I've been blessed!

[old_tv_nut]

Well, I tried the DC power supply, and the blue coil works - seems to have the same sensitivity as the red or green - so it's back to head scratching.
Quitting for tonight, but tomorrow I'll try measuring with the scope again.

[jeyurkon]

Originally Posted by old_tv_nut

Well, I tried the DC power supply, and the blue coil works - seems to have the same sensitivity as the red or green - so it's back to head scratching.
Quitting for tonight, but tomorrow I'll try measuring with the scope again.

If you have a shorted turn in the blue coil as you suspect, it will not affect the DC test if it's only one turn or so that's shorted. But, at higher frequencies, i.e. the dynamic convergence, it will null the field. If you have a ring tester I would try that.

John

[old_tv_nut]

Don't have a ring tester. Tried unclipping the blue and red coils and interchanging their posititon on the convergence yoke, but the result is very confusing when the red and green no longer converge.

I noticed that the blue H tilt circuit uses a different capacitor value than R and G (.47 vs .39) - now I'm thinking that the convergence coil inductance is part of the pulse shaping, and if the blue is 1/3 shorted, it may be impossible to get the right waveform. I tried running the blue H tilt end-to-end, and I can make the B H convergence worse on the right side, but there is no travel to make it worse on the left side. So, this control does not seem to be centered, which again could be due to the convergence coil itself being bad.

By the way, the blue core looks cracked, but I'm not sure that is making a difference, since the mounting clip holds it tightly together.

[old_tv_nut]

Originally Posted by Phil Nelson

Nice pic.


I use one of these to remove copy-protection frick-frack while watching DVDs and tapes.

http://checkhere22.com/stabilizer/

Phil

got mine today - works as claimed

[old_tv_nut]

Originally Posted by old_tv_nut

got mine today - works as claimed

on closer inspection, it seems to be reducing the burst and/or chroma level, and the CTC-5 doesn't exactly like it - will have to make some sweep measurements.

[old_tv_nut]

Through some serial kindness (Ed Milbourn had given a convergence assembly to Bob Galanter, who only needed the connector, and gave the rest to me), I've been able to fix the blue horz convergence.

Before doing anything else, I measured the convergence coil resistances. Turns out the blue coil is 2.4 ohms, just like mine, and the R and G are 3.0 ohms, just like mine. So, it seemed SAMS was wrong in listing all three as 3 ohms - probably as close as they could get at the time.

I went back to the set and:
1) pulled the convergence plug - blue H lines still drooping - so I guessed it's not due to >too much< blue H current. Then I put the current probe on the R, G, and B in turn and noted that all three had about the same H parabola current.
2) with the current probe on blue, started turning H tilt and H amp, noting as before that the tilt had a noticeable effect, but the amp had little or none. The H amp adjustment is a coil, and if you look way back in the thread you will find that I had broken the core and used a replacement from John Folsom. Well, the replacement has a much longer screw thread, so I decided I would just turn it as far as I could CCW and see what happened. Well, after a number of turns, the core started to really move out of the coil, and the current went way up - eventually I could get the blue lines to curve >up< on the ends. Readjusting the tilt (which was now wrong) and amplitude iteratively got the results you see. R and G current is about 0.5 A p-p, but blue needs to be about 1.1 A p-p. I was just too timid on adjusting that core.


All 0.2 A per div:

red


green


blue


result

[Pete Deksnis]

Originally Posted by old_tv_nut;result
[url

http://farm3.static.flickr.com/2626/4234229157_f3b5299406_o.jpg[/url]

Beautiful!

[Pete Deksnis]

Originally Posted by old_tv_nut

on closer inspection, it seems to be reducing the burst and/or chroma level, and the CTC-5 doesn't exactly like it - will have to make some sweep measurements.

I tested one using Cliff's sweep DVD. My feeling is the unit is useless even for semi-serious work. The chroma tapered off a little, but the luma looked like a ski slope.

Pete

[old_tv_nut]

Next big effort is a complete tuner/IF/chroma alignment; figuring out if more video drive can be obtained (video output tube? AGC?), finding out why the luminance frequency response seems too low, trying to reduce the chroma ringing, etc.

See some screen shots:
http://www.flickr.com/photos/4200284...7623116659120/

[zenithfan1]

A very good start to the new year, great work Wayne!

[John Folsom]

Way to go, Wayne! Boy, I wish MY screen shots looked as good as yours! Good luck with the alignment and final tweaking.

[Tomcomm]

Wayne….I blew-up your crosshatch and I’ve never seen a more proper convergence on any roundy screen shot! I haven’t seen a live roundy screen in the last 30 years except my 21CT55, but yours is better. Your color is great but lacks fine detail. I hope you can find the luminance BW problem in the RF and / or video portions of your CT5. Have you been using test DVDs like DVE that have video freq sweeps and resolution wedges? I suggest you install an external composite video injection circuit at the grid of the first video amp and get the best picture possible from your DVD player before you dive into the Tuner/IF portion. This worked for me on the CTC2B chassis, since the RF and video systems don’t cooperate in determining the overall video BW of the receiver. I’ve got a schematic for an ext input circuit if you’re interested……………Tom

[old_tv_nut]

The convergence wanders a bit over time, and I think some red misconvergence is visible in some of the Rose Parade shots - tweaking it could be a lifetime hobby.

I found that fine adjustments of the position of the convergence yoke help, as well as the controls themselves. The R,G, and B should be independent, but they may not be perfectly so. I moved the convergence yoke back and forth until I got the maximum effect, and also tried rotating it slightly left and right for the best overall result. I think the rotation helped get it aligned for minimum interaction between R, G, and B. Mis-rotating the blue lateral from its nominal position can also affect R and G.

By the way, my set has a blue lateral magnet like the CTC-7, not either the CTC-5 DC coil or permanent magnet. It looks oddly crooked with respect to the gun structure when mounted correctly.

[old_tv_nut]

Here a diagram and some photos of the neck components:

[old_tv_nut]

Well, I went poking about the video board to see if there was anything obviously wrong that might reduce the luminance frequency response. All the peaking coils measure the correct resistance. Shorting them or bypassing with a large cap generally makes things worse. The coil in series with the delay line is critical to matching the delay line impedance and preventing reflections that show up as a ghost image. Bypassing or shorting that one increases the high frequency response somewhat, but produces the reflections. Comparing to the CTC-7: the CTC-7 has some different RC values plus an added coil in the cathode circuit of the first video amp. I suspect this is added video peaking.

So, I think the video amp is performing pretty much as designed, which is to say, it could be much better if there was a way to flatten the response to 2.5 MHz or more.

By the way, the spare video output tubes I bought did not make a difference.

This morning, one of them decided to fail, although it had tested good - picture started getting brighter and brighter and control had less and less effect.

Only thing left to try is a full alignment, though I'm guessing it's not affecting the luminance response, since there seems to be plenty of chroma.