Matt from My Twilight Pilot told me that his wonderful Fender Hot Rod DeVille had developed some strange noises. The volume control was really too sensitive, no low end audio, audio clipping, and we were experiencing some general shakes, rattles, and rolls. Could the Unbrokenstring Crew help?
Finally, an appropriate warning label…
This brand new tube chart clearly shows that this is one of the wonderful reproduction units from Fender.
Service literature is easy to get from Fender for this model.
The treble tone cap was replaced with a silver mica unit (already installed.)
The bass tone cap on the right was replaced with the orange film cap on the left. The larger size buys us some reliability as the internal dielectric is a little thicker, a good then when operating at a plate voltage of 350 volts. The mid-range tone capacitor was also replaced with another orange CDE cap of the proper value.
The tone stack capacitors are now soldered in. The leads will be trimmed and the rosin flux will be cleaned off.
When the signal generator was swept through the audio range, a mechanical rattle was heard in the vicinity of the reverb tank. I’ll loosen the reverb tank and do the test again. This thing IS loud!
A quick check of the electrical connections shows that everything is as it should be. But the rattle remains!
The loudspeakers are a little loose, but no rattle here.
Aha! It’s the bottom of the baffle board. All the bolts were loose. Here they are re-torqued to about 5 ft-lbs.
A fresh set of output tubes were run for four hours and re-biased per Fender specs. A 12AY7 was installed in the first preamp. This tube has lower gain than the 12AX7 used at the factory. This change gives a little more ‘spread’ to the volume control, increasing its usefulness.
This is a view seldom seen unless you are in the business! Nice lead dress.
To do the full-power tests, the window is opened and the amp is turned around. Yes, this is VERY LOUD! And quiet when it should be. My job here is done.
Thanks for reading all the way to the end!
Contact – David Latchaw EE
Cell – 281-636-8626
