On 03/23/2012 07:32 PM, John Ackermann N8UR wrote:
My SRS SR-620 counter died last weekend. After superficial
troubleshooting, it looks like there's probably a short on one of the
power supply rails. Symptom is that nothing lights up when power is
turned on, but one or more of the three terminal regulators gets very,
very hot (can't tell which one since they're all bolted to the side rail
as heat sink). The unit had been running continuously for several weeks
when the failure occurred.
I just learned from SRS that they charge a flat rate 25% of the current
list price for repairs! (To be fair, if you're the original purchaser,
it's only 20%.) The SR620 currently lists for about $5K, so we're
talking about a mighty expensive shorted cap (if that's what it is)!
Anyway, has anyone here troubleshot an SR-620 with a problem like this,
or have any general insights about working on one of these beasts?
You have several tantal caps in there. They can have short-circuit as
failure mode. Use the schematic and PDF manual to follow up.
Make a note of which stabs/transistors over-heat and then turn off and
try to see if any of the caps is also hot.
The design has no fold-back on over-current of the power lines.
Cheers,
Magnus
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