[dobulee]

Thanks again to everybody in the forum for helping me get interested in the 6T75 again. This KCS47T chassis has no fewer than 3 alternate schematics floating around, and this set uses the 'latest' RCA build with the improved synch separator and 6SN7 as the vertical oscillator.

I have a couple of issues that I'm hoping some folks have come across and can comment on.

Question 1)In the previous post, I showed some horizontal linearity improvement by adjusting the horizontal drive trimmer. I'd like to also try adjusting the horizontal linearity slug -- but the slug is 100% stuck. I've shown 2 pictures of the linearity coil in the pictures. If I hold the coil in one hand and try to turn the adjusting screw, it won't budge. Has anybody encountered this? Would applying some heat to the coil help? some Tuner cleaner to free things up inside the coil? What works in this case.

Also, how available is the width coil as a replacement part. (sorry I don't have the sams in front of me to get the PN -- i'll post it later!) Is it unobtainable? If it isn't out there anywhere, I'd rather live with it AS IS rather than risk breaking the coil.

Question 2) about Horizontal Synch. The TV's horizontal synch is rock solid. It has the ultracommon synchroguide horizontal AFC circuit. I've adjusted the bottom slug for equal peaks as shown in all the guides. However, sams has an additional adjustment which asks pins C and D of the horizontal oscillator transformer to be shorted prior to adjustment of the top frequency slug. When I short pins C and D, the oscillator stops running. Because of this, I've just made the frequency adjustment without shorting the pins. Has anybody encountered this? I dare not leave it on in that condition since it removes the drive from the HOT. It doesn't seem like a problem, since the lock is good, and it holds horizontal lock even at the extreme CCW rotation, as SAMS says it should. Should I just leave well enough alone?

Question 3) on Vertical Linearity. As shown in the previous pics, the screen is stretched at the top 1/4 or 1/5. After some playing around with the Vert height and linearity pots, It actually looks like the linearity is improved drastically with the linearity pot more centered. However, with the linearity pot centered, no amount of adjustment on height gets the screen to fill vertically (maybe 2/3 at best). The only way I can fill the screen is to stretch it out with the linearity pot. So --I've attached the circuit. It's ultra common, and is the same as the admiral TV currently being discussed, save a few tweaks in values. Honestly, there isn't much else to adjust in that circuit, its just the 6SN7, the height pot and and series resistor R150 (270k). Cap C142 has been replaced. Is this a common experience? Other than checking for a weak 6SN7 (or 6K6 sweep output) and drift on R150, where should I poke around?

Any comments appreciated as always. I have ordered an HDMI to composite converter so that I can use my PC to output some better test patterns.

Schematics and images attached.