7” electrostatic set deflection shortcomings

[timmy]

Specifically in the verticle and horizontal sections

[CJVx]

I’m still struggling with this problem. I agree that mica caps are no longer deemed as reliable. I have seen my share of failures on recent restorations so they have all been replaced in this set and any set going forward.

[timmy]

Is the high voltage up to where it should be?

[CJVx]

Originally Posted by timmy

Is the high voltage up to where it should be?

Yes, I’m able to measure about 4.9 KV Max, but at this point, the picture is the smallest and will not fill the mask. I can lower the HV down to about 4.3 KV and the picture is large enough, but I am losing brightness and sharpness, so unfortunately, that is not an option.

[CJVx]

So updates on some things done on the Tele tone set. I replaced most of the resistors in the HV divider network for the horizontal and vertical plates. The HV focus network resistors checked OK, plus I don’t have enough to replace those at this point.

I checked the measurements per the Sam’s measurements on the horizontal and vertical amplifier tubes and most were spot on, with some differences on the plate voltages as follows:

V15 12SN7 vertical deflection, pin two should be 290 V, and I’m measuring 270, pin five should be 190 V, I’m measuring 204. The cathode voltage was 11.5 versus 12 V as indicate in Sams.

[Yamamaya42]

It sounds like it's almost struggling to make the full 5k HV, and loading down the LV PS.

This may help.
https://www.ebay.com/itm/283515730784
I have one working fine in my Magnavox Brittany tv, It will boost HV a tad bit because it does not have the voltage drop of a normal glass high voltage rectifier, you also don't have the strain of having to light the heater, so more power goes to making HV.

Something to think about.
It's almost as if something is loading down B+ B++ B- as you turn up HV. :O

[CJVx]

Originally Posted by Yamamaya42

It sounds like it's almost struggling to make the full 5k HV, and loading down the LV PS.

This may help.
https://www.ebay.com/itm/283515730784
I have one working fine in my Magnavox Brittany tv, It will boost HV a tad bit because it does not have the voltage drop of a normal glass high voltage rectifier, you also don't have the strain of having to light the heater, so more power goes to making HV.

Something to think about.
It's almost as if something is loading down B+ B++ B- as you turn up HV. :O

Those SS rectifiers are nice, I have one in my CTC5. I don’t believe I have a HV issue in this set, although a bit low, it could be a product of my divider I use to measure it slightly pulling it down. But as the HV increases, the beam gets harder to deflect, hence the picture shrinkage

[timmy]

Are the b+ diodes up to the challenge or are you using the selenium rectifiers.

[Yamamaya42]

As far as I can see, looking at the schematic for my T-tone 149, the energy derived to deflect the beam is taken from the same 5k that is also applied to the anode via pin 9, so as the HV goes up, there should be more energy to defect the beam, via through the .005 caps and the 12SN7 amps and eventually to the -b rail.
Seems you should be able to coax more than 4.9 k out of it.

When I do get to mine, I will go with the SS option.