Pilot tv crt

[Kamakiri]

This is the diode:

https://www.arrow.com/en/products/p6...ponents#page-1

[timmy]

Ok so I subbed the last 3 caps thinking they were bad but not luck the vert size is maxed and the bottom of the pic is up to far and won't come down to fill the screen. Everything I check from caps to resistors test perfect. Is it at all possible that if alignment was out would it raise the raster from the bottom up a bit like I have going on here?

[dtvmcdonald]

We need more info on the vertical problem.

There are two different vertical schematics. One in Riders, one in Sams.

Which do you have?

What value HV caps are you using to connect to the deflection plates?

The Sam's circuit is better, and I recommend increasing the capacitance
from .005 uF to 0.02 uF. 3kV ceramic caps in parallel are OK for this,
though the ASC film caps are "officially" better. My set uses ceramics and
has great linearity.

[timmy]

I have the asc caps ,that it shows in the SAMs but what was in there were single ceramic .004 discs so I put the asc caps .005 6kv. I already tried paralleling these caps and didn't work.

[timmy]

Ok here is what it looks like and had the same problem with Motorola sets but caps fixed the problem but this one, I'm lost.

[bandersen]

I'd check all the large value megaohm valued resistors and the centering control in the vertical deflection circuit. They are used to set a HV DC bias on the deflection plates. It's possible even if one tests good with the low voltage applied by an ohmmmter it could behave differently when HV is applied in the TV.

[timmy]

Ok there is 4.7 meg I think 2.2 meg all these Meg ohm resistors are new and tested perfect so I'll lift a leg off the verticle size control and test that, I think I already did but that's what I'll do. There is no vert centering control just vert size. I guess even new resistors can behave different with hv present, so I may have to change them to rule them out, thanks

[bandersen]

Yes, there is a vertical centering control. It's last on the right on the back. It's R9 - a 2M pot in Sams.

[timmy]

Yes your right I did know there was a vert centering pot my mistake I was thinking something else. Ruled out both size and center pots with others now I'm checking those hi Meg resistors.

[timmy]

Well I subbed the hi Meg ohm resistors around the vert center, size, and tubes. Obviously I am missing something here but wow I went over and subbed everything. I cannot imagine what I'm still missing.

[bandersen]

Could be a bad connection to one of the CRT vertcle deflection plates. If only one plate is being driven, the image will be off center just like you're seeing

[timmy]

Did you see the bottom of the screen how much is missing. V14 SAMs shows 225 Vdc but all I'm getting is 115 Vdc on pin 5 measured from pin 5 of v19 so I did that right could this explain not enough voltage. All other voltages are within where they should be. The neg tube tests good and so does the positive tube but I did read that someone put diodes across I think it was 3-4 and 5-6 on the positive tube because of lows voltage.

[bandersen]

The plate voltage for V14 comes from the HV power supply divided down by R74 through R78. Could be you have low HV or some of those resistors are off or the 12SN7 is biased wrong and drawing too much current.

[timmy]

I don't have an affective way to check hv on this set but I have an analog meter that goes to 1 kv and when I touch to see what it is it shows 1 kv but then the screen blanks out until I remove the meter probe. I check right off the 1b3 to see the hv. The 12sn7 you refer to is the vert a Amp as being possibly biased wrong? I did the resistance test from the SAMs chart and all were perfect except pin 4-8 of v20 positive rec tube it starts running into the Meg ohm area when it states 120k.

[timmy]

Is there a specific cap in the verticle responsible for timing because there are no Micas like the Motorola tabletop sets. There are 1 .02 and 2 .05 caps at both vert tubes so I'm assuming it's one of the three.