Zenith 25X4517 Focus issues - Videokarma.org TV - Video

freakaftr8 · #1 09-11-2008, 11:51 PM

First lemmie start out by saying LONG TIME NO SEE!! Sorry guys, I have been busy w/ a new job and the kid on the way and too much going on with my car and all the other good stuff like that... But I miss this site and the people on here! Hope all has been well!

Anyway my Zenith seems to have drifted on the focus to the point where the focus pot is all the way to the end, but the screen is still out of fucus a bit and could go more but the knob is all the way over. Im stumped...

Yes my house is crammed with vintage sets now! Gotta save em!

Thanks!
Shawn

jpdylon · #2 09-12-2008, 12:17 AM

check around the CRT socket for the icky green corrosion around the focus pin. That can sometimes kill the focus voltage. This set is probably too new for a focus rectifier tube, so it will use a focus rectifier diode (long skinny white tube.) its a rarity for these to fail all together. There are resistors that make up a voltage divider for the focus voltage to the CRT inside the HV cage. They are usually around anywhere from 2.2 to 10meg. They will drift with use and age.

And of course, the regular applies here too. Check high voltage supply, regulator, rectifier, etc.

Let us know what you find.

drh4683 · #3 09-12-2008, 11:09 AM

Yes, check the focus pin at the CRT. Ive noticed many zeniths will focus at one end of the control, but you think it could be even better but run out of adjustment. Sometimes, like in your case, its still unacceptable focus at one end. Proper focus should be obtained near mid rotation of the control. Im many of those cases, I've replaced the focus rectifier diode and it does fix it almost every time. You can't really get an accurate test on a selenium focus diode with your meter as they have very high forward bias resistance. Your best bet is to sub in a new one and it will probably bring back a picture that will blow you away. Its amazing how good the picture is after I put in a new diode. Even if you had a decent picture as it is that you were comfortable with, just putting in a new diode makes it razor sharp! You set has a 23XC38Z chassis, and there should be a 212-48 rectifier diode on the flyback PC board. You can get an NTE-118 but they are rather difficult to find as NTE no longer makes them. Its a selenium diode, Im sure moyers has them though. They might even have the 212-48, but doubt it. Moyer comes up short on NOS zenith parts as they were not a zenith parts distributor.

*zenithfan1* · #4 09-12-2008, 11:57 AM

Nice to see you back Shawn! Totally understand the whole busy thing with the car and a kid ect., congrats BTW! is it a boy or girl? I was going through a similar situation here a few months back. My son is 6 months old now. Sorry that this is OT.

freakaftr8 · #5 09-12-2008, 12:13 PM

Right on! Well we find out Oct. 1st, Ill post in the off topic forums! Thanks zenithfan1, good yo see you guys too! Congrats to you on your baby too!

Well Im calling moyers today, I cannot wait to see this set looks it's best! Now that it's our only tv.. Lol the Sony poofed the magic smoke! You should have seen it, I can still smell it in the house! Thats cool, I got sick of keeping it runnin..

bgadow · #6 09-12-2008, 10:16 PM

I had a Zenith where the focus was fine as soon as the set was powered up but it would right away start to drift until after 10 minutes it was a total blur. I completely rebuilt the focus circuit, including a new diode, with no improvement. I then subbed the HO tube and the problem was gone. I think I would start with the diode, unless you have a spare tube on hand; diodes are bound to be cheaper than that tube.