Troubleshooting Reverb not working on 65 Deluxe Reverb Reissue

[Johnny_March]

Hi Folks. I've never had my reverb go out on me but this week, my Fender Deluxe Reverb reissue's reverb stopped working. Instead of reverb, I got hum that increased as I swept through the reverb intensity. Here are the steps I went through to try to diagnose it:

Checked and reseated reverb cable connections - That didn't fix it
Replaced reverb cable - That didn't fix it
Replaced reverb recovery tube V4 - That didn't fix it
Replaced reverb driver 12AT7 tube V3 - Reverb came back

After the reverb came back I put the original tube back in to see if the problem came back and it didn't. The original tube is in and the reverb works, but I'm pretty confused as to what really caused my reverb to stop working. Does anyone have experiences like this with deluxe reverb reissues? What is a good sequence for troubleshooting the reverb circuit? What signals and voltage levels can I check for to really be sure I have a rock-solid way of isolating the problem.

Any help would be greatly appreciated. Thank you!

[Stevem]

I would be looking for bad solder connections on that at7 socket or intermittent connections in the driver transformer itself, as I have seen them go open.

There are easy quick ways to trouble shoot that circuit when it does act up.
1) you can prove out that the output side of the pan is good and the 12ax7 recovery section is good by slamming the pan around, if you hear crashing then those two are good.

If you get no crash when turning up the reverb but only some added hum, then the output side of the pan is open, or the cable is bad.

2)to prove out if the drive side of the circuit ( tube, transformer and pan input side are good then Jump a 470k resistor across the center of the RCA jacks on the rear of the amp.
If both circuits are good then turning up the reverb pot will produce a volume gain.

Another way to seperatly test the drive side of the pan is to hook up a 8 ohm speaker to that send RCA jack.
In reality that side of the reverb circuit is nothing more than a 1 watt single ended amp, like a Champ but with a 12AT7 output tube!

When testing just the pan, the input side should read about 6 ohms, the output side should be around 180 to 200 ohms, but basically as long as neither end test open the pan is ok.

[Johnny_March]

Thank you for the quick reply. I was able to slam the reverb tank and I do hear the crash, so I’m pretty sure the tank is good. I also checked the cable for continuity and it’s solid.

Per your recommendations, I think reflowing the connections on the reverb driver tube is a great idea.

[Stevem]

Just note that just because you heard the crash confirming that the output side of the pan is good does not mean that the input side does not have a intermittent connection inside the pan!

Many times either the black or green wire as seen in this photo will brake off of the RCA jack, with then having no reverb function or intermittent reverb function when it feels like making contact again.
On all of my pans for my amps and the ones I work on I apply a dab of silicone bath tub call to that terminal point to better hold the wire from vibrating.

[Johnny_March]

I’ll have a look at the tank as well. Thank you!

[Johnny_March]

It looks like the reverb tanks on the reissues have an additional clip that helps absorb any stress on the wires and connections. That part is solid

[Johnny_March]

I looked at the connections at the V3 socket and it looked like the wire connecting the two grids on the 12AT7 was partially broken. I replaced the scrap of wire and reflowed the connection. The problem usually comes in when I take apart the amp and put it back together. This time when I put it back together it had no issues, so I think I got it.

Thank you so much for your help!!

[Stevem]

Good to hear, and yes, that would surely make for that issue you had!