Reverb suddenly quit on Fender Deluxe Reverb amp.

[John Link]

Any ideas on what would cause a bedroom use only, Fender Deluxe Reverb amp to suddenly loose it's reverb?

Has not been gigged or dropped, last week it was fine, today no reverb. It's about 10 years old, a re-issue I think. Any input would be appreciated, thanks.

[Boston Joe]

Could be the driver tube. Could be the connection from the tank to the amp. Could probably also be a lot of other things, but I'd start there.

[neatomic]

10 years is about time for some tube changes...the reverb driver tube- a 12at7 -probably went...check your connections out of the amp to tank as well...

here's a guide to the fender deluxe reverb tube layout...time for some changes

https://www.kcanostubes.com/content/...ecommendations

cheers

[jbucklin]

The same thing happened with mine. Thought it was the tube, but it turned out to be the cable that connects the tank to the amp. Found a much sturdier cable at studiosoundelectronics.com. Search for RC-273 3' right angle RCA cables, if it turns out it's not the reverb driver tube. Certainly wouldn't hurt to purchase a new set of tubes anyway!

[neatomic]

always a good idea to clean the reverb wire rca contacts with a bit of de-oxit...or even a 90%+ isopropyl alcohol..both the male wire leads and the amp back female rca inputs

just for info sake- another weak spot of reverb tanks is inside the tank itself, with the wire connections to the springs themselves..a last resort


cheers

[BeBob]

It's absolutely critical to know whether you're asking about a vintage amp or a reissue. The reverb circuit switching is different.

10 years old? That would be a reissue.

Shooting from the hip, my first guess would be to say that you've either got a bad footswitch or a bad cathode bypass cap on the drive/recovery tubes, which has biased your reverb circuit's tube into cutoff.

Why?

Footswitches are high wear items ... even on bedroom amps. The footswitch works by grounding input to the recovery stage (vintage) or by grounding the output from the recovery stage (reissue). If your footswitch gets stuck in the grounding position then there is no signal and you'll have no reverb. Unplug the footswitch and see what happens.

Those amps have cheap Chinese caps in them. They are notorious for premature failure. To be honest, I'm surprised that a reissue with Chinese caps lasted 10 years. At 10 years even a good cap is at end-of-life, so that would be high on my list of things to consider.


Doing formal diagnostics is pretty easy. Here are some tests that can easily be performed by an end user:

1. Order of suspicion needs to favor the wear items first. Footswitches get stomped on. They break. Unplug it to see if it's got the amp stuck in the reverb bypass state. On a vintage amp you can test for a bad stomp switch by switching the RCA cables to reverse the switch assignment and see if the other switch triggers the circuit. But you can't do that with a reissue amp that uses the 1/4" stereo plug.

2. Check the cables. Footswitch circuits are notorious troublemakers. Unplug it and see what happens.

3. Pull and replace the reverb drive tube AND the reverb recovery tube. Either one could be the problem. You need to have signal going from the driver tube, to the pan, to the recovery tube, and no footswitch bypass, to get reverb.

4. you can check the tank by measuring the resistance on the RCA connectors, pin to ground on each jack. if it's over 2000 ohms the tank is bad.

That's about it when it comes to easy end-user tests. The next problem to think of -- which would be on my very high suspicion list for a 10 year old amp -- is component failure that causes the reverb driver or recovery tube to go out of bias. If you're not comfortable working inside of a tube amp with deadly live voltages then you need professional help at this point. Check the voltage at every pin on the drive and recovery tubes and list them here. If you find a cathode voltage that's zero then you've got an open cathode bypass cap and the tube is biased off. Replacing it fixes the problem.

[KirkP]

Don't change cables or tubes yet until you've isolated the problem.
First step: turn your reverb controls and volume up a bit and bump the amp. Do you hear the spring crashing? If not, the problem appears to be on the output side of the spring. If you do hear it, then the problem is on the input side (the signal exciting the spring).
That test doesn't tell you whether the problem is in the tank, a cable or the amp, but it eliminates some possibilities gives you a clue where to look next.
What's the result?

[BeBob]

Don't change cables or tubes yet until you've isolated the problem.

The steps that I provided are exactly how a professional repair technician would isolate the problem. No professional would recommend banging on a valve amp as a means of diagnosis. That reminds me of the days when people would slap the side of their TV instead of calling a repairman. That never made things better.

There's a reason that tubes and cables are removable, and are attached by plugs and sockets -- they are designed to be easily removed by end users in order to execute fast and reliable diagnostic tests that isolate the problem to specific subcircuits. There's no harm to be done by disconnecting a cable or pulling a tube, and those methods provide fast and accurate results if you know how to interpret them. Of course, if you don't know how to interpret the tests then banging on the amp might seem like a good idea.

First step: turn your reverb controls and volume up a bit and bump the amp.

But if you decide to bang on the amp, which is bad for your tubes, be gentle. Reverb tanks were not designed to be subjected to blunt force trauma for diagnostic purposes.

Blunt force trauma is the primary means by which tubes cause amps to self-destruct and by which reverb tanks get destroyed. On the reverb tank there is not a lot of slack on the ultrafine 50-ga pickup wires that connect the transducers to the input output/jacks. Even subtle jarring motions can cause a reverb tank to be destroyed by ripping apart these connections.

