Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: EKDENTON on August 26, 2016, 02:58:08 pm
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So I looked at what reverb units I could build and decided to do a head type with controls facing forward rather than the controls on top of the enclosure like the traditional fender reverb. I decided that Sluckey's Revibe would be the best for what I want. So far I have the turret board made, and almost finished populating. I lack a few parts that I had to order. I made a mistake and thought the schematic on Sluckey's website was Doug's schematic so that led me to order parts off Doug's BOM. That was not correct because the PS's are different. So I had to order a few more parts for that also. So far other than getting used to the spacing of the parts on the board being tighter than I make on my own turret board designs I have not had any problems. I really like the SS rectifiers that Doug Sells, wish all his resisitors didn't come mixed together in one bag though. The color bands are very hard to tell what they are, most of the colors look brown or black to me. I had to measure each one to find the one I needed.....and the one I needed was always seemed to be the last one in the pile.....LOL.
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I see an error with the jumpers on that board. Once I spotted that I quit looking. Thought I'd give you a chance to find it. This is a good opportunity to click on the link in my signature at the bottom of this message and trace it out.
I think you'll spot it pretty quickly and also be able to verify everything else is correct. I won't leave you hanging long enough to get frustrated. :wink:
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I've find it in a very small time (Happy about)
But I din't wanto to deprive you of the satisfaction to find out for yourself
Only is something that stay on the left instead of the right :icon_biggrin:
Ciao
Franco
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Okay I see it, to the right of the rectifier I was off by one turret. It's what happens when you stay up too late working on one.
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Bingo!
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Got my chassis sheared out and the corners notched for folding. I sheared the .090 5052 aluminum sheet 23-1/2" x 11-1/2". Once folded it will be a finished size of 17" x 6-1/2" x 2-1/2" with 3/4" ears turned out on the ends for fastening to the cabinet. I probably will shelf the chassis until I finish the turret board. Then I will lay everything in and on the chassis and double check how well everything will fit then mark what goes where with a sharpie. That way I don't get things reversed and punch holes on the wrong end of the chassis.
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Made some progress on the Revibe. I finished the chassis, checked to make sure all the parts would fit, punched all the holes and have almost all the parts mounted. I still need one switch. I noticed the layout I am building from has the power switch on the back side of the chassis. I rather have mine in the front with the other controls. I will put it left of the speed switch. I found an old abandoned Carvin footswitch with two switches that I can modify to work just fine. By mistake I made the turret board smaller (my printer printed it 9-1/4" wide and it should have been about 12" wide but it will still work just fine. A few of the parts will be a bit snug. I adjusted my cnc router toolpath, and removed the space where the 22uf cap would have gone with the original power supply so the next turret board i cut will be the perfect size.
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A couple more pictures.
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That is looking very nice.
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you might like this one...6G15, With help from this board
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Very nice.
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Sluckey on your revibe is the vib footswitch RCA jack actually on the opposite corner from the turret board hook up point? Checking to make sure that they did not get moved closer together. Also another question the reverb and vibrato jacks do not show any grounding, do they just ground through the chassis? Two of the RCA jacks Doug sent without washers with the hookup hole so those two jacks do not need them?
Okay never mind I see in your photos what you did.
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I finished wiring the revibe this evening and I am having some issues with it. I am not sure exactly how this thing hooks up but I have my guitar in the revibe input, then a guitar cord from the revibe output to the amp input. With the revibe turned off and only the cord from the revibe to the amp plugged in, I am getting hum. when I switch on the revibe I am getting loud buzz and no guitar sound at all when the guitar is plugged in.
I checked voltages before trying it out and here is what I have:
B+ 263vdc
V1:
1. 148.9
2. -0.04
3. 0.642
4. 3.02vac
5. 3.02vac
6. 191
7. 0.01
8. 0.04
9. 3.02vac
V2:
1. 100
2. 0.00
3. 1.25
4. 3.02vac
5. 3.02vac
6. 148
7. 0.04
8. 0.03
9. 3.02vac
V3:
3. 252
4. 257
5. .02
V4:
1. 214
2. -1.17
3. 2.02
4. 3.02
5. 3.02
6. 207
7. -0.39
8. 0.04
9. 3.02
V5:
1. 172
2. -0.3
3. 1.23
4. 3.02vac
5. 3.02vac
6. 244
7. 0.08
8. 4.72
9. 3.02
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With the unit plugged into an amp, do a pop test on each grid - starting from the stage closest to the output end of the revibe's signal path.
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Your B+ seems low. Which PT did you use? I also see several tube voltages that indicate problems. For example, V1 pin 8 should be about 1.5v. Your voltage indicates V1B is not working. And same with V2 pin 8. And V4 pin 8 is wrong also. In fact, V4 pins 3 and 8 should be connected together, but you show different voltages???
You need to double check your wiring. Did you forget to connect pins 4 and 5 together on the little tubes?
Looks like you followed my schematic, board, and chassis layout. OK, let's divide and conquer. Remove all tubes except V1 and V4. Set the mix pot all the way CCW. This should be dry signal only. The signal path is input jack to V1B to V4 to output jack.
Plug guitar into the input jack and plug the output jack into an amplifier input. You should be able to get a normal dry guitar signal into your amp with no hums or buzzes. There will be no effects.
Tell me what symptoms you have with this minimal setup.
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Okay with tubes 1, 4 still in dwell all the way CCW same issues occur.
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Okay with tubes 1, 4 still in dwell all the way CCW same issues occur.
That should be MIX pot set to max CCW. Continue troubleshooting with just V1 and V4 until you get a clean guitar signal through the unit. First step has to be verify wiring. Click on the link in my signature line in this reply for a good method to verify schematic, board, and actual amp wiring all agree.
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Sorry yes when i checked it I had all the pots set CCW. All parts including Transformers i ordered off of Doug's BOM. Let me double check on V4, I did see that, and I tied those cathodes together. I will double check that. I thought that was odd when i took voltages, maybe i did not have the the test pin on my meter in good contact with pin 8. When i print the schematic and the layout my printer prints the lines very light so they are difficult to see. Let me try to trace the signal.
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One big concern I have is your B+. You should have about 330vdc directly on the positive terminal of that bridge rectifier. And there should be 260VAC between the two PT red leads. What do you actually have for these two readings?
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Testing with V1 and V4 tubes still in I'm getting 248vac on the secondary winding and a B+ is 330vdc. The PT IS A Mojo 779 HT6190-1. I rechecked voltages on V4 3&8 and they are the same at 3vdc.
