Finished 5G9 Fixed! trem.

[Willabe]

1 more, kinda blurry and my meter that I killed the R/C functions on last night. But it seems to still read voltages fine.

[Willabe]

You have a footswitch jack. Insert a footswitch, or connect an alligator jumper from the hot lug to the ground lug.

Work now?

Hi HBP,

Thanks, I tried that last night with the FTS and no go.



                                    Brad     

[sluckey]

Insert a footswitch, or connect an alligator jumper from the hot lug to the ground lug.

That will kill the trem on this amp.

[Willabe]

Here's the layout drawing and schemo for the trem.

The speed pot is wired backwards on the layout, I will fix that on the amp and drawing.


                              Brad    

[tubeswell]

take a look at reply #10 of the u-tube link to Delbert McClinton at the CMAs with his gitar man (white Strat) playing through an old 5G9.

#10? I got 'Too Much Stuff'. Danged if I could see any tweed amps in there. Gotta link?

[HotBluePlates]

Insert a footswitch, or connect an alligator jumper from the hot lug to the ground lug.

That will kill the trem on this amp.

Ah, yes. I see that now.

Different test: unsolder the 22k from the center lug of the balance control. Trem now?

[Willabe]

take a look at reply #10 of the u-tube link to Delbert McClinton at the CMAs with his gitar man (white Strat) playing through an old 5G9.

#10? I got 'Too Much Stuff'. Danged if I could see any tweed amps in there. Gotta link?

No, it should be Somebody to love.

30 seconds in, on the right.

Just looked at it again and it looks to me that the other 2 guitar players got tweeds (maybe copys) and the white strat player is playing a custom amp?

Does it sound like a tweed bias-vary trem to you? Doesn't sound like a BF to me?

  
                     Brad    

Delbert McClinton - Somebody to Love


                      

[Willabe]

Here's the trem tube voltages.

Sluckey pointed out they should not be steady, so the osc is not working.

Here's the trem tubes dcv;

Driver/CF

Plate, pin 1+ 410vdc

Grid, pin 2= 270.4vdc

Cathode, pin 3= 272.4vdc

OSC

Plate, pin 6 =270.4vdc

Cathode, pin 8= 2.06vdc

When I turn up the Depth control pot the amp gets louder, wither the trem FTS is on or off.

                            Thanks,    Brad   

[sluckey]

Gonna put a 100K back on the socket? Will you need to replace the socket too?

[Willabe]

Yes and yes. I'll get to it tomorrow.


                       Brad     

[sluckey]

I still don't know why the trem osc is not wobbling. Near as I can tell, the OSC circuit is wired IAW the schematic. I'll look some more tonight. I think a working ohm meter will be very valuable troubleshooting this.

OTOH...

When I turn up the Depth control pot the amp gets louder, wither the trem FTS is on or off.

That's because the depth control is wired wrong. As is, it's part of the voltage divider network for your bias bal/adj circuit. Changing the depth control changes the bias! That's a bad thing.

I'll attach a drawing later. I'm too frustrated with Doug's nonresponsive server right now.

[Willabe]

I still don't know why the trem osc is not wobbling. Near as I can tell, the OSC circuit is wired IAW the schematic.

I've been over it 12 ways to sunday and I think it's wired up right too. I'm leaning towards a bad socket at this point, will see.

What if the 25uF/25v on pin 8 of the osc. K is bad? Could that be the problem?

The depth pot seems to be OK cause it's changing the bias when rotated.  

That's because the depth control is wired wrong. As is, it's part of the voltage divider network for your bias bal/adj circuit. Changing the depth control changes the bias! That's a bad thing.

Should be fine when I get it working and wire the pot right?

When I rotated the depth pot 180deg. in the layout drawing I didn't flip the 0/X of the pot.  This is another reason just to rewire the whole thing.

When I drew up the layout I thought it might be good to use eyelets on the board and point to point layout and to keep the FTS right next to the tube socket, as to keep all of the circuit together in 1 place, so no osc. leakage problems to anything else, ie, ticking. But it's a pain to see it and to re-work it, so maybe not such a good idea after all?

I think a working ohm meter will be very valuable troubleshooting this.

I'll go over to RS today and get a new meter.



