Probs w. M3119 CXY08 MUX on VAX VMS 7.3

Holm Tiffe holm at
Mon Aug 17 16:11:07 CDT 2015

Jerry Weiss wrote:

> A few quick thoughts:
> 1) Bad non-name USB/Serial converter.  I have one that won?t speak to a MVII console or certain non-DEC DLV11J cards

...sorry, USB in a DEC VT420 _and_ an Bull Compuprint 970?
Image stolen from the web..)

I've only checked the VT420 with the USB Adapter connected to the Notebook
and it was working as expected. I haven't connected the USB Adapter to the VAX.

> 2) LED Analyzer is pulling too much current on the lines


... and it only does this on the MUX. Still not clear why it doesn't work
w/o the LED Gadget.

> 3) Bad  +-15 volt converter on board.    Do you see any activity on control signals or send line?  Try a voltmeter instead of the LEDs.

It think I can even use one of the Scopes.. but the LED's are bright, all
of them and the modem control signals are toggeling with the terminal line
Regardless of this, even with a broken DC/DC converter and NO Device
connected to the lines, It should be possible to write to the port if it is
set to software flow control..but it doesn't. The write times out.

> 4) $Set term txa3:/nottsync/perm/noninteractive  
>     in case the port has picked up a control-s? and try to copy the file again.

..and again and again. I don't post here after a single failurre, I've
wrote that I tried for hours, tried several ports and I've rebooted
the VAX many times.

Sorry, none of those.  It is really not that simple.

I think about a possibly defective clock XTAL Oscillator on the MUX Board.
The Board logic and the "Registers" may be clocked from the QBus, but the
I think the UARTs gettings her clock from the Oscillator since it has a
Baud rate frequency (14,7456 MHz). Otherwise I've got single LF's and CR's
on the VT420 from time to time, but no other characters.. I'll check that.

Please give me a hint how exactly I should setup a line, no problem for me
on unix with stty ..but I don't know much about VMS...


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