Fender Princeton Recording Problems.......Any Experience?

[Pastortom]

I have a problem with my Princeton Recording amp that's out of the norm........(it's a few years old, all tube, with a circuit board)

It has a really weak reverb, and hums as you turn the reverb level up.......These are known for powerful reverb like the old ones, but something's gone a bit wacky.......

I just checked the 12AX's and the 12AT.......I found a 12AX that was basically shot......Kept my fingers crossed and tried a new one.....No difference in the reverb at all.

I don't know if any of you guys have experience with this model, but if you have any ideas, chime in...I'd appreciate it.

[Pastortom]

This is the transformer sitting between the pre-amp tubes....I ASSUME it would be the reverb transformer......Could this be the culprit?  If so, where can I find the correct replacement?

[jojokeo]

I would not suspect the tranny. After testing the tubes and all other "common sense" type of things my first order of business would be to check all connections to/from the circuit board & reverb tank and also inspect the circuit board very carefully for bad solder joints.

[Cups]

Is the reverb solid state on this model? I know there's a bunch of analog effects onboard so it may not be a stretch to see ss reverb.

[Pastortom]

Tube driven reverb....not SS.

This morning, I turned it on to test it further and the attenuator popped it's cookies.......It was shorting a little last night as I played with it, and this morning it was just gone.

I had to drop the thing off at Diversified Audio in Tampa a little while ago.......They have the parts and schematics on this model, so I'm having them change the attenuator pot and check the reverb circuit as well.........

I'll post their results when they find the problem with the 'buzzing' reverb.

[Pastortom]

Well sir, I got the amp back from Diversified.......They changed a pre-amp tube and it came back on (it was dead....it must have shorted right after I changed the one I mentioned.....I thought it was the attenuator, but they say not....checked the solder joints and it's fine).

Anyway, I got it home and tried the reverb.......There is none.......only an ever increasing electrical buzz when you turn the reverb knob higher.....EXACTLY like it was before.

$140. bucks later and I have to make yet another trip to drop it off, then another the pick it up.......If they get it right this time, that'll be over 4 hours travel time on this thing........I am NOT a happy camper.

Sure wish someone here had a previous experience with this problem, but I guess they're just too new at this point to be common......

Off to Tampa I guess............Again.

[firemedic]

I'm in Brandon & I feel your pain. That's why I got on this site to begin with, I couldn't find a local tube repair guy.
PM me if you want to try to work this thing out DIY. My drummer has a '95 Twin RI w/ broken reverb, too, that I'm pretty sure I can fix.

[tubeswell]

They took your money and couldn't fix it?! Don't take it back to them!  

"Princeton Recording" amp? Do you mean a Princeton Reverb? (with tubes?)  If so, 1st thing I'd do is a tube swap (one at a time). If the reverb knob isn't working then my money's on the 12AX7 in V3 to begin with.

Everything else I'm about to say involves tools.

If a tube swap doesn't fix it, then take all the tubes out, and (with the amp off and unplugged), open up the amp and get a decent soldering iron and some 60/40 rosin core leaded solder, and go through the amp re-flowing new solder completely into each joint, focusing on the reverb recovery circuit.

Also check the tension on the tube socket pins. Something in the V3 socket could need re-tensioning with one of those teeny weeny screwdrivers.

If that doesn't fix it, you'll need to get more hi-tech, and (still with the amp off and unplugged) check the DC continuity of the circuit with your R-meter. Look for shorts where there shouldn't be any, and DC continuity where there should be continuity.

And then (carefully) take some idle voltages (at dangerous working voltages) and report those back. You need to take the HT voltages on the power rail and also the idle (DC) voltages on the pre-amp tube plate, grid, and cathode pins, and report back. Don't kill yourself in the process. If you're not totally confident with this step, then don't attempt it. Try to find another tech, or ditch the amp cheaply.

If your amp isn't a tube amp, then I'm sorry I can't be much help.

