Help! Reverb Issue With Rick Amp TR-25

[Barris]

Hey Folks,
I recently picked up a fine sounding SS Rick Amp TR-25 on Craig's List. Awesome amp, but the reverb is not working correctly.......actually, I think the reverb IS OK, but somehow the dry guitar signal is not interacting with the reverb driver circuit.

The tank is fine, the recovery circuit is fine....also when I touch what I believe is the Op-amp/transistor for the reverb driver, it kerrangs loudly when the reverb knob is turned up, but the kerrang does not seem to be interacting with the dry guitar signal.

Also, although the entire path of the circuitry in that area seems to be getting electricty, at some point something is obviously not functioning correctly. (I am only checking this with a lightbulb tracer). Something that does not seem to be working is what looks like an internal 100 K trimpot that seems to be in the reverb path. It does not do anything when turned. There is a similar one in the tremelo path which is working fine that seems to interact with the speed oscilation.

So I don't know if the trimpot is what is holding things up, or if the problem is happening in the signal path before it gets there. Know what I mean?

I have a Schematic I got from the RIC site, but I am not very good at reading it. I would really like to find a way to repair this myself, however. Any tips you guys would try before taking it to an amp tech?

Any pointers would be greatly appreciated!

[johnhall]

While I'm not entirely following your decription . . . . "not interacting" . . . it seems most likely that you could have a problem with the reverb footswitch jack. If the contacts do not completely close when there is no pedal connected, there will be no reverb signal mixed into the dry signal. I'd look at/clean those contacts as the first step.

[Barris]

Thanks for the reply, Mr. Hall. I appreciate you taking the time to comment.

I neglected to mention that the footswitch on/off jack tested fine on both the reverb and tremelo. I know that the switch is on when I hear the springs vibrate through the speaker from the return circuit. Of course, it does the same thing when I turn the reverb knob all the way up. When I hit the footswitch closed, or turn the reverb control all the way down, no reverb crashing can be heard.

I apologize for my weak description...part of my struggle is my ignorance. By "interacting" I mean that it does not sound like the dry guitar sound is reverberating. It is just a dry guitar sound...even when the springs are making the crashing sound.

Its as if there are 2 different independent signals.....the dry guitar sound, and the sound of the springs in the reverb.

With the guitar plugged in and strummed I hear the dry signal, and at the same time (if I tap on the reverb tank or poke the transistor) I hear the "kerrrang" crash.

I hope this makes sense..!

[jps]

The dry signal is not reaching the reverb tank; check the cable going to the input side of the tank to make sure it is not damaged (open or shorted to ground, for example).

[Barris]

Yes, indeed, the dry guitar signal is not reaching the reverb tank, but I know the wire connections are good from the preamp reverb driver to the reverb tank because when one of the driver transistors is touched with the probe, it makes the loud spring noise. This is much louder than just the spring sound the recovery circuit makes when tapping on the reverb tank.

So there must be something amiss on the driver side before the signal path leaves the preamp section to go to the reverb tank. My problem is that I cannot seem to find any bad connection between where the power amp goes into the preamp, and that driver transistor.

I am using a simple lightbulb probe which goes on when a connection is made. Is it possible for there to be a connection which will light the probe, or cause a "pop", but still be bad enough to not allow the guitar signal to go through at some point?

I need some advise on how to actually troubleshoot each component on the pre-amp reverb driver section of the board, and I am unsure about the actual path it takes on the board. (probably why I am missing something).

Thanks for trying to help. I know you folks are flying blind between not being able to actually see and hear whats going on, and my inadequate descriptions...

I will keep trying...

[Full Cleveland]

First of all, in order to troubleshoot this properly you need some real test equipment. An oscilloscope would be best, but in this case you could get by with an audio generator. MCM sells a battery operated one for $64 that is very nice.
http://www.mcmelectronics.com/product/72-505&t=1
What you are going to do is use the generator to inject a known good audible signal, like 1KHz, into the circuit and see where it is getting lost.
I will have a look at the schematic and see what I can suggest as possible causes.

[Full Cleveland]

Also when you get the generator, order a 1uF /100V capacitor:
http://www.mcmelectronics.com/product/31-8735&t=1
You are going to install this in series with the test cables from the generator and use that to inject the signal into the circuit. It will block any DC voltages from the amp from damaging the generator. Also order some test leads, I can't remember if those generators come with them. You need something with banana plugs on one end and either alligator clips or mini clips on the other end. Search for test leads.
Reverb units require a hefty drive level. If the level isn't high enough, that could cause this problem. The reverb unit has a sending transducer and a receiving transducer inside. Because you can hear it jangling, that means the receiving transduceer is ok, but the sending transducer could be bad. Another very common problem is the RCA plugs and jacks connecting to the reverb can get oxidized, so try working them in and out and back and forth and see if that clears it up. If so, sandpaper the jacks with 600 grit sandpaper to get them really clean, and apply some DeOxit to them with a Q tip to keep them from oxidizing. MCM has that, too. Clean the contols with it, too. Spray it into any opening in the body of the control and work it back and forth 30 times. This will take care of any noisy controls.

[Barris]

Thanks Warren...

I'll give those suggestions a try....

[tracy]

The reverb driver may be bad. Alot of those transistors are discontinued but I have one if you're sure yours is bad.

Best of luck.