Electrohome G05 What am I missing?

ELutz

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I've got a G0-5 kicking my butt. I know the problem is on the deflection board.....swapped in a known working deflection board, fixed the issue.

Spot killer LED is lit, image is still being displayed but with retrace lines everywhere. Brightness pot can adjust the screen to black, but it does not get rid of the retrace. Contrast pot does nothing (pot is good). I've picked through the entire spot killer circuit...all resistors test good, all diodes test good, all transistors test good (I even swapped these with a known good board, just to be sure), electrolytic caps replaced. C504 was showing signs of oozing, and resistor R510 was showing signs of heat (it was also replaced). I can't find anything bad....the Z signal is present, as is the 90 volts B+.

Here's the kicker.....if I remove the spot killer LED, the monitor fires up working perfectly! (Yes, I tried a new LED). I'm stumped!

Edward
 
Looking at the schematics, it seems like you must have a couple of issues.

First thing to check, with the game running, check for voltage at Q502-B. Since you've got deflection, it should read zero. If it doesn't, there's something wrong in the spot-killer circuit. I'd verify the pinout of the transistors.

For the constant retrace, it means that when the LED is in, either the z-input is being driven high somehow, or K is being pulled down. I'd double- or triple-check Q502, Q503, Q504 and D506.

-Jim
 
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