Hi Wayne,
I had similar problems with my CTC5. I initially found the CTC5 tough and had difficulty getting good convergence consistent with good purity. Ultimately through perseverence I got excellent convergence. Here is some of the things I found.
It is very important to first fully retract the edge purity permanent magnets. With the mask off, the magnet screws are adjusted clockwise to submerge the magnets into the cups. Then thoroughly degauss the tube. Next you need to aim getting good purity in the center of the tube and ignore poor purity within a couple of inches of the edge of the tube. The edge magnets will fix the edge purity.
The convergence cloverleaf should be located as depicted in the manual. Due to the symmetry of the convergence cloverleaf coils, after when disassembling the coils to clean them, I inadvertently reassembled one coil reversed. This complicated my first attempts to get convergence.
To help diagnose the convergence problems, I reasoned I should aim for good static convergence and address dynamic convergence later. I reckoned that the dynamic convergence circuitry is mainly to makeup for manufacturing tolerances and fair convergence should be achieveable with minimal dc or dynamic convergence control. Once I was able to establish static convergence with the three DC controls (I found one was open), the application of dynamic convergence did improve the edge convergence (once I rotated the coil on the cloverleaf.)
Of course the CTC5 convergence circuitry is early which means there is more interaction between the static and dynamic adjustments on the CTC5. The CTC5 I found tougher to converge than later sets but once you get the feel of the adjustment and pay heed to the RCA notes, you should be able bring the convergence in or at least identify better where the problem is.
Good luck.
Terry
Quote:
Originally Posted by old_tv_nut
When my CTC-5 had a glass 21FJP22 subbed in, I was able to get excellent convergence. When I finally got a 21AX to put in it, I found the dynamic convergence to be much poorer. I recently went back to trying to improve it, and here's what I'm finding:
I have to move the yoke almost all the way forward to get full screen purity. Maybe this is normal, but with the yoke in this position, it appears there is not enough dynamic convergence action to converge red and green at the edges, either vertically or horizontally. Pulling the yoke backwards improves the convergence, but of course then purity occurs only in the center of the screen. I have experimented with the position of the convergence coils, since you cannot see the pole pieces beneath the dag in the neck, but at the point of strongest action there is still not enough.
The DC adjustments have enough range, and generally want to be near center range, which is as it should be.
I am beginning to wonder if the gun is in the right position, since this is a rebuilt tube.
I also need to recheck whether the resistance values of the DC convergence controls that I hacked in (because the original tapped controls were burned) could affect the dynamic current. Not sure yet if they are in series with the dynamic voltages or not. (Apparently burning was a common problem, because the pulled parts some kind people here sent me were burned too, so I had to give up on originals.)
Looking at the top and bottom convergence, I wondered if a weak vertical output could produce low convergence amplitude, but both V and H are bad, so I'm discounting that.
One thing I did learn: the purity magnets have short springs on the base, which apparently act as small pole pieces as well as mechanical mounts, and it helps to keep them properly oriented while the magnetic rings are rotated. One of the rings binds to the base, and if you're not careful, they rotate together, making it more difficult to get uniform purity.
Any thoughts of what I may be missing here would be appreciated!
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