Beta Bass help

[arenavore]

so I recently got ahold of a non-working beta bass head for cheap.  Figured it'd be a good way to learn a bit more about working inside amps.  Anyway, the issue is that it powers on, but the inputs don't work, and no matter where I set the control knobs, all it emits is a sort of mid-range feedback hum that doesn't change at all regardless of where I set the controls.  I haven't yet had a chance to check if the problem stems from the preamp or power sections, but I was wondering if this situation sounds familiar to anybody here?  A forum search didn't turn up quite the same situation, but what I did see come up a lot was amps having somewhat similar problems due to problems with ICs.  I'm going to try and figure out which section the problem arises from in the next day or two, and I should have more info then.  Just wanted to see if anyone more knowledgeable than myself had any ideas.

[Isaac]

No ideas here. Not enough information. There are several people here who could probably diagnose and fix it if we had the amp in front of us, but troubleshooting over the internet is a long and tedious procedure. However, I'd start by splitting between the preamp and power amp. Does the preamp work? Run a cord from the preamp out to a known good power amp and speaker. Then plug into the Beta and play. Do you get sound? If so, then it's a power amp problem. If not, preamp.

Good luck.

[arenavore]

yeah, I'm not looking for a concrete answer, just suggestions for things I could look into.  I checked today, and the regardless of whether I'm using the preamp or post, I get the same results.  One other detail is that the LEDs by the inputs don't come on when I have an instrument plugged into them.

[Isaac]

Okay, try plugging a known good input into the Power Amp In jack. That disconnects the preamp from the power amp, and should give you a different result.

[george]

First download the service manual - I think it still available somewhere on this site.

You've lost the +-15V supply located on the power amp board - that's my guess.

[raybone]

I put my Beta bass on the shelf about 2 years ago, because of what sounds like the same exact problem. It powers up, but just buzzes. I had a local tech look into it, after almost a year (guy is lazy) he gave it back saying the parts needed are not made anymore.  I cant remember what exactly he said was wrong.  Hope you find a solution. I really like these amps when they work.  My was out of a Beta Bass 2X15 combo. I still use the speaker cab, but now there is a hole where the head was.

[arenavore]

well, after being unable to figure out what was going on, I dropped off both this and my broken ('73) Concert Lead off with a tech who lives about two hours away from me.  He figured out and fixed the CL within a week, and kept me updated every step of the way.  Last I hear was about a week ago, when he said he had figured out at least one problem with the Beta Bass and ordered parts.  I'm still waiting for an update, but hopefully I should hear in a day or two.  This dude has proved to be the most communicative and honest tech I've ever dealt with so far, so I'm hoping he's got this situation right as well.