Options for resurrecting VAX 4000/400 and Vaxstation 3200

[Robert Jarratt]

> -----Original Message-----
> From: cctech [mailto:cctech-bounces at classiccmp.org] On Behalf Of Dr.
> Roland Schregle
> Sent: 10 March 2016 12:39
> To: General Discussion: On-Topic Posts <cctech at classiccmp.org>
> Subject: Re: Options for resurrecting VAX 4000/400 and Vaxstation 3200
> 
> 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.


Just powering it on for a few seconds at a time while probing for any really obvious failures would presumably be pretty low risk. Given that the components face to the right though, you might be able to do some probing with just the memory removed?

> 
> 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:
> https://www.dropbox.com/s/2nsx1dfngp1jfq5/TH710065.BMP?dl=0
> 
> 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.

Looks like you have access to some enviable stuff, so replacing the chips might not be too bad. I get an occasional error on my 4000-500 at test 14 (also cache related), it doesn't appear to affect operation, but I am worried something is failing that will need replacement.

> 
> 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,
> 
> --GT
> 
> 
> --
> "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]