More on Sony KV-1380R with shrinking picture

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.

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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.

WINDOZE MAIL AGAIN FAILING TO QUOTE PROPERLY.

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

Mark Z.

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Mark:

Can you give me an approximate location or designation for that cap, I can't seem to find one of that size? This definitely seems to be the regulator dying as the input voltage to the regulator stays constant or goes up very slightly when the regulator appears to die, and the paralleling of the resistor reducing the load on the regulator and thus the heat dissipation seems to allow the regulator to continue to work. The regulator is not the original, I can see the resolder marks on the pwb. I may try remounting the regulator on the heat sink and cooling the heat sink when the resistor is not paralleled to see if that has any effect. Appreciate your responses, and also the good advice you give here, What is your background?

Bob H

Sorry,

I'm not the major expert around here on old Sony's but I've heard of it so many times, and actually found a couple myself - I know it was extremely common on several of the old Sony's.

I tried looking on the servicer's website for a schematic but the model is too old. Sony has schems for many older models there, but not this one.

The one I remember most recently would have been closer to the rear of the set, maybe 3 or 4 inches from the rear edge of the circuit board, maybe a bit right of center as viewed from the rear. Black in color. Fairly large, caps were larger back then. It's not a particularly large or complex set - shouldn't be too hard to locate. I think they used one in the standby area of the power supply, and one in the vertical circuit, or maybe it was the 130 volt line filter...

Once removed from the board, one could often see electrolyte residue on the underside of the cap.

Mark Z.

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I'll take one more look, if I can't find it I'll put the resistor in and just enjoy the tv with stereo sound in my workshop. Altho there's not much on tv that stereo sound can help. Thanx for the help.

Sorry I couldn't be more specific...

Mark Z.