577 U722 thermal insulator?


This is on the power supply board, does this transistor require a thermal pad? Thanks



As I read the manual U722 does not require an insulator. Mine had thermal conductive grease on it.

Reference: 577-D1/D2 Service Manual 070-1414-00 - Sec. 8 Pg.12a for Unit Illustration, showing assembly details and Sec. 8 Pg.11 Item # 78 (U722) showing required mounting parts.

Michael Lynch
Dardanelle, AR


Thanks, I am trying to find any possible situation which would explain the no functioning step generator, something obvious that might be overlooked such as a missing thermal pad or a wire not making connection. When I recapped the power supply board electrolytic and all tantalum it worked perfectly fine. Some how somewhere something went wrong when I was working on recapping the main board excluding ceramic disk. I didn't throw away any of the components I removed, maybe I should start putting them back in? Maybe start with the smallest capacitance tantrums first then possibly a few of those electrolytic capacitors and see if it works while leaving the larger value tantalum capacitors for later.


It's possible that a IC died on me. I might also try to work backwards from the base of the test fixture and see where the broken link is. At the test fixture using an oscilloscope the probe will be on base and the other on ground, correct? I have a differential probe so not as much worries shorting out components with the ground lead.