Vintage Traynor YGM-3 Tremolo Issue

[Pryde]

OK I am going to visit the tremolo issue later because I want to deal with bias issues first

I measured cathode current and am getting 38ma on the EL84 which is way to much. Plate voltage is 400. This is pretty common with these amps I have read. I want to add a bias bot to adjust bias to proper levels.

R39 is the bias resistor (22k). I have a 10k trim pot to use for bias. I want to make sure I do this correct so thanks for the help: Do I remove replace R39 with a smaller value? if so, what value? Then I need to add the 10k trimmer in series to the new R39 and then ground the trimmer right?

Could someone walk me through it (or a simple diagram would be even better) I know 1/2/3 pots lugs so explaining the wiring would probably be fine.

[Chuck H]

Assuming that 38mA is across each tube you already have too little bias voltage. Since R39 is the bottom of the divider you only need to add your trim pot in series with R39 to add more range (more -V) and make it adjustable.

And here is a redraw of the layout. Changes are circled in red. This would isolate the ground for R32, R33, R34 and C25 from any preamp signal grounds. The ground lead between the two modded areas must be added. And if this doesn't fix the ticking I still have two other ideas.

[madkatb]

This website shows photos of the layout of the original and the reissue YGM3's. I just did some work on a three-input 1973 (same as second tan board photo). The typical YGm 3/4 schematic you find on the internet is dissimilar and the capacitor/resistor numbering is different. I would guess that Pryde's amp has all the tubes on the same side of the tagboard, not with V1 by itself, and with the can caps lined up with the tubes. That may change the way you view the grounding scheme.
http://ampworkshop.yuku.com/topic/42...p#.UlGcAtKdFvA

[Chuck H]

I figured it would come up if there was any confusion.

[Pryde]

THank you Chuck H. I installed the 10k bias trimmer in series with R39 (22k) and that did the trick. Biased the tubes at ~20ma and all is great there.

I know there are different schematics/versions out there. Mine is a mid-70's with 2 inputs. It had the long Mallory "cigar" filter caps in it which I just replaced with 50/50 jj cans.

I will look over your diagram and grounding. I can't thank you enough for taking the time and sharing your knowledge.

[Chuck H]

Ok... I just did a short Google search and found that replacing the old ceramic caps with film types seems to cure the ticking problem for most users. Ceramic caps can do some funny things in high gain circuits, so this might be something to try. Most techs pooh pooh the notion that cap type/brand can make a real difference but I've had ceramic caps cause weird problems often enough that I think this may be worth doing.

[madkatb]

Here's the schematic from a 1973 YGM-3:

[kevabilly]

old thread new discovery

Sorry for bringing this thread back from the dead but I had the same issue and solved the puzzle so i share if it can help somebody else with the same issue.
I have a 1973 traynor ygm-4 studio mate same amp as the ygm-3 except 4x8'' speakers. I started to have this issue after a whole recaping and retubing job so i started redoing my ground connections and swapping some caps related to the reverb and tremolo without fixing my problem. So i started messing around with tubes after testing a few 12ax7 in V6 location (phase inverter) i putted an old 7025 (low noise 12ax7) and boom problem solved i tried with others 7025 same result.
Cheers
Kev

[Peter S]

Hi Folks, I also have a YGM 3 with a ticking/pulsing from the tremolo. I have tried 4 or 5 used 12AX7's from my collection in the V6 position and found one tube that got the tremolo pulse down to an inaudible level. I also notice an objectional hum with the reverb turned up half way or more. After shunting all the power supply caps with new caps ( with no improvement), I found that the hum is due to the reverb tank's proximity to the power transformer. Has anyone else found this? I removed the tank, used RCA extension cables and the hum disappeared. I suppose relocating the tank to the bottom of the cabinet would be the solution but the closed back complicates things...

[garytoosweet]

Hi Folks, I also have a YGM 3 with a ticking/pulsing from the tremolo. I have tried 4 or 5 used 12AX7's from my collection in the V6 position and found one tube that got the tremolo pulse down to an inaudible level. I also notice an objectional hum with the reverb turned up half way or more. After shunting all the power supply caps with new caps ( with no improvement), I found that the hum is due to the reverb tank's proximity to the power transformer. Has anyone else found this? I removed the tank, used RCA extension cables and the hum disappeared. I suppose relocating the tank to the bottom of the cabinet would be the solution but the closed back complicates things...

You can see if it makes any difference flipping the tank around. Typically you want the input side closest to the PT.

If that doesn't work it's also an option to put the tank in a bag with shielding. Or located it at the bottom of the cabinet like you suggested, there should already be a hole for the speaker connection.

[The Dude]

Is the tank itself grounded?

[galaxiex]

My Vintage 1970? YGM 3 came with the tank mounted in the bottom of the closed back 1X12 cabinet.
Tank is inside a reverb tank bag and wrapped over with thick foam stapled down.
RCA cables thru a hole in the top of the cab (bottom of the amp "head") to the amp chassis.