Options for resurrecting VAX 4000/400 and Vaxstation 3200
Dr. Roland Schregle
roland.schregle at gmail.com
Thu Mar 10 06:39:29 CST 2016
On Wed, 09 Mar 2016 21:59:27 +0100, Robert Jarratt
<robert.jarratt at ntlworld.com> wrote:
> I think one day I will have to equip myself and learn how to desolder
> and resolder surface mount chips. I don't know how many chips implement
> the B-CACHE, but perhaps you could replace all of them, assuming you
> know which ones they are. Perhaps some careful probing of the board with
> a scope might show if there any chips that are perhaps completely dead.
> You could do the same for the DSSI controller on the other board of
> course, if you can identify that.
Our lab has an EE department with some pretty fancy SM gear, I just have
to practice on it (which would come in handy anyway). The B-cache consists
of 18x CY7C166-20 SRAM plus 5x CY7C170A-25 tag RAM, so they're easily
identified (the KA-675 manual infact points them out).
Replacing 18 SRAMs doesn't sound like a lot of fun, and I have no idea how
to probe the board in the cardcage without disassembling the chassis, in
which case the thing may overheat; opening the CPU bulkhead infact
triggers a prompt reaction from the fan controller.
FWIW, here's a thermography (hope the link works) of the B-cache section
of the KA-675 after being powered up for ca. 30 mins:
Note that the rightmost chip just below the CPU heatsink has a pin that's
ca. 2 degrees warmer than the others. I don't know if that says anything,
but it *is* reproducible. Maybe I should start with that one.
The dead DSSI controller on the other board is easily identified, as it
was physically destroyed in transit. I'm not inclined to transplant a
160-pin PGA as my first foray into SMT... :^\
Thanks for the feedback,
"END OF LINE" [MCP, 1982]
"... nowhere in the standards is it specified that 'programs that use a
lot of memory may randomly crash at any time for no apparent reason'"
[Stackoverflow forum, 2012]
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