Fender Hot Rod Deluxe Reverb

[Davebassman]

Hi,

I've a Fender Hot Rod Deluxe that sometimes the reverb fails, basically I don't have reverb effect. It's a random failure. I've checked the tank reverb and cables, and they seems fine. The fault may be in the electronic part, but I really don't know where to start.

Anybody can help me?

Thanks.

[Mick Bailey]

My suspicion would still be that the tray is faulty. Get it on the bench and use clip leads on the back of the RCA output socket and connect up your DMM on resistance mode. You should read about 220 Ohms. Now wiggle the transducer and flex the green/black leads to see if it goes open- circuit. Most tray faults are the output transducer going open. Either the connecting leads fail, or a break develops where the winding is soldered onto the pins. The fine wire runs in grooves and they break in the groove right by the pin. If this is OK try the input side. The winding rarely fails on the input, but the connecting leads to the RCA connector can break.

[Enzo]

It usually works but sometimes not? How does one check the parts for that. If you test them at a moment it is working, they should test as OK.

So when it quits, rock the amp to make reverb springs crash. Does that come out the speaker?

[Davebassman]

I will try. When the reverb tank fail, I'm going to plug an oscilloscope into TP20 and see if there is any signal. Is it a good test?

Thanks for the suggestions. I will tell you.

[Davebassman]

Okey...

I've check voltage on IC2 and I have 17V on pin 8 and -17V on pin 4, but any voltage on pin 1. But suddenly the reverb work's again, maybe a bad connection with reverb tank? it's very strange.

I check resistance on reverb tank. 70 ohms input and 260 ohms output.

What should I do? replace IC2 and reverb tank rca cables?

[Enzo]

It is working, so the IC is good. ICs don't generally heal themselves. I'd have to say that since it works now, the problems were all of connections.

[Davebassman]

The thing that is a bit confusing for me is that in pin 1 I don't have any voltage, even though the reverb works or not.

should I have voltage on the pin 1?

[Enzo]

No. The reverb drive is like the speaker drive. You sure do not want DC voltage on your speaker, and you don't want any on your reverb either.

The test voltages on the schematic ar AC volts. Note teh round box circling each. DC voltage is in a square box.

[Davebassman]

Good one! thanks!

[Helmholtz]

The opamp is powered by +/-17V. For best performance output pin 1 (as well as input pins 2 and 3) should sit right in the middle between +17V and -17V, i.e 0V.