DIYbanter - Sony KP57HW42

Hi;

This one came in with a shorted HVOT and the regulator thereto. Have no
print. Now that I've found out how much the HVOT costs I am going to
resurrect a test procedure I used to use, but with a bit of a slant.

The main piece of information I need is the nominal voltage at the
output of the HV regulator. Also need the frequency at which to drive
it because it's not NTSC scan. Me thinkst if I put 15,734Hz into it
even at the right voltage supply there may be some problems. What would
help is to know where the HV feedback is and what that voltage is
supposed to be. In fact I would appreciate THAT information VERY MUCH.
A direct reference to the actual versus normal output of the
transformer is the best way to minimize collateral damage.

Escaping smoke elsewhere on the board should indicate the source of the
problem, and to limit possible collateral damage the board will not be
hooked up to anything but this rig and the high voltage circuit. As an
aside, if any of you ever decide to run this test, absolutely and
positively identify the CRT heater circuit and make sure it does not
come from the flyback. In sets with seperate HOT and HVOT you could be
running those tubes with no deflection and no shutdown. DON'T WAIT to
see the spot. That is stupid. If you cannot POSITIVELY identify and
disconnect the filament supply, take the CRT sockets off. I intend to
because it would be faster than tracing it out, and Sony has been known
to have the filament supply in the main supply so different tests need
different precautions.

I will let you know the results, and at least describe the waveforms I
find in this mode AFTER the fault is corrected. I also need to look
around and see if this a multi-rate scan, and if it is I need to see
what the default would be when it's disconnected. I assume when I see
about 20% duty cycle on the retrace pulse I'm close, now it occurs to
me that this a 16:9 set so I wonder if it's possibly shorter. I can't
believe this shop doesn't have a freq counter. (at least one tech has
it on his DVM, but I ain't buying one. I will simply use their time to
figure it out on the scope, no problem).

Anyway, a few specifics would be greatly appreciated. Thanks in
advance. If I see you I'll at least buy you a beer. I said at least.

JURB