7” electrostatic set deflection shortcomings

[CJVx]

Has anyone else experienced short vertical height, only to fold over and crowd past a certain level, and not enough horizontal width, again with crowding past a certain level? Currently working on a Halicrafters and a Tele-Tone. And they both exhibit the same symptoms. The only 7 inch set that seemed to have enough to fill the screen was a Motorola VT71 that I worked on.

Anyway, I have gone through both sets, caps replaced, verified and replaced some tubes, verified filament voltage is correct in the stings etc. Checked all and replaced most resistors in the vertical and horizontal circuits with some improvement, but still not able to stretch the picture fully across the screen. If I lower the HV, this will enable me to accomplish that but now I’m only down to about 3kv and picture quality suffers.

On a variac, the picture doesn’t actually start to shrink until I lower the voltage below 90, and I don’t get any extra picture expansion if I temporarily crank it to 130 V. I do gain some brightness though.

[Yamamaya42]

Bandersen has many videos on u-tube about e-sets, I have little exp in the subject, having yet to finish the T-TONE 149 I got this year, working mostly on tape decks.

The vertical section will always be more fussy when it comes to parts out of tolerance, so it's always good to check it end to end with a very discerning eye, and if any doubt, put in new known good parts, and especially if 2 resistors of same value are linked, like are on the control plates, sample a few, like 10 and pick the closest match, it will help with linearity.
And do watch his videos, they are very helpful.
bandersentv - YouTube

[mrjukebox160]

What did you replace the hi voltage caps with? Disc caps will cause this problem.

[CJVx]

Originally Posted by mrjukebox160

What did you replace the hi voltage caps with? Disc caps will cause this problem.

Hi, I used Wima 6kV film caps on both sets

[mrjukebox160]

I never tried those. I tried Russen disk caps and they didn't work correctly. These worked but are not cheap: https://www.justradios.com/ASCcapacitors.html

[bandersen]

Wima caps should be fine. I've used them in several sets.
Did you replace all the resistors in the HV bleeder network down to the vertical deflection plates?

[Yamamaya42]

Originally Posted by mrjukebox160

I never tried those. I tried Russen disk caps and they didn't work correctly. These worked but are not cheap: https://www.justradios.com/ASCcapacitors.html

that's what I got for mine, the co$t'y ones from Just Radios, I just need to finish the bloody thing, instead I have just focused on 4 tube based tape decks this year. I now have 9 Reel too reel decks, most of which are tube driven, Is that too many? :O

[timmy]

Check ohms on the verticle pots and related resistors. Wouldn’t hurt to confirm b+ voltage.

[CJVx]

Originally Posted by bandersen

Wima caps should be fine. I've used them in several sets.
Did you replace all the resistors in the HV bleeder network down to the vertical deflection plates?

I didn’t replace them but they do measure within their tolerance. There has been a ton of out of tolerance resistors on this set but everything I have found has been replaced. Every resistor on the vertical and horizontal amps have been replaced, and most others on the oscillators.

[CJVx]

Originally Posted by timmy

Check ohms on the verticle pots and related resistors. Wouldn’t hurt to confirm b+ voltage.

I did replace just about all those resistors on that deflection circuits. On the tele-tone tv, B+, B++ and B- all measured within 5% of their Rider manual specs. I was kind of surprised by this, but a good surprise. I still have to verify on the Hallicrafters.

On both sets, the deflection amplifiers just seem to be running out of steam. They will amplify to a certain point until the image bunches and folds over a bit. At this point on both sets, I could get the image just to barely fill the masks, but it would be nice to figure out how to get some headroom

[Yamamaya42]

All new or known good 12SN7s I assume? :O

[CJVx]

Originally Posted by Yamamaya42

All new or known good 12SN7s I assume? :O

Indeed, subbed NOS in the questionable areas.