Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TerryD on July 13, 2017, 01:08:55 pm
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Forgive me for the new thread but my friend has a gig on Saturday. I put in a set of Tube Amp Doctor 6l6s as his bit the dust. These are all I had available. I tried running some crappy sovtek 5881s (I have from an amp) in the Deluxe and the TADs are the culprit running hot. The amp calls for 68-70 millavolts in the way they bias. The sovteks run perfect at half way on the bias dial.
The TADS were running at 76.8 millavolts at the lowest setting on the dial. I swapped the 100k bias resister to 220. That got me to 74 milliamps at the lowest settin. Then 470k, then 1 meg, then 2.2meg and I always get the same reading of around 72.1 millavolts right from the 470k to 2.2 meg and thats the SAME reading on the LOWEST setting on the bias dial while the amp has run for 5 minutes with nothing plugged in.
Thanks for your help.
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Quick answer,
72 milliamps for 2 tubes running at 430-450V B+ is just fine.
(assumption based off http://el34world.com/charts/Schematics/files/fender/Fender_hotrod_deluxe.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_hotrod_deluxe.pdf))
That is not an insane number.
Ship it.