go to the same PT bolt along with all the CTs (HV + HT), the cathodes ground and the stdby switch cap?
If so, can I link caps #2 and #3 and use one wire to ground them or do they need to meet only at the PT bolt?
Sluckey can I keep my floating buss bar with only the right stuff attached to it or do you advise that I get rid of it and reinstall it directly on the pots?
Thanks!
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Remove the underboard jumper between #3 and #4. Jumper #1, #2, and #3 together on the board and use a single #18 stranded wire to connect all to the same bolt with the PT center taps and power tube cathodes.
This is a good thing to do but it's not likely to fix your problem.
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Heater wiring reflowed... Pedals still pop... I'm on my way to remove the board once again...
Hold on hold on... I have just had a long look at my heater wiring... The heaters between V4 and V3 are reversed... That may be the cause of the pops... V4 pin 2 goes to V3 pin 9 instead of going to pins 4/5 and V4 in 7 goes to V3 pins 4/5 instead of pin 9... I'll try this first before removing the board...
If this is it I'm the biggest fool on the planet... :BangHead:
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It wasn't that either... Pedals still pop... :cussing:
I'm off to take the board out.
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I could be all wet, but those pedal pops sound like there is DC voltage on the signal. Two years back I built a XLR mic switcher and if we used phantom powered mics it made a loud pop just like your pedals are doing??? To rule that out, plug a guitar cable into the amp and measure between the tip and sleeve of the other end for DC voltage.
Punky
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OK. Three more hours on this. I took out the board and reflowed some joints, checked my wiring for the fourth time, chose the grounding scheme as per what you said sluckey: Caps #1, #2 and #3 now go to the PT bolt. The rest of the board goes to the buss bar.
And guess what... Pedals still pop, and the amp is even noisier now than it was before.
punkykatt thanks for your help. I turned the amp on with a guitar cord in Bright Channel Input 1 and I have 89.5mV (MM on 200mV range) at the other end of the cable (MM black lead to sleeve, red lead to tip). Would that be enough voltage to cuase the pops? I don't know...
Thanks.
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Try disconnecting the cap to ground on the standby switch. See if that does anything for the pops.
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Is the chassis aluminum or steel? Is there any kind of coating or plating on the chassis that may need to be scraped off at every ground connection?
Oh, and I know this is a stretch, but disconnect the NFB wire from the speaker jack.
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Try disconnecting the cap to ground on the standby switch. See if that does anything for the pops.
I will to this tomorrow morning. I have put it aside for tonight, I have some unexpected friends at home...
Is the chassis aluminum or steel? Is there any kind of coating or plating on the chassis that may need to be scraped off at every ground connection?
Oh, and I know this is a stretch, but disconnect the NFB wire from the speaker jack.
I will sluckey. The chassis is from Mojotone. I have built about ten tweeds using their chassis. I never had anything to scrape off on those...
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Try disconnecting the cap to ground on the standby switch. See if that does anything for the pops.
It didn't do anything for the pops...
Oh, and I know this is a stretch, but disconnect the NFB wire from the speaker jack.
It didn't do anything either, it just added some low frequency hum... Pedals still pop.
Could these pops be the consequence of a bad OT or PT, or choke maybe? I mean, I have tested every single resistance, changed some, the voltages on the sockets are good. I have almost changed every coupling cap. This amp screams "I'm fine" but it's not... What the hell...
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What if it was the 5U4GB I have?
I don't have any direct replacement, all I have is a 5Y3GT and a 5AR4 and possibly a GZ34 (it's not labeled but I think it's a GZ34). Which one can I use as a short replacement just to see if the one I have is any good?
Thanks!
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I don't suspect the 5U4, but I'm about out of ideas, so try it. The 5AR4 (same as GZ34) will work fine. That 5Y3 is too little.
I also don't suspect the transformers.
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I don't suspect the 5U4, but I'm about out of ideas, so try it. The 5AR4 (same as GZ34) will work fine. That 5Y3 is too little.
I also don't suspect the transformers.
Right, I confirm that it's not the 5U4. I get the same pops with the 5AR4...
Jeez... If you're running out of ideas then I'm lost... :cry:
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I'm taking the 5F4 tonight for rehearsal. I have a three-hour rehearsal planned. I'm gonna push this little beast and hope it will explode. If it does then at least I'll know what to change... :cussing:
And if it doesn't then it's going back to its owner on Thursday... :dontknow:
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I just watched your video... you need to be, and can be, more aggressive with your chopstick in specific areas. I beat the shit out of any new build's solder joints to make sure that all connections are secure...poke hard at the pot eyelets , pull on the wires, etc. I've heard this pop dozens of times, and it always comes back to a bad solder connection.
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I just watched your video... you need to be, and can be, more aggressive with your chopstick in specific areas. I beat the shit out of any new build's solder joints to make sure that all connections are secure...poke hard at the pot eyelets , pull on the wires, etc. I've heard this pop dozens of times, and it always comes back to a bad solder connection.
Will try that tomorrow. The point is that I actually do not know when I'm supposed to hear hum when I use the chopstick or not. I mean, there are certain spots that carry high voltage and hence WILL produce noise if I bang them...
Anyway, I'm just back from my three-hour rehearsal. I played the crap out of this amp, with and without pedals. It sounds good. I didn't get any fancy noises. But the pedals do pop. That's a fact.
I noticed one thing at one time though: I had a hum (amp pushed with everything on 9) and then I had the idea to touch my strat pickup and the hum stopped. This happens, right? But then I had the idea to touch the chassis, and bang, the hum stopped too!!! I mean, wherever I touched the chassis with my finger, the amp stopped humming. I tried to reproduce that later on tonight but I couldn't make it happen again. No finger/chassis interaction anymore...
And one last thing: jeez the PT gets hot as hell! I touched it half an hour after having turned the amp off (it had been turned ON and played for two hours and a half) and I couldn't keep my hand on it for more than three seconds (yes, I counted!) Ain't this weird? I mean, the amp has a Heyboer/Mojo export PT that is the same as the one used for tweed Bassmans... And I don't remember a previous Bassman build making the same PT (and hence the chassis!) so hot!!!
Oh well... Please shoot with your ideas!!!
Thanks!
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Can't find it... :dontknow:
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I'm giving up... It's going back. :sad2:
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IIRC, on some amps with VVR/Power Scaling they where having problems with a dcv and would add a coupling cap in the signal wire in to the grid stopper (68K) to the preamp tubes grid.
I can't remember this one but IIRC it's on Akins site. Some guys add a cap from the input jacks hot or was it to the ground lug to ground. This was to bleed off any RF before it got to the preamp tubes grid. I think you have to use an insulated/isolated input jack for it to work.
I don't know if either would help. :dontknow:
Brad :think1: