Digging into the CTC-9

[leadlike]

Wow! Lots of mods to do! I'm not sure if all of them were done or not, but one of my complaints about the picture was that the reds were really too strong, with pink highlights on more intense reds. I'll be out of town the rest of the weekend, and then another order from Mouser

Before I forget, I would like to replace the selenium triple rectifier with three diodes on the convergence board-are they of any special type?

[Phil Nelson]

Originally Posted by leadlike

replace the selenium triple rectifier with three diodes on the convergence board-are they of any special type?

When I replaced the rectifier on my CTC-11 board, I got two opinions.

One guy said he used "ordinary power supply diodes," which I took to mean 1N4007.

Another said those are too slow and sent me some "fast slew" diodes (his term) which I installed. Hard to read the type number when they are installed, but it may be 1937. At least, the last three digits are 937.

If you have a bunch of 1N4007 lying around, you could try those and see what happens. Pretty cheap experiment as long as you don't fry the board.

Phil Nelson

[jeyurkon]

Originally Posted by Phil Nelson

When I replaced the rectifier on my CTC-11 board, I got two opinions.

One guy said he used "ordinary power supply diodes," which I took to mean 1N4007.

Another said those are too slow and sent me some "fast slew" diodes (his term) which I installed. Hard to read the type number when they are installed, but it may be 1937. At least, the last three digits are 937.

If you have a bunch of 1N4007 lying around, you could try those and see what happens. Pretty cheap experiment as long as you don't fry the board.

Phil Nelson

Guess he meant "fast recovery." Any chance those are 1N4937's?

John

[Phil Nelson]

That might be the number. They're close to the board, but using a little dental mirror, the part I can read looks more like 4937 than 1937.

Phil

[leadlike]

I just did the mods tonight. The tv was changed-all three cathode leads were hooked up AHEAD of the 2700 ohm resistor. I suppose that would basically work, as all three cathodes were being driven with equal voltage. Regardless, I added the cap to the HV shunt regulator's filament string (since these tubes cost so darn much, I thought I best to treat is right), altered the RY amp (glad I ordered that extra 10pf cap), and moved the cathode leads to the point specified on the mods.

I installed the chassis, and I gotta say, doing the tracking is a LOT easier now-I'll get some pictures once I get ahold of our camera again.

My main issue is the convergence-I am able to easily line up the red and green guns, but the blue gun seems to be tracking too low. I still have to replace a cap on the convergence board as well as the diodes-not that I suspect that will be such an easy solution...

[Phil Nelson]

I hope your experience with the convergence board is easier than mine with a CTC-11. Replacing the selenium rectifier that had fallen into pieces made a difference. Shotgunning other board components, including some pots, did not lead to miracle improvements. Eventually, I decided I could get edge convergence purty good, but not perfect. I chose the set of compromises that I liked best, and called it done

Phil

[sampson159]

reading about this had me on pins and needles!i have done in excess of 50 cataract removals and never an issue.lucky me,no more.after reading this and dougs story,i think its time to stop.i have a couple nice roundie crt spares and will use them.i had good luck with spraying penetrating oil in the the edge of the safety glass and letting it run before i heat the tube face.never use high heat.it is time consuming but the end result........!i have pushed my luck one time too many.never again!