                              Thanks for the help,      Brad      

 

[HotBluePlates]

The depth pot seems to be OK cause it's changing the bias when rotated.  

That's because the depth control is wired wrong. As is, it's part of the voltage divider network for your bias bal/adj circuit. Changing the depth control changes the bias! That's a bad thing.

Should be fine when I get it working and wire the pot right?

What I was following was that the Speed control was wired backwards, rather than the Depth. Either way, ordinarily, the Depth control setting would not alter the bias. However, I believe the Bias Balance and Range controls provide the alternate path to ground that usually wouldn't exist in that part of this circuit.

What I propose is to unhook the 22k resistor from the Balance control, just to eliminate a variable.

You are right though, that you have what appear to be good voltages and therefore a functioning tube stage in your oscillator, but it's not oscillating. The path around from plate output to grid input most then not be correct, or that 25uF cap is shot; otherwise, the oscillator would oscillate.

Be sure to know that the feedback path is not just the caps, but also the resistors to ground. If any of those don't have a solid ground, they are effectively not in the circuit. If you have only 2 RC stages (series cap, resistor to ground), you will get close to but not all the way to 180 degrees (except maybe at an extreme frequency). The oscillator will ring, but not oscillate.

Be 110% sure of all your oscillators caps and resistors/grounding.

[Willabe]

Thanks HBP,

I was wondering if I had the speed pot wired backwards (O/X) also. I'll fix that too.

I would have lifted 1 end of the 22K as you said but I had snipped out the 100K from across the tube socket. I think I'll tack in a 100K and then lift that 22K or re-wire the speed pot 1'st just to help track down what exactly is wrong. Wont take long.

I bought a new meter at RS.

I need to do some things around the house 1'st then I'll start in on the amp again.


           
                           Thanks guys,      Brad           

[sluckey]

The depth pot seems to be OK cause it's changing the bias when rotated.

NO! THE DEPTH POT SHOULD NOT CHANGE THE BIAS VOLTAGE.

Try this... Monitor the bias voltage on pin 5 of either output tube. (You may want to remove the power tubes for this, or kill the B+.) Now rotate the Depth pot from one end to the other. What is your bias voltage at each extreme of rotation?

The dc bias voltage should be rock solid when rotating the Depth pot. You could even damage your output tubes if the bias voltage goes too low.

Compare the two circuits below. You'll see what I'm talking about. The bias voltage must feed the depth pot from one end only, not be fed into the pot from one end and out on the wiper. Doing it your way just puts another variable resistor in the bias voltage divider string.

===========================

Now, this has nothing to do with the trem osc not working. That's another issue. We can't go any further with troubleshooting the oscillator until you put that 100K back on the socket (and replace the socket if pin 7 is compromised).

[Willabe]

NO! THE DEPTH POT SHOULD NOT CHANGE THE BIAS VOLTAGE.

I'm sorry, it went right over my head earlier when you told me about this.

I checked the bias as you said and yes rotating the depth pot changes the bias. The 6V6's are set for 20mA's each with -41vdc bias.

Rotate the depth pot and it goes from -41vdc to -11vdc.

Next I'll lift that 22K R as per HBP.  

I see/understand you drawings, thank you. I'll lose the balance control. Even though both have the 250K depth pot in series with the bias, with the balance/range control pot in place as I have them, it gives the bias a path to ground _after_ the 250K and that's the hitch.
 
I didn't burn anything up, all is fine, PT, OT 6V6's. The 6V6's never even red-plated.      

RS meter was dead/broken from the get go, took it back. Where you plug in the test leads was shorting and all it did when trying to take R/C/Diode measurement's was buzz for continuity.    It also was a pain to get at the 2 fuses. You have to take out _8_  screws and then pull out a PCB from molex type sockets just to get at them.        

Went to HD and bought a Klein, seems to be solid at the test lead jacks, I think I'm gonna like it.

I spent yesterday with my wife food shopping and we cooked up a couple of gallons+ of spaghetti sauce, ground beef and Italian sausages, well freeze at least half of it. We had a great time and dinner was delicious.      

Now that I have a working meter again, I'll move forward with fixing the term. osc.

Also, sometimes I need time to think things thru. But once it gells in my mind, then I can move forward again.


