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Oscillations in a TSM

PostPosted: Wed Mar 12, 2014 4:36 pm
by steeleyz
I have been beating on a TSM with audible meandering oscillations emanating from any channel module with a propensity to the far end (1) but not exclusive to the first bucket. Reseating or reassigning buss selection seems to kill the oscillations, but they creep back up.
Motherboard connectors have been replaced. Audio supplies rebuilt as well as internal distribution, motherboard connections re-flowed.
Grounding busses and motherboard grounds were retouched. All the dummie stuff like internal ground schemes checked voltages checked with multimeter and scope and connectors cleaned.

A few other techs say maybe the ribbon connectors form the channel MB's to the bay or the bay itself may be the problem(s).

Comments Criticisms advice?

Re: Oscillations in a TSM

PostPosted: Thu Mar 13, 2014 10:53 am
by Jim Williams
Add local power supply decoupling caps, .1 uf's near each opamp. Check each stage for a feedback cap, some are left out. Power modules on the bench to determine if they are the source.