Vector (arcade) monitor interfacing issues

From: Tony Duell <>
Date: Fri Oct 8 17:37:24 2004

> In 1982, when I got a super-early IBM PC (working for
> Phoenix Software) the first thing I did was to burn out the
> fuse in the monitor with the wrong display-type DIPswitch
> setting... apparently the wrong horizontal freq makes the
> monitor draw a lot of current, by some miracle the Q didn't
> protect the fuse.

Presumably am IBM 5151 monochrome monitor (like the one I am using right
now). This thing has no horizonatal osciallator -- the horizontal drive
pulses from the MDA card go straight to the horizontal driver transistor
which is, as usual, transformer coupled to the horizontal output transistor.

You can therefore attempt to get the thing to scan at any frequency, but
the horizontal output stage won't like it. Normally the horizontal output
transsitor fails...

Received on Fri Oct 08 2004 - 17:37:24 BST

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