My recently acquired Corsair II has a failed logic board UV eprom (MC68705P3S)
that prevents me from operating CW. The eprom failure is the keyer "dit" input
stuck close enough to a "low", that about 30 minutes after power-up, the eprom
temp reaches 50C, and the "dit" input is low enough that all I have is a
continuous, uninterruptable transmitted string of dits. Unfortunately, the
architecture doesn't have provision to defeat the keyer function in CW mode.
The eprom temp reaches the 50C temp after about 30 minutes, with an ambient
temp of 22C.
I've talked to Garry Green at TenTec, but they don't have any proms for this
ancient Corsair II. But, the unprogrammed MC68705P3S's are available elsewhere,
and Garry agreed to search the TenTec operation to see if they have the
programming fixture and the Corsair II program. I'm hoping that Garry can find
the fixture and the program. But, I'm not very optimistic he'll be successful.
So, my options are to either find a "surplus" programmed CORSAIR II MC68705P3S
(anybody have a spare or surplus one?), or modify the Logic Board enclosure to
provide forced air cooling in an attempt to keep the processor temp below the
critical 50C.......and hope the processor "dit" input doesn't further
deteriorate.
Does anyone have a spare or "surplus" programmed processor for the CORSAIR II?
Thoughts on cooling/controlling the temp of the processor? Forced air may get
the job done (maybe in combination with a dip heatsink bonded onto the
processor). But I recall (from a former life) that ss heat exchangers for dips
may be a solution that's not as messy as shoe-horning a 25mm pc fan onto the
logic board enclosure, but would necessarily contribute a slight ? temp rise in
the CORSAIR's interior.
Any help or suggestions welcome.
73,
Allen---W7GIF
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