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Yes I have seen cases of weak tubes in some radios...we first replace old capacitors and wiring and then check performance...have found really weak tubes in probably 30-40 percent of tube sets we have worked on.
Really have not seen many cases of just one bad tube except for a 6HA5 in Fisher tuner...usually if one tube is weak the set has a lot of hours on the tubes and they all are likely pretty weak.
Distortion/hum problems, usually caps...weak reception is usually weak tubes.
Power but no audio...usually burned resistors due to bad caps, or leaky caps inside IF cans.
Twin diode triode (such as 12AV6) and triode-heptode (such as 6A8) are usually not interchanged...the former is detector/first audio and the latter is mixer and oscillator...these are pretty different tubes to sub for one another...maybe you meant something else?
Last edited by Chad Hauris; 06-10-2005 at 08:56 AM.
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