Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Diagnostic & Test Equipment

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #1  
Old 09-26-2014, 09:06 PM
footlooseman footlooseman is offline
VideoKarma Member
 
Join Date: Jul 2014
Location: Sioux Falls, SD
Posts: 27
Superior Instruments TV-11 Tube Tester - burnt resistors

I recently bought a Superior Instruments TV-11 Tube Tester. The line adjust control was not working correctly but was working after replacing two capacitors and some resistors that had drifted. There was one that I left in and it was a 330 OHMS. The unit seemed to work well but after doing some testing I saw smoke and thought that the selenium rectifier went bad, but it was this resistor. There was no listing for wattage so I replaced it with a new 1/2 a watt resistor.

WP_20140917_029.jpg

After testing some tubes from my Zenith and Setchell-Carlson TVs, I saw a spark for the unit and unplugged it. Took it outside and found the new resistor bad too.
WP_20140924_007.jpg
Went back to my booklet and found a part replacement list and it listed a 350 OHM 3 Watt resistor. I'm guessing it an oversight on my part and still kind unaccustomed to some of the vintage parts.
What do you guys think made the original resistor fail? Did I over look some other parts? Should I go with a higher wattage resistor such as a 5 Watt?
tv-11.jpg
WP_20140924_007.jpg
Attached Images
File Type: jpg tv-11--v2.jpg (115.3 KB, 24 views)
Reply With Quote
  #2  
Old 09-27-2014, 12:36 PM
N2IXK's Avatar
N2IXK N2IXK is offline
Technohippie
 
Join Date: Apr 2011
Location: Sittin' on the "Group W" bench...
Posts: 799
Yes, the original resistor was much bigger than a 1/2W unit. Your replacement likely burned up for this reason alone. A 5W metal film or wirewound unit would be a good replacement. As far as the 330 vs 350 ohm issue, I would tend to go with the value actually installed, rather than the parts list, assuming that the old unit looked original, and not a replacement from long ago.

The original resistor might have failed from testing a shorted tube (always run the shorts/gas test before testing emission or transconductance), or it may have been underrated from the outset. A 5W replacement would address this.

As the failed resistor is in series, I would check the 10K pot for damage, as well. It should exhibit a smooth change in resistance over its travel, with no open spots or abrupt jumps.
Reply With Quote
  #3  
Old 10-03-2014, 11:35 AM
dieseljeep dieseljeep is offline
VideoKarma Member
 
Join Date: Jul 2010
Posts: 7,562
Quote:
Originally Posted by N2IXK View Post
Yes, the original resistor was much bigger than a 1/2W unit. Your replacement likely burned up for this reason alone. A 5W metal film or wirewound unit would be a good replacement. As far as the 330 vs 350 ohm issue, I would tend to go with the value actually installed, rather than the parts list, assuming that the old unit looked original, and not a replacement from long ago.

The original resistor might have failed from testing a shorted tube (always run the shorts/gas test before testing emission or transconductance), or it may have been underrated from the outset. A 5W replacement would address this.

As the failed resistor is in series, I would check the 10K pot for damage, as well. It should exhibit a smooth change in resistance over its travel, with no open spots or abrupt jumps.
It was always fun to work on Superior Instrument test equipment. They used all kinds of surplus parts, that were purchased cheaply.
Strange tubes and parts values.
The tube checker was one of their better offerings.
Reply With Quote
  #4  
Old 11-13-2014, 10:16 PM
wkand's Avatar
wkand wkand is offline
VideoKarma Member
 
Join Date: Oct 2005
Location: Everett WA
Posts: 260
Superior Tube Tester - Leakage test

What were the leakage test with the neon bulbs designed to do? Are they the same type of test as a grid leak tester?
Reply With Quote
  #5  
Old 11-25-2014, 07:10 AM
VTVM VTVM is offline
VideoKarma Member
 
Join Date: Jan 2014
Posts: 35
Quote:
Originally Posted by wkand View Post
What were the leakage test with the neon bulbs designed to do? Are they the same type of test as a grid leak tester?
The shorts test connects all the tube elements together except for the one under test at the moment. Any short or sufficient leakage lights the lamp. As the switches are thrown into test position and back, one by one, it goes through the combinations of tube elements.

If there is a short indication, the testing is over because the tube could ruin the tester if a emissions test were attempted on the shorted tube. There are some exceptions given in the manual that allow for a dim glow on certain element's short tests on certain tube types due to a normal high grid leakage in certain tubes.
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 12:59 PM.



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