8 Oct
2004
8 Oct
'04
1:37 p.m.
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...
-tony