                        Thanks for all the help,    Brad    

 

[Willabe]

I want to see how your bias works out.  I've got a bet it is better than dual bias.  I am going the dual bias method, but I did get the mini 25kl pots so if yours is best I can copy.

Hi Ed,

Well it's not going to work in this amp.    

But, I did find it _very_ easy to use and it was _no_ problem to adjust the 2 tubes @35mA each to within 0.2mA and that was with only 1 meter. Not to shabby.  

Now they were a matched set and I didn't mess with it very much, but I'm a beliver at this point.

I'll try it again in the next build with grid bias for sure.


                       Brad      

[tubeswell]

Bias wiggle trem is less effective if there is too much tube current in the 6V6s, because trem wiggle ends up 'fighting' the output tube current.

[Willabe]

OK thanks, I remember you and others posting that before to help guys get their trems working.

When try to post the link to Delbert it goes to the pic. screen for the clip.

Just look up Delbert McClinton, Somebody to Love, on you tube.


                   
                            Brad     

[sluckey]

When I first saw your bias/balance/trem circuit on Ed Chambley's Princeton thread, I thought it was simple but elegant. But then when you said changing the depth changes the volume, I decided to look more closely. And there it was! It finally hit me! And now that you say the bias drops to -11vdc, I know you have to change that part of the circuit or risk burning up your output tubes.

If you insist on splitting the two 220KΩ grid resistors to be able to balance bias, then I don't see any way around using a dual pot for depth control of the trem. Tell me, do you REALLY want to be able to balance tube bias to the gnat's ass, or do you just want that swamp trem sound on that video? You decide, but either way, you gotta change that bias part of the circuit.

I started drawing out a schematic using your circuit but with a dual depth pot. It's 80% done, but I decided to hold off until I see where you're headed with this issue. I vote KISS, single bias adjust and single depth control. Heck, the original didn't even have adjustable bias and it was a good amp.

Now, back to the trem circuit... The fact that the oscillator is not working is totally unrelated to the bias circuit problem(unless you hosed the wiring somehow, and I don't think that's so). Let us know when you have the socket changed out and the 100K plate resistor installed on the socket.

[Willabe]

I see/understand you drawings, thank you. I'll lose the balance control.  
I didn't burn anything up, all is fine, PT, OT 6V6's. The 6V6's never even red-plated.      

Now that I have a working meter again, I'll move forward with fixing the term. osc.

Also, sometimes I need time to think things thru. But once it gells in my mind, then I can move forward again.

I know the post was long so I boiled it down to the above.

I think your right, I'll lose the balance and just go with a bias adjust control, that'll be just fine.    

And yes swamp trem it is. That is, too me, the most important part of this amps sound.

And yes I don't need to balance the PP pair of tubes down to a gnats butt.           But it is nice to know it will work fine on a PP grid bias amp without bias vary trem.    

With that being said, I thought about how to get around the depth control and I thought it might be to use a dual pot. I figure you need 2 paths for the PP bias. For future reference it would be interesting to see your idea later.


                              

When I first saw your bias/balance/trem circuit on Ed Chambley's Princeton thread, I thought it was simple but elegant.

I wish I could say it was my idea, but it's not. (and I said that then) It's from Kevin O'Connor's TUT books.

Edit; But it was not on/for a vary bias trem. amp, I tried to add it in and now I see it will not work in that amp.  


                                       Thanks,     Brad    

                

[sluckey]

OK, I'll finish the drawing. I might name it Rube or something appropriate.  It will be very similar to Ed's cut/paste drawing, but refined in Visio. I'll keep following to see when we can resume troubleshooting the trem osc issue.

[Willabe]

Yes, I've heard of a MR. Goldberg.     

And thanks again Sluckey.   


                       Brad     

[Ed_Chambley]

Well guys, I just finished cutting the chassis to fit a dual pec pot.  They will not fit in the angle front.   BWT, I am replying on a brand new I7 processed 17 inch dell laptop.   I do not foresee any problems.  The PE pot is acurate as hell and the 2 mini 25kl bias pots are as well as they are PEC as well.  I have gone a little crazy with mods, so the build is slow.  I wired the heaters and am waiting on a couple of caps.  I have finished the schematic and cannot see any reason why it will not work.

Yes Leo did do it without all these additions, but he never built a blackface with bias vary tremolo with a mid and and adjustable NFB along with a Dual Rectifier with a Deluxe OT with 4-8-16 ohms and used 7c5 power tubes with loctal sockets.

