Hi Snowy,
Trust all is well with you. Back in the day, 1980-1990 when I worked on
a lot of that kind of equipment, pro and amateur but using similar
devices, we found 4558 dual op-amps and 4016 CMOS switches to have
particularly bad yields, at least both were very sensitive to damage it
seemed. Recall this was before a lot of people, including companies,
took anti-static precautions seriously so you have a lot of product
potentially out in the world with devices possibly harmed to the point
of a shortened life.
I don't know the particular application but as a mic amp I would expect
you should have DC supply on 8, a good ground on 4 and mid rail approx
on the inputs and outputs. A few mV of audio on the inputs should see a
gain at the output as per R choices. Anything other than that is a dead
chip and I would pull it. Measure supply and bias volts on the board
before you fit another to be sure its not somewhere else.
Martin, HS0ZED
On 10/6/63 04:21, ROLAND HOWELL via TenTec wrote:
Hi Gents
This may be a duplicate of an email already sent, however I may have
sent it to the wrong email address, so here is my plea again.
I have just put a Argosy 525d on the bench, TX is fine on tune and cw,
50 watts at full power or 5 watts with rear switch in low position,
the reported problem is no TX audio on SSB, tried another mic, still
the same.
Looking at the diagram I see mic audio goes thru' a 4558 I/c, are they
a known problem or should I look elsewhere, going to do voltage checks
Wednesday.
Have any of learned gents met this problem, if so what did you find.
Stay well and healthy
73
Snowy G0HZE
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