Proton VT-290 TV, need schematics

[UFO]

Looking for schematics or the S-M for this circa 1987 Color TV. If you have
anything, appreciate if you could send it to: shearnes( at )adelphia.net

 

[[email protected]]

I have worked on a couple of Protons. Sounds like the same model.

They squel when they have a short and that seems to usually be a
shorted HOT. That is usually caused by bad connections in the H drive
circuit.

Also had opens in the SMPS. Simply open, bad, oxidized solder that was
a better insulator than,,,,,,,,, you get what I mean.

Did you do a physical inspection yet ? I am gonna tellya right now, it
will be VERY VERY difficult to get service info on that, I never had
it even when they were new.

IIRC, check the HOT, if shorted run the traces back to the H drive
Xfmr. Most likely. The jungle IC is not a very advanced design, but it
has some enhancements. It may have been an LA7644 but it needs to be
exactly the right type. Like a Sharp, in some cases.

Inspect ALL circuit boards, especially the SMPS. You might be able to
get it running without the print.

JURB

 

[Chuck]

I have worked on a couple of Protons. Sounds like the same model.

They squel when they have a short and that seems to usually be a
shorted HOT. That is usually caused by bad connections in the H drive
circuit.

Also had opens in the SMPS. Simply open, bad, oxidized solder that was
a better insulator than,,,,,,,,, you get what I mean.

Did you do a physical inspection yet ? I am gonna tellya right now, it
will be VERY VERY difficult to get service info on that, I never had
it even when they were new.

IIRC, check the HOT, if shorted run the traces back to the H drive
Xfmr. Most likely. The jungle IC is not a very advanced design, but it
has some enhancements. It may have been an LA7644 but it needs to be
exactly the right type. Like a Sharp, in some cases.

Inspect ALL circuit boards, especially the SMPS. You might be able to
get it running without the print.

JURB

Some other things to check for on that set. A primary to secondary
short in the flyback or a leaky B+ diode. It sometimes checks good in
circuit. Chuck

 

[UFO]

Thanks guys for the replies.

Problem is dark screen w/ sound. Crank up G2 and you have a green tinted
screen with retrace and you can see a faint pix in the background. Also the
channels dont change via remote or panel. I dont know if that means its a
tuner problem? The fact is that there is one or 2 tips floating around for
this kind of problem:

Symptom ~ Picture very dark, remedy open resistor R441 (10 ohms 0.25W) and
shorted diode D425 (RGP01-20). Diode checks good but fails under a load.
This was done on the set already by another shop. I think they used a
RGP01-17 / RGP02-20 diode as the other one is NLA. Problem persists
anyway.
There is another tip saying the focus - scrn control part of the flyback is
bad, but thats apparently not the case here. I have yet to check the
seperate RCA video input jacks, but I suspect the problem is there too.