28 Aug
2003
28 Aug
'03
3:22 p.m.
Hello,
Thanks to the help of several of you, I have, after
reparing the power supply, been able to verify that
the CPU is running, and using the .PDF service manual,
am able to get a signal on the video pin (8) after
replacing the contrast pot. However, the monitor
still produces no output. I have a couple of
questions:
1) Is there a SAMS or some other document that
discusses the monitor operation?
Yes, I'll have to dig for it in the rubble here.
2) What's the simplest way to use an external monitor
for testing?
Wasn't there some sort of video adapter that plugged in where the jumper
was on the front panel.. ISTR it was a standard b/w NTSC monitor. One of
the surplus electronics places in CA was selling said item for about $4 or
so.
3) Does the monitor use the +12V line on the connector
from the CPU board for all its power, including the HV
converter?
I'd have to check the schematic, but it sounds logical (sorry Spock!)
Unfortunately I don't have an HV probe at the moment,
so I'm being cautious about poking around the CRT.
Well, using a screwdriver, pry up the cap over the HV lead on the CRT so
you can get at the metal --- and draw an arc to see if HV is present. Use
an insulated screwdriver, and don't tie it to ground. You should see a
small arc of maybe 1/4" or so. Sometimes you can hear the static
electricity around the CRT when it powers up as well, but being that
small, might be hard to hear. Sometimes with the static electricity you
can feel your hairs react as you take the back of your knuckles or hand
over the screen
I'd look at HV, then the grid voltages at the CRT, and then the video
output transistor that drives the cathode for proper voltages, etc.
Thanks,
David.
Gary Hildebrand
St. Joseph, MO