Like I said, I am having a ball with this build and I assure you when I am done and i am playing through this things with a tweed with 2 10's and 2 single 12's, 1 4 ohm and the other 16 ohms with blond tolex, it will be unique.

[Willabe]

The PE pot is acurate as hell and the 2 mini 25kl bias pots are as well as they are PEC as well.

I got my mini 25KL locking pots from Weber. Please tell me/us more about your mini pots.


                      Brad       
                           

[DummyLoad]

Please tell me/us more about your mini pots.

called RV6 pots - miliary designation for the form-factor. RV4 are the 24mm pots you're used to seeing that are made by PEC.

291 in stock...

http://www.digikey.com/scripts/dksearch/dksus.dll?lang=en&mpart=RV6LAYSA253A&vendor=98&cur=USD

--DL

[Willabe]

Thanks DL.


                   Brad       

[Ed_Chambley]

The PE pot is acurate as hell and the 2 mini 25kl bias pots are as well as they are PEC as well.

I got my mini 25KL locking pots from Weber. Please tell me/us more about your mini pots.


                      Brad       
                           

Brad, man I am soooooooooooo sick of the inferior crap from overseas.  In most places Alpha pots work, but they are NEVER close to accurate.  Check out one of their audio tapers to a cts and you will see what I mean.

1   2   KKA2541S28-ND   POT 250K OHM 2W DUAL LOG TAPER      0   34.37000   $68.74
2   2   RV6L253C-ND   POT 25K OHM CARBON 1/2W      0   10.04000   $20.08

Here are the part numbers at Digikey.  PEC are made in Canada.  I had about 40 Alpha pots.  Yesterday I traded all my Alpha pots to a friend for come cabling.  I am done with them.  Bourns will be used in non-critical areas like if I am doing something like an adjustable NFB.  CTS linear are pretty good.  I had a 1meg Alpha pot in the volume position of a custom amp I have been building and having trouble with.  New pot.  Put a MM on it and it measured 420k full turn.  I thought there was something wrong with my meter.  Checked it with another and got the same thing.

Maybe I am just snakebit where Alphas are concerned.  A lot of the guys here use them and make wonderful amps.  I checked the reverb pot on a deluxe I built a couple of years ago.  It is supposed to be 100K.  Been having trouble with the reverb.  It measured at 1/4 turn 110K then dropped a little the I passed half a turn and it went flying by 100K and ended up at at 180K.

As Weber in concerned.  I love their speakers.  They stock very few good parts, but do sell Mercury and Heybour.

I do check them before installing them and know it in advance of using them so it is stupid on my part, but it you order a list of materials sometimes it is the only one you have.  I have many 1 meg pots, quite a few 250, but I usually dont stock up on 100K as there are not many uses for them.

I did not check any more.  I checked all my amps and ordered the CTS Doug had.  I called Steve at www.apexjr.com as he has very nice NOS pots and Bournes and got what he had that would work and ordered the rest from Digikey.

Sure they are expensive from Digikey, but we put a lot of hours in these builds.  If I have to build one less amp because I am using a quality pot, so be it.

As you can probably tell, I am a little more than irritated with the Taiwanese bullcrap.

[Willabe]

The _Swamp Tremolo_ is Now Working!         Wa Wa Wa Wa Wa .......    

And it sounds _very_ good to me. Waaaay better than my old BF SR and BF PR trem's, no doubt at all.        And I haven't even run it with the stand alone reverb yet!                

Good news is it's working fine, so far. Bad news is I don't know exactly why?    

The osc. was wired right, but the speed pot was wired backwards and the bias/balance was a problem.

I wonder now if HBP was right about the bias/balance having a 2'nd path to ground and bleeding off the term. signal, just like it was messing with the bias? I never lifted the 1 end of the 22K R as HBP suggested because I would have had to tack a 100K R back in across the socket and I just wanted to get it fixed.

