The nationally known "guru" was most definately not Gerald Weber. Also, I am not by any means criticizing the work that was done previously on the PR - I have no idea if the work was good, bad or mediocre. I am a know-nothing neophyte out to learn a little bit and have a good time. For what it's worth, I find Gerald Weber's books and videos to be informative and enjoyable.
As always, thanks for the feedback.
RL
Princeton Reverb Cap Job
Moderators: pompeiisneaks, Colossal
Re: Princeton Reverb Cap Job
I don't see how you'd put a metal-film cap in the bias supply. It just needs one 22uF cap to filter ripple.
Depending on the vintage of the PR, it may have come standard with (likely) a 5U4 rather than a 5AR4/GZ34. A 5U4 will drop much more voltage than a 5AR4, and a 5Y3 is even less. With a 5AR4 you are going to be running the B+ noticeably higher (let's say 10%) and given that the amp is probably already running marginally very hot B+ given that it was originally built with an expectation of 105-110VAC power and nowadays it's 10% higher than that or more, you may very well find that most new production 6V6s will red plate without a bias adjustment. The 5Y3 is probably a very good choice for a PR (that's what mine has) running on modern line voltages to make it work with current production tubes. With a 5U4 I am seeing more like 430-435VDC B+ in my SFPR, and the schematics indicate designed spec 420VDC with a 5U4GB.
I think power supply design has an enormous effect on the dynamic feel of the amp, and the keystone to this whole thing is the rectifier tube. However, if you go to change it to "close to stock" as you suggested, then you will probably either be limited to JJ 6V6s, NOS 6V6s, or you will have to do some other thing to drop the B+ 40-50V to get it to work with most normal 6V6s. Or maybe add a bias adjustment. Point is "as close to stock as possible" may not really be all that possible. But 20/22uF caps should work just fine for this amp. I would stick with a 5Y3.
Depending on the vintage of the PR, it may have come standard with (likely) a 5U4 rather than a 5AR4/GZ34. A 5U4 will drop much more voltage than a 5AR4, and a 5Y3 is even less. With a 5AR4 you are going to be running the B+ noticeably higher (let's say 10%) and given that the amp is probably already running marginally very hot B+ given that it was originally built with an expectation of 105-110VAC power and nowadays it's 10% higher than that or more, you may very well find that most new production 6V6s will red plate without a bias adjustment. The 5Y3 is probably a very good choice for a PR (that's what mine has) running on modern line voltages to make it work with current production tubes. With a 5U4 I am seeing more like 430-435VDC B+ in my SFPR, and the schematics indicate designed spec 420VDC with a 5U4GB.
I think power supply design has an enormous effect on the dynamic feel of the amp, and the keystone to this whole thing is the rectifier tube. However, if you go to change it to "close to stock" as you suggested, then you will probably either be limited to JJ 6V6s, NOS 6V6s, or you will have to do some other thing to drop the B+ 40-50V to get it to work with most normal 6V6s. Or maybe add a bias adjustment. Point is "as close to stock as possible" may not really be all that possible. But 20/22uF caps should work just fine for this amp. I would stick with a 5Y3.