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PANASONIC 36" REGULATOR PROBLEM

This one is turning my beard an even whiter shade of grey. I hope someone can give a suggestion (other than hair dye). Set is a model CT-36622V chassis APEDP288. Uses a STR58042A regulator. Came in with shorted HOT and shorted 150V zener protection diode. Regulator was running very high feplacig several electrolytic caps fixed this. Set now has decreased width (about 1/2"). Width and PC adjust seem to be functioning. Checked all tuning caps in width circuit-all ok. Replaced PC modulator diode-no effect. Changed regulator (yes, I used the A version). No change. Wondering now is the power supply running at proper voltage? Measures 132V no ripple at input to flyback transformer. Anyone know if this is correct for this set? Any other ideas?

Reply to
Thomas Sedlemyer
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On Fri, 22 Apr 2005 13:39:28 -0400, "Thomas Sedlemyer" put finger to keyboard and composed:

Does this set use an optocoupler for feedback from the B+ rail to the STR58042A regulator? Is there a TL431 voltage reference or a zener diode connected to this optocoupler? If so, what are the values of the resistances in the potential divider at the input to the voltage reference?

- Franc Zabkar

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Reply to
Franc Zabkar

Oops! Regulator is a STR58041A. Opto isolator on this chassis appears to be used for over current shutdown as it is wired "backwards". Horiz. B+ is a hot ground and photoisolator diode is on B+ side, photoisolator transistor is on isolated side and feeds back to the microproscessor. Excessive beam current trips isolator and puts set into shutdown.

Regulator

now

A
132V
Reply to
Thomas Sedlemyer

On Sat, 23 Apr 2005 17:40:44 -0400, "Thomas Sedlemyer" put finger to keyboard and composed:

I suspected as much.

Damn. I was hoping that the circuit would follow the application example in the STR58041A datasheet. It would then have been easy to calculate B+ from the formula ...

V = 2.5 * (1 + R2/R1)

... where R1 and R2 are the resistances in the potential divider.

- Franc Zabkar

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Reply to
Franc Zabkar

If it's not too late, check the width control itself. It should be labeled 502/ 5000 ohms. It will probably check low at around 2000 ohms, which results in insufficient width. The same goes for the pincushion pot too.

Ron'sTV

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Ron'sTV
Reply to
Ron'sTV

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