Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Early Color Television

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #16  
Old 11-09-2013, 10:27 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,575
Tim, that TV had probably been sitting since the 70s, I got it from the estate of a deceased repairman-his nephew told me the man never owned a color tv (?) I sorta think he never did anything with it. I think the main thing wrong with it when I got it was a bad power switch. I seem to recall that I eventually replaced the filter caps because I noticed them running warm. I don't recall any vertical issues on that one.
__________________
Bryan
Reply With Quote
  #17  
Old 04-07-2014, 04:23 PM
philtar0079's Avatar
philtar0079 philtar0079 is offline
VideoKarma Member
 
Join Date: Jan 2014
Posts: 62
Zenith color 25MC30

Quote:
Originally Posted by dieseljeep View Post
I wonder if that is the yoke with the nylon fish line strings for the horizontal and vertical centering.
I used an RCA yoke for the last replacement. The centering was close enough.
I have this Zenith TV now and I'm trying to get it to work. I got a nos yoke for it but I don't know what the nylon strings are suppose to do. I also can't find the vertical height adjustment pot on the chassis.
__________________
Looking for a Commodore PET, always wanted one.
Reply With Quote
  #18  
Old 04-07-2014, 05:39 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 9,998
The nylon strings are centering controls.
__________________
Tom C.

What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4

Reading between the scan lines since the mid 2000's.
Reply With Quote
  #19  
Old 04-07-2014, 06:00 PM
dieseljeep dieseljeep is offline
VideoKarma Member
 
Join Date: Jul 2010
Posts: 6,315
Quote:
Originally Posted by philtar0079 View Post
I have this Zenith TV now and I'm trying to get it to work. I got a nos yoke for it but I don't know what the nylon strings are suppose to do. I also can't find the vertical height adjustment pot on the chassis.
IIRC, the vertical height is on the front auxiliary control panel. It should be identified on the label. You have to remove the knob to adjust it.
Reply With Quote
  #20  
Old 04-07-2014, 08:20 PM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 950
It could likely be the vertical output transformer. My set went through two of them. The convergence winding goes bad and it can take out the two resistors that provide B+ to the vertical stages. It is not a difficult part to replace but may be a little hard to find. If you already have a new yoke, I hope that fixes it. These sets really perform well when correctly set up.
__________________
Just look at those channels whiz on by. - Fred Sanford
Reply With Quote
Audiokarma
  #21  
Old 04-07-2014, 09:51 PM
philtar0079's Avatar
philtar0079 philtar0079 is offline
VideoKarma Member
 
Join Date: Jan 2014
Posts: 62
I'll take another look. Thanks for the help.
__________________
Looking for a Commodore PET, always wanted one.
Reply With Quote
  #22  
Old 04-11-2014, 08:07 PM
oldtvman's Avatar
oldtvman oldtvman is offline
Larry Melton (oldtvman)
 
Join Date: Jan 2005
Location: Mishawaka, Indiana
Posts: 721
Quote:
Originally Posted by Kamakiri View Post
It's in the correct position, that was my first thought. I'd be further inclined to test the switch, were it not for the very noticeable "ticking" noise.
I do have a changer in a mid 60's rca home entertainment center, I'll look and see what model it it.
__________________
[IMG]
Reply With Quote
  #23  
Old 07-12-2014, 09:14 PM
Kamakiri's Avatar
Kamakiri Kamakiri is offline
Administrator
 
Join Date: Jun 2002
Location: Buffalo, New York
Posts: 5,061
Well, this set is now back in my possession from a trade deal

So here's where I'm at.....

Now that it's got a new yoke (installed by Preston), it's got a picture, but it's rolled up at the bottom. Picture shows it with the vertical size absolutely maxed, and it still won't go to the bottom of the screen.

Now, before I go any further, he gave me the old yoke back in the box, along with this paperwork which was included in it. I'm thinking that this yoke has to be modified somehow to work in this set, but I'm not wholly sure anything was, or how to do it if it does need to be done.

Take a gander, I've scanned the paperwork in. Suggestions are appreciated
Attached Images
File Type: jpg 100_4444.jpg (45.2 KB, 89 views)
File Type: jpg zenith1.JPG (34.8 KB, 62 views)
File Type: jpg zenith2.JPG (47.5 KB, 51 views)
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia."
Reply With Quote
  #24  
Old 07-12-2014, 10:43 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,839
Quote:
Originally Posted by dieseljeep View Post
When Kennedy and Cohen came to town, now defunct, they used an inexpensive B/W set as a leader. It was branded "Kenco", made by Sampo. of Taiwan. They sold them for $38.00, a lot of them!
I got several of them as freebees, as the customer thought, that it was so cheap, it wasn't worth repairing. I don't remember what went wrong with them, but was a simple cheap repair. They worked well and IIRC, I sold them for $35.00.

