[Adam]

This set recently lost its horizontal sync. I've been messing with it since 3 this morning. I recapped the whole set and checked all the tubes when I first repaired it last summer.

Today, I swapped the horiz osc tube for a new one, no difference. I had already replaced R77 and 79, now I went and rechecked all the resisistors I thought could have anything to do with this (by pulling up one end first) and found R75 to be at 120k (instead of 100k) and replaced it, I replaced the 15M R76 even though it tested really close to what it should be. I also replaced R49 which tested a bit high. I've replaced a number of ceramic capacitiors that I didn't replace before: C54, 57, 55, 51 A and B, 50 A and B (with 68pf instead of 51 because that's all I had), 41, 29, and 25. All this work has improved my situation a bit from no sync to just a very unstable sync, but I really think whatever my original major problem is is still there.

Now all the voltage readings on the horiz osc tube 6GH8 are all good except for pin 1 and pin 2 which both read a bit on the low side. Also all the pins on the sync seperator tube 6BU8 read a bit lower than they should (but the tube itself tests good).

The power supply reads a strong 270v, so that isn't a problem.

Now when you look at the 3 waveforms i posted down below, W 12, 13, and 14 on the schematic (posted in that order from left to right), only W13 is weird. Now when I turn the AGC all the way up to where the picture is all white W13 becomes as it should be and all the voltages and everything look fine (except now the picture is all white).

I also looked at those 2 waveforms taken at pin 6 and 7 of the 6BU8 (w3 and 4 on the schematic, posted in that order on the 2nd line of pics) and they look like absolute gibberish, not even close to what they should be, while the one at pin 3 of the 6BU8 (w6 on the schematic, posted 3rd on the 2nd line) looks just fine.

Now as I mentioned a long time ago in this thread, I bypassed this bad coil (L7) with a wire. (I circled the coil in that 2nd section of schematic I posted.) Now the horiz sync has never been that great on this set, could that have anything to do with it? But it is still a lot worse now than it was when I first fixed it last summer so I don't know if that could be it.

Oh, and I also tried replacing that 2 part diode (M1) with another one I knew to be good from a junk chassis, and it made no difference, and after I removed the old one it tested good with the ohm meter.