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Icom IC- 751 Mods
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IC751.4
Subject: IC-751 Bad Cap Problems
From: WB2HBZ@WB2HBZ
downloaded from USENET
This info may be helpful to ICOM-751 owners with units approaching five
years of many operating hours; two UNRELATED problems occurred, both due
to a similar 10uf electrolytic opening up. The first was the input cap.
to the 5-volt regulater chip which supplies PLL board. Proper by-passing
is required, probably to prevent internal oscillations in the chip.
Replaced it with a tantulum. (Also arbitrarily replaced electrolytic on
the output side of the 5-volt reg. chip). The symptoms were 3 or 4 minutes
delay before unit would function. Also the screw holding the reg-chip to
its heat-sink was a little loose...probably due to COLD-FLOW characteristics
of aluminum. This can also occur in pheof aluminum. This can also occur in phenolic P-C boards whethe ground-
foil is supposed to be bolted tightly to the chassis. It would probably be a
good idea to use small split-ring lock-washers (along with flat-washers) in
these cases to maintain tension over time.
CONTINUED IN FILE IC751.5
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