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  #46  
Old 01-02-2015, 02:19 PM
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My thinking exactly. I just figured that a pair of 2.2K resistors were a lot more commonplace which is why they used them.
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  #47  
Old 01-02-2015, 04:05 PM
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I highly recommend you get am ohm reading from the red lead of the vert out to ground WITH the convergence plugged in. should be around 8-10k
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  #48  
Old 01-02-2015, 05:46 PM
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Could you adjust the vertical linearity control so the picture just fills the mask? It looks like the linearity was adjusted to compensate for the lack of height.

Can you display a test pattern or crosshatch instead of program video?
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  #49  
Old 01-02-2015, 06:31 PM
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That's exactly it. I used the linearity control to get proper height....couldn't do it any other way.

The resistors will be in next week..... so I'll pick it up then and see where we are at. Keep the test ideas coming..... I think I may have nothing to do tomorrow
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  #50  
Old 01-07-2015, 07:24 AM
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Well, we're sure looking good!!!

The resistor replacement yielded a linear picture. Obviously the convergence is a mile off and the focus isn't what I'd call great. Can't seem to get any color out of the picture either. But hey, progress is progress!

Though the chassis has been recapped, the convergence board is still running the original caps....so that's next on the list before I try to adjust anything.
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  #51  
Old 01-07-2015, 07:41 AM
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That's some picture you got there......

.
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  #52  
Old 01-07-2015, 01:24 PM
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Nice Job Tim, looks like a great start of a purity-convergence set-up. Just make sure you de-gauss the whole cabinet.

Funny how that set looks "identical" to the one I got a few months back, just has a different chassis, 24MC32.

I plan to send you the vertical output transformer once I bake, re-test and re-varnish it.
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  #53  
Old 01-07-2015, 01:46 PM
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Quote:
Originally Posted by DavGoodlin View Post
Nice Job Tim, looks like a great start of a purity-convergence set-up. Just make sure you de-gauss the whole cabinet.
Would this set benefit (if it's not already there) an auto-degausser circuit? You could grab the coil of wire and its thermistor from most any BPC set and install it in a similar pattern in this set. Would being a delta gun vs in-line gun make any difference?
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  #54  
Old 01-07-2015, 07:04 PM
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Got new caps on the convergence board, but the convergence is still off, and I have no color.

I can adjust the red, blue, and green guns and get bright red, blue, and green screens, but no real color on shows. Color killer control does nothing, and the controls on the convergence board itself really don't do anything either.

Advice?

Here's a pic of where I'm at now, obviously I need to tone down the blue drive a bit. And my very skilled 11 year old trainee doing the convergence board caps. That kid is good
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  #55  
Old 01-07-2015, 07:57 PM
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It is possible the seleniums on the convergence board are bad usually after caps are changed and resistors checked those are next on my list of suspects.

You want to replace them with shottkey diodes. Silicon diodes like the 1n4007 likely will not switch fast enough at horizontal frequency.

EDIT: have you checked the color circuit tubes? On my zenith roundy the color did not work because the tubes were simply dead out of cathode emission.
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  #56  
Old 01-07-2015, 10:11 PM
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Ha! Great idea! So often we forget about tubes.....they were tested and good a while ago but it couldn't hurt to check them again.
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  #57  
Old 01-09-2015, 08:50 PM
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Quote:
Originally Posted by Electronic M View Post
It is possible the seleniums on the convergence board are bad usually after caps are changed and resistors checked those are next on my list of suspects.

You want to replace them with shottkey diodes. Silicon diodes like the 1n4007 likely will not switch fast enough at horizontal frequency.

EDIT: have you checked the color circuit tubes? On my zenith roundy the color did not work because the tubes were simply dead out of cathode emission.
Tubes are good, and there are no seleniums on the convergence board. What's next I can check?
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  #58  
Old 01-10-2015, 01:06 AM
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Quote:
Originally Posted by Kamakiri View Post
Tubes are good, and there are no seleniums on the convergence board. What's next I can check?
Does that mean you or someone else recently replaced the convergence diodes? The convergence diodes in all TVs into the 70's were selenium types, though after a while they packaged them to look nothing like the seleniums found in 40's and 50's power supplies that we are used to seeing. The newer packaging did not make them more reliable, and I have had sets as new as 1972 develop convergence problems from diode failure.

As for the color check to see it the 3.58Mhz reference oscillator is running. If so try adjusting the color killer and fine tuning* to see if you can get some color. Also many Zenith roundys had a switch on the color level control to turn off the color if that switch is bad it would explain no color reaching the screen. If all that is good and still no color then grab a scope and start following the color signal from the place the color splits off of the video to the CRT.
*I usually tune the same program on another set and tweak it so that saturated colors show a slight checker board on the monochrome limited set.

When one runs out of possible low hanging fruit trouble shooting, the next logical thing to do is usually signal tracing.
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  #59  
Old 01-10-2015, 08:08 AM
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I was wrong! You're right, I was looking for a big sucker! There it is, a little tiny one

Five connections on this little sucker too....two of which go to ground. I assume three diodes are needed, and do these little seleniums, when replaced with diodes, require a change in the resistor values? Happen to have a link to which diodes I should use?
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  #60  
Old 01-10-2015, 02:01 PM
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I'm fairly sure you don't need resistors in this application.

I don't know what I used last time, but I replaced a part that the sam's says was equivalent to ECG 116, the data sheet of which can be found at the below link.
http://www.datasheetarchive.com/dlma...A879000-31.pdf
A few shottkey diodes that meet or exceed those specks should do the trick.
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