Princeton Reverb Problem on a new build

[KDakaWalt]

  Fired it up Sounds good. Tremelo OK. When the reverb pot is turned on at all, volume goes down to nothing. I've posted voltages. I've been double checking all day. I need some input of what to look at. I've checked the tank on a different amp. Swapped out the AT7. Thanks in advance for any thoughts.       

[sluckey]

When the reverb pot is turned on at all, volume goes down to nothing.

Got to be a wiring error. Take a break and come back with fresh eyes.

Which schematic and layout are you using?

[tubeswell]

yes. What Steve said. Wiring error. Go back and check each part of the circuit that's in the signal path with your R meter, looking at your layout and the schematic whilst you're doing that. Check for continuity where there should be continuity and vice versa for no continuity. Maybe the grid from one of the pre-amp tubes might be wired up to the reverb pot or some such somehow??

[KDakaWalt]

 :dontknow:Thanks guys. I did go back through as suggested.  This is the AA1164 schematic. I did find the reverb pot connected directly to the plate of tube 3 (12AX7).  Once corrected it no longer kills the volume when turning on the pot.  However, still no reverb. I’m wondering if I damaged the transformer. I get green to black 1.3 Ohms.  Red to blue 1K Ohms.

[sluckey]

I’m wondering if I damaged the transformer. I get green to black 1.3 Ohms.  Red to blue 1K Ohms.

Sounds OK to me.

Also, look at wiring for V3 circuit closely. Voltages for pins 1 and 3 are waaaay wrong.

[KDakaWalt]

The voltages  on V1 changed when I got the wiring correct. I only found the one spot. I have to go play tonight, so it will be tomorrow before I post the changes. All of the voltages looked low. From the rectifier on. But the uloaded AC of the transformer was dead on. Thanks again for looking. 

[tubeswell]

:dontknow:Thanks guys. I did go back through as suggested.  This is the AA1164 schematic. I did find the reverb pot connected directly to the plate of tube 3 (12AX7).  Once corrected it no longer kills the volume when turning on the pot.  However, still no reverb. I’m wondering if I damaged the transformer.

As long as you have the right sized (100k) plate resistor on the reverb recovery stage, it should be okay. With the reverb level pot connected directly to the plate, all you would be doing by turning the reverb level up is putting DC onto the grid of the following stage, but that won't affect the B+ because you are still dropping the load across the recovery stage's plate resistor, so its not as if there's a B+ short to worry about.When you install the coupling cap there, everything should be 'normal'.

Incidentally, what are the idle voltages (all around)?

[KDakaWalt]

Just got back to this. New tube voltages file 11534. V4 pin 1 is unstable going from around 150 to 170 and back. PS from high to low 267V, 261V, 218V 175V. The previous voltages are still on the same file as before.  

EDIT by sluckey... Here's a direct link to the voltage data.
http://www.el34world.com/charts/valve/ValveData.php?e=view&f=11534

[sluckey]

V4 pin 1 is unstable going from around 150 to 170 and back.

That's what it's supposed to do. It's the trem oscillator. I bet turning the speed knob will speed up or slow down the changing voltage. Plug in a footswitch and turn the trem off if you want that voltage to be steady.

All your voltages are low. V3 pin 8 should be about 50v instead of .7v. Your bias voltage on pin 5 of the 6V6s needs to be about -30v to -35v. You're probably cooking the 6V6s with that low bias. Pull the 6V6s and check the voltage on pin 3 of the 6V6s with the tubes out. What do you get?

Also, look at the schematic. The proper voltages are printed on it. You may still have multiple problems. Fixing the bias voltage would be my top priority.

[KDakaWalt]

I pulled all the tubes and start checking voltages.

With only the Rectifier inserted,  B+=434V. B (as marked on the schematic) 433V. D= 426V.   Top of the tag board, at the 18K resistor = 431V. I adjusted the bias voltage to be -38V. Pin 3 of the pwr tube socket was  434V.

After adding the two 6V6, B+ = 335V. B = 331. D = 330V.  Top of the tag board, at the 18K resistor = 330
Pin 3 of the pwr tube socket was 332V. Bias was -32.8V.

[tubeswell]

With only the Rectifier inserted,  B+=434V. B
After adding the two 6V6, B+ = 335V.

Quite a big drop for 2 x 6V6s. I wouldn't expect that much of a drop. So...

1) Did you measure the tube current in the 6V6s? (They could be biased too hotly, pulling down the B+)

2) Did you try with different 6V6s? (in case the tubes are partly shorted)

3) I wonder if maybe your PT is partly toasted, or it is not rated for the load you are putting on it.

[KDakaWalt]

tubeswell - Yes. Current was around 15mA. I have gone back and looked at the pwr tube wiring. I too thought the drop was severe. I don't have any other 6V6 to try at the moment. I do have some throw away 6L6. The pwr transformer is an Allen TP25.

[tubeswell]

tubeswell - Yes. Current was around 15mA. I have gone back and looked at the pwr tube wiring. I too thought the drop was severe. I don't have any other 6V6 to try at the moment. I do have some throw away 6L6. The pwr transformer is an Allen TP25.

I see the spec for the TP25 is 310V-0-310V @ 150ma, 6.3V at 4.5A, 5V at 2A. 50V bias tap. You aren't trying to use a 5U4G rectifier by any chance? (I know the BFPR used a 5U4G, but that needs a 3A rating on the 5V winding).

[KDakaWalt]

Rectifier is a JJ GZ34

[tubeswell]

I would triple-check the wiring again