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
  #31  
Old 12-27-2015, 01:18 AM
Penthode's Avatar
Penthode Penthode is offline
VideoKarma Member
 
Join Date: Jun 2009
Location: Kitchener/Waterloo Ontario Canada
Posts: 1,059
Quote:
Originally Posted by old_coot88 View Post
If the last IF is causing ringing/'ghosting', it does not change with the fine tuning.
...
Alas, you are incorrect. If the last IF tube was indeed bad as suggested, the ringing would change with the fine tuning adjustment.

Since it had been suggested the last IF tube may be responsible, think for a moment the consequences in the change in the IF response which would result in the ringing or ghosting. A peak in the IF response would occur and when the fine tuning is changed, the video band would sweep the peak in the faulty IF response so that the frequency of the peak in the demodulated video band would change as a consequence. In other words, the ghost spacing would change as the fine tuning is adjusted.

If adjusting the fine tuning does not change the ringing spacing, then the problem must be after the second detector eg in the video amplifier. As has been pointed out, a badly terminated delay line would alter the baseband frequency response.

Last edited by Penthode; 12-27-2015 at 01:22 AM.
Reply With Quote
  #32  
Old 12-30-2015, 01:22 PM
DaveWM DaveWM is offline
VideoKarma Member
 
Join Date: Feb 2009
Location: Orlando FL
Posts: 5,607
Did you try a direct injection of a composite signal at the 1st video amp? that should clear everything (tuner/IF/detector diode) before it. divide and conquer.
Reply With Quote
  #33  
Old 12-30-2015, 04:50 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,159
Swung by last weekend, the ghosting is changing with adjustments to the fine tuning so I think this is going to be either an IF alignment or tuner link issue. We had to get better convergence before delving into that though, and found that the blue horizontal pot did nothing. It wound up being burned up and open in places, so Larry is looking for a new 120 ohm wirewound pot to replace it. Once that's fixed, we can solve the ghosting problem.
__________________
Evolution...
Reply With Quote
  #34  
Old 12-30-2015, 08:56 PM
old_coot88 old_coot88 is offline
VideoKarma Member
 
Join Date: Sep 2009
Posts: 2,541
Quote:
Originally Posted by Penthode View Post
Alas, you are incorrect. If the last IF tube was indeed bad as suggested, the ringing would change with the fine tuning adjustment.
You may be right, and probably are. It's been a lotta years ago, and I don't recall noting whether it correlated to fine tuning.
Just curious, how many cases of last IF ringing have you actually encountered? I've seen it in 3 stage strips as well as the oddball two stage (6EH7, EJ7) strips).
Reply With Quote
  #35  
Old 01-17-2016, 04:54 PM
VA561's Avatar
VA561 VA561 is offline
VideoKarma Member
 
Join Date: Apr 2010
Location: norfolk,virginia
Posts: 210
I've decided to just live with it. It has a pretty good picture otherwise. I have to remind myself that this is a 56 year old tv. I'm just glad it functions when I turn the set on.
Reply With Quote
Audiokarma
  #36  
Old 01-17-2016, 06:27 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,159
I do think it could be a little better, trouble is making it better means a complete convergence setup. I don't think it's worth all the effort, it's good enough now.
__________________
Evolution...
Reply With Quote
  #37  
Old 01-17-2016, 07:15 PM
walterbeers walterbeers is offline
Old TVs are better!
 
Join Date: Jun 2011
Location: Omaha NE
Posts: 463
I know delay lines seldom fail, but just for curiosity's sake try putting a clip lead across the 2 ends of the delay line. Don't clip anything to the ground side. and see if the ringing (or ghosting) disappears. I battled this exact problem for months before I found it. The "new" delay line solved the problem. I guess I'm really curious myself if that's your problem or not.
Reply With Quote
  #38  
Old 01-17-2016, 10:28 PM
miniman82's Avatar
miniman82 miniman82 is offline
First Light: 1952-2011
 
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,159
It's not the delay line, I've seen it in person.
__________________
Evolution...
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 12:36 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.