CTC-7 metal table top

[DaveWM]

new xtal made a little difference, I think its more a poor horz sync than anything else. both the vert and horz are pretty weak locks, so I think I will need to look into the sync sep circuits.

anyone have the setup procedure for the sine wave coil on a CTC-7?

[DaveWM]

never mind, found it, short the sine wave coil, gound pin 2 of the horz osc tube, adj the horz hold for somewhat sync pic, remove coil ground, adj sine wave coil to bring back in sync, jump the coil again to check.

did all that but I still have maybe 1/4 turn at most to flop the osc (using the hold adj), and since it does indeed flop my guess is its a weak sync pulse. I subbed in new sync tubes (sep and amp) but no real change, still very narrow sync range. I am going to have to scope the output from the separator and see whats coming out. My guess is some voltage issue from a drifted resistor. will check the video out as well, maybe something getting clipped before in the IF?

[DaveWM]

may have a break thru on the horz instability. while wiggling tubes (1st thing to do) I notice when I pushed the horz osc way over it went out of sync, by adj the hold while holding it over I was able to sync it back AND it had a lot more range once I got there. I will have to go over all the solder joints and tube pin connections, but at least I have something to shoot for now.

[DaveWM]

you guys that have predictas know the drill, broken tube socket right where there is a bridge between the pin socket and the pin insert to the pcb.

checking for continuity with the tube out (touch the probe to where the pin goes in and then the other side to the pcb shows good continuity. insert a tube socket extender with test points and try it again, now no continuity, moral of the story is if you see a predicta like tube socket, and something is not right, better check it with a tube socket extender to simulate an actual tube pin inserted. I have the correct tube socket so will replace it soon.

[DaveWM]

that was it. I put a new socket in (better q than the old predicta style). Reset the sine wave coil, Now has very good sync. I guess there was just a hint of sync getting thru the tiny gap (like a small cap) that made it work at all before.

The contrast is not that great, and of course the focus is a bit weak (but that may just be the test jig, its got a very dirty safety glass AND a bad cat, so not sure about a focus issue. the contrast is ok, I tried jumping the cathode bypass cap just in case it was weak, not much improvement. there is some video smear but again its hard to say with the lousy test jig. the color demodulation is good, and the tint range is perfect. I will need I will check out all the peaking coils later. I need to see if the filter caps are getting warm. I will prob go ahead and re stuff them since its coming along pretty well. I don't know the condition of the convergence assy, I just have the plug in the socket but not on the CRT.

Its full of those brown drops so I am sure they need to be replaced as well. I wonder if leaky brown drops on that board will be putting an undue load on the fly?

[DaveWM]

finally some working pics...

had to load again, goofed it as I ran out of space.
anyway the old angle of the screen shot is due to my test jig location, not the best, so I had to rig up a mirror just to see it.

there are a few brown drops left in, they checked fine, and I was out of new. I will have to order some more from mouser.

the filter caps seem to be doing just fine, not getting hot, but will keep any eye on them until I get around (if) to restuffing them.

[DaveWM]

pics

[DaveWM]

some pic of the boards

[IsthmusTV]

Congrats, Dave it's really coming along. The tube sockets really are crappy. I'm hesitant to replace the video output socket since the board is probably quite brittle from years of heat. Since it's working OK now, I'm going to leave well enough alone.

As I mentioned before, I haven't replaced the maroon drops on the convergence board. It never occurred to me that they could be increasing the load on the fly. I'll get them in the next round

I'm surprised to see the cat on your CRT. You must have a sub and not a CYP (maybe you mentioned that and I missed it).

-Clark

[DaveWM]

what you see is a test jig, the set had a dead CYP (red filament out) but I have a 21FBP to replace it with.

I will do a quick test on the effect of the board soon. Right now I am running it with a jig plug in the convergence socket (no load, just a 150 resistor), I also have the correct convergence board, its just not installed anywhere.

So the plan is to leave the digital meter hooked up, and do a test run with the board plugged in and then a quick comparison with just the 150 ohm jig plug. should be interesting. IF there is a difference (which I presume there must be) then of course the next logical thing to do would be to recap the convergence board (assuming the caps are all bad which is likely), and do another run.

I have other roundie convergence boards that are newer and have better caps. I assume they are wired the same (at least the ones with the octal plugs). would be nice to just try one and see as well (effect on current).

[DaveWM]

did a quick test, maybe 2ma drop but that could be anything. Of course I don't even know if the convergence board is functional so just plugging it in really proves nothing at this point.

the horz osc has an annoying problem with not alway starting, I can see the current spiking, a quick fiddle with the horz hold coil and it starts right up. I hope its just a tube issue. I could not see any loose wires on the hold control.

I will go back and reflow everything on the horz board if the new tube does not do the trick. It seems like it would have to osc, unless something is biasing it off on startup (gassy/weak).

[DaveWM]

another tip, if the horz hold is a bit touchy (it was much better after the tube fix, about 3/4 turn range vs 1/8 range, it was still not right.

I checked the resistor across the horz hold coil, a 68k, I assume it damps out the coil, making it less peaky, so had to remove it from the circuit to check, sure enough 381k, so that one got replaced. While I was there I checked a 270k power resistor, it was about 330k, but it was a 5% so I changed it as well. two changes were noted:

MUCH easier to set hold you can turn it several times and still stay locked in.

Drive bar was gone even a the lowest drive setting. (before a drive bar was present but could be dialed out with the drive control pot). HOtube current is up just a tad to about 175ma with drive set to max.

for fun I am going to replace that drifted power resistor and see I can get the drive bar back.

I am pretty sure the 68k damping resistor will account for the better hold control, but maybe it also altered the drive wave form (and subsequent need to adjust out the drive bar).

[DaveWM]

I little more work done lately. I removed the tuner to clean it, as I was getting some problems that seemed to be due to the tuner.

1st order of bus was to get the tubes out and make sure the pins were clean, both were stuck, one really badly stuck, but I got them out and cleaned up the socket and pins.

2nd I pulled the cover and cleaned up the wafers, I have seen worse but it still had some dirt on there. I use a contact cleaner and q tips, don't like hosing it with spray, and risking getting spray where it does not belong.

3rd dunked the VERY rusty cover into some muriatic acid. in just a few min all the rust was gone. neutralized in some base water (baking soda) rinsed, dried, oiled.

Replaced the AGC cap that was on the tuner, and then hooked it all back up, no more touchiness. I should have installed some quick disconnects, but no big deal.

I think its pretty much done so I think I will take it off the bench and clean up the mess so I can start thinking about the cabinet.

[DaveWM]

something of note, while looking for any reason for "soft" pic, I remembered some discussion about intentionally skewing the IF curve upward on the high side to improve video response (think it was a CTC-5 iirc). Just for the heck off it I diddled the 47.25 trap (I know I know should not diddle the IF unless prepared to do a full on IF alignment). anyway a very small adj while on some still frame text allowed me to remove a LOT of smear. I plan to do a full alignment at some time in the future, but just wanted to make note of it. Prob a 1/5 turn at most of that trap.

I may try swapping in some new IF tubes as well just to see the effect.

[DaveWM]

still coming along, had a convergence issue, made a video of the fix

http://www.youtube.com/watch?v=2wYn3xLrZj0