Need help to repair two phase 400 amps

LarryD said:
Hello Gepetto, Well now I know! LOL1 Thanks
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See you did know what a bias transistor is Larry. They are 2N3403 transistors in the stock amp, as it is labeled on the P-strap. The P-strap is the aluminum bracket around this transistor that is shaped like a P when you look at the end of it.
 
Gepetto said:
See you did know what a bias transistor is Larry. They are 2N3403 transistors in the stock amp, as it is labeled on the P-strap. The P-strap is the aluminum bracket around this transistor that is shaped like a P when you look at the end of it.
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I am writing everything down as we go. Thanks
 
laatsch55 said:
On the main forum index page, to the right of the "Latest Topics" box is a small double arrowed box. If that tab is enabled There will be another long box that says " New Forum Posts". That is much handier to see if you or I have posted as opposed to hitting the refresh button. You can bounce between the main forum page and your thread by use of that box too.
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Ok Lee, got it. I didn't think the thread was that far back.
 
Ok here is where I am at , I re soldered the diode that we checked. Cleaned the heck out of the amp. I am ready for instructions when you are.
 
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On the main forum index page, to the right of the "Latest Topics" box is a small double arrowed box. If that tab is enabled There will be another long box that says " New Forum Posts". That is much handier to see if you or I have posted as opposed to hitting the refresh button. You can bounce between the main forum page and your thread by use of that box to
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The bias transistors can be checked in circuit. Do the standard NPN BJT transistor test...Joe just gave you the pinouts.
 
RED C / BLACK B
1 O
2 O
RED C / BLACK E
1 O
2 O
RED E / BLACK B
1 O
2 1.653
BLACK C /RED B
1 .903
2 .776
BLACK C / RED E
1 .956
2 .751
BLACK E / RED B
1 .905
2 .777
 
Last edited:
RED C / BLACK B
1 O
2 O
RED C / BLACK E
1 O
2 O
RED E / BLACK B
1 O
2 1.653
BLACK C /RED B
1 .903
2 .776
BLACK C / RED E
1 .956
2 .751
BLACK E / RED B
1 .905
2 .777
 
LarryD said:
RED C / BLACK B
1 O
2 O
RED C / BLACK E
1 O
2 O
RED E / BLACK B
1 O
2 1.653
BLACK C /RED B
1 .903
2 .776
BLACK C / RED E
1 .956
2 .751
BLACK E / RED B
1 .905
2 .777
Click to expand...


Please don't edit a post. Make a new post....If you edit posts I'm not in the habit of looking back. and your change may go unnoticed...
 
LarryD said:
Where did Joe find the pin outs?
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If you google a transistor number you can find a data sheet that shows the pinout designations.


Desolder and remove the bias transistor leads from the back of the board and test again beginning wiyth red on base and black on emitter. Then red on base an black on collector.
 
List them as "left" bias transistor and "right" bias transistor with the left being the one closest to the transformer...
 
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