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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 16th Apr 2018, 5:02 pm   #21
Lucien Nunes
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Default Re: Microvitec Cub 1431 Power but no picture.

Field shift link is PL301, adjacent to the scan coil connector. One of the outer pins is ground, the other is the 24V rail. The link plug is inserted between the middle pin and whichever side gives better centering. Remove the plug and you can access both. Follow the 24V rail for other options of test point, such as L401 in the supply to the pincushion IC.

The reason that cap can pull down the HT is that a short on the flyback supply overloads the line output stage heavily and causes it to pull enough HT that the PSU goes into current limiting, possibly accompanied by the squealing noise. Obviously other overload conditions can cause this but I remember it being a frequent offender.
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Old 18th Apr 2018, 10:15 pm   #22
qsilver
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Default Re: Microvitec Cub 1431 Power but no picture.

I tracked down PL301 and there is no jumper or link on here. Should there be?

I checked the resistance on all the pins. Found the ground, tested the other pin and it started low and then charged to 38k at which point I removed my probe. The centre pin read 11k so does that look ok?
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