4906 loss of vertical size after tube swap

creepykenny

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so, i had a nice looking tube lying around & decided that i should swap it into a good (i think) 4906 chassis that i had lying about, there were no identifying numbers on the donor tube, but it came out of a 4600 chassis that was left out side for years so i hoped it would be a simple drop in & basically it is except i cannot get the vertical size to fill the screen.

see attached, ignore the inverted / reversed images - i swapped the red & blue wires going to yoke and fixed that one up

tried adjusting pots on board to no avail, not sure where to test the B+

any ideas on where to start?

thx, kenny
 

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well nope, i didn't due to laziness but i suppose, now i should

thanks, will change yokes & post results
 
now i have the yoke swapped & picture does indeed fill the screen, my assumption that the yoke was part of the tube assembly is definately incorrect, now i have a degaussing problem, i used the 4906 parts for this and did not swap the old parts that were attached to the donor tube, now i will try to swap those parts and see if that fixes the new problems
 

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Yoke position can cause purity problems.

You should degauss the tube before you start any convergence.

The magnetic ring assembly STAYS with the particular tube.
 
working on building a degaussing ring from last monitor, yes, magnetic ring stays with the corresponding tube

i assume that moving the yoke either forwards (if even possible) or backwards would change purity

.... thanks for pointing me in the right direction

will post (hopefully positive) results once obtained
 
had to completely remove old wedges, which allowed me to move the yoke around a bit while using a solid red test screen, was able to improve the display some what by repositioning the yoke, when i had to yokew to the best position possible, i then fiddled with the two purity rings a bit to fine tune the red screen getting a little purer and completely removing the color distortions, it now looks great / fantastic (at least to me). next step is to some how reinstalled the three rubber wedges & apply some nail polish to rings, i am hesitant to even touch it now that it looks as good as it does.

not as difficult as one might imagine, i was rather intimidated by all of this, but for no reason at all it turns out.

thanks for the very helpful advice Mr. K. Layton
 

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so what exactly is the point of using the rubber wedges if the yoke is tightened upon the neck of the tube where it cannot move?
 
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