Just got a Princeton Reverb SF, need some info

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bradb

Well-known member
Joined
May 5, 2005
Messages
523
Location
Brooklyn, NYC
Hey guys,

I just got a Fender Princeton Reverb SF. Its in good electrical and cosmetic condition. I'm going to re-cap it and probably put a new speaker in it as well. I've got a few questions:

I'm trying to understand what the difference between the Silverface and blackface versions are. Schematics that I have found have been blurry! I am considering "blackfacing" this amp... some have said this is quite simple to do.

I'm also trying to understand what "blueprinting" the power section is. Is this just matching the resistors on the power tubes...

Third question, grid stoppers... whats the recommended value, wattage? What else do I need to know about these?

At this point all I can do is recap the thing and put the 3-prong cord in... sigh!

I love the atmosphere here at prodigy, but if there is a more suitable forum out there for these questions, please let me know!

thank you!
 
I'm not sure the exact date, but there is a 5U? rectifier in there, not the GZ?. The Fender has a tail and there is no silver piping around the grill.


Sorry for the vagueness, i'll get the code tonight!
 
I've never found many differences in the Princeton circuits when they switched from blackface to silverface. The main differences seem to be
that the lead dress changed a bit (more sloppy) and the power transformer was beefed up a bit which required the change to a 5U4GB
instead of a GZ34.

I wouldn't worry too much about the circuit - just recap, put in good tubes and change the speaker. There are some mods for these amps, but I kinda prefer the stock sound of these guys.

I think http://www.ampwares.com/ffg has some schematics for the PRs.
 
1971 was not a special year. The sound of th early to mid 60's PR's is amzing and unique. But anything early 70's was pretty much ordinary.

Other than the collectable value which is out the window with any mods I would just try to get it updated and clean it up.

The early 60's amps had more volume, a better midrange and smoother distortion. I think the speaker and the output transformer probably dominated the sound.

I say all this as someone who owned both a 1963 and a 1972 PR from 1975-1980.

Steve
 
If you want to know what the Black Faces really sounded like go listen to a Blues Jr. The Blues Jr is really close only it actually sounds a little better imo.

Steve
 
First why are you going to recap it?

If the amp has been sitting for some time I turn it on outside on the driveway (nothing that can catch fire) and look at the output tube plates to make sure thay are not glowing RED(for bad coupling to output tube caps). If not I plug in a cord to the input with the volume down then turn up the volume until I just hear noise and hum and let the amp run for some time(hours) If I don't hear any pops and loud cracks I will turn the volume up and let the caps and cathode oxides reform if they still can. I do this outside on and keep an eye on the amp for smoke etc. Often the amp will reform the caps etc in 1/2 to 1 hour.

I do think it is good to power up a tube amp every 6 months to keep the parts in shape

If you have a varic set it for the rated voltage 110 etc, my house measures 125 most of the time and some of the older fenders can run the caps close and even over the rated voltage with todays higher wall voltage when in standby(because of no load on the B+ supply).

I have measured old electros in some fenders even ones that leaked and they measure good even after 20 or more years. Value, ESR, DA and leakage at working voltage 450V 500V etc.

I like electros with 1.5ohms ESR or lower per 20uf at 450V or 500V in guitar amps. I have measure some newer caps as high as 8 ohms per 20uf.
This is using a sencore lc102

Next if it works play it before you go changing anything you might like how it sounds

Don't believe all the stuff on web

SOME of the new caps don't measure or sound good compared to some old ones. High ESR causing ghost notes etc.
 
Ya know Gus, I've been playing this thing and it sounds pretty incredible.


I'm thinking what you are thinking. I've had a twin that sounded way nicer once i recapped it.... so

its a 2 way street.
 
I had '71 Princeton, non-reverb. I bought it mint with cover, warranty card, and cover for $125. It was one of the most articulate little amps I ever had. I needed money so I put it up on ebay. It got bid up to nearly $600. I made a nice profit but I miss it all the time.

Anyone that says the Blackface is a better amp is hearing with their eyes. Amps age differently. You can have identical amps from the same year, with the same tubes and speakers, and I'm sure they would sound different. Blackface and Silverface. Who cares. If it behaves then play it. :thumb:
 
[quote author="MikoKensington"]If it behaves then play it.[/quote]

And if it misbehaves, play it harder! :twisted:

I have a mid-70s SF Deluxe Reverb and a SF Vibro Champ. Love 'em both.

A P
 
bradb

Yes caps do go bad and changing them will often help.
I have heard changing them making it worse funny it was certain brand cap in a twin.

Sometimes the old ones are still OK this is not a keep it vintage thing sometimes they still sound good.

I try to test all the electros I remove and test the replacements before I install them. I noted that some old caps still were over the rated cap value and the leakage and ESR and DA were still good readings.

When you remove the caps weigh them if you can and measure them,
then weigh and measure the replacements.
 
There were some good silver face amps made.
Fender ran out of faceplates before they ran out of xfmr's speakers, tac boards, but gradualy, CBS cheapened up the silver face. pc boards, different components, so you have to watch out for what rev you have. If you see small caps from plate to grid, this is a sign that you have one of the later CBS amps. The caps cured instability from a bad layout. They steel sound, so the amps sounds not as good.

There are a million other differences, all covered in Gerald Weber's books.
 
Fender really didn't change the circuit designs on the little amps when they went silverface - as CJ said, it was the components that gradually cheapened. The big pre/post CBS (aka blackface/silverface) change really affected the big amps the most, where they did some circuit changes which were later removed.

That being said, I don't think there's anything wrong at all with the little silverface amps. I've got a nice little Princeton Reverb, and if the mortician can find the space it's going to be in my coffin.

Incidentally, if you see a silverface amp with metal trim around the grillcloth area, it's likely one of the amps from when they'd changed the cosmetics but hadn't changed the innards yet. In other words, a blackface in sheep's clothing.
 
I just did the 3-prong plug update and played the amp thru a newer jensen speaker.. I don't even think this speaker is beat!! I'm just gonna roll with it.


some of the caps seem very similar in size and construction to orange drops and they're rated at 600V. That doesn't seem very cost cutting since the schem says 400V minimum rating for all caps.



yay!
 
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