Diagnosing DRRI that cut out on client

[Choan]

Howdy everybody. I have a deluxe reverb reissue on the bench that a client says has cut out on several occasions. He’s playing with the volume on five or six typically, and he’s gotten it to come back on with a good whack. However, the Amp is behaving perfectly fine on the bench, after several hours of use, stress tests, testing the exterior and internal cabling, chopsticking every component, the visible solder joints on the board connecting to the faceplate…. Everything is fine.

I hesitate to shotgun all of the solder traces because I’ve had a bad experience on a reissue before.  I have not inspected the underside of the main component board, but I have apply a good amount of pressure to every component and not a single crackle. Every component looks healthy and non are discolored from heat. Every wire has been poked and flexed at multiple angles.

The pilot light was a little loose and I tightened that, restoring the full glow. A power tube is slightly microphonic, the bias supply is healthy. 

It is very difficult to try and find a possible bad connection when everything is working just fine! Any other tips on how to smoke out this infrequently recurring issue? A note from the client is that the volume completely drops out all of a sudden with no major pop or crackle, or slow volume fade.

[stratomaster]

It's likely the cable he's using at the amp input.

Also check the speaker cable. If it has the stock one, those have been known to go flaky. 

[Platefire]

First thing that came to mind on your post was ribbon cable connectors

[tubeswell]

Tell the owner to check their guitar cable.


Also, before you send it back, do some routine retensioning of the socket pin clamps, and check the spade connector terminals for signs of loosening.

[dogburn]

Could be an input jack issue, but I assume you tested both of them on the amp. But if not the guy's instrument cable, it could be the input jack on his guitar, or even the guitar's pickup switch. Did he say whether he had this issue with different guitars?