[vcf-midatlantic] SASI Hard Drive Controllers

[Jonathan Gevaryahu]

On 12/17/2016 11:03 AM, Dan Roganti via vcf-midatlantic wrote:
> On Sat, Dec 17, 2016 at 10:06 AM, william degnan via vcf-midatlantic <
> vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>
>> Related to my post yesterday, I have a SASI XEBEC 104526 rev 4 that works
>> ok when there is a fan blowing on it but overheats after a while.  It
>> controls a SASI external hard drive used by a Visual 1050 computer.  OK, I
>> will look through the electronics and replace failing components and sure
>> it up.  Seems like the typical course of action for an XEBEC and other
>> (SASI) external controllers.  I am also thinking about the CBM 9090 and
>> related 5-10Mb drives. 35 years in, they all seem to be failed or failing.
>> Similar XEBEC controllers for things like IBM PC's seem to have fared
>> better.  Why?  Or just a coincidence?  Is there a common component that
>> fails more often in SASI controllers but not IDE and others of the era?
>>
>> I know the history of SASI/SCSI and I have some XEBEC docs.    I can
>> research further on my own, but maybe someone who actually supported these
>> back when they were new has some casual knowledge to pass along.  How
>> reliable were these when they were new/current?
>>
>> Bill
>>
>
> ​I don't have any repair history of that board, I think that's a long shot
> Unless you find someone who worked at XEBEC, they would have a more
> comprehensive view of failures.
> And most if not all of those components are well beyond their mtbf rating
> already.
> So that basically means, anything can go wrong.
> But the basic repair steps for something like this include several options
> One of which is using a ol' tried and true method of finding the hot
> component, your finger :)
> That's if the slot has room for you to get in there.
> There's other options such as using a temperature probe[thermocouple]
> adapter for your DMM.
> So you can measure the heat from each component.
> Also, for these tricky problems it helps to have a thermal imager - they're
> getting cheaper every year.
> Then you can pinpoint the source of the heat, but first turn off the Fan :)
> Dan
> .
>
Can't you use a FLIR or similar thermal camera to figure out which IC or 
capacitor has a partial/internal short, and replace just that one?
Keep in mind that some ICs normally get hotter than others, though.


-- 
Jonathan Gevaryahu
jgevaryahu at gmail.com
jgevaryahu at hotmail.com