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Testing with V1 and V4 tubes still in I'm getting 248vac on the secondary winding and a B+ over 330vdc.
That's better. Initially you said your B+ was 263V. But that was with all the tubes in. The 6V6 is the only current hungry tube, but it should not have dropped the B+ that much. Makes me think there's something wrong in the 6V6 circuit or that PT is just not up to the task. I've never seen any voltages for the Hoffman revibe with that Mojo PT, so I don't really know what's the norm. You may have noticed that my PT came from Weber. I chose it because it was beefier than the Mojo PT. Maybe Doug can post the voltages on his revibe with the Mojo PT?
Let's put a pin in it for now. You have other issues that need to be corrected. Have you verified that everything is wired correctly and that the component values are correct? I think it's time to post some hi rez pics of the inside of the amp.
PS... I have my revibe on the bench now so I can easily make comparisons to yours if needed. Just let me know.
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Working on tracing with a highliter now. Will see if I can work through it. I
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I highlighted and checked the wiring. On the schematic. I had a 680 ohm resistor rather than a 680k on the plate of V2B. I had 110k resistors rather than the 220k resistors between the mix wiper and the plates of V4. I'm also reading 280k on the two resistors on the plates of V4 that should be 470k. that's about all I could see that needs some work. I havent wired the LED yet because I want to get the faceplate on first so I don't have to disconnect the wires.
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I had a 680 ohm resistor rather than a 680k on the plate of V2B.
Uh, that resistor needs to be 68K. This is not causing your problems.
I had 110k resistors rather than the 220k resistors between the mix wiper and the plates of V4.
Nothing wrong here. That's exactly what you should measure if the MIX pot is max CCW. Those two 220K resistors are basically in parallel. To accurately check them you would have to unsolder and lift one leg.
I'm also reading 280k on the two resistors on the plates of V4 that should be 470k.
Nothing wrong here either. That's exactly what you should read when measuring in circuit. Those 470Ks and 100Ks form a series/parallel network. To accurately check them you would have to unsolder and lift one leg.
Have you verified all the board jumpers are in the correct positions???
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Verify the four underboard jumpers are securely in place. If you missed that long one you will have no guitar signal.
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Verify the four underboard jumpers are securely in place.
I only see 3 that you hi-lighted.
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The crooked one is actually 2 jumpers. Here's a better pic showing 3 of the jumpers. And the long one near the top of the board makes four.
(http://sluckeyamps.com/VAC15/underboard_jumper.jpg)
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Yes i did the under wire connections the same way I ran them all the way through the turrets and bent them over so when i solderd components the wires will not drop out the bottom. I will try to get some hi res photos up soon but in the mean time i will keep checking, it's probably a wire in the wrong location. Thought it may be a missing ground but i sure dont see one yet......
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The crooked one is actually 2 jumpers.
Ok, I see it now. :icon_biggrin:
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Dunno if it is too late now, but it is better not to make underboard connections, I found it out the hard way(missed one and couldn't see it after the amp was all mounted and wired) now all my connections will be on top where they can be seen.
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So i unbolted the turret board and lifted it enough to get a mirror underneath so I could double check the underboard jumpers. They are in place as they should be. Here is a link to the high resolution photos. It is acting like an amp with a missing preamp ground. Bound to be a wiring mistake....just having trouble seeing it. This layout with double rows of resistors and wires under the board makes it hard for me follow the signal path. I traced the signal path as best as i could on the schematic. I did see one 100k resistor on the schematic that i could not find on the layout. All the parts are hooked up except for the LED.
http://s1266.photobucket.com/user/Ed_Denton/library/ (http://s1266.photobucket.com/user/Ed_Denton/library/)
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Looks real nice. :icon_biggrin:
But 1 of your power switch(?) lugs looks extremely close to a bolt just under it.
You might be over filtered in B+. A number of guys here like only a 10uF/8uF for the preamp input stage. Over filtering can change the preamp tone, make it thin sounding and/or have less chime and be less touch responsive.
You have 100uF/choke/100uF(?) then another 100uF and a last 100uF. The last 2 - 100uF's could be a 20uF or 10uF/8uF and the very last could be 10uF or 8uF. Or even just 1 - 10uF/8uF.
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I saw that in the photo. It's actually about 1/4" away, for some reason it looks a lot closer in the photo.
On the caps I believe Doug's BOM is off the original Fender schematic which has two 100uf, one 47uf, and one 22uf. Your probably right it may be a bit of overkill. I went off Sluckey's design that has the two double 100uf cans. For fitting parts or buying can caps maybe he found it simpler to just do the two 100/100 cans. I don't know enough about reverbs to know if too much filtering would have a bad effect. Maybe it is different for reverbs than with amps? Since they are just there to smooth the dc ripple it seems like it wouldn't have any bad effect :dontknow:
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Since they are just there to smooth the dc ripple it seems like it wouldn't have any bad effect :dontknow:
Over filtering can change the preamp tone, make it thin sounding and/or have less chime and be less touch responsive.
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I did see one 100k resistor on the schematic that i could not find on the layout.
I count 7 100Ks on the schematic and I count 7 100Ks on the layout. Which one are you talking about?
Those 100µF caps ain't a problem in this unit. There are about a half dozen of these identical units out there (that I know of) and they all work very well.
I'll take a look at your pics and see if I can spot anything.
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Those 100µF caps ain't a problem in this unit. There are about a half dozen of these identical units out there (that I know of) and they all work very well.
I'm sure they will work great but they might sound a little different and have a different touch to them. :icon_biggrin:
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Your input jack is wired wrong. Fix that and see where you are.
I know you say your underboard jumpers are all OK. But I can't see any sign of a jumper on the turret I labeled as "A" on the attached pic. Please humor me. Check for zero ohms between turrets A and B. Then I'll shut up about it.
:icon_biggrin:
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Ed, I've looked over your board and it looks good to me. However, there are a couple resistors that I can't verify the value. Probably just my eyes and the angle of the pic. Anyhow, component values need to be verified.
I've attached a B&W pic of the board that can be printed and used to verify all component values. Use a highlighter to mark each verified component. I would verify resistors by color code AND an ohm meter. Just remember that some resistors may not measure accurately in circuit.
Oh, and one other thing... Remove the green wire from you EIC socket. It creates a ground loop that will likely cause hum issues. You can alternately leave the green wire in place, but use a cheap 2 prong to 3 prong "ground buster" AC adapter.
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Okay will do. Dang I had a feeling I wired the switch wrong ....since I usually make that mistake. I bet I looked at it more than anything else. Let me see what fixing that does.
