Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Fresh_Start on September 19, 2010, 10:28:22 pm

Title: Blackface Princeton Reverb on bench
Post by: Fresh_Start on September 19, 2010, 10:28:22 pm: I finally built my new workbench and am ready to start working on (and stop playing :wink:) my friend's Princeton Reverb.

Here's a link to a SLIDESHOW (https://www.photoshop.com/express/index.html?user=Chip59Pics&galleryid=3f5fe68add5e47bcad84e0de2265fd10&wf=share&trackingid=BTAGC) of the guts.

(ARGH! please let me know if the link works - trying new hosting method. I hate video tutorials. Doesn't anyone else like to READ how to do something, such as link to a slideshow?)

Please let me know if you see anything unexpected, unusual, or needing attention.

The power cord is a 2-prong, brown lamp cord which does not look old enough. Replacing it with 3-prong anyway.

The exterior of the cap can looks relatively new & clean.

At least one of the cathode bypass caps looks discolored at one end. There are 2 double Astrons and 2 single Mallory's. The Mallorys are different colors...

The power tubes are both marked exactly the same - GE 6V6GT - but the bottles are different heights??? :huh:

I'll post any info printed on the cap can, transformers, chassis, etcetera in a day or two.

Cheers,

Chip
Title: Re: Blackface Princeton Reverb on bench
Post by: stingray_65 on September 20, 2010, 02:49:32 am: Chip,
the link works for me.
Man you take a good picture!
You got a steady hand

Ray
Title: Re: Blackface Princeton Reverb on bench
Post by: plexi50 on September 20, 2010, 08:19:00 am: Nice!
Title: Re: Blackface Princeton Reverb on bench
Post by: Fresh_Start on September 20, 2010, 08:45:47 am: Quote from: stingray_65 on September 20, 2010, 02:49:32 am
Chip,
the link works for me.
Man you take a good picture!
You got a steady hand

Ray

Tripod.

Chip
Title: Re: Blackface Princeton Reverb on bench
Post by: bnwitt on September 20, 2010, 09:53:42 am: Ooooo.....air conditioning in the shop! Nice. Good looking amp. What is it doing wrong?
Title: Re: Blackface Princeton Reverb on bench
Post by: Fresh_Start on September 20, 2010, 10:54:40 am: Quote from: bnwitt on September 20, 2010, 09:53:42 am
Ooooo.....air conditioning in the shop! Nice. Good looking amp. What is it doing wrong?

I'm from New England and can't understand how ANYONE lived in Virginia before air conditioning!

The only thing the amp is doing wrong is shocking its owner (and me) because of the Ground switch/2-prong cord/death cap. Oh, the tone pots are scratchy making me think there may be a leaking cap or two. The owner wants adjustable bias, so I'm going to pull the vintage board with leads, save it, and make a new board.

BTW I hope to post voltages in the next day or two. I'm really interested to see how far the carbon comp resistors have drifted. I do NOT want to change any resistor values - this amp has a wonderful warm tone. In fact, I'm going to try matching resistor values in my PR clone to see if I can get closer to the tone of this vintage amp.

I suspect the big problem in trying to match the tone will be the OT though. That may be where the MOJO is hiding :wink:

Cheers,

Chip