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Heathkit IO-101 Vectorscope/Pattern Generator Insanity .
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04-15-2017, 08:05 PM
Kevin Kuehn
Workin' Late Again
Join Date: Jan 2011
Location: WI
Posts: 3,824
That was it. The vertical sync pulse was so long it was blanking too far into the beginning of next frame. All it needed was a 1.5k resistor from ground to the vert sync input of the sync mixer gate, so now the vertical blanking width control works as expected. The way it was, the gate input couldn't recognize the change in pulse width(RC differentiator) because it had no DC reference. Apparently that was an inherent design flaw. Now I have to wonder if Heathkit at some point implemented a fix for that small oversight.
Last edited by Kevin Kuehn; 10-21-2017 at
08:55 PM
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