Bass amp problem

Carson Leighton · Post by **Carson Leighton** » 30 Jul 2001 5:06 pm

Our bass player's amp just quit right in the middle of a song. The on light still comes on and you can hear a low hum, but there is no sound coming out of the speaker from the instrument. Could it be the transformer? It's a Yamaha B115. The cables are good, and the amp has never been abused. Any help would be appreciated....Thanks, Carson

Jerry Hedge · Post by **Jerry Hedge** » 30 Jul 2001 5:50 pm

Have your local amp tech check the diodes in the power supply for the power amp. I own a Yamaha Bass amp that had the same problem. If it's a model with a direct out see if you're getting a signal out of it. Mine had a separate power supply for the pre-amp and the power amp. By the way, if that's the problem, some of diodes are out of production-BUT-you can use a standard,high amp bridge rectifier from Radio Shack to replace them.[This message was edited by Jerry Hedge on 30 July 2001 at 06:50 PM.]

Carson Leighton · Post by **Carson Leighton** » 31 Jul 2001 11:28 am

Jerry, thanks for the reply and the advice......Carson

Bob Metzger · Post by **Bob Metzger** » 31 Jul 2001 12:57 pm

Is this a tube or solid state (transistor) amp? 90% (or more) of all problems in solid state amps are in the power supply. In addition to what was suggested above, check the main filter caps and power transistors. If any transistors are bad, you'll have to check the parts adjacent to them as some will/may go south at the same time. Get a schematic to do this work or take it to a competent tech who has worked on this type of amp before.

Bob

Carson Leighton · Post by **Carson Leighton** » 31 Jul 2001 5:31 pm

Bob, the amp is a solid state and is quite old, probably over 25 yrs. It looks like new though and it really hasn't had a lot of use. We only use it for practice now and we use another one for gigs. I don't know much about electronics, and unless it's something simple like a fuse or loose wire, I probably couldn't fix it. I will say something about this amp, it has a great sound, really deep and soft and not harsh at all. Again, thanks for the advice. This certainly is a great place.....Carson[This message was edited by Carson Leighton on 31 July 2001 at 06:34 PM.]

Bob Metzger · Post by **Bob Metzger** » 31 Jul 2001 6:31 pm

Carson,
If this is a good sounding amp that you enjoy, why not fix it? Find a competent tech in your area. Ask musicians and music stores. Ask the tech if he's had experience with amps like this one. Believe me, I'm all for hobbyists but you need a pro now. Put out the feelers and something good will happen. Yamaha amps are generally very well made and I don't see why, after a little service, that this amp isn't ready to perform for another 25 years. That's how I would recommend approaching this situation. You never know, maybe it'll become a gigging monster once again.

Bob

Dave Seddon · Post by **Dave Seddon** » 10 Aug 2001 12:43 pm

I've only just seen this so I'm probably too late but it sounds to me like smoothing capacitors in the Power sopply, Possibly 4,700uF.
Cheers Dave.