Bassman 100 combo amp randomly....quits?

[nsmar4211]

I have a fender bassman 100 combo amp (Bassman 100 (15" Speaker) - Bass Gear Reviews at TalkBass.com) that I've had for about 3 years I guess. Played with it in two bands for two years with no issues, only played it a couple of times in the past year after last band quit. It was stored in a houses' garage at reasonable temperatures. Got new band, played on it for about 30 minutes before gig no problems.

Fast forward to gig. 100ft away only power, had to daisy chain 3 electrical cords to power amp since my 100ft cord was going to the PA (same circuit, different outlet). Go to play amp, get bzzt bzzt (which did light up the input light), and not much else. Sounded like the battery died in the bass or the cable went really bad. Switched 3 cables out, tried a passive bass, no cigar. Figured amp wasn't getting enough power (although a power conditioner on the PA showed 119-120). Plugged in baby practice minx amp and played gig through that with no issues (same electrical line!!!).

Other half took amp to his house, plugged it in, no problems! He played on it for abou 30 minutes, left it on for an hour, played a few more minutes, no problems! Figured it was a fluke.

Fast forward to tonight. After about an hour of practicing playing, amp decides to do SAME thing ! Sound goes away, if you pluck a string it goes bzzt bzzzt........then after about 30 seconds it came back on and played for another 30 minutes with no problems!

So, different power. Different extension electrical cord. Diifferent bass. Different bass cable........which eliminates all those as possiblities.

One thing I found tonight was the nut around the input jack was a little lose, I was able to tighten it 1/4-1/2 a turn with my fingers. Could that possible cause an issue like this?!?! Where do I start with trouble shooting? Because now I'm scared to use this amp at a gig (and my other option involves a 4x10 ampeg cabinet that doesn't like my 5 strings). Other half thinks it might just come and go but I've done the "dead amp during song" dance and don't want to risk it....

Things we tried at the gig: Ground lift both ways. Active/passive button both ways. Compresser all up, compresser all down. All tone knobs turned in both directions. Three different cables. Unplug the 20ft christmas lights and single clamp light that were on the same cable. Passive bass, active bass. Different outlet extender. No outlet extender.
Gently jiggling input cable (no crackles or nothing).

I also noticed the power cord is a little wiggly (where it plugs into the amp), but gently wiggling it didn't recreate the problem or have any effect or noise.......

...........hoping someones had something like this happen before

[BassmanPaul]

If the amp is fan cooled it could be that your cooling tunnel needs to be vacuumed out. Also try junpering your effects loop with a signal cable and see if that helps.

[nsmar4211]

If it was an overheating issue, I could understand it after it'd been played for a while.........but at the gig it was nice and cool (70s) and it did it the moment it was turned on!

What do you mean jumpering my effects loop? Put a instrument cable between in and out? Or would it be a speaker cable?

Thanks for the suggestions

[RickenBoogie]

Yes, a short instrument cable in the fx loop in/out.

[nsmar4211]

Ok, the shortest cable I have is 10 ft. Will have to try that tomorrow...trying something else right now.....

Called a friend who knows more than I do. He told me maybe moisture got in the amp from sitting for a while (we live like 2 miles from the ocean). Told me to turn the amp on and leave it on overnight to drive out any moisture, try it in the morning.

I had already pulled thee speaker to check for a loose connection (nada), pulled out the head part and eyeballed for loose connections or anything suspicious (nada), sniffed for any kind of burning smell (nada), sprayed contact cleaner in all inputs....

So it's been on next to me for a couple of hours. Every now and then I hear a soft buzz , even when it's set to mute. It's not the fan turning on, I can hear that seperatly. First time I heard it I plugged in a bass and it played fine. This last time (amp has been on 3 hours), when I plugged in it sounded like interference from something was coming through the amp. However, when I jiggled the cable at the bass it stopped (so perhaps the cable wasn't in all the way? that usually makes a crackle noise though). Currently I'm waiting for the buzz again, left the bass plugged in this time and every now and then I reach over and thump a string...


I don't understand why cabling the effects loop would matter though?

[Mr. Foxen]

Leaving it on whilst moist is a really bad plan. Leave it off, in a dry place for some time. Cabling the effects loop tells you if trouble is the contacts in the fx loop switch, the jacks that switch to straight through when nothing is plugged.

[nsmar4211]

It's not moist per se like it got wet. The humidity here is usually pretty high (80% ish a lot), I'm in South Florida. He was making a point that with temperature changes /lots of rain we've had moisture can build up inside, and if it's not been played there's nothing to drive that moisture ouut.....which would make more sense that it was horrible at the gig (which was by the water) but worked for a while at home before doing it.

Ok I see on the effects loop point.....although I've never even plugged anything in those . I'll try that tomorrow if the "on overnight" doesn't work...... no further buzz for 30 minutes so far.... (figures).......