After the cans were in and I was sure the chassis wasn't going to go Cheech and Chong on me again (up in smoke), I put it back in to see where I was at. Big disappointment. In order to get any picture at all, fine tuning had to be at the extreme left. Things were jumbled up, sync sucked, and the colors were all wrong. Too many problems at once, so it had to be a common fault throwing the whole thing off. Out came the chassis again to have a look at the alignment with the 415, which I'm beginning to really like using.
First thing I noticed is that no matter what I did to try and tune in the signal, it was always skewed off to one side and frequency response was terrible. I tried what the manual suggested and attempted to tweak the osc in the tuner and also tried the slug for the channel I was on (4), but no joy at all. This issue was still global in nature because it happened on any channel, so the problem was in the tuner or IF. It ended up being the core for the fine tuning coil had been tampered with; a few little turns put all my channels back where they should be, so I moved on to IF response.
IF response actually wasn't too bad, but the tuner link was jacked. After sweep aligning those and making the peaks in the curve look right, I had a look at chroma response which only needed a slight tweak to the right side to get perfect. About 1.5 hours, and I was satisfied with the tuner/IF stuff. Chassis went back into the cabinet for a check. Another big disappointment: now I had nothing but a blank white screen...hmmm, had I completely gone wrong with the alignment?
Nope, this problem ended up being the audio tube which was removed for alignment because it was causing strange interference with the signals. It was the buzz going through the speaker wires that radiated into the IF strip when the cover was off that was the problem, so I'd taken it out. Because it's part of the power supply circuit, I suspected putting it back in would have an effect. Boy, was I right! The bottom half of the audio output tube feeds the plate circuit of the 1st video amp (it's a sort of voltage divider I think), so no wonder it wasn't getting a picture. With the audio output back in and the IF shield installed, this is what I got!
Huge improvement now, it's starting to look like a real color TV. All the picture noise from before was now gone, and the fine tuning works like a champ. Colors lock solid right away, and sync is rock stable in vert and horizontal. Things that still need to be done to get the picture perfect:
1. CRT hasn't been degaussed at all, which is the reason for the random impurities with the color bars.
2. convergence is slightly off, but not enough to make me want to mess with it at this point.
3. The color bars on the left are not correct, which likely means the CW driver transformer needs a touch or two. I will probably perform a full chroma alignment on it, to make double sure things are in order.
4. I still only have about 18kv on the CRT anode, which causes the picture to bloom pretty bad at high brightness. Everything in the horizontal section looks good for right now, so I'm suspecting the HV regulator is not at the correct set point. Since this set has fixed HV regulation, I will have to mod the grid circuit of the 6BK4 to add a pot so I can adjust HV into range. It's pretty simple, just copy and paste the fixed 1.5m resistor and 500k pot in from the CTC-7 schematic. It goes from the grid to ground, shunting the B+ boost away and changing the bias of the tube. Hopefully I can get it to conduct less, and HV will come up a bit. I will monitor shunt reg cathode current before attempting this mod, to confirm my suspicions.
5. Probably need to go through the CRT drives, to make sure grey scale tracking is spot on.
Hopefully after all that, I'll be able to post a proper set of Wingate color bars.
