VAXstation/MicroVAX 2000 CPU/FPU overheating?

[Allison]

>
>Subject: VAXstation/MicroVAX 2000 CPU/FPU overheating?
>   From: "Dave Dunfield" <dave06a at dunfield.com>
>   Date: Sun, 24 Feb 2008 22:50:56 -0500
>     To: cctalk at classiccmp.org
>
>Hi Guys,
>
>I've just acquired a VAXstation 2000 (thanks Mouse!) which exhibits what appears
>to be an overheating issue.
>
>Powered up ir runs for about 10 mins or so (just sitting at the console prompt
>doing things like TEST 50 to display the configuration, pressing ENTER to get
>another '>>>' etc.). After about 10 mins (give or take) it fails, sometimes
>appears to reset, hangs etc.
>
>Firt thing I noticed is that the two surface mount chips with the round heatsinks
>affixed to them get *HOT* ... Hot enough that you wounldn't want to keep your finger
>on either of them for very long.
>
>I believe these are the CPU and FPU chip? - Is this normal for them to run this
>hot? They don't heat up alarmingly quickly, but after a few minutes they are
>hotter than I'd think normal.

Yes, CPU and FPU.  They do get hot.

Makes sure then fan is running and there is airflow.

>Aside from the eventual failure, it seems to run correctly - the self tests
>(including the FPU test) pass (except for those which don't have hardware installed,
>loopback connectors etc.
>
>When I got the system, it was jam packed with cards, including the main board,
>color frame buffer, double-sided memory expansion and an ethernet interface.

A maxed out machime.

>During my testing, I've removed all of these except for the main board, and am
>running the system as a MicroVAX. I do have the resistor/loading card installed
>as is recommended when running the system lightly loaded.
>
>Power rails all look good - There is a 9V supply which the technial manual
>describes as "for loading" which has a separate supply and return. Relative
>to ground I measure about +5.6v on the supply and about -3.3 on the return,
>which I'm assuming is normal (?)

Makes sure the 5V line(s) is good and really at 5V.

>Anyone know where I can obtain anything resembling a schematic? Other technical
>information (I have a PDF of the technical manual, however it's mostly "system
>information" from an operational point of view). Any known issues etc.?

One of the signals from the PS is power good.  Makes sure that line isn't 
bouncing.  I think it's an orange or white lead it's been a while since Ive
been in one.

Allison


>Regards,
>Dave
>
>
>--
>dave06a (at)    Dave Dunfield
>dunfield (dot)  Firmware development services & tools: www.dunfield.com
>com             Collector of vintage computing equipment:
>                http://www.classiccmp.org/dunfield/index.html