Fender Hot Rod Deville troubleshooting

[j3041]

Hi everyone thanks for reading this. I have a Fender Hot Rod Deville that pulled something very strange on me the other day all of the sudden I lost all sound and only heard a scratching sound in the speakers. I plugged a guitar into the power amp in and still no sound so I determined it was in the power section not the preamp section. I removed all the tubes and replaced them with good tubes and it worked. But here is the strange thing to find the bad tube or tubes I replaced the old tubes back in the amp one at a time and it worked all the way until I had all the old tubes back in it. Now it works again. I was driving it hard with the gain all the way up when this happened. So far it hasn't happened again but I haven't driven it that hard yet. Any thoughts, sound familiar? Thanks

[Robert M. Martinelli]

Hi and welcome to the "place"!

Do a little search on the forum about "Hot Rod" and you'll find tons of threads/posts dealing with "strange" issues like yours....

The reason your amp worked after changing the tubes is that it probably had the time to cool down while you were installing the new tubes. This would also explain why the amp also worked after throwing the old tubes back in.

Your problem is most likely a thermal issue related with the zener dropper resistors used in the preamp's PS section. This is a very common issue on HRDs.

Hope this helps

Best regards

Bob

[Enzo]

Take the rear cover off. Look at the solder on the pins of the powr tube sockets as they poke through the circuit board. Look CLOSELY. I bet you see some cracks in that solder. I recommend resoldering all the pins on those sockets even if they look OK.

When you shove tubes in and out of the sockets, it flexes things around, so cracked solder can touch and start working again. At least until it settles to some place where it no longer touches. Just wiggling the tubes while in the socket might show you. With the amp running, does wiggling the power tubes side to side make the amp react? it should not react.

Of course it could be totally something else.