I did check all the resistors and replaced the 680 ohm to the 68k. Theo other 4 that were reading off you mentioned should read off unless I unsoldered them for a reading.
I can't tell what these little blue metal film resistors are by the color code. They all came mixed in one bag, I had to search one at a time by measuring them for the right resistor. The color bands all look black or brown to me. I saw one with a faint yellow tint....LOL. I like the tan color resistors better I can see what color the bands are.
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Fixed the jack before going to work. Now I have some guitar signal. Plenty of hum. I disconnected the green wire on the power cord receptical. No change in hum. Signal is weak. Reverb controls seem to be working vibrato controls are not. Does the LED anode connect to the cathode of the 12ax7? It's not lighting ...thought I had it oriented correct.m
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Does the LED anode connect to the cathode of the 12ax7? It's not lighting
Yes. The LED will be flashing at the tremolo speed if the oscillator is working.
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All your voltages seem low to me. What voltages do you measure at cap A, B, and C? What voltage on V3 pin 8?
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Caps
A supply= 298vdc
B supply= 274vdc
C supply= 188vdc
V3 pin 8=26.52vdc
Secondary voltage at the transformer= 234vac
B+ node= 304vdc
Mojo 779 multi-tap transformer, i am using the black and white wires on the primary for 120vac line power. their is a 100vac tap that would raise the voltages. Our line voltages here are usually right at 120vac.
http://el34world.com/Transformers/files/MOJO779.pdf (http://el34world.com/Transformers/files/MOJO779.pdf)
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I just pulled out the 6K6 and took voltages at the same locations:
B+ node=324vdc
A supply=322vdc
B supply=295vdc
C supply=242vdc
Could this NOS 6K6 tube be bad?
With a 6v6 in:
B+313
A=308
B=295
C=194
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6V6 voltages look better. Node C is the only one that bothers me. Check that 10K on the cap can. Unsolder one lead if it doesn't check good in circuit.
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It's 10k.would the bleeder resistor cause the voltage to drop? I have it on the C node to ground 270k.
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What bleeder resistor? You don't need a bleeder in this little circuit. But that ain't dragging node C down.
There is a discrepancy between your tube voltages and the voltage drop across that 10K resistor. The currents should add up but they don't even come close. I'd like you to measure the voltage at node B and node C again. And also measure the voltages on all pins of V1 and V2 again. I want to make it all jive.
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Okay, will do. I don't get home until late but I will post it soon as I can
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Here are the voltages with using the 6v6 with all the tubes in.
V1
1. 148.5
2.-1.1
3. .745
4. 2.98
5. 2.98
6. 197
7. 0
8. 1.52
9. 2.98
V2
1. 103
2. 0
3. 1.31
4. 2.99
5. 2.99
6. 109
7. 0
8. 1.32
9. 2.99
B node 292
C node 199
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C node should be around 290v?
.029mA*10,000
The 6G15 has 12ax7, 6k6, and a 7025. Maybe this PT is too small for the extra two tubes?
I was also looking at the schematic and layout. They both show a 1 amp slow blow fuse. That may be a little small, I put in a 2 amp fuse. The filaments will draw around 1.5.
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They both show a 1 amp slow blow fuse. That may be a little small, I put in a 2 amp fuse. The filaments will draw around 1.5.
The 1 amp slo-blo fuse is picked for the total mains acv/current draw, the heaters are pulling 1.5A but at 6.3 acv, it's a different thing.
I'd put the 1 amp slo-blo fuse back in.
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Take that 220K bleeder resistor out. What does Node C voltage read now?
Put the 1A fuse back in. It was fine. That 1.5A filament current only causes 79mA of current to flow through the primary fuse. The only reason I used a 1A SloBlo was because I don't have any 1/2A SloBlo.
I don't really suspect that PT. It's been used in quite a few Hoffman style revibes. It's lighter duty than the PT I used, but it should be fine. It does account for the slightly lower B+ than I have.
What I don't get is why is your Node C voltage so low. The currents don't add up correctly. There is twice as much current flowing in your Node C as in my Node C. Why? Either some of your voltage measurments are unreliable or the resistance values are incorrect. That's why I wanted you to verify every component value on that board. Have you done that yet? And the results?
Take a look at the attached chart and you'll see that the currents just don't add up. If I apply the voltage readings from my revibe to that same chart, then Node C current equals total plate current equals total cathode current, just as it should.
I've lost track of what the symptoms are at this point. What works, what doesn't work, hum, etc. Please tell me again.
Does the tremolo LED work yet? There's a good chance that if you connected it backwards at some time it will never work. If that's the case, you need a new one. It's important to use a red or yellow. I used yellow because there are already too many red LEDs in my world.
I was hoping to spot something obvious from your pics, but not so. I've studied your pics and I just don't see anything at this point. I'm at a point to try some signal tracing, either with a sig gen and scope, or listening probe. Do you have any of that stuff?
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The plate resistor on pin 6 of V1 was wrong so I changed it. That was the only one I found that did not agree with the layout.Took off the bleeder. Now for voltages I'm getting B+ 269
A. 265
B. 248
C. 215
Right now I am getting some guitar sound but it's with my amp turned so high it should be blasting my face off. It's also burried under the hum.
No go on the led with the anode (flat side of LED) to the cathode of the tube. On colors I may have to order those colors all I have is ultrabright blue or green.
I don't have any signal generators or even a scope. Wish I did.
Maybe we can go back to the divide and conquer idea and disconnect the vibrato section and see if just the reverb works?
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Check voltages for V1, V2, and V4 again. Also all B+ nodes.
Right now I am getting some guitar sound but it's with my amp turned so high it should be blasting my face off. It's also burried under the hum.
That hum is a big clue. We gotta find what is causing it. This unit puts out a signal that is only a little hotter than your guitar. It ain't much. And it's easy for hum to become a major factor.
I agree we need to divide and conquer but I think we should disconnect the reverb and fix the vibrato path. The reverb circuit is the tubes across the top of the schematic. The normal dry signal goes through V1B and V4. And V5 simply adds tremolo to the normal signal. If the oscillator is not working you just don't get the effect, but the normal signal should still pass through V4.
The color of the LED determines the voltage dropped across it. Yellow and red work the best in the oscillator circuit. White, blue, and green all have a voltage that doesn't work well. And since your B+ voltages are so low those colors may not work at all.
So, post those voltages once more. Maybe there is a power supply causing the hum. Could be PT, caps, or diodes.
And which make/model voltmeter are you using? Got a fresh battery?
