Fender Bassman 100 and crackling noises

[moishelichtfuss]

Hi,

I've got a problem with my trusty old early 70s Bassman 100 that even two check-ups haven't been able to solve so far (which included cleaning and replacement of a couple of parts, though I'm not really sure which ones). It works very well, but without anything triggering it, it randomly emits short crackling noises.

For the first time in a long while I have it here at home. I turned it on and filmed it with my iPhone for about an hour in order to have some documentation of what it sounds like. Here's the edited version (15 secs):



This is just the amp, connected to 2 2x10 cabs and turned on. Any clue what might solve this? It's not that huge a problem, but if there's an easy way to get rid of this, I'd be happy. Thanks in advance!

 

[MrCash]

That almost sounds like something shorting out or arcing.
I would suspect.
The tubes.
The tube sockets arcing at the connections or very bad connection to the tubes.
A bad solder joint somewhere.
Or a bad capacitor.

It needs sorting asap imo and I honestly would not use it till its been sorted out. If something is shorting out or arcing then if it lets go then it could do a lot of damage.

I assume you have tried a different instrument cable and a different speaker cable to rule those out?
No harm in also giving all the jacks a clean with contact cleaner either. I've heard dirty jacks make odd noises.

 

[Linnin]

arcing

Yep, I think you're right on the money.
@moishelichtfuss, you need to take it to better amp technician.

 

[moishelichtfuss]

Thanks. Good to know. I've been using it like that for a couple of years now (no heavy use though). I've tried some contact cleaner and so far it hasn't made a peep. But I'll leave it running (in my presence) for a couple of hours tomorrow to see what happens. Thanks!

 

[moishelichtfuss]

Well...it's been running for an hour now and the crackling noise is gone. Hard to believe that these amp techs (the first, to be honest, seemed rather incomepetent; the second has a good reputation) worked on it, but were too cheap to clean the jacks and tube sockets...

 

[agedhorse]

Lots of wild ass guesses here (including the 'ol bad capacitor theory) without much troubleshooting help.

You can eliminate 2/3 of the possible causes by determining if it does this with the master volume up or down for example. If it does it with the master down, you can eliminate all the preceding preamp circuitry from the equation of possible causes.

 

[moishelichtfuss]

Well happy end...brought it to another tech who replaced a cap, a preamp tube, fixed some unstable solder joints and did some cleaning...all good now! Still love that amp.