So... I took out the term. socket and everything that was wired to it and put in a new one. Put in all new R's/C's that were wired to the socket, pots and my 1 solder eyelet lug I had made, which is the true point to point section of my layout for the term. I made sure I measured all the new R's/C's (just as I did last time too) and also once again measured all the other R's/C's on the eyelet board, all were right. I changed the cathode by-pass 25uF@25v for the osc, even though the 1'st one measured fine, figured why not? Re-wired the bias to a single bias adjust and re-wired the backwards speed pot so it's now correct. I also had to re-do 2 sections of the twisted pair heater wires for the term. tube, that ran from the pilot light to the term tube, then to the PI tube because the heater wires insulation was a mess after taking out the term. tubes socket.

All in all it took me a long time, 8 hours? This point to point wiring with it's lead dress is IMO, _much_ harder than using an eyelet board and running the wires back to the socket, much, much easier, IMO. Also, I had to keep looking back at the schemos with ever step to make sure it was wired right.    I do think the lead dress is better this time and looks better too.

I still need to play with the bias R's a little to limit the high and low ends of the bias swing.

And I do need to slow down the term. a little more. Right now the osc. has 2 @ 0.02 and 1 @ 0.01 for the caps. So I need to increase the cap values a little? It's got way more than enough depth. The term. on/off FTS works fine, no pops.

I'll post pics in the next day or two.

Thanks to _ALL_ of you for your technical and moral support!!!!! As always, You guys are the best!!!!!



                       Brad      

[tubeswell]

I do need to slow down the term. a little more. Right now the osc. has 2 @ 0.02 and 1 @ 0.01 for the caps. So I need to increase the cap values a little?

Glad you got it sorted. Yep try tacking .01uF in parallel with that first .02uF off the LFO plate

[Willabe]

Glad you got it sorted.

Thanks, me too.    

Pete you were right, these bias-very trems are killer, whaaayy more soul than roach style trems!

Yep try tacking .01uF in parallel with that first .02uF off the LFO plate

Ok, thanks, that's what I thought.


                  Brad      

 

[sluckey]

Congratulations! I has a feeling the trem would heal itself during the socket replacement.   

Here's that dual bias circuit I was working on.  I bet you like the amp just as it is though. Sometimes too many bells and whistles are just that!   

Play on...


Oh, and here are a couple pics of the only dual bias I've done. Pots are the RV6 type. Amp is Sunn Sceptre.
http://home.comcast.net/~seluckey/amps/sunn/mod_1.jpg
http://home.comcast.net/~seluckey/amps/sunn/mod_2.jpg

[Tyrannocaster]

Hey, you got it going! What a lot of work! Well, all I can say is persistence paid off and now you get the reward. They are such neat amps and yours looks like a killer; I'd be proud to have one as nicely built as yours. Will you post a sound clip or two?

Congrats!

[HotBluePlates]

Congrats!

I don't know that my suggestion to simplify the bias while troubleshooting was the root of the problem. That was just to remove extraneous issues while you were sorting the oscillator.

I'm betting something wasn't quite right with the Speed pot, feedback components, the socket or the oscillator's 100k load on the socket. All the things you did to revamp that area managed to catch the one item that was holding up the show.

[tubeswell]

Thanks for sharing that schematic Steve.

FWIW I've found (with 5G9s) the trem slam becomes even more intense if that 1M resistor (that's in the voltage divider after the CF) is decreased to about 470k. This saves you having to cool the 6V6 bias down 'too much'. You may have to tinker with final values (or adjust the bias) in order to prevent 'helicoptering' and depending on taste. (@ brad - not saying that everyone should automatically do this - its just more of a tweek-thing if you're bored, after the circuit has been built and is working)

[Ed_Chambley]

Great, I am glad you got it

[Ed_Chambley]

Congratulations! I has a feeling the trem would heal itself during the socket replacement.   

Here's that dual bias circuit I was working on.  I bet you like the amp just as it is though. Sometimes too many bells and whistles are just that!   

Play on...


Oh, and here are a couple pics of the only dual bias I've done. Pots are the RV6 type. Amp is Sunn Sceptre.
http://home.comcast.net/~seluckey/amps/sunn/mod_1.jpg
http://home.comcast.net/~seluckey/amps/sunn/mod_2.jpg

Thanks for the Schematic.  It looks familiar.  I have a couple of questions.  What is LFO?  Why do they call the control Depth and not Intensity?  On the schematic, you have 2 caps without values and resistors as well.  Is that because they will vary according to the bias tap voltage and also the application of the circuit?

