Microvax 3800 Soon to arrive

Glen Slick glen.slick at gmail.com
Wed Oct 28 13:07:05 CDT 2015

On Wed, Oct 28, 2015 at 10:02 AM, devin davison <lyokoboy0 at gmail.com> wrote:
> Hello. I seem to be getting quite a big assortment of DEC equipment over
> here as of late. Back in July I made a trip to Miami to pick up a PDP 11/34
> with related equipment a while back and posted about it here on the list.
> I'm still working on getting the power supply on the pdp 11 fixed but am
> making good progress and learning a lot in the process. Recently a deal
> popped up on a microvax 3800 that was too good to pass up so I jumped at
> the chance to get it and it is on it's way to being shipped here.
> I have never dealt with any Vax hardware before. The closest I've been to
> one is running a simulation of a machine in the simh emulator. Is there any
> special hardware I will need to get this up and running? I have a couple of
> VT 100 terminals that go with the pdp 11 that should work nicely with the
> Vax. Is there anything a beginner with such hardware should look out for? I
> would like to try and disconnect the power supply and test it separately if
> possible to save myself the headache I experienced with the PDP 11.
> Any suggestions or other info much appreciated.
> --Devin

A standard MicroVAX 3800 should be an M7625 KA655 CPU board with at
least one and up to four M7621 8MB and/or M7622 16MB MS650 memory
boards in twelve slot BA213 chassis.

A BA213 has mounting room for up to three full height 5.25-inch
drives, either SDI RAxx drives or DSSI RFxx drives. I think DSSI RFxx
drives would be standard for a MicroVAX 3800, in which case you should
also have an M7769 KFQSA DSSI controller. If you have a M7769 KFQSA
but the RFxx drives have been removed you can find RFxx drives on
eBay, but you might be better off going with a Q-Bus SCSI controller
and SCSI drives instead.

You should likely also have an M7516 DELQA or M3127 DESQA Ethernet
controller, and also an M7546 TQK50 controller and TK50 drive or M7559
TQK70 and TK70 drive. I have removed the TK50 and TK70 drives and
controllers from my systems as they aren't worth the bother to me to
try to get them working.

To connect a terminal to the CPU you need an MMJ cable to connect to
the console port on the M7625 KA655 CPU bulkhead panel.  On the inside
of the CPU bulkhead panel there should be a 3-cell NiCad battery pack.
If the battery pack hasn't already been removed you want to do that
before it leaks and corrodes things, if that hasn't already happened.

There may be an M9060-YA load module in the slot 7-12 side of the
BA213 chassis. The power supplies will shut down without a minimum 5
amp load on each of the two power supplies.  If you had two M9060-YA
load modules I think you should be able to remove all of the other
boards from the chassis and install one M9060-YA load module in the
left half and one in the right have and check if both power supplies
come up OK.

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