Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Early B&W and Projection TV

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #1  
Old 10-29-2017, 01:20 PM
ShartZenith's Avatar
ShartZenith ShartZenith is offline
VideoKarma Member
 
Join Date: Jul 2011
Posts: 50
Arc from 1Be plate cap lead to high voltage cage

Working on a Zenith round tube TV. Fired it up for the second time. After it ran for about 30 minutes we heard a noise. I saw a blue arc inside the high voltage cage. After opening the cage it appears the arc was jumping from the plate cap lead of the 1B3 tube to the inside of the cage where the flyback live. Why is this happening and what can we do to eliminate this problem? Thank you.
Reply With Quote
  #2  
Old 10-29-2017, 02:12 PM
MadMan's Avatar
MadMan MadMan is offline
'A Disgusting Brony'
 
Join Date: Oct 2016
Location: Chicago
Posts: 361
Well, I'm no expert, but I'd imagine whatever the plate cap is connected to is probably open. So that should be the flyback, right? Bad flyback?
Reply With Quote
  #3  
Old 10-29-2017, 02:29 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 8,926
If you have light on the screen (heck even arcing off the 1B3 top cap) the flyback is fine...

Run the set with the cage off to determine exactly which to points the arc is jumping between and report back.

If it will not arc with the cage off because it is arcing to the cage then you need to clean the surfaces and area around the arcing points...Eliminate any sharp/pointy edges at the arcing points and possibly add insulation.

Pictures of the places it is arcing from and the condition of the HV cage and it's contents of will help in providing less general advice.
__________________
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
  #4  
Old 10-29-2017, 07:00 PM
timmy's Avatar
timmy timmy is offline
VideoKarma Member
 
Join Date: Jan 2011
Location: ferndale ny
Posts: 1,843
Maybe lots of dust on top of the 1b3 or the cage .
Reply With Quote
  #5  
Old 10-29-2017, 09:52 PM
ShartZenith's Avatar
ShartZenith ShartZenith is offline
VideoKarma Member
 
Join Date: Jul 2011
Posts: 50
The arc I saw and heard while looking through the holes in the top of the cage were going from the top of the tube or the lead to the nearest metal which was the inside of the cage. A distance of not more than one inch. We've since opened the cage, removed the tube for testing and will replace it with a known good tube. The cage, chassis, everything is very clean. This was a very clean chassis from the beginning. I cleaned it thoroughly and made it shine. Dust, well there might be a very thin film of dust on everything since we hadn't touched this TV since June. Can't imagine that would create the intense arc I saw and heard twice. The fuse at the bottom of the cage you see is still intact. Other than replacing the 1B3 with a good tested one, what else should be check before we attempt the next fire-up of the TV? Thank you for your previous reply.
Attached Images
File Type: jpg IMG_20171029_204014554.jpg (68.3 KB, 44 views)
File Type: jpg IMG_20171029_204800691.jpg (67.1 KB, 56 views)
Reply With Quote
Audiokarma
  #6  
Old 10-29-2017, 10:00 PM
Eric H's Avatar
Eric H Eric H is offline
Administrator
 
Join Date: Jun 2002
Location: So. Calif
Posts: 11,277
There are tall 1B3’s and short ones, you may need a short one.
Reply With Quote
  #7  
Old 10-29-2017, 10:18 PM
old_coot88 old_coot88 is offline
VideoKarma Member
 
Join Date: Sep 2009
Posts: 1,848
If the arc was going to the side of the cage (instead of the top), it wouldn't matter whether the tube is tall or short.

The arc is not going to hurt the tube, as the tube is 'downstream' from the arc's current path, "out of the loop" so to speak. But the flyback sees the full overload current of the arc.

If an arc were 'downstream' from the tube, then the tube would carry the current. It would be a DC arc producing a very loud 'SNAP!' or series of snaps.

Last edited by old_coot88; 10-29-2017 at 10:22 PM.
Reply With Quote
  #8  
Old 10-30-2017, 10:12 AM
Bill Cahill's Avatar
Bill Cahill Bill Cahill is offline
Super Moderator
 
Join Date: Mar 2005
Location: St. Petersburg, Fl.
Posts: 1,269
Post

From the looks of the insulated wire, I'd say a new wire is needed. Do not use standard wire. This wire has to be insulated for nothing less than 15,000 volts.
Another temporary repair would be corona dope.
Bill Cahill
__________________
"Tubes are those little glass things that light up orange unless there is a short.. Then they light up all pretty colors..."
Please join my forum.
http://tuberadio.heavenforum.com/ind...c8c9de9e96fd7d
Reply With Quote
  #9  
Old 10-30-2017, 12:06 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 8,926
I agree with oldcoot and Bill.
If the tube was good before the arcing,then it should still be fine. The arcing from that point should not hurt it.
I would probably replace that wire with a 15-40KV rated wire....In lieu of that corona dope is one option, but I'd first try to put as many layers of heat-shrink tubing over the wire as I could. The tubing I get at Ace Hardware is 600V rated and some brands may be rated higher. Two layers of 600V insulation is 1.2KV extra insulation 5 layers is 3KV and so on.

Three other observations: Dress the lead as far from the cage as you can. It looks like the grab fingers/terminals on the 1B3 top cap/spring have been pointed at the side of the cage....You probably want them pointed away as they could form an arc point. Have you measured the HV, and compared it to spec?...If the HV is substantially higher than designed insulation may break down, and arcing may occur.
__________________
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
  #10  
Old 10-30-2017, 12:22 PM
WISCOJIM WISCOJIM is offline
VideoKarma Member
 
Join Date: Sep 2005
Location: Grand Chute, Wisconsin
Posts: 1,728
Quote:
Originally Posted by Electronic M View Post
It looks like the grab fingers/terminals on the 1B3 top cap/spring have been pointed at the side of the cage....You probably want them pointed away as they could form an arc point.
Yes, there doesn't appear to be much clearance there.

.
Reply With Quote
Audiokarma
  #11  
Old 10-30-2017, 01:24 PM
jr_tech's Avatar
jr_tech jr_tech is offline
VideoKarma Member
 
Join Date: Sep 2009
Posts: 3,588
How close is that end of that screw that protrudes into the cage above the 1B3 to the 1B3 plate cap/clip fingers? It looks like it could possibly be a point for corona/arc generation?

jr
Reply With Quote
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 09:54 PM.



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