Nomad 55 Head reverb not working

[Wutz]

Just as the title says, the reverb on my Nomad 55 isn't working. It worked for a long time, as long as I had the amp. I didn't play it for about a year and then went back to it and the reverb didn't work. The amp is great so I just turned the reverb knobs all the way down and kept playin' the hell out of it.

Well, I finally decided I wanted to stop using a delay pedal to simulate a reverb and I set about diagnosing and fixing the problem. I searched on the forum here and, following the advice suggested in other threads, I pulled the RCA cables and plugged 'em back in to try to re-seat the connections (as suggested by a thread on this forum). Plug in guitar, light fire, step away, slam strings...no reverb. I tried switching the cables at the send and return of the reverb loop (just to make sure I didn't hook 'em up wrong like a jack-***) and all it did was add a whole pile of noise...no 'verb.

I swapped a new RCA cable for each cable individually and beat on my strat a little more, no reverb still.

Just out of curiosity, I connected the output of Send of the reverb loop to the return of the reverb loop and I got a really odd high-pitched squeal. Adjusting the reverb pot changed the volume of the squeal which did little to reduce my annoyance but it seemed to varify that the pot is still working (which was another "thing that could go wrong with the Nomad reverb" from another thread).

I'm thinking that it could be the reverb tank. I'd like to test that theory but I don't have a clue how to do it. I'm imagining I'm going to have to pull the tank out and, in order to do that, I'll have to pull the rest of the amp out of the head enclosure. How do I avoid killing myself? I'd like to think I have something to live for and one of those things I live for is ambience in my guitar playing. How do I pull everything out of the enclosure without dying?

I'm officially confused. Any ideas and/or guidance?

 

[shytfayse]

With the reverb up on the back on all channels, no guitar plugged in, reasonable amount of volume on the front, rap the reverb tank with you knuckle. Do you get a responce at all? You should hear the springs banging around. Do you own a ohmmeter?

 

[thelastleroy]

I ran into some trouble with a reverb tank once. One end of the tank had gone completely dead. I ended up taking it apart and actually re-winding one of the tiny coils inside. Painstaking work, because even the accutronics tech guy couldn't accurately say how many turns are on these coils. I had to count the turns as I unwound the plastic bobbin and then re-count as I wound the new wire on. I believe I used magnet wire from a garbage single coil pickup I had lying around.

Try and check the resistance on the RCA jacks on the input and output (test one at a time from the center of the jack to the outside). You'll need to see some kind of reading here, I forget exactly how much to be honest, but if it's open or shorted, your reverb won't work. If you politely Email [email protected] with your tank model, they might just tell you what reading you should have on either end. If the reading on your tank checks out, the problem lies in your amp.

If you determine the fault is the tank, you might be able to repair it. The glue that accutronics uses to seal the tanks is a pain, it might help to warm it up gently with a hair dryer. Make sure none of the jumpers from the jacks to the coils have broken off. If your wiring is continuous from the jacks to the coils, you could try to roll your own. Or, if you aren't as cheap as me, buy a new tank and call it a day.

Do you have access to a known good tank? Maybe your local music shop has one lying around in the back you could plug in and test?? Or bring a set of LONG RCA cables with you and plug into a tank that's installed in a friends amp?

 

[Wutz]

Hey, guys, my multimeter just showed up today so I should be able to check resistance and continuity fairly soonish.

Just as a quick couple of thoughts: Should I test for continuity from one end of the tank to the other or will that not give me any real information? Also, testing for resistance was mentioned: I just got my meter so I don't know how to do that - what's the proper procedure for that?

I'm also looking into the fx loop mod (the one that replaces the cap) and the mud mod, what do I need to know about this amp (and amps in general) to get in there and successfully not die?

 

[shytfayse]

Measure between the center pin and the shield on both jacks and you should get some reading on your ohmmeter. You should not get and overload of ohms or an open. if your meter is not auto-ranging set it to around 200K. There should be no continuity from one rca jack to the other.

 

[thelastleroy]

Measure between the center pin and the shield on both jacks and you should get some reading on your ohmmeter. You should not get and overload of ohms or an open. if your meter is not auto-ranging set it to around 200K. There should be no continuity from one rca jack to the other.

Correct.

Be sure when measuring in this range of resistance not to accidentally touch the tips of your meter probes with your fingers. The electrical resistance of your skin will actually read out on your meter and may cause you to take a false reading. As far as poking around inside the amp; the chassis is fairly easy to remove, but don't get in there until you can properly identify and discharge the filter caps. On my Nomad, the filter caps were big blue 220uf. Do a search on "drain filter caps" for the procedure. I will not tell you personally how, as there may be a liability issue here. DON'T play with your life. Understand that these capacitors store a high voltage charge and can kill you. Respect the equipment, read a lot and when you are confident, enter at your own risk. Just keep one hand in your pocket!

The circuit board mods are fairly straight-forward, so long as you can remove and replace the components without damaging the pads/traces. The boogie PCBs seem to be pretty robust.

 

[Wutz]

Yo, y'all!

I just wanted to give everyone an update. I did a bit of testing, found that my cables and reverb tank were fine, so I took it in for repair.

The repair guy ended up replacing the opamp and the J175 FET. The reverb works great again...I think I'd like to get a tank with a shorter 'verb length eventually but I'm not too worried about it.

Thanks for the help, guys!

 

[NomadExpress]

I'm, glad that it was easily fixable.

Enjoy!