Randall RM100 Problems

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thenunbus

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Oct 29, 2006
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Theres somthin wrong with the biasing system on my amp, i recently changed the tubes from 6l6's to EL34's at first they were runnin fine at around 38mV so i cranked the up to 42.5 mV and the sound just went all crappy and crackly. And when i checked what power they were runnin at they were right down to around 1.6mV. What does this mean? Thnks in advance
 
Sounds like one of your new 6L6 tubes is bad. If the bias readings were good when you first changed the tubes, I would switch the tube that is reading low back to an EL34 to see if that tube can be set to the right setting of 35-40mV. If so, then one of your new 6L6 tubes is indeed bad.
 
If the tube went bad or was bad wouldn't the RM kick that tude out of the loop and keep on playing and the little red light would come on?
 
thats what i thought, at first i thought they migh not be matched properly but they were workin at first, my 6l6's work fine but the EL34's wont, i dunno why
 
Probally just a bad tube, ive found out that the little red light dose not always come on when a tube is bad, you should never go higher than 38mV or 39mV with 6l6s. Also I would check your fuses if I were you. It dosent matter if the tubes are matched or not, you just always bias each tube to be the same when you put it in, all the tubes should read the same mV when your done.
 
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