[vcf-midatlantic] SASI Hard Drive Controllers

[Herb Johnson]

> I have a SASI XEBEC 104526 rev 4 that works
> ok when there is a fan blowing on it but overheats after a while.
>  Is there a common component that
> fails more often in SASI controllers but not IDE and others of the era?

Short answer: I don't know, but here's how to diagnose heat-failing 
components: controlled heat and freeze. The trick is in finding the 
physical location.

I simply don't know if there's a common component on XEBEC products 
which fails. I do know there are heat-related failures on decades-old 
computers; so I look for such things when I repair them. Obviously one 
can just replace "hot" components, but they may not be the source of the 
problem. Long-term, excessive heat is an enemy.

Small hand-held IR thermometers are your friend. I bought one at Radio 
Shack decades ago for $50. Now they are $15; I'm still using my first one.

If you freeze-spray a hot component and the board  operates again, 
you've established cause-and-effect.

A temperature-related failure mode can be a solder joint. Or a 
printed-circuit board through-hole which does not contain (enough) 
solder: the copper plating of the hole cracks over time and separates 
when hot or flexed. Components can crack too.

I isolate heat-failing components, by putting the board in a freezer, 
then I install the board back in the device, after heating a SELECTED 
portion of the board with a hair dryer. Heating different parts of the 
board, and smaller sections, in succession, should isolate the failing 
location.

"Teach a person to fish...."

Herb

-- 
Herbert R. Johnson,  New Jersey USA
http://www.retrotechnology.com OR .net