[TenTec] Corsair II UV EPROM failure

A R raf_3 at msn.com
Wed Feb 19 15:50:35 EST 2014

Good news update to the "band-aid" remedy of a fan to reduce processor temperature:
For what it's worth, the installation of a 30mm x 30mm x 10mm, 12v, 1.8cfm fan to move a little air thru the logic board enclosure, has reduced the internal enclosure temp rise by almost 20C. The small fan is a brushless ball bearing fan, fits nicely onto the rear of the rear of the enclosure lid with minor sheet metal modification, draws only 50ma, is essentilally noise free. The 1.8cfm flow is enough to just move air thru the enclosure, and keeps the processor temp low enough to prevent the stuck-almost-low input gate from deteriorating to a stuck-low gate (as perceived by the processor). The fan cost $10.

Unlikely that others have experienced this identical processor failure, but thought the results of adding the small fan to remedy my unique failure condition may be of interest to others. My Corsair II has now been operating with no CW-mode issues for 8 hours with the 20C lower internal temp of the logic board enclosure. Life is good.....

Pursuit of a permanent remedy is still underway, but in the meantime, the cooling fan band-aid is getting me by.

  ----- Original Message ----- 
  From: A R<mailto:raf_3 at msn.com> 
  To: tentec<mailto:TenTec at contesting.com> 
  Sent: Friday, February 14, 2014 5:43 PM
  Subject: [TenTec] Corsair II UV EPROM failure

  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.


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