Convergence Woes - Videokarma.org TV - Video

veg-o-matic · #1 09-22-2005, 09:17 PM

Well, I got the DVD of convergence patterns from ETF and started going about converging my Slyvania. Problem is, I think I made it worse.

Followed the directions in the SAMs. A couple of the knobs on the convergence board didn't seem to do anything at all. I located the pincushion correction...thingie...and that didn't seem to make any difference either.

Convergence is good in the center but toward the edges it's just terrible. Am I doing something wrong? Well, duh, of course I am!

Here are some pics of the "progress". The "before" pic is in the thread "Got The Sylvania. The rest are after I started messing with it. There's a closeup of the corner so you'll see what I mean.

Thanks for any help!

veg

Chad Hauris · #2 09-22-2005, 10:31 PM

Each of the controls on the convergence board should have some effect on the picture. If turning a control doesn't do anything there may be an open connection in the pot.

Looks like the blue is lined up good but the red/green horizontal lines controls on the left and right sides are what needs adjusting the most.

old_tv_nut · #3 09-23-2005, 10:16 AM

It's hard to tell from an off-center photo which lines are really straight - since the red and green fall on top of each other at left and right, I'd be tempted to suspect one of the blue controls is open that would get blue to be on top of red and green - but what do I know? Happy hunting!

outlawmws · #4 09-23-2005, 01:53 PM

Hey, is there a convergence jpg that could be used on a PC? I was thinking you could make it the desktop pic and go to it...

Dumb Idea?

old_tv_nut · #5 09-23-2005, 02:59 PM

If your PC has an NTSC video baseband output, you can use that directly on a set with video in, or by going into a VCR and using its channel 3 output. There are CDs and DVDs of test patterns, but for convergence you can just use the computer Paint program and draw a black background with some white lines.

bgadow · #6 09-23-2005, 10:30 PM

Maybe a dumb question, but I've done it myself: is the covergence board plugged in? I think it would be further out if not, but...

veg-o-matic · #7 09-24-2005, 09:14 PM

Yep, the board is plugged in. As I say, only some of the knobs don't seem to do anything; others work just fine. Can I get replacements?

I did the static convergence before I started messing around on the board.

veg

#8 09-24-2005, 09:58 PM

Most vintage color tv's have either a triple or quad
section selenium diode pack installed on the
convergence board for peak detection and waveshaping.
I think the problem you are seeing with the blue
lines sagging at both sides is caused by this diode
either being open or shorted or leaky.I can't
remember which failure mode it is but it's one
of them.These diodes develop the same problems
that the horiz.afc diode unit does.I think you
could use regular 1N4148 or 1N4007 silicon
diodes in place of the multisection selenium
to see if it fixes the problem.Otherwise you
could have an open control which has been
mentioned in the previous posts.Those controls
are wirewound and are relatively fragile especially
if they have not been operated in decades.
Regards,
Swanson

outlawmws · #9 09-24-2005, 10:15 PM

Well I think I found the issue with My NEC monitor, I found a 2 X 2 board on the back of the tube yoke area with five 1 turn pots. Adjustments don't do much, but if I push on one of the pots, convergence is perfect. I'm betting its a cracked solder joint...

Unfortunatly there are 6 wraped and soldered wires that make it imposible to lean up and resolder. The wires go into the tube yoke area. I'll see about desoldering them tomorrow.

Anything I shold be discharging in the area before going in? I know there has to be some HV in there some where waiting to bite...

kc8adu · #10 09-25-2005, 08:42 AM

Quote:

Originally Posted by outlawmws

Well I think I found the issue with My NEC monitor, I found a 2 X 2 board on the back of the tube yoke area with five 1 turn pots. Adjustments don't do much, but if I push on one of the pots, convergence is perfect. I'm betting its a cracked solder joint...

Unfortunatly there are 6 wraped and soldered wires that make it imposible to lean up and resolder. The wires go into the tube yoke area. I'll see about desoldering them tomorrow.

Anything I shold be discharging in the area before going in? I know there has to be some HV in there some where waiting to bite...

i heat the pins from the top and feed solder to the bottom of the joint.
common problem.
the bleeder in the fly will likely discharge the hv.

kc8adu · #11 09-25-2005, 08:45 AM

Quote:

Originally Posted by veg-o-matic

Yep, the board is plugged in. As I say, only some of the knobs don't seem to do anything; others work just fine. Can I get replacements?

I did the static convergence before I started messing around on the board.

veg

you most likely have some bad pots,bad selenium rectfier,or both.

outlawmws · #12 09-25-2005, 10:58 AM

Quote:

Originally Posted by kc8adu

i heat the pins from the top and feed solder to the bottom of the joint.
common problem.
the bleeder in the fly will likely discharge the hv.

Unfortunatly, no access to pins from the top.

These pots are square pots with pins out the bottom. One turn of adjustment would be being generous...

andy · #13 09-25-2005, 12:24 PM

You can always cut and splice the wires if you have to. You only need to cut enough of them to get to the bottom of the bord.

#14 09-25-2005, 12:27 PM

The other problem old color tv's had with convergence circuitry
was lots of interaction between the other pots and coils.If you
have not already tried this,you should unplug the convergence assy.
(some tv's like rca's need to have a jumper installed to ground
the cathode of the vert. output tube for the set to work without
convergence board)So check the schematic first to see what has to be
done.With the dynamic convergence removed you can now set
the static convergence without having interference from the
dynamic circuitry.you can then set all the controls and slugs
to their mid position and reconnect the convergence board.
Make sure to turn the power off before reconnecting.You may
not even need to disconnect the board,just setting everything
to midrange and then starting over may solve the problem.
Maybe this will solve your problem.You may get some needed
range on the controls that had no effect previously.I would try
that first and then check the resistance on the pots and coils.
If everything checks ok and you still have the problem,I would
look at subbing some new diodes in place of the selenium to see
if that fixes it.
Regards,
Swanson

veg-o-matic · #15 09-28-2005, 08:23 AM

Well, I tried it again the other night. Set all the convergence board controls to mid-position and then started with the static convergence.

Here's an odd thing I noticed when doing the static: aren't all three colored dots supposed to be the same size? I'd swear at least one of them (red, I think) was bigger than the others. Maybe two were big and one small (if it happened more than 5 minutes ago, it's gone forever...)

Anyhoo, the center looks pretty good but the edges and corners still suck. Actually, the picture might be acceptable if the set were a roundie

I tried cleaning the convergence--coils?--and some of them still didn't work. I seem to be having most trouble with the horizontal yelow and green. Can I get replacement coils (or whatever) for the convergence board? Or maybe replace the whole dang thing?

Should I be concerned about my dot size?

veg