VAXmate PSU fixed, but no video

[Rob Jarratt]

Some of you may recall seeing me post about the VAXmate PSU failure. Thanks
to members of this list I found the failed part in the PSU and the PSU is
now working again. However, it looks like the PSU failed because of a
failure on the monitor board. There is a burning smell coming from it,
possibly the flyback transformer, but I am not 100% sure. I don't see
physical damage, but of course that doesn't mean there isn't a problem. When
I took the monitor board out again after this, I wasn't sure if the EHT lead
was making good contact with the CRT anode. The monitor board is described
in section 4.4 of this document:
http://bitsavers.org/pdf/dec/vaxmate/EK-PC500-TD_VAXmate_Technical_Descripti
on_1987.pdf

 

 

I need some advice on diagnosing the problem, I have a few questions:

 

1.	If the EHT lead was not properly connected to the CRT anode, could
that cause problems?
2.	Is there anything I can safely do with a bench power supply to
isolate the problem?
3.	Any other suggestions for diagnosing the problem?
4.	There is an outline spec of the flyback transformer in the section
4.4.3.2 of the VAXmate technical description, what chance of finding a
"modern" replacement?

 

I have posted about the PSU repair here:

 

https://robs-old-computers.com/2020/04/18/vaxmate-h7270-psu-fixed-but-no-vid
eo/

 

Thanks

 

Rob