Traynor YGM-3 Reverb Help & Tremolo Tick

[misterc57]

What are the voltages on V6A plate and cathode? Also, reverb footswitch was not grounding signal when you did this test?

No reverb footswitch being used.

V6A pin 6 plate = 87 VDC
V6A pin 8 cathode = 0.65 VDC

[g1]

That sounds about right. Is the reverb pot good?
As far as the touch test on the plug, sometimes if you are holding the plug ground at the same time, it won't make much hum. How about if you turn the reverb all the way up and crash the tank?

[TimmyP1955]

Turn the reverb control all the way down, connect the reverb send and return together, put a signal into the amp, and carefully turn up the reverb control. If it gets loud quickly, the send and return are good, unless the input impedance of the tank drags down the send when it's connected.

[misterc57]

Should I open a new thread to discuss preamp voltage?

That's the rub with a lot of the Traynor schematics. There are lots of transitional changes that were not noted in the schematics. It's hard to say exactly what you have, but I'm wondering if it isn't closer to this YGM1 schematic. You'll have to compare and see.

[ATTACH=CONFIG]52812[/ATTACH]

So, the YGM1 schematic looks interesting to me. It looks like it could apply except for the rectifier section, I have 2 diodes, not 6. The tube line-up matches my amp. The two resistors (12R and 56K) after the rectifier in the power supply filtering match what was originally in my amp. I changed them to 470R and 22K. And now I see that according to the schematic I am using, my preamp plate voltages are higher than they should be. 295V vs 220V.

I never checked the plates of my preamp tubes until now. I wonder if I should put the 56K back in, but I would guess it would bring that supply rail closer to 220 VDC.

Not sure how to calculate the voltage drop if I want to go from 390 to 220 VDC. Amp is drawing about .5 amps.

Here are my pre-amp plates versus what the schematic shows.

plate, my reading, schematic

V1 pin 1, 38 VDC, 85 VDC
V1 pin 6, 100 VDC, 180 VDC

V2 pin 1, 251 VDC, 135 VDC
V2 pin 6, 253 VDC, 147 VDC

V6 pin 1, pulsing from 237 to 252 VDC, 255 VDC
V6 pin 6, 87 VDC, 70 VDC

V5 is on the 390 VDC supply so these numbers look okay, except that 375 seems excessive for a 12ax7, datasheet states max voltage of 330.
V5 pin 1, 375 VDC, 380 VDC
V5 pin 6, 375 VDC, 380 VDC

Another odd thing I notice on the YGM-1 schematic, where is the negative bias supply?

[misterc57]

Back to the reverb issue.

A few suggestions have been made that I will try (hopefully tonight).

More things I observed;

The reverb pot is working. Tested both at the pot and at the wires connected at the board.

If I swap the reverb cables at the amp chassis, I get a hum. Which I think varied with the reverb pot, and could be defeated by the reverb footswitch.

[misterc57]

voltage drop

So, the YGM1 schematic looks interesting to me. It looks like it could apply except for the rectifier section, I have 2 diodes, not 6. The tube line-up matches my amp. The two resistors (12R and 56K) after the rectifier in the power supply filtering match what was originally in my amp. I changed them to 470R and 22K. And now I see that according to the schematic I am using, my preamp plate voltages are higher than they should be. 295V vs 220V.

I never checked the plates of my preamp tubes until now. I wonder if I should put the 56K back in, but I would guess it would bring that supply rail closer to 220 VDC.

Not sure how to calculate the voltage drop if I want to go from 390 to 220 VDC. Amp is drawing about .5 amps.

I think I calculated the voltage drop. First I calculated the current at .004 based on the current drop from 390 to 295 across the 22K resistor. So if I multiply a resistor value * .004, this should equal my voltage drop.

To go from 390 to 220 VDC I would need a 42,500 ohm resistor.

With a 56K I would see a 224V drop bringing that rail to 166 VDC.

[g1]

1) You are looking at a schematic that is not the same version of your amp
2) That schematic is not official, and has been re-drawn by someone who did not notate who they were
3) The voltages on that re-draw are not from an official schematic and I would not trust them

If you are going to fix the reverb, keep the amp (or put back) as you found it until you get it working right. Then build it into a different version if you want. For the version you seem to want, better to use the re-issue schematic from the factory.

[misterc57]

1) You are looking at a schematic that is not the same version of your amp
2) That schematic is not official, and has been re-drawn by someone who did not notate who they were
3) The voltages on that re-draw are not from an official schematic and I would not trust them

If you are going to fix the reverb, keep the amp (or put back) as you found it until you get it working right. Then build it into a different version if you want. For the version you seem to want, better to use the re-issue schematic from the factory.

For now I will leave it alone since the amp is working, focus on the reverb. Thanks

[misterc57]

Okay, finally got the reverb working. It was 2 problems.

First, the input and output cables were reversed at the amp, I was thrown by a marking someone had made on where to plug them in.

Second, one of the cables did not have a ground to ground connection at each end, only at one end. This was causing a huge buzz sound when engaging the reverb, further leading me to believe the wrong marking. I swapped that cable, huge buzz sound gone, reverb working!

Hopefully that does it. Thank you all for the great help and suggestions.

MarkO