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@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@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. Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/