Fender Reverb Stopped Working...........

[Pastortom]

I just turned on my 79 Deluxe reverb closet queen (was working perfectly), and the reverb suddenly does not work..........I can hear it when it's jostled, but not from an input signal.......no bad noise from the pot.........the switch makes no difference.......I used a shorted RCA on the switch socket and no difference........checked the in-out cords and they're correct.......

Refresh me here...exactly WHICH tube runs the reverb circuit? (and explain it simply.....no code......I don't know a "t-3" from the moon).........Help me out here.....which tube exactly?

[Dave]

Looking from the back of the amp..... Third tube from the right. It is a 12AT7.

Any good 12A?7 series tube will work for testing purposes. They will all make reverb in that slot if you don't have a proper 12AT7.

The next tube (on the other side of the small transformer) is the reverb recovery tube and is a 12AX7. If it is bad, the reverb will not work either, but since you can here the springs jangling, I would assume, for now, that that is not the problem.

Dave

[Pastortom]

Thanks Dave...........I appreciate the quick reply! 

[Pastortom]

 :shocked:......Well, I guess I shouldn't be shocked, but I changed the tube out for a brand new 12AT7 and there's no difference.........This is funny really in a sarcastc sense, since my Bandmaster Reverb head has the EXACT same problem, and I've even changed out the reverb transformer on that one to no avail.......

I just don't get it.......One minute the reverbs work, and the next they don't........

On the Bandmaster I've changed and interchanged the tank, the transformer, the tubes, etc.....No go.....Now the same stinking problem on my Deluxe.......Good grief.........

There MUST be something in that circuit that's a common problem if just ONE person has 2 amps with exactly the same gremlin.......

Shorted tanks are simple...switches easy to figure....blown tubes and/or transformers the same.......but this is not an obvious problem.

Any ideas?  I really wish someone had a board illustration (a photo) showing the entire circuit.........

[tommytornado]

There are schematics and layouts all over the net..

Look inside the tank andmake sure the little wires inside are still solidly connected? (if not, solder it/them back on their terminals).  Cycle the  the footswitch through a few clicks (does it work?), then unhook it and give it a try.  Check to see if your reverb input/output cables are reversed.

I can't think of anything non technical to look at beyond those things.  Most of my reverb problems have always been the little wires inside the tank breaking loose from their little terminals.  Shoot me a private message if you live in the Dallas/FtW area and I'll (try to) fix it for the cost of parts.   

FWIW, looking at the back of your amp.. from Right to Left the tube functions are>

1.  12AX7 Normal channel preamp
2.  12AX7 Reverb/trem ch preamp
3.  12AT7 drives the reverb tank
4.  12AX7 reverb recovery..  V4A boosts the signal coming off the tank.  V4B boosts the mixed dry/reverb signal and feeds it into the phase inverter.
5.  12AX7 tremolo
6.  12AT7 phase inverter
7 & 8  the power tubes
9   tube rectifier     

[eleventeen]

Yes, I will confirm, that the tiny wires inside the reverb can often break. The good news is that 3/4 of the time they can be just be resoldered to the RCA jack. 

You can test this, crudely but easily, by reversing the reverb can wires and seeing if you still get reverb crash when jostling the amp. You say the amp makes moving-reverb sound when you move it, which means the recovery side of your reverb circuitry is working. If you flip the wires (at the chasis rear panel) and move the amp and suddenly get no surf-sound, then the input side or the reverb can is open,  whether it's bad wires or a bad coil at the "send" end of the reverb can.

OR, you indeed have a reverb driver defect requiring skilled tech intervention, counseling, and rehabilitation, and diversity training.

[FYL]

Yes, I will confirm, that the tiny wires inside the reverb can often break.

Ditto for the crummy leads from/to amp/tank.

[rzenc]

I had the same problem and it took me days to finally figure out a bad ground connection on the jacks of the reverb tank.
Just my $0.02

Best Regards

Rzenc

[bigdaddy]

I had the same issues and it was bad grounds on the RCA plugs from the return and send. It was intermittent.

The fact that it has happened to 2 amps might be something, do you live in a very humid climate? If you do then maybe it's something on the circuit board caused by the humidity.

I think you at this point have to check every voltage and see if something is wrong in that respect. If you are getting that crashing sound it could be something as simple as a poor ground somewhere. It's a process of elimination so making sure all the voltages are correct is part of that process.

Good luck.

[Pastortom]

Well, I cleaned the jacks & plugs and rechecked the cord continuities........Cords were OK as I figured, but whoever mentioned "humidity" as a possible factor may have had something........

I have NEVER had to clean a jack's surface to get a good connection (the RCA's, that is) on one of these amps.......Never crossed my mind........But since the reverb is working perfectly now, I guess I'll start.  (answer to humid climate inquiry.......We may as well be living in the Rain Forest this year here in Central Florida......all it's done is rain, and the temps have been averaging in the high 90's for months).

Now if the Bandmaster Reverb were only that simple............

[phsyconoodler]

Quote :"I have NEVER had to clean a jack's surface to get a good connection (the RCA's, that is) on one of these amps"

Well get used to it.Poor cable connections are the number one cause of no reverb.

[Pastortom]

I stated that with over 40 years of playing and gigging experience with Fenders.......I didn't say it lightly........I've had dozens of problems with the "plugs" shorting, but NEVER a problem with a socket...merely removing and replacing the plug will usually provide plenty of clean steel by which to get a decent connection.

I would have to say the cords and RCA plugs would be the number one cause of non-working reverb.......with all due respect.

[EL34]

I have seen many a Fender in Florida where the jacks and plugs had corroded and needed some steel wool and cleaner spray

To make better connections:
The jacks had to be tightned down to the chassis
The inner jack tip clamps sometimes had to be squeezed together
The plug outer conection had to be squeezed together

[Pastortom]

Yep, I'm beginning to believe that's a greater problem down here than I ever suspected........I've been here for only 5 years, previously based in New York.......the humidity, especially this year, has been a KILLER..........

My amps usually sit in the shop for at least weeks, sometimes months before coming into climate control........the shop is usually 70 to 80% humidity........a LOT higher than I'm used to.

I'm gonna have to start cleaning all of the contacts I guess, and make no assumptions.......Down here, all bets seem to be off.