PCM501ES Repair Tip C906 Reset Circuit

This is where we talk about testing, measuring and repairing things. Sometimes we have to repair the equipment we use to test, measure and repair other things. It's an endless cycle of fixing the broken things we need to fix other broken things.
Post Reply
User avatar
mediatechnology
Posts: 3276
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

PCM501ES Repair Tip C906 Reset Circuit

Post by mediatechnology » Thu Mar 06, 2014 5:50 pm

I was going through some old service manuals that included the PCM601 and PCM701.

At one time - back in the late 80s? - I had repaired a PCM501ES and found this note to myself:
Power on reset. PCM501ES. Found in SN800905. Reset circuit. C906 silk screen on top of the PC board shows incorrect polarity for C906. Bottom screen is OK. Some units have this capacitor installed "correctly" (according to the silkscreen) but the actual polarity is reversed. The cap will fail over time, hold the unit in reset, and prevent output or meter operation.
I'm putting this note here so Google will find it.
That way I can throw this piece of paper away...

Oh, and some of the MCI JH-24/110-series transports also have this same problem (a wrong polarity cap) in the tape roller opto tach circuit.
But that's for another day...

Post Reply