Princeton Reverb AA1164 Tremolo problem

[AnalogDok]

I've got everything working except the tremolo. AO29 iron.
I changed the 1M series plate resistor to 330K, pulled it up and tried tons of other values.

I just can't seem to get any effect at all with or without a footswitch. There is zero tremolo effect.

[tubeswell]

How hot are your 6V6s biased? (They want to be around 18-22mA at 430V to get the bias-vary them working well)

[sluckey]

Disconnect the footswitch so you wont accidentally have the tremolo switched off. Now measure the voltage on V4 pins 1, 2, and 3. If pin 1 is a steady dc voltage the oscillator is not working. If pin 1 is constantly changing (appears erratic on a dmm) then the oscillator is working. What are your results?

[AnalogDok]

Tubeswell,

Thank you,   
The bias is at 18mA and 22mA depending on which 6V6 tube I select. In the layout I went through my CC resistors and found the 29.6K gave me the correct bias current. I had a 25K trim pot in there before but I thought maybe that was the culprit so I removed it. Same issue.
22K was 26mA, 35K was 11mA. Good thing I buy lots of CC resistors at a time so I have a good spread of values. I'll put the trim pot back in after I get the tremolo working so I don't succumb to drift. I know my voltage is a little elevated.

[AnalogDok]

Sluckey,

Thank you,
In the layout (Hard to see) I have V4 pin 1 at 256V steady and V4 pin 3 at 2.48V steady. I don't have a workbench so setup and teardown on the kitchen table takes a few minutes. I'm trying to keep Wifey happy. I'll check pin 2 later today after we get back from the DMV...Daughter is 16 and wanting to drive. I don't think there is any oscillating happening as the voltage is steady on my Fluke 75 when I took the measurements.

[sluckey]

The oscillator is not working. Check for wiring errors and correct component values in the oscillator circuit. Post some hi-rez pics so we can see too. Post a link to the layout. Your pic is too small to see detail.

[AnalogDok]

This is the current version of the build with all the current values and voltages I found (Attached). I have gone over the circuit so many times, my eyes are bleeding. I ran all the jumpers on the rear of the board and triple checked them. I used a high intensity LED strip (Flute pad light) to check again. I took an original layout and traced every circuit to troubleshoot a different issue. Turned out I had the OT wires reversed to the speaker jacks and that made the amp howl when the NFB was connected. Color codes are corrected to my OT colors on the DIYLC. I document everything these days to verify what I did for future mods or troubleshooting.

A couple of thoughts. My bias voltage is -39v instead of -34v.

I do have all 3 Orange Drop Caps in the oscillation circuit at .022uF and the series resistor to the plate at 330K to get a nice slow tremolo. I can change the .022 caps back to .01 if that is the issue.

I've had too many Honey-do's the last couple of days to get it all setup and do more testing. Happy Wife, Happy Life...

[tubeswell]

triple-check your LFO tube wiring again (make sure you haven't got the plate and the cathode connections the wrong way around etc)

[AnalogDok]

Tubeswell,

I checked the layout for the 7th time and verified it is correct. I checked the voltages again and Pin 1 was steady as was 3 so no oscillation but there was zero voltage on pin 2 V4, so I knew something was pulling down the voltage to ground. I looked again at all the resistors and caps to verify the values were what I thought they should be and I noticed a resistor with the wrong color code. I tested it and lo-and-behold I accidentally substituted a 100K resistor for the 1M. Correcting that gave me oscillation. I decided to go back to my adjustable bias and reinstalled the trim pot. I lowered the bias to 17-18 as the voltage is steady at 436V. It seems to work excellent now. I have very strong intensity and can get the speed really slow for some super swampy CCR sounds. It almost sounds like a Julia or a Flanger when turned down really slow. Digging it. There isn't much headroom on a Princeton and this behaves as expected with the sweet spot from 1/2 to 3/4 volume.
I originally had an accutronics 3 spring long decay box in there but the decay was toooooo long and all the notes got jumbled up. I found an old O.C. Electronics Inc. #247 tank I pulled out of some amp along the way, years ago. 1980's tank to go with the 1960's trannys with the old AA1164 schematic.

So all is working as expected. I'm waiting on some decent Fender style knobs to arrive. The last 2 sets I ordered were garbage.
I'll post pics of the completed amp as soon as they arrive. She is pretty....

Thank you and Sluckey for the help.

[sluckey]

there was zero voltage on pin 2 V4

Zero volts on pin 2 is what you should have.

[AnalogDok]

She came out real purdy.
I ordered the standard 2 spring tank as the 3 spring I'm using is too crazy reverb. Also some 90 degree RCA cables.

It started like this.


Finished