800RB losing signal

[snowblinder]

I was wondering if anyone might be able to diagnose the problem I'm suddenly having with my 800RB. Up until a few days ago, it had been operating fine. However, now when I play at normal stage volume, I hear an intermittent crackling noise through my speakers, and then the amp will typically lose all volume. Sometimes if I switch it off, or if I remove the instrument cable from the input and re-insert it, the volume will come back. I've done the normal routine of checking all of the cables, and they seem to be working fine. The issue is not in my pedal chain, as they all work fine through other amps. And my bass itself doesn't have any electronic issues. So, it has to be something in the amp. I should probably also mention that I'm using both the 300 watt and 100 watt power sections simultaneously, and the crackling noise and loss of volume is occurring in both cabinets, so the problem is not limited to just one of the power amps.

Mostly, I'm wondering where I should start before I take the amp to my tech. Should I try spraying contact cleaner into the amp's input jack?

[winston]

I have an '87 400RB.
The most common malady with these amps is corrosion in the FX return jack, which causes intermittent crackling.
Clean all the jacks with a high-quality cleaner (like Caig De-Oxit) and insert/remove a 1/4" jack a number of times to clear out the gunk.

Hope that does the trick!

[nanookofnj]

That actually sounds like what happened to me at a winery show in September. Slight crackling during soundcheck and lost all volume at the end of the show 5 hours later. Froze one of the 12's in my cab to boot.

Played it with no troubles the following weekend and end of that show it lost all volume for good. Sent it to Stockton.

Tech said it was cold solder joints. $70 fix and it's coming back next week.

Good luck.

[Bill Whitehurst]

In general, G-Ks are almost indestrustructable.
Still, after a lot of years and use, they can have corrosion or damaged solder joints,
just like anything else.
One thing to check is the wiring from the preamp board on the front, to the power/output board in the back.
My 400RB had that problem and I found that a little contact cleaner and a slight tightening of the spade connectors made it reliable and ready for another 20 years of hard service.

[mav]

I had intermittent sound cutting out. Inserting a small patch cable into the FX send FX return and leaving it there solved my problem.