super reverb output values, please

[JC@]

I have a problem with a super reverb, reissue, gz34 rectifier.
It sounds weak, low and distorted and I suspect that the OT could be the problem.
The primary winding looks ok, but the secondary shows .29 ohms between leads.
Is that too low?

Thank you.

[greekie]

The secondary is supposed to be connected to a 2 ohm load, so it is indeed very low. Have you scoped out the signal?

[JC@]

Yes I have. Looks horrible, completely distorted and weak.

[greekie]

Straight at the input? Before / after the phase inverter? Or just at the output? You need to poke around to find the source.

[JC@]

You need to poke around to find the source.

there's where I am now. It begins just before the PI, but I still think it could be the output transformer..

[Tom Phillips]

... It begins just before the PI, but I still think it could be the output transformer..

No offense but your last statement is actually humorous in that it indicates a case of incorrect mindset troubleshooting.
There are many faults that could cause low power output. Don't just assume that the most expensive part in the amp is bad. Step back for a while, think about it and then continue with your troubleshooting.

I hope you find something simple like an open ten cent plate resistor.
Good Luck to you,
Tom

[imaradiostar]

2 ohms is the output IMPEDANCE of the transformer- the DC resistance will measure somewhat lower than that, much like your .29 ohms.

How and where are you injecting a signal into the amp?

jamie

[JC@]

imaradiostar, I always like to ask just in case, thank you. So as there are no shorts to the Xmer core, the primary winding is ok and the secondary winding seems ok too...
I will have to look somewhere else arround the PI. I put a new set of power tubes and the redings are correct. I get B+ on their plates and screens, and the bias is correct.

I inject the signal to both inputs, that is, normal channel and then the vibrato channel. Everything looks correct until it reaches the PI. I believe the vibrato and reverb are not the problem as they are no switched on (I don't have the pedal switch and the tank is unconnected)

ps: The test signal comes from a generator.

[imaradiostar]

are you injecting the signal into both channels at one time?

jt

[J M Fahey]

there are no shorts to the Xmer core, the primary winding is ok

How do you know?
2) When you say "signal reaches the PI", do you refer to the PI input or its output (plates)
In the second case, we are talking over 50V RMS levels or more, maybe your scope can't handle it.
If the bias and voltages are good and a healthy signal reaches the power tubes grids, even more if the amp pulls the max power current from the PSU and yet you have poor, garbled output, yes, you may have a shorted turn (perforated insulation) in your output transformer.

[JC@]

no no. I checked preamp tubes on the avo tube tester just in case, then I checked the signal in both channels one at a time.
Then I tested signal coming out from the plates of the preamp tubes.
Still, "something" is telling me it is the OT... But I have to make sure that the circuit around the plates and cathodes of the PI is ok.

[JC@]

J M, at the moment I am away from my bench. I better step back as Tom Phillips said, and double ckeck everything.

[J M Fahey]

Even without a scope you should be able to get around 2 to 4 V RMS at the PI input and around 30 to 40 V RMS or more at the plates and on the power tube grids.
Beware that some poorly designed multimeters do not have DC isolated inputs (what were they thinking?) and even without signal show a high value, because they misread DC present there.
In that case, put a .047 or .022 x 600V in series with your probe.

[loudthud]

When running a signal through both channels, they tend to cancel at the input to the PI because they are out of phase. There is an extra gain stage that inverts the signal on the vibrato channel.

[dumbassbob]

Check TEST all the tubes????