AB763 Single Channel Reverb Troubleshooting

[purpletele]

Greetings,

I am starting a little troubleshooting on my Deluxe Reverb Head, the first of the two that I built.

The reverb just stopped without any event, I just noticed it recently. 

The amp plays really well, the bias is spot on.

I just started, but here is what I know:

1. The voltages on the reverb transformer are 458 V on the Blue lead and 455 on the Red lead.
2. I get a slight buzzing from my meter when I touch the output negative jack for the reverb, like it is picking up a signal.
3. I do not get anything from the positive green lead from the transformer.

This is my first Reverb amp and I know there are funny issues with the jacks, any advice or steps for testing and isolating?

Thanks,

BV

[purpletele]

Update

I checked the Reverb tank by hooking it up to another tank without change.

That leads me to the reverb transformer.

I am going to perform a continuity test on the leads before I pull it off of the chassis.
Is there an easier way to test the Reverb transformer while it is in place?

UPDATE I checked continuity on the reverb transformer.  I get 1.5 Oms on the blue and red and about the same on the green and black, so I don't think I have a short in my transformer.

I used different reverb cables.

I have eliminated the tank and the cables.
The reverb transformer appears to be operating correctly.

I sprayed Deoxit in the reverb jacks without change.

I haven't touched the tubes, they seem to be working fine and the voltages were good. 

Any thoughts?

[sluckey]

UPDATE I checked continuity on the reverb transformer.  I get 1.5 Oms on the blue and red and about the same on the green and black, so I don't think I have a short in my transformer.

I get 1240Ω between my red and blue and my reverb works!   

[purpletele]

UPDATE I checked continuity on the reverb transformer.  I get 1.5 Oms on the blue and red and about the same on the green and black, so I don't think I have a short in my transformer.

I get 1240Ω between my red and blue and my reverb works!   

We'll with my past history with transformers, I happen to have one in stock.

I'll see how that goes.

[purpletele]

2nd Update: 

I rechecked my resistance again and I had read my meter incorrectly, it was actually 1.2K on the primary side and I am getting 2.5 Ohms on the secondary side.

I am reading 1.1K on the new transformer not installed, and 1.2 Ohms on the secondary.

So it appears that the transformer is operating correctly.  Here is what I have tried so far.

1. I hooked up another tank to the amp without favorable results.
2. Cleaned the reverb jacks
3. Tested for continuity on the reverb transformer
4. Verified the resistance with another reverb transformer.
5. I have not changed the AT7 tube, it is illuminated and the amp sounds fine other than the reverb being down.

Now that I clarified a mis-read, any ideas of things to check?

BV

[sluckey]

In a tube amp the very first thing to try is swapping tubes.  Second thing, check voltages. Not just the plate voltage. Cathode and grid voltages are important too, even if zero volts.

LMK how that turns out. I have a couple quick checks that will be helpful for that reverb circuit.

[purpletele]

In a tube amp the very first thing to try is swapping tubes.  Second thing, check voltages. Not just the plate voltage. Cathode and grid voltages are important too, even if zero volts.

LMK how that turns out. I have a couple quick checks that will be helpful for that reverb circuit.

Use error!  A month or so ago I changed tubes in that amp and must have switched my reverb cables and didn't notice it wasn't working.

I had the leads crossed on the reverb cables.  All good now I hope.

Thank you for the help

BV

[2deaf]

In a tube amp the very first thing to try is swapping cables.

[purpletele]

In a tube amp the very first thing to try is swapping cables.

I actually did that, but I followed the same pattern and crossed the leads.

The key is to mark my jacks so I don't do that again, which I did.