DIYbanter - View Single Post - More on Sony KV-1380R with shrinking picture

Mark Zacharias[_2_]

"hr(bob) " wrote in message
...
On Dec 31 2009, 10:37 am, "hr(bob) "
wrote:
On Dec 30, 9:49 pm, Sylvia Else wrote:

hr(bob) wrote:
Just saw the picture shrink and the HV drop from 25KV down to 20KV.
Found what appears to be the regulator, which appears to have already
been replaced and will have to find the output terminal and watch what
it does when the trouble reappears. Did find out that just clicking
the power button off and then back on, within 10 seconds or so, the
picture returned to normal and the HV went back up to 25 KV. More
detective work to do. Regulator has markings STR 30135 6NO1. Five
terminals, only 3 have connections, other two terminals may be for
conducting heat out of the unit.

Seems odd. I thought it was agreed that a drop in HV would result in a
larger, but dimmer, picture.

Perhaps the HV is being dropped *because* the picture is shrinking.

Sylvia.

I agree, it is driving me up the wall, but I have so many other things
going on I can't just sit there and wait for something to happen. If
the lower HV coincides with a reduced drive to the deflection coils
and at the same time the picture is blanked out during horizontal and
vertical retrace as before, you would expect to see some change in
brightness, but the picture size would be dependent on whether the
reduced deflection current or the reduced high voltage dominated.
Will look some more this afternoon if I don't have to go out.- Hide quoted
text -

- Show quoted text -

WINDOZE MAIL AGAIN FAILING TO QUOTE PROPERLY.

Just found that the output of the voltage regulator drops when the
picture shrinks. The regulator stops passing any current. There is a
200 ohm 20 w resistor across the input/output of the voltage
regulator,m and that is the only source of B+. If I parallel a 33 ohm
resistor across the 200 ohm resistor, the B+ comes back up and the set
works perfectly. There is only a slight (not visible around the edges
of the picture) shrinkage when the voltage regulator dies. But, with
the resistor permanently in place, the regulator does not die, as
apparently the 33 ohm resistor reduces the power dissipation in the
regulator to the point where it does not die. It is not a solution I
would use for a paying repair customer, but for a garage tv for me it
will be fine, I will have to check the 33 ohm resistor for heating
before I put the set back together. I'd replace the regulator, but
they are obsolete and I don't feel like making the effort to try to
find a replacement for a garage tv."

I'm still thinking 33uF 160v capacitor...

Mark Z.