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?

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

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?

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?

Any other ideas?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

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.

Tom
"Franc Zabkar" wrote in message
...
On Fri, 22 Apr 2005 13:39:28 -0400, "Thomas Sedlemyer"
put finger to keyboard and composed:

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?

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?

Any other ideas?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

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

Oops! Regulator is a STR58041A.

I suspected as much.

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.

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
--
Please remove one 's' from my address when replying by email.

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