Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jukelemon on July 12, 2013, 09:49:04 am

Title: 1965 Princeton Reverb Trem very weak
Post by: jukelemon on July 12, 2013, 09:49:04 am

Hi all.  Several years ago I built one into a P12N.  It has been such a great amp.  But the Trem never worked right.  Just weak.

I posted a few years back on this and got several good responses.  I cannot find those old posts.  Sorry.

I swapped tubes.  No change.

It is there and I can hear the changes in Speed, but it is just weak.

No loss of power.

It is like the Intensity of the effect is ~10% at full range if that makes sense.

I believe it is photo driven.  I wish I would have built to be bias modulating but...hindsight.

Any ideas?

Thanks

Juke

Title: Re: 1965 Princeton Reverb Trem very weak
Post by: sluckey on July 12, 2013, 09:56:16 am

A stock PR is bias trem. Search this forum for weak tremolo.

Title: Re: 1965 Princeton Reverb Trem very weak
Post by: tubeswell on July 12, 2013, 01:48:39 pm

First thing to try is swapping the tube that contains the tremolo LFO stage.

Biasing the output stage cooler also helps increase the 'slam'.

Title: Re: 1965 Princeton Reverb Trem very weak
Post by: tubenit on July 12, 2013, 03:08:55 pm

Did you look in Archives?

http://www.el34world.com/Forum/index.php?topic=604.0 (http://www.el34world.com/Forum/index.php?topic=604.0)

With respect, Tubenit

Title: Re: 1965 Princeton Reverb Trem very weak
Post by: jim on July 12, 2013, 03:59:01 pm

Check the bug in a dark room. It could be leaking too much light. If the rest of the trem circuit is OK you should swap it out for a spare.  Jim

Title: Re: 1965 Princeton Reverb Trem very weak
Post by: plexi50 on July 12, 2013, 04:32:25 pm

Check the 25/25 cathode cap pin #3 on the LFO stage