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
  #1  
Old 04-21-2007, 09:17 AM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
Zenith Roundie HV Question - Help Please

I replaced the horizontal efficiency coil in my '65 Zenith (chassis 25MC33) and the horizontal output tube. The trouble was no Horiz. output, raster etc. I now have horiz. output (neon lamp test glows) but no HV and damper tube arcs and when damper arcs I see purple glow in CRT neck. The neon glows at the plate cap to the HV rectifier so I believe the flyback is alright. I feared a shorted CRT but the tester reveales full emisson on all guns with no shorts. When I disconnect HV rect. there is no purple glow in CRT. I have not replaced the damper, HV rect, HV regulator or focus rectifier. Could any or all of these account to no HV and purple CRT glow? The CRT neck only glows/flashes purple when damper is arcing. I have yet to see a raster or any kind of light on the screen.

Any advice would be appreciated as I am now ready to finally get this old set going. Thanks as always.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
  #2  
Old 04-21-2007, 01:57 PM
roundscreen roundscreen is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: buffalo ny
Posts: 376
The purple glow in the crt could be loss of the focus voltage.
Yes,The damper tube,hv regulator and focus rectifier could be your problem.
Also check for bad caps and resistors in the horz output circuit too.
Ed
Reply With Quote
  #3  
Old 04-22-2007, 01:12 AM
Bill R Bill R is offline
VideoKarma Member
 
Join Date: Oct 2004
Location: Jackson, TN
Posts: 846
I usually would replace the damper, regulator, and hv rectifier tube if I did any work in the HV section.

Bill R
Reply With Quote
  #4  
Old 04-24-2007, 12:59 AM
reeferman's Avatar
reeferman reeferman is offline
VideoKarma Member
 
Join Date: Jun 2004
Location: St. Louis
Posts: 500
Get ahold of a Sam's Photofact. Most of them have resistance charts in them (measured resistance from point A to point B is... scenario) great place to start.
Before you waste a lot of time, try that, and let's hear what happens. Good luck.
Reply With Quote
  #5  
Old 04-24-2007, 08:32 AM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
I have the Sams for my set. I have ordered the power tubes from AES. They should be here tomorrow. I'll let you know what happens. I would at least like to get a picture on this set before I have to disassemble it completely to send the cabinet for refinishing. It is going to take me a while to get all that vintage dust and crud off of the chassis. I suspect that mos of the set is good because I have sound, tuning, I can hear the vertical oscillator running and I can get some output from the flyback.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
Audiokarma
  #6  
Old 04-28-2007, 09:59 AM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
It looks like we're missing some posts here. Anyway, I contacted Scotty at Hawkeye and he says he can rebuild my tube. I plan to ship it to him next week. A real plus is that he can get rid of the green halo. I was prepared to live with it even though it bugs me. In the meantime I will start cleaning up that chassis and getting the cabinet ready for the refinisher. This is the most ambitious restoration I have ever taken on not to mention the most expensive. I don't know how some of you guys manage to restore and maintain multiples of these sets. It is definitely a labor of love.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
  #7  
Old 04-28-2007, 01:34 PM
Chad Hauris's Avatar
Chad Hauris Chad Hauris is offline
VideoKarma Member
 
Join Date: May 2003
Location: West Texas
Posts: 2,085
Also make sure the grounding of the CRT outer aquadag coating to the chassis is good.
__________________
Chad Hauris
http://www.youtube.com/user/retrochad
Reply With Quote
  #8  
Old 05-14-2007, 05:34 PM
julianburke julianburke is offline
VideoKarma Member
 
Join Date: May 2004
Location: Knoxville, Tennessee
Posts: 558
When I was doing Zenith TV's (others too) and you are not getting raster, the first thing is to pull the damper tube out slightly and if it arcs on the socket it is good and conducting. If it didn't arc you would replace the damper tube for starters to go on to the next step. (or fixed it at this point) If damper is good, next pull the cap off the the HV rectifier, stick an insulated Xcelite nutdriver or other in the cage and touch it to the cap from flyback. (don't ground it-any arc or corona is enough test) If you get arc there, you have a bad 3AT2 (or 3A3 in other sets) rectifier. Usually the HV rectifier filament opens and then will "lay" on the plate internally creating a short and keep HV from building so disconnecting the cap will prove this point. The focus 1V2 or 2AV2 rarely goes bad and if it does, will not cause loss of raster. If you still can't get it to work, measure resistance between the two caps of the HO tube and the HV rectifier (power off of course) and the resistance through the flyback should be about 75 ohms. If near zero or infinity, fly is bad. Julian
__________________
julian
Reply With Quote
  #9  
Old 05-15-2007, 08:09 AM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
Smile