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When i started the build i went off the color bands on the layout and I have no idea how i did this but I had wrote down 3M for the resistor that is parallel with the .047 off V4 pin7. You probably would have spotted that but that resistor is under the cap. When i was writing down the values i must have picked up a color band of a resistor next to that one. So i put the correct 1M in that spot. Rechecked every part again, and now I think i have all the resistors and capacitors correct. I tried it for sound and changing the 3M to the correct value 1M now there is no guitar sound at all now, just back to only hum.
When I get home tonight I will dig for a red LED, swap that out. and Re-measure all my voltages and post them.
Meter is a new Fluke175. It has a new battery.
You know the probablility of me making a wiring mistake is probably much higher than a bad component, but at this point I am not ruling anything out. I may also swap some tubes out maybe there is a bad one and it is passing the ac from the filament into the signal?
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...the resistor that is parallel with the .047 off V4 pin7... So i put the correct 1M in that spot.
You better take a close look. That resistor/cap does not connect to V4-7. It should connect to V5-2.
While you are at it, verify that all the wires for the tube sockets go to the correct turrets on the board. That's one area that your pics don't cover very well.
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Okay, yes your right it is.
I should have added that (its the one in series) with the 1M's to pins 2 and 7 of V4.
I will (re)check all the leads again tonight.
Does this Yellow LED look okay?
This 5mm (T1-3/4) clear lens yellow LED is a very bright 5mm LED. Forward voltage is about 2.9V, forward current is 50mA. Very nice, intensely bright LED. Color: Yellow Stock #: G18200
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That LED voltage is too high. You want one with a voltage between 1.7v and 2.0v and about 20mA. Do you still have a Radio Shack? They have a cheap variety pack that contains the LEDs like you need.
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No sadly they closed our store years back. Their is nothing here..... it's like living on Mars. I ordered the LED's at electronic goldmine. They have all kinds i just did not know what the forward voltage and amperage should be. They had some red 2V 20mA, they only sell in a 100 package for $5. Got some other colors and sizes also since they are so cheap.
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I bought a bunch from eBay a few years ago. I can send you a care package if needed. LMK. To get the oscillator working you can just put a 4.7K and 22µF parallel on the turrets the LED connects to. Cap negative to ground. Then replace with the LED when it's convenient. Also, if you suck the solder out of those two turrets you can just poke the LED leads into those holes to easily see which ones work best.
Send me a pm if you want to use the exact LED that's in my revibe.
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I found a couple 3mm red already have the mounting socket. If i am checking this correct (haven't checked an led with the meter yet) the led lights and the meter reads 1.83v forward voltage. So I will try these. If they don't seem to work i will try the R/C until the order arrives.
I found one that lights red with the red lead of the meter on the anode and lights green when you put the red lead on the cathode.
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Okay I found a red led that is works good. It is flashing with the vibrato all the time even with pots full CCW (is this normal?)
The good news is I am getting some guitar signal through now and the reverb is working and the vibrato seems to be working.
The bad news is the signal is still weak and there is still tons of hum and buzz. I pulled the tubes out one at a time hoping a tune replacement might fix it but there was no change in the hum.
After tracing the schematic and the layout several times with a highlighter finding the two incorrect resistors and correcting them I believe everything agrees with the schematic and the layout. I do still have the 6v6 in place of the 6k6. I did remove the bleeder.
So here are the voltages now.
B+267
A.263
B.245
C.211
V1.
1. 131
2. 0
3. 1.2
4. 3vac
5. 3vac
6. 137
7. 0
8. 1.1
9. 3.0
V2.
1. 109
2. 0
3. 1.42
4. 3vac
5. 3vac
6. 116
7. 0
8. 1.42
9. 3vac
V3.
3. 258
4. 264
5. .002
8. 20.66
V4
1. 227
2. -1.29
3. 1.97
4. 3vac
5. 3vac
6. 218
7. -.42
8. 1.97
9. 3vac
V5.
1. 174
2. -.22
3. 1.27
4. 3vac
5. 3vac
6. varies with vibrato 94-167
7. varies with vibrato .2- to .60
8. 1.58
9. 3vac
Voltages taken with all pots full CCW.
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Finally. A good set of voltage readings that make sense. Everything is in agreement. Your power supply voltages are consistently lower than my voltages by about 50 to 60v but that's just due to the difference in secondary voltages. I'd like for you to temporarily hookup the 100VAC primary tap and recheck only the filter cap voltages. Also measure AC filament voltage because it will increase as well. I don't expect this to help the hum/buzz issues, but you never know. If filament voltage is extremely high don't leave the PT on the 100V tap for too long.
Now let's divide and conquer to determine where the hum/buzz is coming from. Disconnect the wire between the board and the output jack. This will leave only the reverb circuit connected. Reverb will probably sound weak without the normal signal. Does the hum/buzz go away or get better?
BTW, what kind of amp is your revibe connected to? Can you try a different amp?
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On the 100v tap PS voltages are B+ 301
A-296
B-271
C-236
Filaments are too high at 7.01v
Could try and lower it with resistors?
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On the 100v tap PS voltages are B+ 301
A-296
B-271
C-236
Filaments are too high at 7.01v
Could try and lower them .5v with 2 150 ohm (no center tap) one on each wire. Should only need to be 1 watt but my math is not that great. :icon_biggrin:
I like those voltages! Those readings are only 25v lower than mine. Probably didn't help the hum/buzz???
I have several amps that run just fine with 7VAC on the filaments. I think I'd leave the 100V tap connected.
Did you disconnect the wire yet?
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No it's connected still let me see what it sounds like
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Volume seems pretty good now let me disconnect the wire to the output jack and see what happens
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Ed, read this thread. Start with reply #104 and read through to the end. It's not too long.
http://el34world.com/Forum/index.php?topic=17195.msg174718#msg174718 (http://el34world.com/Forum/index.php?topic=17195.msg174718#msg174718)
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Thanks. I'll check it out. It will be after an hour or two. My grandkids are in town and we are visiting.
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Guess I'm done for awhile, I was trying to take a tube shield off V2 and the tip of the tube broke. That was the only ecc81 I have. Guess I can use ecc83 while I'm troubleshooting until I can get an 81.
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Sorry to hear that.
In most cases you don't need to have any tube shields on while trouble shooting.
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Thanks.
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I read that thread and tried all of the suggestions you and Doug had for that revibe build that I had not already tried. It stays about the same with everything tried so far. With his the hum was better with the ground lift with mine there was no noticeable change. I tried two different amps. I listened to his video and unless it is just the video volume his hum was minor and sounds different. Here you can listen to how it sounds. Sounds like a test from the emergency broadcast channel or almost the pitch when you get an Amber alert. Can it be 120 cycle?