[HotBluePlates]

Here's that dual bias circuit I was working on. 

I wonder if his circuit as-is could have a bias balance that replaces the 220k bias feed resistors?

Say, the Depth pot wiper feeds the wiper of a 500k linear pot, whose outer lugs then go on to the output tube grids. Or a 250kl pot, with 120k build-out resistors on either end.

What is LFO?

Low-Frequency Oscillator

Why do they call the control Depth and not Intensity?

Gibson and Gretsch amps often call that function "Intensity". Fender just said it different. And there are some amps out there that say "Frequency" instead of "Speed".

[DummyLoad]

congrats! glad you got it working.

--DL

[sluckey]

you have 2 caps without values and resistors as well.  Is that because they will vary according to the bias tap voltage

Actually there are 3 caps. 10-50uF should be fine. I didn't show resistor values because you need to juggle depending on the AC voltage input. Willabe's values should be just about right for his circuit.

[Tyrannocaster]

Could you post a sound sample of the now working tremolo, please?

[Willabe]

Thanks guys.

I has a feeling the term would heal itself during the socket replacement.  

I wasn't so sure, I kept looking to see if I had wired somthing wrong, but other than the speed pot being backwards it was correct. All the parts values were correct too.      

Thanks for your dual bias idea and drawing. Looks good to me. I saved it. I'm going to leave the bias it like it is.

FWIW I've found (with 5G9s) the trem slam becomes even more intense if that 1M resistor (that's in the voltage divider after the CF) is decreased to about 470k. This saves you having to cool the 6V6 bias down 'too much'.

I'll keep that in mind. So far it's got plenty of depth as is.

Could you post a sound sample of the now working tremolo, please?

I'm sorry T but I don't have any recording gear any more. I haven't realy put it through much playing yet, but I will say it seems to be a little cleaner than my 5E3 and to me, the trem sounds rounder, warmer, smoother and deeper that a BF roach trem.


                              Brad      


                                  
                                        

[Ed_Chambley]

Thanks guys.

I has a feeling the term would heal itself during the socket replacement.  

I wasn't so sure, I kept looking to see if I had wired somthing wrong, but other than the speed pot being backwards it was correct. All the parts values were correct too.      

Thanks for your dual bias idea and drawing. Looks good to me. I saved it. I'm going to leave the bias it like it is.

FWIW I've found (with 5G9s) the trem slam becomes even more intense if that 1M resistor (that's in the voltage divider after the CF) is decreased to about 470k. This saves you having to cool the 6V6 bias down 'too much'.

I'll keep that in mind. So far it's got plenty of depth as is.

Could you post a sound sample of the now working tremolo, please?

I'm sorry T but I don't have any recording gear any more. I haven't realy put it through much playing yet, but I will say it seems to be a little cleaner than my 5E3 and to me, the trem sounds rounder, warmer, smoother and deeper that a BF roach trem.


                              Brad      


                                  
                                        

Just plug a microphone in your computer and use windows medial player and record.  It won't be like pro tools, but we will get to hear the amp.

[Tyrannocaster]

Yeah, without sound clips it doesn't exist. 

[Willabe]

Ok, I'll look around for a mic, my 2 good mics (that I still have) are at a friends. I need to change my strings too.

I might as well learn how.   

I've only had a computer for about 3 years so I know very little about different things they can do and how to make them do it.    


                       Brad      

[cbass]

Don't feel bad it took me years to figure out my computer could do other stuff besides looking up nude pics of women.

Glad to hear you got it going.Can't wait for the clips.

[Willabe]

Thanks buddy.   

I'm not doin to bad with it, but learning more is always good.


                    Brad     

[Platefire]

Alrite Wilabe

So ya finally arrived!! Except a few tweaks 

Ye haw!! Boy the drama was getting intense---now I can relax   

[Willabe]

Ye haw!! Boy the drama was getting intense---now I can relax

 

Thanks Plate. She go wiggle now.      Wa Wa Wa Wa Wa Wa Wa...... 


                     Brad    

[Willabe]

I found an old RS condenser mic and put in a new battery. But when I record with it on playback all I get is a _very_ low volume even with the speakers turned all the way up, all 3, the speakers and on the Real-Tech and on the computers screen.

I'm going to put this in Audio/Video.


                Thanks,        Brad