wrote in message
ups.com...
So you got what I needed about 7 years ago. Marvelous.

I got it free about five years ago. Worked pretty good until a "tuning?"
capacitor on the deflection board smoked. Worked another couple of years
and the old white HV transformer died. Bought a set of boards on eBay and
it worked another four months. I have no idea how long my "fix" will last.

You know what you got there, a piece of technology that isn't made
anymore.

Probably for more than one reason... Very few integrated circuits and
discrete components that can be tested and replaced with a little
know-how...

I will splain.

The main 130 volt regulator in that set is the HVOT driver. The
regulation can be so tight that the picture shrinks on high brightness
due to the mass of the electrons. Therefore they have a secondary
regulator. See, in a PTV raster size must stay pretty constant. If not,
convergence would never follow. I mean they had a chart for every
kilovolt that dropped per milliampere.

Magic, eh?

The main regulator is synced of course, and as it spreads it's on time
to handle the load, and HV is increased pre-emptively. It is a
wonderful system, but a real bitch to work on. They were a bit
self-destructive, with 320 VDC on tap it was not hard to go poof.

Yeah, not knowing what some of the zener values are doesn't help much
either...

Amma tellyas one more thing about the early PTV300s, do not work on
them in a basement, even WITH an isolation transformer. Just don't do
it.

I don't trust electricity to follow the rules. As a hobbyist, I unplug the
set first, verify that there is no voltage on the test points and THEN use
clips to hook the meter up. Place the meter on top of the set, verify the
wires are out of the way and then plug it in. The only thing I'm
comfortable testing on live are old digital circuits like Arcade games and
only then on my test bed; not mounted inside the machine with open line
voltage connections.

Like falling off a ladder, you may only get one strike and be out...

Thanks for the info...

Kirk S.
T