Here's a photo of a reverb tank that got trashed by a ham-fisted user when he tried to diagnose what was wrong with his twin reverb by banging on it. Notice that the black wire has been ripped off of the hair-thin transducer wire at it's solder connection. Instead of just replacing a bad driver tube on his own for $15, he ruined the tank and added another problem to the list of things that needed fixing. The result was that a simple $15 tube swap ended up costing him $200 in parts and labor.



I would not recommend jarring the amp -- that transmits force to both your tubes and your reverb tank. Rather than jarring the amp, go around to the back and tap gently with one finger on the reverb tank.

[grahambop]

Reverb stopped working on my 1970s Fender Twin so I removed the reverb tank and opened it up. Turned out one of the connecting wires had broken so I soldered a new piece of wire in. I was amazed how flimsy the original wire was, it was like a human hair almost. I suppose the idea of such a thin wire is to avoid damping the free movement of the springs etc. But it makes that wire very vulnerable.

[KirkP]

The steps that I provided are exactly how a professional repair technician would isolate the problem.

Hey BeBop - I hadn't seen your diagnostic steps when I wrote my note. I think it's easy to shake an amp hard enough to hear the reverb rattle but gently enough to not risk damage, but I think I used the word "bump" not "shake", and agree someone might read that to mean something more forceful.
I was responding to earlier posts that it's time to change tubes, not yours. Your diagnostic method is better.
There are some other quick checks one can do to isolate the problem without opening the amp, such connecting another signal to the reverb return input on the amp, or sending the reverb output to another amp (or even one of the instrument inputs on the same amp).

[Flannels]

I just had that problem, and it turned out that the ACR cables (the red and white cables that connect the reverb tank with the amp) were not fully plugged into the amp. I actually had to squeeze the castle part of the cable (the part that surrounds the male part of the plug) a little bit until the cables were snug into their plug. Don't squeeze them in too much though, because then it won't fit.

[Hammertone]

... I actually had to squeeze the castle part of the cable (the part that surrounds the male part of the plug) a little bit until the cables were snug into their plug. Don't squeeze them in too much though, because then it won't fit.

Shocked!
I thought this was a fambly-friendly forum.

[rpjazzguitar]

I have a 54 year old Ampeg which I used to move around all the time. The reverb spring doesn't lock down. I've wondered why it has never broken. If somebody bumps the amp it sounds like thunder.

But, I digress.

The reason I'm posting is to point this out. The reverb tank cables were RCA jacks, like at the back of a home stereo to connect components.

The RCA jacks have little wings that make the connection.

I lost reverb at one point. I pressed the jacks into the sockets on the reverb tank and they seemed secure.

Several years and hundreds later, I discovered that the wings weren't making contact and fixed the problem for free in 10 seconds with a needlenose pliers.

So, I'd check that, swap the tube with one known to be good (is there another of the same tube in this amp?) and I'd wiggle the pot a few times (amp off). That would be the limit of what I know how to do. The idea is that the main thing that screws up tube amps is vibration, so you're looking for something that can be damaged that way.

[Little Jay]

Don't change cables or tubes yet until you've isolated the problem.
First step: turn your reverb controls and volume up a bit and bump the amp. Do you hear the spring crashing? If not, the problem appears to be on the output side of the spring. If you do hear it, then the problem is on the input side (the signal exciting the spring).
That test doesn't tell you whether the problem is in the tank, a cable or the amp, but it eliminates some possibilities gives you a clue where to look next.
What's the result?

When my Fender Blues Deluxe's reverb stopped working I did the same: (gently) tapping the reverb pan revealed that some noise came out, so it was the input side of the reverb. (Blues Deluxe has solid state op-amps driving the reverb, not tubes as your Deluxe Reverb). Cables were not the problem, turned out to be the reverb pan itself: one of the little cables connecting the little coil to the springs had snapped off (exactly as in bebop's picture). Very tedious work to solder it back on, but I managed.

So check cables first (just unhook and reconnect should be enough), than tap the pan to see if you can hear that thru the speaker. It could be tubes as well, you could take the 12ax7 from the normal channel (V1) and swapp it with the reverb driver and reverb recovery tubes ((V3 and V4) to see if that solves the problem (don't worry about one of them being a 12at7, for the testing you can't damage anything). If that doesn't work than the problem is likely in the reverb pan itself, a broken wire being the most common failure.

Now if all that doesn't reveal the problem, then it's time to open up the amp and 'chopstick' the reverb circuit on the PCB to find a faulty connection. But if 'chopsticking' doesn't ring a bell it's probably tech-time! (Watch out! Potentially lethal voltages inside!)

[cosmic gumbo]

Yeah, the OP got it fixed 1 1/2 years ago, thanks anyway, zombies.

[Little Jay]

Yeah, the OP got it fixed 1 1/2 years ago, thanks anyway, zombies.

Haha! Never checked a date. Well, think of it as adding information for future reference. I never understood the fear of reviving a ‘zombie-thread’ anyway. It’s all good to me.

[guildx500]

I have a mid 1990s ‘65 Deluxe and the reverb failed in it more than once. The last time I diagnosed it myself rather than take it to a repair shop and indeed it was that the thin wires inside had broken loose of their solder connections. I replaced the whole reverb tank and the new one I bought has been reliable but sounds slightly inferior.