Yamaha / Soldanop T100

[Enzo]

Is that 200 ohms the coil in the reverb pan?

[Valvehead]

Is that 200 ohms the coil in the reverb pan?

same with tank un plugged

[Enzo]

OK, we have a very weak return. You measure 200 ohms to ground from grid pin 7 of the return tube V6. Even with the reverb pan unplugged.

The schematic shows a 220k resistor to ground from the grid. You got 200 ohms there. I see three possibilities. One is you read the meter as 200 ohms when it really said 200k ohms. Two is there is a 220 ohm resistor in there instead of the 220k that belongs. Three, there is something shunting that line to ground with 200 ohms.

Correct this and it might restore your reverb level..

[Valvehead]

Im sorry-- i meant to say - 220k to ground with pan un- plugged

200 ohms with pan plugged in

i tested that 220k resistor and its ok

possibly the cable to the pan ?? Ill have another look when i can

[Enzo]

I'll believe it.

Here is my reasoning. The resistor might be OK by itself, but everything is a circuit. SO if we measure pin 7 to ground, we are measuring not only the resistor, but also the circuit path connecting it to the rest of hte circuit.

200 ohms is about what the output end of a reverb pan ought to measure, so I'd have to guess the cable is not shorted.

I am still wondering why both channel reverb controls are active.

[Valvehead]

Ok, is the actual rev tank supposed to be grounded to chassis....or floating?

i was testing tonight and found that-- if i remove the green wire from the Rev xformer and its floating in the air...it is going to chassis ground.

the cable from the tank (the + pin of the rca ) = its going to ground when plugged into the rev tank yet un-hooked at the spot where it connects to the xformer green wire

i tried reversing the tank wires also---nothing..

[Enzo]

The transformer winding is low impedance and so will have very low DC resistance. That is the drive end, remember you have weak return circuit?

If you want to show yourself the drive end is working, play into the amp and connect a small speaker to the reverb transformer - you should hear your guitar there.

[Valvehead]

I just went back through the amp. I decided to isolate pin 7 , V6 from the pcb with a new 220k to ground.....new cable to tank ....so completely isolated.....and I have no verb.

I cant find anything wrong....could it POSSIBLY be the reverb transformer ??

I DO have a new one here somewhere...maybe i should try that because Im stumped.

[Jazz P Bass]

You could run the reverb transformer into a speaker.

Or test the voltages.

43Vac in should yield 750mVac out.

Reverb Voltages.pdf

[STK]

i have a pcb and the original schematics here.
want them? pm me

[Valvehead]

its finally working now.....had a bad transformer !