[TenTec] Corsair II failure

[dslosty]

Just had the first failure in my Corsair II.
The digital readout either doesn't come on or comes
on after 5 minutes or so. When the rig is warm and if it is turned
off and then on, the readout will not reappear. All digits are blanked
out,
with the exception of the decimal point with is fed directly by Vcc.
Also the readout will occasionally freeze and not update.

I think I've traced the problem to the MC68705P3 on the logic board.
When the malfunction occurs, the processor's output enable 1 and enable
2
signals vanish. Also the keyer functions stop working. With no enable
signals being sent to the LED driver chips, they obviously stop working.
Thus the processor is probably at fault. All supply votages are normal.

Have others seen this problem? Is a failure of the MC68705P3 common?
Hopefully Ten-Tec still stocks these since the onboard firmware must
be custom.

73,
Doug/WA1TUT

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