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Turning the mix pot max CCW clearly kills the hum. That's not what you have told us. That indicates the problem is in the reverb circuit.
Divide and conquer. Disconnect the wire I asked you to disconnect. Hum should still be there. Is it?
If so, reconnect the wire.
Now pull V1. Is hum still there?
If so, now pull all tubes. Is hum still there?
If so, you have a power supply problem. Leave all tubes out. Get an electrolytic cap to use for testing. 20µF, 40µF, 100µF, just whatever you have. It must have a higher voltage rating than your B+ voltage. Now connect the negative end to chassis and connect the positive end to node C. You can do this on the board or directly on the cap can, whichever is easier. Gator clip test leads makes this very easy. Does the hum decrease?
Repeat this test for the other three filter caps.
If that hum does not decrease with the above filter cap test it's possible that your bridge is bad. Replace it. You can use four 1N4007 diodes if you don't have another bridge. Doug sells two bridge rectifiers that look almost identical. One is rated for 50V, the other is rated for 1000V. If you used the 50V bridge then it is very likely bad now. Can you verify you have the right one?
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Yes, I did say that nothing had any effect on the hum but that was when the wire was connected to the output jack.
Once i disconnected the wire from the output jack, turning that pot CCW does kill all sound.
I still have the wire disconnected
That was one reason I did the video so you can see what the controls are doing, and what the problem sounds likesound is like.
So I will reconnect the wire and go through the steps listed.
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In case you don't have it fixed by now, I want you to check the ripple voltage on all four filter caps. If you are not familiar with the "MIN MAX" recording mode of your Fluke 175, then read the attached file first.
Now let's do it. You are gonna read the ac ripple voltage on the filter caps and record the average reading for 60 seconds. Here's how...
Set your meter to read AC volts. Connect the black probe to chassis. Connect the red probe to the positive lead of the bridge. (Gator clip leads are very handy for this test.) Press the "MIN MAX" button four times to put the meter in record mode and display the average AC voltage reading. (The display should also show "MIN MAX" and AVG. If not push the "MIN MAX" button some more to cycle through the display modes. Stop when you see AVG in the display.) Sit back and let it record for one minute. Then write that number down.
Move the red probe to Node A. (I did all my readings right on the board) Press and hold the "MIN MAX" button for one second to exit the record mode. Now press the "MIN MAX" button four times to reset the record mode to AVG. The display should show "MIN MAX" and AVG. Sit back and let it record for one minute. Then write this number down.
Repeat this procedure for node B and node C. Compare (and post) your numbers. Here are my numbers listed below...
B+ = 530mVAC
Node A = 116mVAC
Node B = 40mVAC
Node C = 11mVAC
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Working on reply #73.
I reconnected the wire and confirmed that turning the mix pot full CCW does nothing to the hum.
I pulled V1 and no change. So I pulled all tubes and there is no sound but my amp.
The rectifier matches the photo of the 1000v on Doug's page.
Should I move on to the tests in reply #75 on the capcitors?
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So I pulled all tubes and there is no sound but my amp.
I take this to mean the hum/buzz is still there?
Should I move on to the tests in reply #75 on the capcitors?
Yes. Put all the tubes back in while you are checking the ripple. I think you are about to find the source of the hum.
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The buzz was gone with all the tubes out.
All the AC ripple voltages are way off compared to yours. They are as follows:
+ on rectifier 63vAC
A. 62vAC
B. 169 mvAC
C. 2.8 mvAC
Since the measurement on the rectifier is that far off would that be the problem? It is the 1000v rectifier.
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It "appears" that the first cap can (the one with the choke connected) is bad. Or the bridge is bad. Maybe both. Reflow all three solder connections on that can. Any better?
Get an electrolytic cap to use for testing. 20µF, 40µF, 100µF, just whatever you have. It must have a higher voltage rating than your B+ voltage. Now connect the negative end to chassis and connect the positive end to B+. Does the hum decrease? Now move the positive end to node A. Does the hum decrease?
Where did you get your cap can?
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Here's a procedure to check the bridge. You must remove the bridge to check it. Set your meter to diode.
1. Connect the probes across the "AC" leads. Meter should read OL. Reverse the probes. Meter should still read OL.
2. Connect the red probe to "+" lead and the blk probe to "-" lead. Meter should read OL.
3. Connect the blk probe to "+" lead and the red probe to "-" lead. Meter should read about 1V.
3. Connect red probe to "+" lead. Connect blk probe to either "AC" lead. Meter will read OL in either case.
4. Connect blk probe to "+" lead. Connect red probe to either "AC" lead. Meter will read about .5V in either case.
5. Connect red probe to "-" lead. Connect blk probe to either "AC" lead. Meter will read about .5V in either case.
6. Connect blk probe to "-" lead. Connect red probe to either "AC" lead. Meter will read OL in either case.
If any of the above steps does not give these results, the bridge is bad. If you replace the bridge, replace that first cap can also because it has been severely stressed.
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Oh, BTW... You can connect your meter across the speaker terminals and measure the frequency of that loud hum. Just set your meter to measure AC volts and press the Hz button. Should read 120Hz.
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I connected a 47uf cap to B+ and the hum is almost gone just a faint hum changing with the vibrato.
The caps I got fir antique electronics. They are our neighbors in AZ.
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You need to replace that cap can.
That video you posted was invaluable. That kind of hum is most often associated with power supply problems. On a new build it's easy to steer toward chasing wiring errors. And it's easy to overlook the possibility of having a brand new bad component.
Looks like AES sells a JJ 2x100 can. I've had good luck with JJ electrolytics. And I've had good service from AES also. I'm sure if you point them to the last few replies in this thread they will send you a free replacement can.
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Okay thanks.
I will still check for the 120Hz.
It's a bit frustrating but I learned some good troubleshooting from this build.
I thought the hum was different, and once you posted the video of the other guys revibe even my bad ears could hear a big difference
This evening when I get home I will measure at the output jack and post the results for future reference. Hopefully this thread will help someone with the same problem sometime.
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Question. Would the bad filter cap effect the voltages? Just wondering if there is any concern about going back to the original primary 120v tap, or if this transformer just has low voltages?
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When you replace the can your B+ should increase. Once you have everything up and running measure the B+ and A,B,C nodes and compare to your last reading. Recheck ripple too.
If everything works good go back to the 120V primary tap. If works good on the 120V tap, I'd call it done. Your PT spec says 250V on the secondary. Mine says 260V on the secondary. Your dc voltages should all be a little lower than mine.
