Quote:
Originally Posted by N2IXK
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.
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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.
