might be the thread you were remembering. It has to do the the ability of the DST50 to interface properly with the JVC DH30000, and whether or not 5c and updated EPROM's had anything to do with it.
Unfortunately, the thread bears the stamp of the infamous Richard Adams
, so everything he said has to be reevaluated in terms of a possible hidden agenda.
Regarding your questions:
The updates are accomplished by changing the programming on the four 1 mB EPROM's to a later version. I suspect that the technicians have an EPROM burner and a supply of blank chips, and burn the "latest" software version on a stack of blanks. The technicians would have no way of knowing what was in the software; it would just be part of the repair procedure to update the EPROM's on older machines.
It is possible to buy blank EPROM's from Panasonic, but not pre-programed sets, which is why I think the techicians do it themselves.
About reversing the fan, I would not recommend it unless you went to the trouble of measuring the internal temperature before and after the change. Radio Shack makes an inexpensive remote temperature guage that would do the job. If you do get inside the case please tell us what firmware version is marked on the eproms.
I've got a couple of questions:
1) Did they remove the heavy aluminum shield that lines the inside of the top? You should be able to tell by looking through the perferations on the top and comparing with your other DST50.
2) Did they say which chips were replaced?
Analog -- Always out of adjustment.
Digital -- Always one more bug.