At 8:58 PM -0600 11/20/06, Lewis D'Aubin wrote:
>bruce.gettel@myactv.net wrote:
>>Is it possible that the xistor tests good out of circuit because it's not
>>under "load"? Could it be breaking down once voltage hits it? Did you
>>try replacing it even though it tested OK?
>
>Yeah, I did... well, I didn't have new ones but did have spare ones
>from a third 'parts' board. I desoldered a bunch, and took the best
>three for Q201, 202 and 203. I did notice some of them had gotten
>some stress.
>
>Maybe I should remove parts further down the line and just test that
>way without a load?
>
>Guess if NOTHING else works I could just start swapping parts
>between the X and Y axes, but it's really tough to work on the
>monitor without a test rig (it has to be fully disconnected, moved,
>and reconnected for me to do any soldering alterations it) I was
>hoping that I could quickly zero in on the problem with a scope and
>a VOM but here we are after three days and I'm still scratching my
>head. *sigh*
>
> -Lewis
You can run the monitor with the yoke unplugged, but you MUST always
leave the output transistors plugged in. With the yoke unplugged
there is little risk of damage to the transistors as they are
unloaded. Next you can also unplug the picture tube and remove the HV
lead from the tube - I stuff it into a clean glass or porcelain mug
to hold it away from me when I'm testing - a nasty zap is possible
otherwise!
Now you can simply set the monitor chassis on the bench with a cable
to the game to supply the voltages and signal levels, you can flip it
over to test the bottom, etc. Much easier to troubleshoot this way!
I can not recall if any Vectorbeam/Cinematronics boards have a simple
crosshatch generator, but that would be useful for someone to cook up
as a drop in for the ROMs to aid in troubleshooting the monitor.
John :-#)#
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Received on Mon Nov 20 23:57:10 2006
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