1964 Fender Princeton Reverb restoration
Moderators: pompeiisneaks, Colossal
1964 Fender Princeton Reverb restoration
A client brought me a beautiful '64 PR. Untouched...EXCEPT...someone had removed the reverb tank, transformer, RCA jacks, two tube sockets and all related components. Before:
The amp played OK in this condition, though the power was anemic, and it wouldn't get very loud. I convinced owner to let me recap, update power cord, and replace the reverb circuit to full function. After:
All great now, very nice overdrive, 430 on plates with a JJ 5Y3 recitifer, and running at 11 watts clean output. The reverb is very strong--only need to turn it to 3 for a big 'verb sound. However, when I turn the amp up to overdrive, it's very raspy and gated. As soon as I disconnect the Reverb Send RCA cable, all is good, no ugly distortion. With the reverb tank plugged in, even with the Reverb pot set to zero, the overdrive is really bad. The connection to the tank causes the symptom to appear.
So, did I get the right reverb transformer (Hammond P-T1750A) and tank (Mod® 9AB2C1B)?
The amp played OK in this condition, though the power was anemic, and it wouldn't get very loud. I convinced owner to let me recap, update power cord, and replace the reverb circuit to full function. After:
All great now, very nice overdrive, 430 on plates with a JJ 5Y3 recitifer, and running at 11 watts clean output. The reverb is very strong--only need to turn it to 3 for a big 'verb sound. However, when I turn the amp up to overdrive, it's very raspy and gated. As soon as I disconnect the Reverb Send RCA cable, all is good, no ugly distortion. With the reverb tank plugged in, even with the Reverb pot set to zero, the overdrive is really bad. The connection to the tank causes the symptom to appear.
So, did I get the right reverb transformer (Hammond P-T1750A) and tank (Mod® 9AB2C1B)?
You do not have the required permissions to view the files attached to this post.
I build and repair tube amps. http://amps.monkeymatic.com
Re: 1964 Fender Princeton Reverb restoration
I confirmed the reverb tank and transformer are appropriate.
So, anyone know why I'm getting nasty distortion in the signal path with the tank attached, but regardless of Reverb control position?
So, anyone know why I'm getting nasty distortion in the signal path with the tank attached, but regardless of Reverb control position?
I build and repair tube amps. http://amps.monkeymatic.com
Re: 1964 Fender Princeton Reverb restoration
I used a Hammond 1750A reverb driver on my last PR build and it works well. I put a log taper Reverb pot on mine for a more usable sweep. No idea about your reverb tank distortion. Maybe the RCA jack bus bar creates a ground loop with the chassis? Those RCA jacks are chassis-grounded, yes?
Edit: Not sure, but your gold RCA jacks maybe look isolated to me. Fiber washers?
Edit: Not sure, but your gold RCA jacks maybe look isolated to me. Fiber washers?
Just plug it in, man.
Re: 1964 Fender Princeton Reverb restoration
Yes the RCA jacks are of the isolated type, but I have grounded them to the chassis.
I build and repair tube amps. http://amps.monkeymatic.com
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
1 others liked this
Re: 1964 Fender Princeton Reverb restoration
Very weird… a reverbectomy. The new driver and tank are correct for BF reverb. I’d guess you have parasitic oscillation when the signal level gets high enough. Look at the Fender layout at the reverb driver tube socket, particularly the plate jumper.
-
- Posts: 3079
- Joined: Sun Jul 22, 2007 7:48 pm
- Location: Mobile, AL
- Contact:
1 others liked this
Re: 1964 Fender Princeton Reverb restoration
I always wondered why Fender did the plate jumper differently. That may be a factor. Here's a '64 DR pic. PR layout is the same.
Re: 1964 Fender Princeton Reverb restoration
Yes! I looped that anode wire around the socket, and kept it away from the green output wire. Very good! Issue solved. Thanks, Steve!
I build and repair tube amps. http://amps.monkeymatic.com
Re: 1964 Fender Princeton Reverb restoration
Hey, I was just playing on Martin's lead. Maybe he has a theory about this???
BTW, Hoffman did his PR reverb driver jumpers pretty much the same as you did. Never heard of any issues. Go figure.
BTW, Hoffman did his PR reverb driver jumpers pretty much the same as you did. Never heard of any issues. Go figure.
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
1 others liked this
Re: 1964 Fender Princeton Reverb restoration
Steve, I suggested moving that jumper because I have heard of it causing problems before. The difference I see in the picture you posted vs. Arron's amp is that the jumper is raised up above the socket on yours. Perhaps it has to be some distance from the tube base, either above it or off to the side.
-
- Posts: 3079
- Joined: Sun Jul 22, 2007 7:48 pm
- Location: Mobile, AL
- Contact:
1 others liked this
Re: 1964 Fender Princeton Reverb restoration
This discussion made me dig up some pics of a single channel AB763 DR that I built in 2006. I thought I did my jumpers the same as xtian did. Turns out I put the jumpers up high enough to clear a shield pin in the socket.
You do not have the required permissions to view the files attached to this post.