[vcf-midatlantic] SASI Hard Drive Controllers

[Dan Roganti]

On Sat, Dec 17, 2016 at 6:17 PM, Mike Loewen via vcf-midatlantic <
vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:

> On Sat, 17 Dec 2016, Dan Roganti via vcf-midatlantic wrote:
>
> On Sat, Dec 17, 2016 at 6:04 PM, Jonathan Gevaryahu via vcf-midatlantic <
>> vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>>
>> 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.
>>>
>>>
>>> ?that was in my 3rd option
>>
>
>    Don't neglect the simple resistor as the culprit in your
> troubleshooting.  Back in the day, I used the freeze spray/heat gun method
> to track down a problem in the floppy controller of my TRS-80 Model 4 to a
> resistor whose value changed just enough when warm to make the controller
> fail.
>
>
>

​Naturally, I was just using the term IC's in general, but I try to mention
components in general.
Dan
​