When you are satisfied that everything is working well, take a full set of voltage readings and write them on your schematic. Might come in handy sometime later.
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Okay I have the cap replaced and that was the cause of the loud buzz hum. The reverb section works very good and the vibrato is working but may need some adjustments.A
The voltages were too high on the filaments after changing the cap so I switched it back to the 120v primary tap. Voltages all look good now.
B+ is 322v, A=317v B=313.7 C=312 not much lower than yours.
It may need a few adjustments though.
The revibe is pushing either amp I plug into to distortion even on the cleanest settings. I did replace that V2 tube I broke with another 12AT7.
Another thing I noticed is that the vibrato speed pot does not do anything. The speed switch works good but not the pot.
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Also I forgot to mention that the JJ brand 12AX7 does not work well in V5 the 60Hz hum is too loud. I changed that one to a JAN brand tube and its much quieter. There is still some hum, but I will keep fiddling with it to get it as low as possible.
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The revibe is pushing either amp I plug into to distortion even on the cleanest settings.
On the schematic look just to the right of V4. You will see a 330K and a 10K voltage divider. Be sure those values are correct.
EDIT... To quickly locate these two resistors follow the wire from the output jack back to the board where it connects to a 220K resistor. The resistor on the left side of that 220K is the 330K and the resistor on the right side of that 220K is the 10K. (orientation is front panel up.)
The speed switch works good but not the pot.
You forgot to connect the wiper to the left lug.
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Those two resistors are correct.
I did not see that jumper on the wiper on my printed layout....should have checked schematic LOL.
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I'm thinking it may be the LED bias. If I went with the original R/C bias would it be 4.7K and a 25uf? From the old fender schematic it looks like that are the values.
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4.7K and 22µF or 25µF are correct. But just pull V5 first. That will totally eliminate the oscillator circuit. Still distorting? If so, then the LED ain't your problem. AFAIK you are the first to have this distorting issue.
Turn the mix control to zero. Still distorting?
"The revibe is pushing either amp I plug into to distortion". I interpret this statement to mean the signal out of the revibe is too hot and overdriving your amps. Plug your guitar straight into your amp and set the controls as you normally would. Then connect your guitar to the revibe and the revibe to the amp without touching any controls on your amp. Does the amp get much louder, or does it stay about the same volume you had with the guitar connected straight to the amp?
Post a hi rez pic of those resistors I asked about. I'd like to compare to this pic...
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Pulling V5 and turning the mix full off CCW has no effect. The volume is approx the same direct into amp or through the revibe.
I just assumed the revibe is pushing the amp harder, it could be possible that it is distorted before getting to the amp. It's not a desirable sounding distortion. If you want I can try to record it and post a link this evening.
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If you want I can try to record it and post a link this evening.
Yes, do that. We had pretty good results from the last one you did.
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Okay here I made a short video and strummed a few chords so you can hear what I hear.
https://www.youtube.com/watch?v=TdDjUUFulEY (https://www.youtube.com/watch?v=TdDjUUFulEY)
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Not supposed to do that. That distortion is coming from V1 and/or V4. Try a bunch of tubes in those sockets. I used 5751s (gain of 70) for both of those. Maybe try some 5751s, 12AT7s or 12AY7s.
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Okay. I don't have a lot of tubes so I borrowed the 5751 from my plexi PI and put that in V1. I have the ecc81 in V2. That did not have any effect. Still the same.
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Try it in V4 also. And you can pull that 12AT7 from V2 to try swapping into V1 and V4.
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I spent the evening swapping tubes. I found about 10 12A_7 tubes of various brands. I tried rotating those around with the 5751. It didn't change the distortion. It must be something else causing it.
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Try clipping in that test filter cap across node B cap and then node C cap. Make any difference in either position?
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Okay I tried that, and I had some sparks when connecting the cap to B and also C. It didn't do that when I was testing with the capacitor before when I had the bad capacitor. I checked and I did have the cap connected with the correct polarity. Playing through it the distortion was still there and I also noticed that the vibrato had stopped working. I took voltages of V4&5 and for some reason I only had 87v on pin 6 - V2. So I don't know if connecting the cap had anything to do with that or if it was a coincidence? Anyway I tried the JJ, Tung Sol, and a China made 12ax7. All those were way too much hum. So I had a Sovtek and it is quiet and the voltages are back to normal.
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It's normal to get some sparks when connecting a filter cap into a live power supply circuit. You also should discharge the cap before moving from one B+ node to another. It's very common to just touch the positive lead to chassis. Expect a small firecracker spark.
What guitar are you using to test the revibe? Got another?
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Yes both electrics I have do have pretty hot pickups, so I have an acoustic that has a weak piezoelectric pickup under the bridge. It also distorts. I'm going to get a scope from a friend today. If you can tell me what points to connect it maybe I can determine closer the problem spot. I am wondering if because I made the board smaller than it should be by mistake all my leads are short and resistors are very close to turrets. Soldering that close.....possibly overheated something?
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Get a signal generator too if he has one. You will need a clean 400Hz to 1KHz sine wave to apply to the input jack. Amplitude should be about 0.2v to 0.5v peak to peak as viewed on the scope at the input jack. Signal path is simple. You only need to trace input jack, V1B grid, V1B plate, v4 grids, V4 plates, output jack.
I suppose it's possible you have overheated some component. But the workmanship looks good. And you did verify all the resistors, right?
Download the new version of my schematic. It will come in handy when tracing circuits. You may have to hit reload or refresh to get the new version.
http://sluckeyamps.com/revibe/revibe.pdf (http://sluckeyamps.com/revibe/revibe.pdf)
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Okay I had a hard time figuring out this signal generator but i think i had it set on 1Khz. The first photo is on the grid of V1B, the second photo is on the plate of V1B it looks basically the same as the grid but about about half the size. Checking anything on V4 is difficult because of the vibrato. When i set the pots full CCW i'm getting a single horizontal line. when I change the intensity or what i call depth pot the horizontal line moves up and down with the speed changing with the pot and switch. (photo 3) The same behavior is at the output jack. So I thought i would be seeing a sine wave with some clipping or odd behavior but i am seeing a good sine wave up to V4 then I do not know if what I am seeing (this horizontal line) is normal or if it is the issue that i am having with distortion.
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If I've followed the ball, this test should be done with only V1 AND V4 plugged in, on other tubes, is that correct?
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Just looking at scope pics is not very useful. We need to know the measured voltage at the input jack, grid of V1-B, plate of V1-B, both grids of V4, both plates of V4, and the output jack.