[phsyconoodler]

Ok,you need to check your reverb tank with a DVOM. Remove it and test the resistance in ohms between the two wires on each side where the RCA cables plug in.One side will be about 220 ohms and the other will be around 8 ohms of so.
  If it reads close to that the tank is good.If not,it isn't.
 The symptoms you describe means that the driver tube is trying to send a signal but the recovery stage isn't co-operating.
If the tank is good,make sure the cables are good.
 I bet the tank has either a broken wire or one of the little transducers are shot.It's NOT the reverb transformer.

[Pastortom]

I haven't taken the amp back yet........I'm gonna pull the reverb tank and check everything again to be sure I didn't miss something to begin with.......

In answer to the question about this being a "Princeton Reverb", NO.......It is a Princeton Recording.....effectively a Princeton Reverb tube amp, tube driven reverb, 18 watts, but with an ADDED mess of goodies.......Compression, Overdrive, and an Attenuator (a real one that allows you to drive the tubes full bore, then attenuate the finalized signal DOWN for playing it in the house, bedroom, or even all the way off for use with headphones ......it has a headphone jack too).

The attenuator, however, uses an all solid state circuit......So, you're effectively "solid stating" your tube amp at the final stage when you use the attenuator......but at FULL setting, the attenuator is taken out of the circuit altogether, and you have an actual Princeton Reverb (with no vibrato/tremolo) that can still be compressed with the onboard stomper.

[phsyconoodler]

Yes,I know what the amp is,being a Fender warranty tech.They are a mess inside but they do sound just fine.
 

[jojokeo]

I still stand by my original statement. I bet it's an easy fix but finding it is the problem and what seperates the men from the boys. Hey phsychonoodler do you remember a show, "Name that tune"? I can fix that amp in 32 minutes...

[Pastortom]

I backtracked this morning over my checklist from my previous bench of the Princeton.......I did not write down an actual test of the tank......Don't know why.......Another senior moment I guess.......It's a standard Accutronics 4AB3C1B like they use in the new Vibrolux's and such........I swapped it out for a duplicate out of my 69 Bandmaster Reverb (that one is awesome) and tested it........IN the Princeton, it is as quiet as a mouse and really deep, with NO BUZZ.  Problem solved.  It was the stinking tank.

So, I hooked up the tank in question to my 69 and tried it.......The reverb is there, but extremely weak....and NO BUZZ.  The Princeton Recording's circuit apparently cannot stand a problem tank without making all kinds of racket.  Never hearing such an electrical buzz before relative to a tank, I assumed it was electrical in nature.  I was wrong.     (Yeah....I WISH I was laughing).

So, I paid $140. to have the shop change one pre-amp tube and NOT ADDRESS the reverb problem which is why I took it in.  With that, I'm definitely changing shops should I ever need one again.

So, I'm a happy camper with a lighter wallet, and $140. chalked up to my continuing education.  I'll check with the IRS to see if I can write it off.

[Fresh_Start]

I'll check with the IRS to see if I can write it off.

Isn't there a deduction for losses due to theft?

Really glad you solved the problem.  Reverb tanks and cables can drive you crazy when troubleshooting.

Cheers,

Chip

[Tone Junkie]

Luckily you had the other amp to take the reverb tank out of to check how does one have an extra onew sitting around.                 
Bill

[Pastortom]

Actually, my front room looks like a music store, so says the wife..... I buy and sell some vintage stuff, build custom guitars, restore amps, etc........

I wish I'd tried the tank before I was out the  dough....I was stumped by the "buzz"   

[phsyconoodler]

Nothing stumps a good Fluke meter.That and knowing to check obvious things before shelling out cash to hack repair guys.

[m2dad]

I have a Fender Princeton Recording Amp.  I bought it used.  It worked fabulous.  Took it to gigs.  However, one night I was trying to be extra quiet for the neighbors' sake and I turned the attenuator almost all the way to lower the volume, while using a chain of special effects pedals.  I heard a sizzle, and then smoke came up through the top grill.  Anyone have an estimate as to cost to repair this thing?  Since I bought it used I am assuming Fender doesn't warranty it.   Thanks, Gary