3 Jul
2025
3 Jul
'25
10:21 a.m.
On Jul 2, 2025, at 8:48 PM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 7/2/25 11:25, Paul Koning via cctalk wrote:
Yes, we had an FE replace components on an 11/45. But, they certainly NEVER did
component-level repairs on an 11/780 or uVAX-II.
Jon
The last one I remembered was an 11/45 also, an MMU data path failure. We (Josh Rosen and
I) diagnosed it while waiting for the DEC FE to show up. Josh pointed to a particular
chip (we had found a stuck bit somewhere in the MMU) and Jim asked why that particular
chip. The answer "because that's the most expensive one in the signal
path". Jim said "we'll see" but shortly afterwards pulled out his
parts box, soldering iron, and solder sucker to remove -- yes indeed -- that particular
chip. :-)
Once DIP chips started being replaced by PGA or other hard to replace parts, replacing
them on site became impractical. I suspect someone also did the economics analysis to
show that carrying a set of boards, diagnosing to the failed board only, and swapping the
board in question was faster and easier.
Of course it led to jokes like this one:
FE is driving down the highway. Suddenly, the ride gets very rough. He mutters
"must be a flat tire", pulls over, puts on the spare. He drives away, car still
goes "bump bump bump". He grumbles "I guess it wasn't that tire"
and pulls over again to swap one of the other tires.
paul
On Jul 2, 2025, at 11:13 AM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 7/2/25 06:08, P Gebhardt via cctalk wrote:
That makes some sense. Print sets were needed in older machines because FE
would actually replace failed components on a board. With "swap the failed
board" repair procedures, it isn't all that useful for support engineers to know
how a board works, much less what the detailed circuitry looks like. Dear list members,
I was wondering if anybody is aware of VAX 86x0 schematics having survived the product
life cycle within DEC? I searched the web extensively but could not find any hints on
this.
It seems that DEC never published such details as schematics for the successor of the VAX
11/78x systems, not even on microfiche, maybe due to the macrocell array implementation
(just a guess). All I could find is that there were illustrated parts list on microfiche.
However, maybe Hewlett Packard handed DEC-internal documents over to a museum such as the
CHM? Or a former designer still have schematics in their archives?
Any pointers would be greatly appreciated!
I did have a KA630-AA print set at one
time. That was about the latest prints I have seen.
Jon