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|30th January 2009, 12:25 PM||#1|
Join Date: Jan 2009
Music Angel KT88 Bridged /Bias problem
Have Bridged 2stk Music Angel KT88
These have problems with the bias, the first one, one of the channels(2pcs pipes) the bias will not go down to 0.25v it is stuck about 0.33v = 66ma
Before I adjusted bias for this was that between 80 to 100ma this is quite high! but never been used as this, only testet.
Amplifier have new chassis and power lines have been replaced, but the pipes are put where they stood as it is strange bias has changed so much
The other amplifier I have a channel (2pipes) that will not go up enough, one tube is 0.155v and another on 0.18v (31ma and 36ma)
I try and adjust systematically, when I turn pot meter for one tube for the bias to go up, the another tube on the same channel goes down, is this correct?
Resistance between ground and pin 8 is 5ohm, ie 0.25v = 50ma
I Also have a bias tool that confirming this
When I play music in this sounds good in 20-30 sec. So the sound is bad, treble disappear almost completely ... ..
The bridging is that one signal in is 180 phase and GND on output transformer is short-circuit, this should not effect bias?
Has been my little stuck here, hoping for some good advice
(Sorry my English)
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