Sunn beta lead issues

[emily]

hey ya'll.

So ive had my beta lead for awhile, its older and been on a few tours. So when it started having some issues, i wasnt all that surprised. but, now it keeps having the same issue, even after I get it worked on. I'll turn it on and everything sounds great, its not until playing through it for about 5 minutes that it cuts out. it doesnt stop making noise completely, it just sounds like its only putting out about half it power or something. Another thing I noticed while trying to figure out what was making it do this is when the amp is at full volume (5-10) and i turn the drive all the way down, it should have a realllly nice clean sound. Instead its just crackely, hardly even there awful noise. Any body know what could cause this?

Also, sometimes if I just keep playing it will come back to full power for a while, but it will eventually start to cut out again. this amp is really hit or miss for me! But it sounds so good when its having a good day!

[mckinnon audio]

  Hi there,sounds like you have some bad solder connections and possibly a bad control or two.I'd take it all apart and scrub the pc boards,(solder side) with some De-Oxit D5 and a toothbrush,look for small cracks and bad solder joints,check your controls also.Good luck,Mel.

[theJJ]

Hi Emily:

Your problem sounds similar to one I had with my Beta Lead.  When the power output drops, does it also get kinda "crunchy?"  Mine did. (See my earlier thread: "Sunn Beta Lead Problem")

I tried some of the suggestions on here--isolating pre-amp/amp circuits, cleaning circuit boards, checking solder joints, etc.--but could NOT get it to work.  But I do think its worth taking a look at those items to see if it can be easily fixed.  Obviously BE CAREFUL when working on electronic circuits.  Some of those capacitors still hold a hefty charge, even when the power is off.

Ultimately I determined the problem was beyond the testing equipment I had available and beyond my admittedly-limited expertise in amp circuitry.  I found a place nearby that works on vintage equipment.  They were able to diagnose the problem, get the parts and get it fixed for under $150.

Good Luck!

JJ