Victory is mine!!

[Fritz]

http://forums.macresource.com/read.php?1...sg-1249581


Yea it took a while, but I finally figured out what was wrong. A hi watt/hi voltage zener diode in the 5v StandBy circuit died. Subject to much stress and heat.

I got one from the shop today and Voila! It's fixed. No telling if the "fuse"/diode caused any other damage, but so far............ $100 saved, minimum, for the ps board.

And the thrill of victory at component level after not touching a electronics in 25 years.

I f@rt in Sharps general direction.

[mrbigstuff]

how did you figure that out? with inet help or with testing equipment? If the latter, I would be very curious to hear how you possess the knowledge of what to test.

BTW: congrats! It is a great feeling to repair something like that. back in the day, I figured out how to repair video heads that were no longer reading the tapes.

[Fritz]

both interweb and a dig multimeter.

I've kept in contact with another tech that use to work at one of the rec'dg studios in NYC that I teched at.
He continued to work as a tech and took his business to the midwest and his clients followed him.

Then there was a guy whose post I saw on TV Repair forum.
He had me check the 5vDC standby circuit and the PS On leg that goes high and turns on the set if all is well, metering thru the circuit, such as it is, without a schematic.

We checked off different "passive" components in the mi repair shop that neighbors my office.
And checked various points of the primary for high voltage. Fuse, exploded caps, etc.
Made somewhat difficult by the lack of a schematic, but the board is silkscreened with some test points and voltages.
The PS is always the first place when the thing won't turn on.
But with modern TVs, you can't extract a board for testing without a jig, which I don't have.
So metering has to be done "in house".

Before I ordered up a PS board, I decided to check the diodes in the primary. I found this zener that exhibited a short in both directions. Since in circuit isn't a true test and since this is a "hard working" "passive" device, I checked it out of circuit and it was shorted.

Finding this kind of HV zener is rather difficult in NYC (the city where you can find anything, 24/7) these days. There are no parts shops like there was when I worked in studios. Even my shop only had 2 of these diodes and It's a huge facility.

Sure is satisfying as well as $ saving. .39¢

[Fritz]

Here's the site.

http://television-tech.com/index.html