Thanks for the useful information Julian. I did get the HV to work if I pulled the CRT socket. With the CRT connected, I get no HV although I can hear the Horizontal oscillator squealing and I was getting pink and purple glow and flashes inside the CRT neck. I have sent the tube to Hawkeye for rebuilding. In fact he should be working on it this week. The cabinet is still at the refinisher's. I will be so glad to get this put back together. In the meantime, I'm doing a lot of parts and chassis cleaning. I can't wait to watch Star Trek on it.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
  #10  
Old 05-15-2007, 01:16 PM
julianburke julianburke is offline
VideoKarma Member
 
Join Date: May 2004
Location: Knoxville, Tennessee
Posts: 558
CRT Problem

You have an easy one here. Your CRT is broken or cracked and has aired. When a CRT has gone down to air, it will arc internally all over the guns or half down to air will produce a strong blue or pink glow internally. When down to air, tube is "shorted" and will build HV and arc internally but no raster and I have seen some tubes that are internally shorted (perhaps not down to air-your case) and by removing the CRT socket will build HV again. Remember, any arcing around the guns indicates your tube has "aired". When first you see this condition, turn set OFF immediately as it is very hard on the sweep circuit (short across flyback) and will ruin the HO tube and/or flyback if left on. Julian
__________________
julian
Reply With Quote
Audiokarma
  #11  
Old 05-15-2007, 03:07 PM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
I'm sure my tube has not completely gone to air because the filaments did not burn out. I suspect that the tube was the cause of most of the problems. The chassis seems to be in good shape. I just love the way these Zeniths were built to last. I'm hoping to get many years of service out of this set. I plan to connect it to a digital set top box/DVD recorder combo.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
  #12  
Old 05-15-2007, 09:33 PM
julianburke julianburke is offline
VideoKarma Member
 
Join Date: May 2004
Location: Knoxville, Tennessee
Posts: 558
Zenith Manufacturing

Contrary to popular belief, Zenith did build a quality set BUT that's not the main reason they built them like that. They were expensive and labor intensive to manufacture because they were too cheap to upgrade their facilities! They did too little to late to upgrade and this is the main reason they went out of business sooner than they should have. Zenith always shouted "QUALITY AND HAND BUILT" but no one else was doing this in the competitive market. Julian
__________________
julian
Reply With Quote
  #13  
Old 05-16-2007, 08:01 AM
compucat's Avatar
compucat compucat is offline
1949 Motorola 9VT1
 
Join Date: Apr 2005
Location: Suffolk, VA
Posts: 914
I'm glad Zenith was slow to upgrade. Tubes and PC boards are not a good combination. Restorers of RCA roundies have to contend with broken connections, loose grounds, brittle boards and crumbling tube sockets. The heat just tears them up. PC boards are fine for solid state although I think heat generating components like large wattage resistors and power transistors should be chassis mounted. When it comes to tubes, handwired is the only way I'll go.
__________________
Digital TV, as Shakespeare would have said "It is to suck".
Reply With Quote
  #14  
Old 05-16-2007, 01:02 PM
Carmine's Avatar
Carmine Carmine is offline
...enjoys spaghetti.
 
Join Date: Feb 2003
Location: Detroit area
Posts: 1,574
Quote:
Originally Posted by julianburke
Contrary to popular belief, Zenith did build a quality set BUT that's not the main reason they built them like that. They were expensive and labor intensive to manufacture because they were too cheap to upgrade their facilities! They did too little to late to upgrade and this is the main reason they went out of business sooner than they should have. Zenith always shouted "QUALITY AND HAND BUILT" but no one else was doing this in the competitive market. Julian
This was mentioned before, and I don't know if I buy it. Seems to me that Zenith didn't skimp on the R&D money, afterall they gave us a lot of great radio innovations, ever-smaller & better hearing aids, and in the TV world:

Wireless Remote Control
Phone-o-vison (ok, that didn't catch on)
Chromacolor CRTs
Stereo TV (I think)

...didn't they also have a "better" color demod circuit?

And when they finally went to PC boards, the chassis were still tanks.

They were also the number 2 set maker, so being as how they must have been pretty profitable, I'm sure they could have gone to PC boards and made even more cash by cheapening the sets and laying-off a lot of solderers!
__________________
From Captain Video, 1/4/2007
"It seems that Italian people are very prone to preserve antique stuff."
Reply With Quote
  #15  
Old 05-16-2007, 01:27 PM
ChrisW6ATV's Avatar
ChrisW6ATV ChrisW6ATV is offline
Another CT-100 lives!
 
Join Date: Feb 2007
Location: Hayward, Cal. USA
Posts: 3,310
Quote:
Originally Posted by Carmine
Stereo TV (I think)
Yes, Zenith invented the U.S. (BTSC) analog stereo-TV audio format.

Zenith also invented the digital TV system now in use in the USA, Korea, and other countries. When the commission was formed to study and approve high-definition TV, three other companies came up with analog proposals but Zenith invented a digital format. Zenith's signal was so superior, the commission (ATSC) told everyone to give up on analog entirely.
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 09:09 PM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.