software

Hi!
I have a 5-10 year-old SA-2 Perfect Timbre pickup/preamp in my guitar. When I purchased this guitar (used) a couple years ago, it worked *great*! After a year-long guitar-playing hiatus, I plugged my guitar into my amp, and it now has a fairly loud 60Hz hum. I can hear the guitar if I turn it up enough, but the hum is bad enough that it is unusable for performing. It hums with all amps and all cords I've tried, so I'm reasonably sure it's the SA-2 preamp in the guitar.

I'm an electrical engineer, so given time, I should be able to find and fix the problem, but before I start drawing out the schematics, I thought I would ask if (or anyone else) has schematics available for this pre-amp? Or if not, does anyone know which caps (I'm assuming it is a bad cap or two) are likely to have failed, causing my new hum?

(This is my first post, so if I'm violating any rules by asking for schematics,
please let me know, and I'll rescind my question.)

Thanks for any help!
Regards,
Andy

hi andy

welcome to the SDUG forum

no worries on your request ... it'll either be a 'yes' or a 'no', but no one will be angry for your asking

i'd recommend that you call customer service and explain wassup .. they are really good people and want to be helpful when they can ... will be quicker and more definitive (one way or the other) than waiting and hoping for someone here to be able to helpdoes the guitar hum in other amps? ... does the amp hum with other guitars in it? ... was this hum present only in the presence of a CRT computer monitor or other source of EM noise?

if none of these diagnostics yield fruit, i am suspecting an 'open' ground wire somewhere ...

good luck
t4d

Thanks for the quot;Welcomequot;!

A quick answer to your trouble-shooting questions:
Guitar hums in the 3 amps I've tried.
Guitar hums with the 4 different cables I've tried.
A different guitar does not hum with any of the above-tried amps or cords.
The 3 amps were in 2 homes and a church, with no CRTs, fluorescent lights, or other quot;typicalquot; EMI/RFI sources nearby. Shielding on the cables all looks good, with no measurable leakage between shield and conductors. All resistors measure as marked, no caps measure as shorted or open, diodes all pass basic go/no-go test. I don't know the specs for the pickup itself, so I can't check it out. But there's no way it can be quot;creatingquot; 60Hz hum, so I don't think that's the problem.

There are about 27 components total in this preamp, all Rs, Cs, and diodes except for a TI op-amp. Total cost to replace them all (includeing the op-amp) would be well under $10--but not all the caps are clearly marked, so I'd really like the schematics or a parts list.

I will give the Tech Support folks a call, and see what they can tell me.
Thanks again!
Andy

well, you wrung it out for sure ... nice work

here's hopin' tech support can fix you up .. let us know how it goes

good luck
t4d