| Electronics > Repair |
| Fix vertical hold on a monochrome monitor |
| << < (5/7) > >> |
| rea5245:
Here's a pic of the vertical sync. |
| james_s:
That sync signal looks fine to me, if it's crawling it's due to the trigger settings on the scope, you'll have to adjust those to get it to display properly there. The frequency readout changing is also totally normal, scopes are not precision frequency counters. The sync at whatever point you are measuring is ok, but it must be disappearing somewhere before it gets to the vertical oscillator. |
| PKTKS:
--- Quote from: rea5245 on June 13, 2021, 02:02:49 pm ---Here's a pic of the vertical sync. (Attachment Link) --- End quote --- Place BOTH waves using the OSC as primary trigger... The SYNC is failing to adjust the OSC properly.. if it is deviating due to aging components *you may* see that.. Paul |
| vk6zgo:
--- Quote from: rea5245 on June 13, 2021, 02:02:49 pm ---Here's a pic of the vertical sync. (Attachment Link) --- End quote --- The 1054 should have no trouble triggering, but the very low displayed signal level may be a bit problematical. It would probably be a good idea to reduce the volts/div so the display is say, 5 divisions in amplitude, then try retriggering. Another idea is to reduce the time/div setting, as you don't really need to look at so many cycles. |
| rea5245:
--- Quote from: vk6zgo on June 14, 2021, 01:39:26 pm ---the very low displayed signal level may be a bit problematical. --- End quote --- According to the MDA spec, high voltage levels are 2.4V to 3.5V. See http://minuszerodegrees.net/oa/OA%20-%20IBM%20Monochrome%20Display%20and%20Printer%20Adapter.pdf, page 9. I'm surprised. I would've guessed 5V. But apparently not. |
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