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Post subject: Princeton Reverb Export Silverface AA764
Posted: Mon Jan 16, 2017 8:02 am
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Hi everyone,
I'm Axel, 26 years, from Germany. I live in Bremen, study naval architecture and I've found a very nice and possibly rare Fender Amp in Hamburg. (Was also a bargain).
I'd like to have some Information about original date of manufacturing, price back in the time, tips for maintanence, infos for spare parts, and general tips for using old amps, since I never had one before.
The Amp was basically lieing around in a practicing cellar and wasn't used for 10 years.

What I know for certain is the following data:

Fender Princeton Reverb
Export version
3 wire powercable for EU-Sockets including a ground wire
"Silverface"
Tubeconfig: AA764
Stamped Serial No.: A 25901
Printed Serial No.: 32014

Link to imgur for Images

From an optical point of view the amp is in pretty bad shape.
Someone spilled white paint over it, sprayed the logo of a band called "Epsilon" with can and stencil on the side.
The mesh / grill / frontcover (whatever you call it ; ) ) is missing.
And someone fitted a metal speaker protection mesh.
It basically shouts "I was used for punkrock when it was new" at you, what I really like.

From a technical point of view, the amp is basically flawless.
Everything works except the power indication lamp, that is missing. (Anyone got specs for a spare?)
The knobs produce do crack a bit if you turn them ("fireplace potentiometers") but if you don't move them, the amp is completely silent.
No humming, no hissing, it just produces a very nice sound.
(I use a Gibson Les Paul Studio (2009) with it).

Maybe you can help me out with dates, specs, figures and general tips and advice.
Also if someone has an educated guess what the amp might be worth... I'd be interested, although I'm keeping it ; )

Cheers,
Axel


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Mon Jan 16, 2017 11:24 am
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The serial number indicates the amp was made in 1971. As you've indicated, it's a factory-built export model. The speaker is not original to the amp. The correct driver would be an Oxford 10J5. You'll often find replacement grill frames with the correct silver/white/turquoise grill cloth available on Ebay. Mineral spirits or mild lacquer reducer can be used to remove the offending paint stains from the cabinet.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Mon Jan 16, 2017 11:35 am
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Location: Coastal Bend, Tx.
Here is a link of non-export specs from ampwares an also one for dating fender amps.
http://ampwares.com/amplifiers/fender-silverface-princeton-reverb/
http://www.superiormusic.com/page195.htm

A little de-oxit or other brand electrical contact cleaner sprayed into the noisy potentiometers should fix the issue.
The bulb should be a type 47
The amp is worth a decent amount of money in good original condition, but as long as its yours its priceless.

It would probably be a good idea to take it to a tech for a service, it may cost a few hundred dollars but would be worth the expense if you plan on playing it regularly.


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Mon Jan 16, 2017 12:41 pm
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sfceric64 wrote:
A little de-oxit or other brand electrical contact cleaner sprayed into the noisy potentiometers should fix the issue.
The bulb should be a type 47
The amp is worth a decent amount of money in good original condition, but as long as its yours its priceless.

It would probably be a good idea to take it to a tech for a service, it may cost a few hundred dollars but would be worth the expense if you plan on playing it regularly.

+ 1 on taking to a tech unless you know what you are doing on the inside of the amp, as it is fairly old it may need new Electrolytic caps as they do dry up in time
mud


Last edited by mud on Tue Jan 17, 2017 9:26 am, edited 1 time in total.

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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Mon Jan 16, 2017 3:46 pm
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mud wrote:
+ 1 on taking to a tech unless you know what you are doing on the inside of the amp, as it is fairly old it may need new Electrolytic caps as they do have dry up in time
mud


Correct.

A new cap can is mandatory, as well as cathode bypass caps and power-rail resistors. New tubes might not be a bad idea either (check them first before discarding them wholesale).

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Tue Jan 17, 2017 8:20 am
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Thanks, I'll look into this myself.
In a german forum someones said, that the main transformator isn't the original one and is probably undersized and offered me helping restoring it.
I think this is bait, since the amp wasn't touched in the last years when it was used, and worked properly on stage, while rehearsing and in a studio.
So why should it fail now?
How ever this got me a bit paranoid. So I'll have a look into this.

I already thought about a capjob. I've done some "analog electronics" in college, so I know that electrolytic caps have a limited life span.
I also know how to use an oscilloscope or a soldering iron. So I'll give it a shot when I have a bit of free and spare time.
And yes I know to be carefull, unplug the main, that caps can be loaded after the amp is turned off, etc...
I'm familiar with fixing electrical components. This just happens to be my first tube amp.

I also found some controversity according my tube chart.
Some say that it is a missprint, how ever I found this Youtube Video: "Fender Princeton Reverb AA764 Chassis.....Fact, Fiction, or Typo ???" and that looks reasonalbly researched to me.
There's also a link to a electrical schematic for an AA764
How ever this seems to be the non export version, and the work of a german physician. Who edited an AA1164 chart to match one AA764 Amp he had in his shop...

Do you think the caps of the none export version alter from the export version?
In my understanding the exportversion is equipped with a different transformator, with a selector for the primary coil so it can handle various AC Voltages from the main.
Past the transformator the amps should be identical. Am I right?


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Tue Jan 17, 2017 8:41 am
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An original power tranny for a US-spec (non-export) Princeton Reverb would be marked with the Fender P/N of "022772", with an EIA manufacturer's code of "606-XXX", but I'm not sure how either of those numbers correlate to a variant built to overseas specs. As for the caps, they would be the same, regardless of what the primary wall-socket voltage is.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Tue Jan 17, 2017 9:58 am
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Ax3L_S wrote:
Thanks, I'll look into this myself.
In a german forum someones said, that the main transformator isn't the original one and is probably undersized and offered me helping restoring it.

