VAX4000 VLC diagnostics/console

Adrian Graham binarydinosaurs at
Wed Jul 14 02:32:35 CDT 2021

> On 13 Jul 2021, at 23:20, Antonio Carlini via cctalk <cctalk at> wrote:
> On 13/07/2021 22:34, Douglas Taylor via cctalk wrote:
>> On 7/13/2021 3:30 PM, Adrian Graham via cctalk wrote:
>>> Hi folks,
>>> Powering up with nothing attached apart from an MMJ/H8571 cable I get
>>> nothing on the console, I'm using PuTTY via a genuine COM1 port on a PC
>>> which is one level above what I used last time I powered the machine up
>>> (FTDI USB adapter to a laptop). Diagnostic LEDs cycle through the tests and
>>> end up at '1111 0011' which according to the manual is 'entering the
>>> console program'.
>> There are 2 ways to have a console on the VAX4000/VLC.  A switch on the back selects either; (1) graphics console mode, or (2) terminal attached to the serial port.  It sounds like you have the switch set to graphics console mode, in that case you get nothing from the serial port.
>> I can't remember where the switch is on the back, bitsavers or someone who remembers can help.
>> Doug
> If you look from the front it's on the right hand side and marked "S3", between the grey reset switch and the keyboard connector. I think that S3 needs to be UP otherwise it would expect a monitor and keyboard to be attached.
> The MMJ connector is on the back (but obviously Adrian has found that ... or he's pushed really, really hard into either the keyboard connector or the phone connector :-))

Bear in mind I’m an old DEC head and have been since the early 80s ;) Though I HAVE seen customers get RJ11 cables jammed in MMJ ports before, because ’they look alike’.

Both of you missed my sentence where I said ‘It doesn’t matter what position I have S3 in’, and IIRC even with S3 set to graphics you would still get a dead sergeant on a VT once init had completed, you just wouldn’t see POST. 

Anyway, I’ll hook up a VT today at some point and see if anything happens.


Adrian Graham
Owner of Binary Dinosaurs, the UK's biggest private home computer collection?
t: @binarydinosaurs    f:

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