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CTC187 picture too big

Found a shorted diode in the pincushion circuit, ordered an exact replacement part and installed it. Pin is now fine however it appears the image is a bit too large, I'm not sure yet how large but when I change channels the very edge of the text runs past the edge of the screen. Pic looks good other than this fault, nice and bright with good color.

Is there a common cause of this? I almost wonder if the EEPROM got slightly corrupted though with everything else working fine I'm worried that a fault may still be present so I hesitate to adjust anything.

Reply to
James Sweet
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If you found CR4403 bad, did you check C4407 with a cap checker? Check the other big diodes, & blue caps in the area. Also, is the B+ too high? Dani.

James Sweet wrote:

Reply to
Dani

I checked the capacitor both for value with my multimeter and for leakage by charging it up to rated voltage with a variable HV PSU, didn't think to check ESR on it though. I'll check the other caps and diodes, what should B+ be on this set? 180V?

Reply to
James Sweet

Standby B+ can be about 145 volts, & about 140 running....approx. You didn't say if the pix is too high also...B+ could be too high. I don't think the EEPROM is corrupt, but if it's just too wide, & not keystoned, it MAY need a tweak. Dani.

James Sweet wrote:

Reply to
Dani

It's pretty hard to tell really, when I get the chance I'll drag the DVD player down there so I can put a test pattern on it.

Reply to
James Sweet

Don't have schematic handy for this chassis, but a lot of these have a set of ceramic caps that form an AC voltage divider across the pincushion diodes. Failure of one of the capacitors commonly causes diode to overheat, and of course any problems in the pin circuitry affects picture size. My guess would be look for open ceramic cap connected to the diode that failed.

Reply to
Bill S.

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