Telefunken CH815 - Too much width

[dieselriot]

This is a solid state black and white tv. The picture is too wide. Someone mentioned to me that the capacitor responsible for the width may have gone bad. I have the schematics for this set and believe the capacitor in question is C606. It's near the "0.5" voltage rating in the attached picture of the horizontal circuit.

So, two questions:

1. Is this the probable cause for too much width, and in this circuit, is C606 the cap responsible for the picture's width?

2. This is a polypropylene capacitor. Those are expensive and hard to find. Can it be replaced with a regular polyester film cap?



Thanks a lot!

[R_J]

Re: Telefunken CH815 - Too much width

C606 is not for the width, it would effect the horz. frequency, post the complete schematic. or at least the rest of the horz. output section.
It is more likely C712 that could be open

[dieselriot]

Re: Telefunken CH815 - Too much width

Thanks for replying. I'm attaching the full schematics.

On a side note, I replaced all electrolytics when I first got this set trying to fix some weird picture problems.

They were high quality Siemens caps that probably still worked fine after all these years, but I didn't have the schematics back then so I was trying anything I could think of.

In the end I found out that someone had messed with R711, making the "U2" voltage lower than 32v. Probably a cheap attempt to fix the width problem I'm facing now, since doing that actually narrows down the picture, while creating various other artifacts.

[R_J]

Re: Telefunken CH815 - Too much width

When the power supply is adjusted to the correct -33 volts, check the two secondary voltage on the flyback, +18 volts (U1) and +158 volts (U3),
There is not too much that controls the width, C712 would be my first choice, D711 might cause the fault if it went open but not likely.
Check that T710 is the correct horz.output transistor and not a sub.
It can be hard to find the problem if someone else was into it and making modifications trying to repair the fault

C609 is a capacitor that goes bad on a lot of crt tv's so be sure to replace it. but C609 usually does not effect the width.

[dieselriot]

Re: Telefunken CH815 - Too much width

Can I damage the set if I replace C712 with a 57nf cap instead of 33nf? I've got a polyester film cap that was removed from the horz. circuit of a PC monitor. It seemed to serve the same purpose as C712 in this circuit.

I checked the transistors, all the big ones, including T710, are untouched. The smaller ones seem to have been replaced before (I can tell from the burnt flux and bad solder job), but I already tested all of them a while ago, checked if they were the proper ones and resoldered.

I'll try checking the voltages on the flyback again later, but I'm pretty sure I've done this before.

[R_J]

Re: Telefunken CH815 - Too much width

I believe C712 is there to determine the width, so without the correct value it could be wider or narrower than it should be but if the 33nf is open the 57nf should be ok to try