Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on March 10, 2022, 02:21:16 pm

Title: Princeton Reverb build trem problem
Post by: punkykatt on March 10, 2022, 02:21:16 pm

Hey Guy's, I have built many PR amps over the years without any problems or issues. This one is Doug's layout. Everything works fine except when I ground the tremolo  circuit to shut the tremolo off the amp sounds like someone lit a string of fire crackers. What would be causing this? I quadrupled checked the wiring, cap and resistor values in the circuit. Any suggestion are much appreciated.  :BangHead:

Title: Re: Princeton Reverb build trem problem
Post by: sluckey on March 10, 2022, 03:01:08 pm

Quote from: punkykatt on March 10, 2022, 02:21:16 pm

I quadrupled checked the wiring, cap and resistor values in the circuit. Any suggestion are much appreciated.  :BangHead:

I assume you are grounding the circuit at the FS jack?

Step 1.  Repeat the above checks.
Step 2.  If still no joy, repeat step 1.

Title: Re: Princeton Reverb build trem problem
Post by: shooter on March 10, 2022, 03:46:55 pm

have you rung out the FS?, sounds like the FS-switch might be onNoffing many times before it's happy, or the shield is, or see above post  :icon_biggrin:

Title: Re: Princeton Reverb build trem problem
Post by: punkykatt on March 10, 2022, 06:03:50 pm

Fixed.  Clipped in additional .01 caps over the caps in circuit that tested good on the cap meter before installation. Found two that didnt like being in that circuit causing the problem. The problem causers still read spot on, on the cap meter out of circuit. Go figure. :icon_biggrin:  Thanks Steve for telling me to keep on keeping on.

Title: Re: Princeton Reverb build trem problem
Post by: tubeswell on March 11, 2022, 12:16:24 am

Could’ve been a cold solder joint in the LFO circuit (and if the crackling sounds are gone after you put new caps in, may’ve been one of the joints around those cap leads).

Title: Re: Princeton Reverb build trem problem
Post by: punkykatt on March 11, 2022, 03:51:15 pm

The sounds were loud pops/snaps like a machine gun or a string of Ladyfinger firecrackers going off.

Title: Re: Princeton Reverb build trem problem
Post by: PRR on March 11, 2022, 06:27:14 pm

> string of Ladyfinger firecrackers

Steady forever? Or just for a second?

Title: Re: Princeton Reverb build trem problem
Post by: punkykatt on March 11, 2022, 07:40:29 pm

The tremolo worked well, when you stepped on the switch to shut it off. The fireworks sound lasted until you turned the tremolo back on. I did not let it go for anymore than several seconds in fear of my test speakers getting damaged. I also disconnected the ft sw and grounded the circuit with a clip lead. Same results.

Title: Re: Princeton Reverb build trem problem
Post by: PRR on March 11, 2022, 11:43:09 pm

So you built a multivibrator.

I think we are still on Sluckey's Reply #1.

Title: Re: Princeton Reverb build trem problem
Post by: punkykatt on March 12, 2022, 04:26:34 am

Reply#3 Fixed. I replaced those caps and its working  as it should. :icon_biggrin: