CTC-15 line pairing

[DaveWM]

oh well at least the vert hold is working right now, I get sync lock right in the middle, can roll it both ways by going to the extremes. I still have the line pairing issue, moving the vert hold just moves the paired lines up and down but never fills in the middle.

Next up will be to check the B+ for horz noise, check the HOT screen decoupler cap a .1 right off the screen.

[DaveWM]

well while messing about with the tv I noticed the shunt tube seemed to be glowing hotter than normal (and the FLY was getting quite hot as well even though the HOT current seemed right a 185ma) I need to check the V drop across the shunt cathode resistor before doing anything else. The voltage regulation seems fine, able to dial in right at 23kv, but I did not check that shunt tube current so will do that before I do any more testing on the pairing issue. I did try several 6Gf7's much to my surprise the pic vert and lin remained pretty constant, as did the line pairing issue. It seemed like one tube did a little better but its not right. if I take it to the edge I can get rid of it, so I know there is room for improvement. My scope lead took a dump so I will have to fix that and go in search of horz rate noise.

[DaveWM]

checked the shunt tube current/v drop across the 1k cathode resistor. between .5 and 1.0 so no excess there. I did see a rather ghastly green which may be normal considering the voltages, but I replaced it with a C (had a B installed) tube. Don't see the green anymore, v drop about the same.

checked the voltages at the HOT screen was about 165v grid was -55 tube current was 185ma so all looks good there. I still don't under stand the high heat of the FLY but for now will just have to live with it (and not run set very long, I never leave any vintage set unattended).

I will get back to the pairing after Thanksgiving holidays.

[DaveWM]

while waiting to get a new scope prob (to check the PP on the output from the vert integrater) I decided to look at the input from the sync sep to the integrater. there is a 220k resistor from the output to ground, could not test it in circuit, so lifted a leg and get 1.2meg, hmmm I am hoping that this maybe allowing too high a PP input into the integrator, which would then be too high and output (including horz noise). A hint MAY have been the 8ka8 in place fo the 6ka8 tube used. Perhaps a tube jockey attempting to reduce the sync output but running a tube cold. keeping my fingers crossed. If this works it will be something I check on some of the other sets that seem to have problems with line pairing. I don't recall the plate voltage (the resistor acts like a voltage divider as its on the plate), I should have checked there but since its already out I will just replace and try again.

[DaveWM]

replacing that resistor brought the resistance check amount right in line with sams. Guess now is a good time to go thru the rest.

[DaveWM]

well not sure if there was any improvement, I still seem to get an excess amount of pairing but it does seem like I can dial in and out a little bit with the vert hold.

dont think I will be able to do much more till I get my scope leads fixed. I want to poke around some and look at the vert sync pulse and the b+ for any errant horz hash.

[DaveWM]

more pics

1st is the closeup of the vert sync pulse off the plate of the sync sep tube, this is using a composite video from the converter box injected at the grid of the video amp. this produces a very nice pic, no line pairing or as I have recently read "scan lines".

2nd is using the tuner and a RF signal from the same converter box, this results in "scan lines" that can not be dialed out with the vert hold.

3rd is the grid of the 1st video amp, I prob should have looked at the plate from that to see if the video amp acting up as well, that is the bottom trace, the top is the composite video from the converter box.