I think I have a problem in my Sunn 1200S (the Hybrid from the end of the Sunn/Fender era)
Went to play a back yard BBQ last week and about 15 minutes into the first set
my speakers started to emit a crackling/buzzing noise. At first it seemed to be particularly from one of the 10" speakers in my Avatar B210Neo. I unplugged that cabinet and began to just play thru the remaining Ampeg SVT115E speaker and within a few minutes that started making the same noise. Checked/wiggled/changed out cables. Each time I stopped playing and did something the problem seemed to go away, but then upon resuming play it would start again after a few minutes. I changed my Bass to amp cable before the third set and made it thru the 3rd set ok, even with the B210 plugged back in. The only other difference was that by then the sun was down and it was a bit cooler then when we started (we played from about 6:15 to 9:30 PM).
Back at home I checked everything again, speaker cab. by speaker cab, cable by cable
and finally think I've isolated the problem to the amplifier itself and maybe even particularly to the tube pre-amp section (although I'm going by sound alone, I'm not at all versed in electronics). I changed amp heads (to my Concert Bass) and playing thru the same cabs and cables no problem. I've also played thru a rehearsal now with the Concert Bass and no problems).
Could it be something as simple as a tube going bad (to produce that crackling sound)
or is it likely something more ominous ?
I want to get a schematic to give to the Techi when/if I take it somewhere for repairs.
Does anyone have a schematic of the Sunn 1200S to save me the time and the money for sending away for one?
Opinions please, that might help guide the tech guy. (He's a throw-back to the days when our local music store was an authorized Sunn Dealer and has done Capacitor work on my Solarus. Seems to know what he's about).
