Zenith 23XC38Z Chassis Losing Horiz. Width

[DaveWM]

the plug in tuner makes it a easy chassis pull. Its going to look great with a new CRT. watch out for the little black electros with red tops.I had one of those go one me in the AGC circuit, made it HYPER touchy in the adjustment.

[fsjonsey]

Originally Posted by DaveWM

the plug in tuner makes it a easy chassis pull. Its going to look great with a new CRT. watch out for the little black electros with red tops.I had one of those go one me in the AGC circuit, made it HYPER touchy in the adjustment.

I put this off for days thinking it would be a massive project, but Zenith really designed this chassis for easy servicing. It took less than 30 minutes to pull the chassis. Zenith was smart enough to emboss all the chassis connection points for the power switch, degauss coil, speaker, etc.
DaveWM: Thanks for the advice, I'll look out for those little caps.
I'm still amazed I got almost four years of regular use out of this set, with mostly original components. It was still hooked up to a digital cable box and plugged in when I removed it from it's original home in a Duplex in the Collinwood neighborhood of Cleveland back in 2011.

[zeno]

Originally Posted by fsjonsey

I put this off for days thinking it would be a massive project, but Zenith really designed this chassis for easy servicing. It took less than 30 minutes to pull the chassis. Zenith was smart enough to emboss all the chassis connection points for the power switch, degauss coil, speaker, etc.
DaveWM: Thanks for the advice, I'll look out for those little caps.
I'm still amazed I got almost four years of regular use out of this set, with mostly original components. It was still hooked up to a digital cable box and plugged in when I removed it from it's original home in a Duplex in the Collinwood neighborhood of Cleveland back in 2011.

And if you pull the tuner there is a few spare screw on the back to mount
it to the chassis. RCA also did it.

Our first color set was one of these ( or a Y line). Got it for the '67
world series. Under warranty a rectifire shorted but after that ran
til abt '77 no repairs. Sold it used & only replaced the 6HA5 RF
amp to perk it up.
NOTE when changing a 6HA5 try to find the short envelope version.
For some reason all the "tall" ones were noisy, enuf to kill a deep
fringe signal or make a fringe station grainy.......

73 Zeno

[fsjonsey]

Well, I replaced all the caps and the bottom of the horiz has started to collapse again. I can't get the HV over 22KV. The Flyback still looks good and resistance is in spec. I looked at the VDR, and it's already been replaced at least once, some other tech tacked a pink and white Zenith replacement VDR onto the leads of the original. I ordered one of the replacement Speer MOV's that Doug recommended in another thread. It should be here today. I'll let you all know the results once I solder it in. It would be hilarious if the caps were either fine or marginal and the VDR was the real culprit. If that's the case, I guess that'll teach me not to trust a $30 Chinese ESR cap tester.

[fsjonsey]

I soldered in the new VDR. HV control is back, but the picture is still shrunken horizontally on the bottom third of the screen. It gets worse as the set warms up. I know for a fact that the Yoke is not the issue, as this is a NOS Thordarsen replacement. Once the set warms up, the bottom corners of the CRT shrink to black and the picture almost looks like a trapezoid. There are three white vertical lines centered in the bottom of the screen that fade out about a third of the screen up. Where the ticker on a cable news station would go, as an example, the text passes these lines, it shrinks and expands back to a normal size as it passes the vert. lines.

I really need help with this. I'm stumped.

[DaveWM]

a pic would be helpful

[DaveWM]

fyi, part of the pincushion correction in a zenith uses a pulse from the vert to modulate the output from the horz out tube. If you look a the circuit you can see a connection to I think a 40 uf cap (C7) that ties the screen of the horz out to the vert out.

This presents as a subtle narrowing and slight keystone of the pic (much less keystone than a bad yoke).