Pull all tubes except V1 and V4.
Set the output of the sig gen so the voltage at V1B grid is .5V peak to peak. That's measured from the most positive peak of the sine wave to the most negative peak of the sine wave. The signal voltage at the plate of V1B should be considerably BIGGER than the signal on the grid. The signal voltage at the grids of V4 should be about the same (maybe a little less) as the signal voltage on the plate of V1B. The signal voltage on the plates of V4B should be BIGGER than the signal on the grids. And the signal voltage at the output jack should be much less than the signal voltage on the plates (due to the 330K/10K voltage divider. Ideally, it will be about the same amplitude as the voltage on V1B grid.
You need to set the vertical input to AC coupling so the baseline does not keep shifting on you. You will have to change the vertical sensitivity (gain, volts/div, whatever it's called) Should not have to change the time base settings, except the trigger level if you are triggering internally on the signal you are looking at.
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Okay all the tubes are out except 1&4, I have the signal generator set for .5v on the grid of V1B peak to peak which is the height of one square on the display. When I switch over to the plate I get a flat line. Looks way smaller. No signal at all on the output jack. What did I do wrong?
You mentioned earlier set the signal to 1KHz but this generator starts at 100 KHz. I was able to get a sine wave to .5v by adjusting the frequency range.
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You mentioned earlier set the signal to 1KHz but this generator starts at 100 KHz.
That sig gen is no good for audio circuits.
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Okay I got a workaround. I found a 1KHz mp3 file online, hooked up my phone as a signal generator and adjusted my volume for .5 v. The plate voltage is way higher thanbthe grid as you said...peaks are off the screen. V4A plate is less, V4B plate is about 1.5v. the output jack is about 2/3rds the input
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peaks are off the screen.
Turn the volts/div knob so you can see the peaks. I like to set the display for about 4 divisions. How much voltage is at every point I asked you to check?
And since you have a distortion problem, what does the waveform look like at every one of those check points? Do you see any sign of the sinewave squaring off on the peaks? Post pics and post peak to peak voltages foe all those check points.
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V1B Grid .5v.@ div .5 Sine wave good
V1B Plate 1v @ div 5 sine wave good
V4_1 1-1/2v @ div 5 and probe at 10x top 1/3 of sine wave flat
V4_6 2v @ div 5 sine wave good.
V4_2 1.7v @ div .5 sine wave good
V4_7 .75v @ div .5 sine wave good
Output jack approx. .5v entire top of sine wave flat
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V4_1 1-1/2v @ div 5 and probe at 10x top 1/3 of sine wave flat
Flat top is your distortion.
Carefully measure dc voltages for V4 pins 1, 2, 3 and 6, 7, 8.What are they? Unsolder the 100K that connects to V4-1 and measure resistance. Unsolder 100K that connects to V4-6 and measure resistance.
I still have no idea what your signal voltages are. Please interpret these... "V4_1 1-1/2v @ div 5" and "V4_2 1.7v @ div .5".
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Okay i will get the dc voltages asap.
V1 pin 6 would be 5v
V1 pin 7 and the input tip would be .5v
V4 pin 1 is 75v
V4 pin 2 is 1.7v
V4 pin 6 is 10v
V4 pin 7 is .75v
output jack is .5v
I am learning to use the scope as I type this, so be patient. Pin 1 on V4 was peaking way off the screen so changing the division as much as i could to 5v did not even get close to bringing the peak into view so i had to set the probe on 10X. So let me know if I did this wrong:
With the probe at 10X and Div set at 5v the peak to peak of the sine wave is the height of three horozontal bars. My original signal setting was .5v peak to peak at the height of one horizontal bar. at the new setting I measure 1.5v peak to peak. So to find the voltages I did 1.5*10*5 to get 75v.
the photos of the clipping the first photo is at the output jack at .5v then i changed the div to see the shape of the clipping better in photo 2, photo 3 is V4 pin1
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With the probe at 10X and Div set at 5v the peak to peak of the sine wave is the height of three horozontal bars.
Signal is 3 divisions high and Volts/Div is 5 so the display reads 3x5=15V. And since you are using a 10x probe that 15V display is really 150V. This all assumes that the variable is set to the cal position. Variable must be in cal position anytime you are measuring voltage.
The first photo is named 3.gif. Third photo is named 1.gif. Very confusing to me.
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sorry i numbered the photos backwards, should have said the first second and third photo in the order they are posted, rather than by the number of the photo.
I have the scope set in the cal. position.
Also when I set the scope division to .5v then i adjusted my signal tone to be peak to peak just one division on the screen so peak to peak three divisions would be 1.5v not 3v correct?
Also on the dc voltages, do you need them with just tube one and four in, as it is now, or do i need to put all the tubes back in for those measurements?
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three divisions would be 1.5v not 3v correct?
correct
do you need them with just tube one and four in, as it is now
yes, otherwise you would be "adding unknowns" to the process
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okay thanks, wish i had more time to work on it, right now its just a few minutes here and there because of work.
Here are the dc voltages
V4
1. 291v
2. .002v
3. 2.8v
6. 289v
7. .005v
8. 2.8v
Both plate resistors I unsoldered and they check out at 100k
The ones on either side of the 100k also check out at 470k.
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The #'s look good to me, BUT, wait for Sluckey, since he has a working system, mines in a heap.
Do you happen to have a 12AU7 laying around?, if so, put it in V1, then redo your AC (signal) checks.
logic, it's a lower gain tube, to me, your distortion apears more a gain thing than a R or C thing.
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I tried lower gain tubes in all positions but it's the same with any tube. Pin 6 on V1 has a good sine wave so whatever the problem is it is between there and V4 I think. Will see if there is anything Sluckey wants me to check now when he is back.
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V4's architecture is over my paygrade for helping Troubleshoot.
It might be fun to unplug the revirb tank, and if you have a RCA to 1/8" cable, jack your phone signal into J3, and see what that sounds like out the revibe and into your amp.
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It'll be very quiet with only V1 and V4 plugged in. :wink:
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It has a good sine wave at V4 pin 2 so that rules out anything before that point. Then at V4 pin 1 we have clipping. I have checked part values so many times and do not see anything out of place. I think I will replace all of the circled parts anyway just to be sure there is not a bad part. Is there anything else that would cause the first stage of V4 to clip? I have had several tubes in V4 and no matter what tube is there high or low gain the amount of clipping is about the same. Once i get the clipping stopped on that stage I can move on through to the end of the signal path.
