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Author Topic: Model T Bias problem  (Read 2199 times)

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Offline Sanford

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Model T Bias problem
« on: April 14, 2004, 09:06:59 am »
I retubed my amp and set the bias but the lowest reading I get is 59mV but it sounds better at 70mV. I was told it should read 55mV. WHAT DOES THIS MEAN? My 1200s is the same way. Both amps have JJ KT88's.
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Anonymous

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Model T Bias problem
« Reply #1 on: April 14, 2004, 11:11:23 am »
maybe yoru tubes are sturdyer than normal?

a vintage model t right?
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Anonymous

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Model T Bias problem
« Reply #2 on: April 14, 2004, 02:42:10 pm »
yes early 70's
what do you mean by sturdier?
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Offline JoeArthur

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Model T Bias problem
« Reply #3 on: April 15, 2004, 09:28:04 am »
I don't know what our guest meant, but if you are really measuring bias voltages in the millivolt ranges, then for all intents and purposes, you are operating without any bias.  

Since you haven't destroyed the output tubes yet, I assume that there is something wrong with your measurements.  Maybe the positive lead isn't grounded secure... or you have some crud in the negative bias measuring port... or you have the wrong scale on your meter... or your meter has a bad lead... or... etc.
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