They also sold a Kenco branded Sylvania-built hybrid 19" color table model for $177.00. Unheard of at the time.
I recall Kennedy and Cohen being in the Delaware Valley (media speak for Philly-Jersey-Delaware). I also remember the cheapest set was a 1975 Sanyo 12" BW for $59.66 when all the others were $80+
__________________
"When resistors increase in value, they're worthless"
-Dave G
Reply With Quote
  #25  
Old 07-12-2014, 11:19 PM
ChrisW6ATV's Avatar
ChrisW6ATV ChrisW6ATV is offline
Another CT-100 lives!
 
Join Date: Feb 2007
Location: Hayward, Cal. USA
Posts: 3,321
Quote:
Originally Posted by Kamakiri View Post
Take a gander, I've scanned the paperwork in. Suggestions are appreciated
Tim, from what I can see in the instructions, you need to look at the original yoke (if you have it) and/or the schematic for the Zenith set, and remove (or add?) parts to make the new yoke match what the old one has. The schematic of the new one is in the one page you posted. Other may have a better way to describe this. I have not worked on any Zenith color sets, though.
__________________
Chris

Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
Reply With Quote
Audiokarma
  #26  
Old 07-13-2014, 11:22 AM
DaveWM DaveWM is offline
VideoKarma Member
 
Join Date: Feb 2009
Location: Orlando FL
Posts: 5,598
I doubt its the yoke, I would take a look at the PP drive signal, and/or voltages in the vert circuit. This is another place the TV analyst comes into play, a good source for a Known vert drive.
Reply With Quote
  #27  
Old 07-13-2014, 07:26 PM
Kamakiri's Avatar
Kamakiri Kamakiri is offline
Administrator
 
Join Date: Jun 2002
Location: Buffalo, New York
Posts: 5,061
Yep, just got a text from Preston. He made the appropriate changes to the yoke before installing. Now, to get a Sams....
__________________
"Restoring a tube TV is like going to war. A color one is like a land war in Asia."
Reply With Quote
  #28  
Old 07-13-2014, 08:38 PM
DaveWM DaveWM is offline
VideoKarma Member
 
Join Date: Feb 2009
Location: Orlando FL
Posts: 5,598
if you don't have the scope or tv analyst, the 1st place to go is a sub of the vert out tube and if used a vertical osc, IIRC Zeniths used two tubes for vert sweep (unlike the multivibrator dual triodes used in RCA).

I would test by subbing tubes.

after that you would want to check the voltage from the height pot. Assuming it uses boost voltage in the osc circuit, there is often a high meg resistor in series with a height pot. check to see if the pot and or resistor has drifted high.

The other likely suspect would be any eletrolytic that is a cathode bypass of the vert out. If that cap opens it kills the gain and output of the tube.

If you have a scope the 1st thing to look at would be the PP at the grid of the vert out, this would quickly narrow down to either the drive signal (vert osc tube) or the output (vert out tube). from there you can focus more closely on where to look.
Reply With Quote
  #29  
Old 07-14-2014, 07:21 AM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 2,839
Tim,
I checked my Zenith service manual and it confirms DaveWM on a resistor that feeds 870 volt boost to the V height pot.

Also noted that the .1 mf/600 V cap from boost to one leg of the horiz eff coil will cause the HV to be intermittent.
It notes this should be replaced with a 1000 volt cap.

BITD, I worked on maybe one or two of these sets, compared to RCA, Zenith roundies were not seen much.
Good luck
__________________
"When resistors increase in value, they're worthless"
-Dave G
Reply With Quote
  #30  
Old 07-14-2014, 08:46 AM
Zenith26kc20's Avatar
Zenith26kc20 Zenith26kc20 is offline
VideoKarma Member
 
Join Date: Apr 2009
Location: New Orleans
Posts: 804
For the problem pictured, I would go for the vertical integrator. Looks like a three legged brown ceramic disc but it has three wires coming out of it.
Reply With Quote
Audiokarma
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 12:31 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.