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Post subject: the red knob twin problems
Posted: Tue Mar 10, 2009 2:30 pm
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Hello. Can someone out there help me please.I got a red knob twin that hums even when its unplugged.
When I pull out V3 or V4 the hum disappears. I have some problem with the level selection.When I switch over to+4db and-7db the voltage drops on one anode of the four output tubes. I have checked all the soldering on the board
and tube sockets. I have also checked some of the caps that have connection to these tubes.

:?


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Post subject:
Posted: Tue Mar 10, 2009 3:57 pm
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Did you change tubes. May be check the bias


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Post subject:
Posted: Tue Mar 10, 2009 4:47 pm
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When you mention that it disappears when you remove the tube sounds like a bad tube to me.


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Post subject: Re: the red knob twin problems
Posted: Wed Mar 11, 2009 3:26 am
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xt8h wrote:
Hello. Can someone out there help me please.I got a red knob twin that hums even when its unplugged.
When I pull out V3 or V4 the hum disappears. I have some problem with the level selection.When I switch over to+4db and-7db the voltage drops on one anode of the four output tubes. I have checked all the soldering on the board
and tube sockets. I have also checked some of the caps that have connection to these tubes.

:?
There are new tubes i n the amp and the bias is also set. The hum disappears only when V3and V4 are pulled out. V3 is the fx-send return-loop. I have even replaced the new tubes but the hum is still there.


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Post subject:
Posted: Wed Mar 11, 2009 11:32 am
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Is there an amp tech in the house?


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Post subject:
Posted: Wed Mar 11, 2009 8:10 pm
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Sounds like a ground somewhere


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