I think this is bait, since the amp wasn't touched in the last years when it was used, and worked properly on stage, while rehearsing and in a studio.

So why should it fail now?
How ever this got me a bit paranoid. So I'll have a look into this.

I already thought about a capjob. I've done some "analog electronics" in college, so I know that electrolytic caps have a limited life span.

I also know how to use an oscilloscope or a soldering iron. So I'll give it a shot when I have a bit of free and spare time.

And yes I know to be carefull, unplug the main, that caps can be loaded after the amp is turned off, etc...
I'm familiar with fixing electrical components. This just happens to be my first tube amp.

I also found some controversity according my tube chart.

Some say that it is a missprint, how ever I found this Youtube Video: "Fender Princeton Reverb AA764 Chassis.....Fact, Fiction, or Typo ???" and that looks reasonalbly researched to me.

There's also a link to a electrical schematic for an AA764

How ever this seems to be the non export version, and the work of a german physician. Who edited an AA1164 chart to match one AA764 Amp he had in his shop...

Do you think the caps of the none export version alter from the export version?

In my understanding the exportversion is equipped with a different transformator, with a selector for the primary coil so it can handle various AC Voltages from the main.
Past the transformator the amps should be identical. Am I right?


Do you have a photo of the insides of this amp? I restored a couple of late silverface/1980s "blackface" reissue style PR that had export power trannies. The PT are $$$ and kinda hard to find. The amp should have red knob and voltage adjustment plate on the backside, if it stared life as an Export from Fender.

AFAIK, the Princeton Reverb circuitry stayed more-or-less the same through the blackface and silverface eras. The AA1164 circuit being the main iteration. The most difference between whether a GZ34 or 5U4GB rectifier was OEM. The GZ34 amp having higher B+ voltages.

http://ampwares.com/schematics/princeto ... aa1164.pdf

Cleaner image of later B1270 circuit:

http://ampwares.com/schematics/PRINCETO ... AB1270.pdf

The CE cap can is an excellent replacement for the OEM Mallory or Sprague. Very affordable. I like the higher 525VDC rated one. The extra capacitance in first stage (30 versus 20mfd) seems to have no consequence to tone or rectifier life. These last a long time.

https://www.tubesandmore.com/products/c ... 30202020uf

Be sure to check the resistors on the power rail. Actually, I just replace them with same nominal value metal oxide or wire-wound resistors and be done with it.

Grid-to-ground 220k-ohm resistors on the 6V6GT output tubes should be checked. Should be within 5% tolerance of each other (or why bother with "matched" tubes). Use CARBON COMP resistors. These definitely effect the final tone of the amp.

Check the coupling caps for DC leaks. Esp important on input tube and phase inverter sections. Should be less than 2VDC on grid side. If you need to replace, the type/make will depend on the tone you are after. I like Vintage Jupiter (yellow) or Russian PIO K40Y-9 mil spec caps. Both are long lasting and maintains most of vintage Fender tone (clean, good midrange, not strident or too bright).

Good luck! Need to see photos!!! :lol:

EDIT. Photo of a PR I worked on. With new cap can and ww-Mills rail resistors. Russian K40Y-9 coupling caps on PI section. Note, the replaced grid stopper (metal oxide) and added screen resistor (470-ohms) on sockets. Done by previous tech and left on, by owner's request.

NOTE #2 See the lines going to back of amp to the PT? Those are for EXPORT version with voltage selector.

Image


Last edited by BMW2002Ti on Tue Jan 17, 2017 10:22 am, edited 1 time in total.

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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Tue Jan 17, 2017 10:20 am
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Here's photo of PR with new Mercury Mag PT. Replaced PSU rail resistors with metal oxide ones.

Image


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Fri Jan 20, 2017 6:07 am
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Hi everyone.
I made some pics.
They can be found here

I also found the company that now sells "Engel transformators" today and phoned them.
If they have any specs, they'll send it to me.
Also the red mains selector is completely dead. : D

Edit:
My Amp seems to be missing a tube.
The spot, where according to the tubesheet, a 5U4GP should be, is empty.
How ever I haven't found a rectifier either... yet
I have no idea if these are the original tubes or already spares...

But still, sounds great. Love it.


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Fri Jan 20, 2017 10:01 am
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The "missing tube" should actually be a 5U4GB (not the 5U4GP you indicated).

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Fri Jan 20, 2017 10:21 am
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true that, actually a typo.
But still. Didn't find a rectifier yet.
Maybe it's hidden under the plate under the wires...


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Fri Jan 20, 2017 7:47 pm
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Ax3L_S wrote:
true that, actually a typo.
But still. Didn't find a rectifier yet.
Maybe it's hidden under the plate under the wires...


Uh... not sure what you mean. The rectifier has its own socket. On side by power transformer.

Image


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Sun Jan 22, 2017 11:54 am
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Yeah,
that's what I'm about.

Check my pictures.
My amp only has 6 valves...

Image
Check the empty spot on the far left.
Not even a socket.


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Post subject: Re: Princeton Reverb Export Silverface AA764
Posted: Sun Jan 22, 2017 12:27 pm
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It appears someone in the past converted your amp to solid-state rectification. I believe the bridge is the blue item attached to the red & white lines of the power transformer (in your photo).


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