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Sony TV, collapsed field

Sony KVX2142, ae-1c chassis. Picture is severely squashed vertically, with bright band in the centre. Preliminary investigation suggests that the HT is ok (I get a picture), and the horizontal drive is also ok. The 27V for the vertical deflection circuitry sits as 12V; there must be some path from the

12V to the 27V. According to the circuits, the FBT generates the 27V supply via a resistor (0R47), diode, and a elec cap. There would appear to be no volts either end of the res. This would seem to indicate the FBT is kapput, but only the secondary that is used for the 27V bit. Is this possible/likely? Before I splash out £50+ for a replacement, I'm wondering if I could make a separate 27V supply. Comments? Ta
Reply to
Grumps
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Very unlikely to be a bad flyback, sounds like something is shorted in the vertical deflection circuit and pulling the supply down.

Reply to
James Sweet

Thanks. I thought that too. But why can I see 12V on the 27V supply, but nothing on the anode side of the diode from the FBT? But then, I can't find the path (from the circuits) from 12V to 27V either! The power supply circuit for this 27V seems quite simple; winding on FBT,

0R47 resistor, diode, and 680u cap. I can't see anything (Tek scope, not multimeter) on the winding, res, or diode anode. Only see 12V when you get to the other side of the diode.
Reply to
Grumps

My mistake. I had not looked under the circuit board, so just assumed which was the FBT feed to the resistor. I got the wrong end! The 0R47 is open. Q is, why did it blow?!

Reply to
Grumps

Replaced 0R47 res after I decided to measure the voltage on the res properly, doh! TV now works :-) I wonder why it broke. Could it be linked to our new policy of switching off at the mains and not leaving it in standby?

Reply to
Grumps

I see Sony sets with only a resistor in the supply from the FBT secondary open often enough with no other issues to not worry about it any more. I think the resistor is just sized conservatively. I doubt that it has anything to do with your power configuration. We do see a lot of bad solder joints on the vertical outputs and that could play a role. Like the HDT, we always resolder the vertical output when we service a Sony.

Leonard

Reply to
Leonard Caillouet

Thanks. I'll rest assured.

Reply to
Grumps

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