Princeton Reverb

[rfgordon]

I haven't posted in a while, since I'm not building much. I've been doing a lot of repairs, though. Most of that is pretty routine stuff, but every once in a while something odd comes across the bench.

I picked up this silverface Princeton Reverb today. The owner was unhappy with it after a tech in another city did what was alleged to be "the Joe Barden mod" on it.

I confess I've never heard of that, but the amp was harsh and too loud and aggressive for the guy now, who plays mostly archtop stuff.

From what I can tell, most of what was done is an odd, super-overkill cap job. The first filter, the big one in the picture, is 80 mF. That's way too much for an amp like this, and I'm surprised the Chinese 5U4 hasn't gone fireworks in a bottle because of it.

The second filter is two 100 mF caps in parallel. Seriously? Who puts 200 mF on the screens of a pair of 6V6s?

The other black caps are all 100 mF.

Whew. No wonder the amp is like a cold slap in the face!

So, here's my question: Is there really such a thing as the Joe Barden mod, and is this really it?

I'm gonna put back in a 40/20/20/20 can so the amp will sound and feel like it should.

[xtian]

Wow. Same amp tech that boogered "Hobart"'s Pro Reverb? Enough with the filtering, already!

[Blackburn]

Actually, I don't think the 80uf for the reservoir is all that bad. With no standby switch wired up, stress on the rect is limited to start up and I don't believe there is much, if any. I think going more than that is risky. Not sure why going with 200uf is even considered! I'd say leave in the 80uf and go with 40uf for the screens and then 20uf, 20uf. Amp should stay real tight and focused. I think this would be an improvement because I have a '66 with all original everything and it's sloppy joe and not tight at all, not that I like it dirty anyway, with that cathodyne inverter and all. Nice and clean, with fantastic verb and vibe! Great amps, these are.

David