|
K, I did some poking around this afternoon on the drive issue. Some things went well, others puzzled me.
On the CTC-9 when adjusting the horizontal efficiency coil, the reading on my meter would drop as I turned the slug inward then start to climb again after a certain point. In other words, there was a midpoint which gave the lowest overall reading, and on either side of that cathode current would begin to rise.
On the 7, I can twist the slug all the way in till it bottoms out and current is still falling. This would seem to indicate to me that either the coil does not have enough range to get to a low (best) indication on the meter, or there is something else amiss in the damper circuit. I subbed the 6AU4GTA in from the 9's chassis, but the result was identical. Although current is now below the 'safe' level of 210ma outlined in the manual, I know it could be lower.
I did the flyback rining test with Mark's neat little Sencore unit, and everything looks good there. Drive waveform also looks good on the scope at the 6DQ5 grid, though I had to insert a 60k resistor in the drive circuit to offset a drifted 250k drive pot (it drifted low to 180k).
After all that, I did some looking in to why the colors were so wacky. Turns out the chroma phase transformer was a tweak or 2 away from where it should have been, so I nudged it to where it ought to be and now I have mostly correct colors. For some odd reason though, I can't get cyan to show up. I have decent magenta, red, green and blue, but no cyan no matter what I do. Also, the brightness control varies red and blue like it should, but when I turn it all the way down, I still get clear green bars...
It's not the drives either, it seems like the g-y amp is being driven when it ought not to be. Guess that'll be the next issue I tackle when I get back on it on Sunday.
__________________
Evolution...
|