Also Sluckey have you put a scope on your revibe to see if there is any of this going on maybe to a lesser degree on your build? I know you have higher voltages because of the different PT. Just stabbing for anything i can think of ....could the lower voltages have anything to do with the clipping at V4?
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I'm gonna check mine with a scope later today so you can compare. You're using 12AX7s for V1 and V4, right. And your input signal is adjusted to .5V peak to peak at the grid of V1B, right?
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yes that is correct.
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OK, my revibe is on the bench with only V1 and V4 plugged in using 12AX7s. All pots are max CCW. 0.5Vpp 1KHz test signal at V1-7. My output has compressed (flat) tops too. V4-A is being overdriven. When I back the input signal down to 0.2Vpp the signal is clean at every point from input to output.
Then I replaced the two 12AX7s with lower gain 5751s. With these tubes plugged in I can jack up the input signal to 0.4Vpp with no distortion. Even with 0.5Vpp input the output is only slightly compressed on top.
Real world test with my low output single coil Strat plugged in... Output sounds clean with either 12AX7s or 5751s. I don't have a high output pickup to try.
Try this. Reduce your input test signal to 0.2Vpp. Look at the output with the scope. It should be clean and approximately the same amplitude as the input signal. (I had my probe connected directly to the input and output jacks.) Is it clean?
Bottom line... I think a pair of 5751s will solve your distortion issue.
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Okay I will try that and see what hapoens. If it looks better I will order 4-5751's.
If you still have it hooked up could you try the same test with it plugged into your Variac adjusted to where your B+ is around the voltages I have? B+ 322?
I did at one point pull the 5157 from my plexi and had it in V1 and a 12AT7 at V4. I didn't have the scope at that time but I could still heat it.
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If you still have it hooked up could you try the same test with it plugged into your Variac adjusted to where your B+ is around the voltages I have? B+ 322?
I did this. Results are identical to the results above except with .5V in the output was about .44V, down from .45v with my B+ at 360V. I don't think your lower B+ is a factor.
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I worked with my Revibe quite a bit yesterday and have come up with a solution for the distortion issue. It's a simple mod that lowers the gain of V1B and V4 and then changes the 330K/10K voltage divider to make the output level the same as the input level. No more distortion with 0.5Vpp input level.
I'll be keeping this mod in my unit. Looks good on the scope and sounds good with my Strat. Mod instructions are in the attached pdf.
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Ciao Steve
is this mod to be considered a mod to the original project or is to be applied only in particular situations ?
Franco
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This mod applies to any Revibe that follows the Hoffman schematic or my schematic. V1B and V4 circuits have a LOT of gain. Then there's a 330K/10K voltage divider to knock the signal back down to instrument level at the output. The problem with this is that hot pickups will cause the signal to distort at the plates of V4. This is a permanent mod to my unit and I will be updating the info on my website.
When I built my Revibe in 2013 I dealt with the excessive gain issue simply by using lower gain 5751 tubes. My unit worked fine like this and I had no reason to look any further... Until Ed's distortion problem popped up. I started testing my unit to try to discover the cause of his problem. When I put 12AX7s in my unit to try to duplicate his problem I saw the distortion on the scope with a hot signal (0.5V). V1 was not distorting the signal, but it was supplying a large signal to the input of V4, and this caused V4 to overdrive/distort. Plus, V4 has it's own gain problems, so the distortion was just magnified.
So, I decreased the gain of V1B in order to not overdrive V4 when the input jack has a 0.5v signal (hot guitar). I also decreased the gain of V4 to produce a very clean, but lower amplitude signal at the plates. Finally, I tweaked the output voltage divider to provide unity gain from input to output.
Bottom line, the output signal looks almost identical to the input signal, tremolo effect is still very good, and the reverb circuit is untouched. And you get this with cheap 12AX7s, rather than pricey 5751s.
BTW, I did take a look at Weber's Revibe schematic and noticed he dealt with the V1B gain issue by using split load plate resistors (voltage divider) to decrease the signal being fed to V4.
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Thanks
Franco
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Sluckey, thanks for working on this so much and figuring out a mod to get it cleaned up for higher output signals. I will do the mods tonight and check it out. Can't wait.
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Did the mod tonight and it took care of the distortion. With the scope hooked up and using the same settings this input and output signal are the same and pin 1 at V4 has no more clipping. It sounds very good now with either amp using my guitar with active EMG pickups. I think I am done with this one.
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Hey, this has been a tough one. Glad it's finally done. Now just enjoy it. You may never need to build another reverb or tremolo circuit. I've used my Revibe in front of all my amps. The reverb and vibrato are really nice on my clean sounding amps. I don't really care for reverb on the gritty sounding amps but the vibrato is nice.
I'm also glad the distortion problem with high output active pickups surfaced. Back when that vibrato circuit was introduced, there were no high output active pickups so it was never a problem. Your scope work pointed out the problem. Thankfully it was a pretty simple fix. I've left the mod in my unit and am now running with 12AX7s, so our units should be identical, except for the PT, and I don't think the slight differences in B+ is a factor.
Oh, you may want to put that 220K bleeder back in. I now have one across my B+ cap. Those 100µF caps take forever to drain without that bleeder resistor.
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Thanks. I learned some troubleshooting techniques in the process. Using my friends scope was fun so I got to looking on ebay and found an iwatsu japan made scope that is in really good condition for $100. I want to learn more about using them. Once I get my cabinet from Mathier I will post a few photos of my Revibe.
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Glad you guys were able to track down the problem and find a cure.
This has been a frustrating quest for you guys but it has also been a great thread IMO. :icon_biggrin:
:bravo1:
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I got my cabinet in today. It turned out great. This is a very good tube effects project. it does seem to be finicky about what tube is used in the vibrato circuit. I made a list of 7 brands and only two were usable the other 4 had a loud hum increasing and decreasing with the vibrato. With the right tube it doesn't do it at all. I would recommend it because you can use it with any amp. The cost was pretty low to build because of the small trannies and one output tube. Thankfully Sluckey didn't give up on me getting it fixed and helped throughout the project. Thanks to Sluckey and everyone else that helped out!
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Sexy!
it does seem to be finicky about what tube is used in the vibrato circuit.
I did one additional mod that will take care of the picky tube. I added a level pot for the signal feeding V4. Now I can switch between 5751s and 12AX7s with no problems. Take a look...
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... it does seem to be finicky about what tube is used in the vibrato circuit. I made a list of 7 brands and only two were usable the other 4 had a loud hum increasing and decreasing with the vibrato. With the right tube it doesn't do it at all. ..
Beautiful !!
Please share which tubes did you tried and which ones did work without hum !!
I got similar issue with a vibrato.