Hi Charlie,
40 years ago, my job was field service of audio and video systems, many
of them large and spread out. Experience taught me that the first thing
to look for was a short to ground, which nearly always accompanied cable
damage, and which nearly always accompanied work by some building trade
in the area of the wiring. At Wrigley Field, I was often able to quickly
find damage to loudspeaker wiring by asking where building trades had
recently been working. The same techniques applied to low level wiring
(like mics and control lines).
There are other reasons for Fault 17, and I've encountered them with a
newly acquired 87A that seems to be in excellent shape. One is a memory
tuning that doesn't come close to matching the load, and the amp
instantly faults to 17. This can be tricky to solve, but I've done it at
least once by copying a memory setting from a nearby band segment to the
band segment in question.
Another cause seems to have been bad data in RAM -- killing power and
restarting eliminated the fault.
Based on my limited experience, I would recommend exhausting these
possibilities before opening up the amp. I'm not criticizing your
troubleshooting, which is certainly excellent, but rather to caution
others not to unnecessarily open a can of worms.
73, Jim K9YC
On Tue,1/10/2017 10:19 AM, Charlie Young wrote:
Besides correcting a few issues following a blower change, the main problems
preventing the Alpha from working were in the wiring harness. The first issue
was an open wire on the Rbias monitor circuit which resulted in a hard fault 1
when the operate switch was pushed. This wire runs from the TR output module
over to the microprocessor board. Not only was this wire open, one side of
the wire was at chassis potential.
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