CTC-9 focus resistors

[DaveWM]

there are 3 22meg in series with the focus lead.

all three are 30meg, just wondering if since they are all 3 more than 20% high if that would warrent replacement. I do seem to be a the extreme end of the focus range.

[DaveWM]

bridging a 22meg across one of the resistors brought it down to 12meg so now I am at 30+12+29=71 meg total, closer to the 66meg it should be, will see if that improves the adj range any.

next problem, as I was going thru the set I found a S clipped in B+ fuse. Had not checked it before but figured it would be a good idea.

Its a littlefuse brand 250v but no amp rating. It did have a C5 stamped on the end of the fuse (not the side) I am guessing a 5 amp fuse as the fuse wire looks to be pretty hefty. So will hold off any more testing until I get the right fuse in there. argh...

[mstaton]

DO NOT use a 5 amp fuse!!! It should be a 3/4 amp fuse. Don't worry about the voltage rating on the fuse so much just the amp rating. I would suggest changing that ASAP. Having a fuse clipped to the original is normal. originals were soldered in and was easier to clip one on when the original went.

[compucat]

I replaced the focus resistors in my Zenith roundie because the control was at one end of the range and it made no difference whatsoever. I think it must have been at one end of the focus control range from the factory.

[DaveWM]

oh for sure I am not going to use it, I have been scouring my stash for a 3/4 but to no avail, will hit ratshack tomorrow, pretty much the only thing they are good for. I should have checked it before trying out the set, its been working fine, but I realized that I had not checked that one, and knowing how peeps will just stick any old fuse that fits made be look at it.

[DaveWM]

being as there is practically no load on the focus grid, I am not suprized about the zenith. This is a little different as the resistors are not in series with the focus pin, but are connected from the focus tube cathode to the ground. Anyway I will see if it makes any difference after I get the correct fuse. I will also do a quick B+ current check just to see if in spec. Will be easy to do since the fuse clips are on the top of the chassis along with the PS diodes. Does not pay to stick you hand back around that.... there is even a tube shield about 1/4" away from the 385v B+.

[DaveWM]

since I am talking about the CTC-9 a little background. after going over it and doing a slow power up, it came up with HV and signal but no horz lock, could not adj enough to flop the horz.

I completely recapped the sweep boards, replacing most of the dipped caps. I left a singe .01 and .22 that tested perfect.

there was a bumble bee on the IF board that was part of the sync sep, replace that one of course.

for good measure I replace the 2kv ceramic tube cap on the audio board, and the coupling caps for the audio that are mounted under the chassis.

there were a few dipped caps around the HV section, the AGC take off cap and the eff coil cap. the eff coil cap leaked (as did almost all the 200v dipped caps).

replace a coupling cap on the video out tube and a few others, bypass caps, on the video board.

prob in total 80% of all the film caps were replaced with about 1/2 of those showing leaky and the rest showing weak on the cap tester.

there were two or 3 single electrolyiics vert, video and AGC I think. the 3 cans all tested like new so I left them alone.

when I was all done it worked but I had what looked like a hum bar and some horz shakes. I assumed it was HK or one of the cans had failed after the prelim test.

the scope showed a very clean B+ so I moved on short testing on the tube tester, one IF had a very minor short so it got replaced.

Tried again an no real change...

finally I backed off the noise and then the AGC controls. the pic started to wash out and then went completely out of horz sync. I touched up the horz hold and the pic synced right up and the shakes and hum bar was gone! I turned up the agc until the pic got overly dark and lost sync, backed off about 1/8 turn and all was good. adj the noise inverter CW until lost sync, then backed that back 1/8 turn CCW.

After that the shakes were gone good color lock (oh yea that was iffy too before) and the hum bar was gone.

the hum bar was really what threw me off track in the 1st place, not sure what that was all about.

the set has really good color and excellent sound, not a hint of sync buzz or any other nastiness. oh yea the tuner was noisy so that got taken apart, cleaned, lubed. All good now.

[DaveWM]

got the CTC-9 fuse in, looking good. Just need to do a degauss to see if the purity cleans up a bit. Not sure if the focus range changed much, seem maybe a tad more centered but not sure about that. Just need to button it all back up and then will get started on the finish. The wood is in good shape as is the back, pretty sure it will just need some howards restore a finish. I prob should pull the safety glass and clean inside, it been a while since I did that, will have to refigure out the retaining clips.

[DaveWM]

still a little bit of snow, and the yoke is just a bit tilted, but otherwise pretty good. will get some superb owl shots later to get some better material to analyze the color with.