#1
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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 |
#2
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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. |
#3
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Strange tubes and parts values. The tube checker was one of their better offerings. |
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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?
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#5
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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. |
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