[TenTec] Centurion Bias Transistor Follow on post

[w3ka at lycos.com]

Hi Mike.. When troubleshooting the same problem on a Ten Tec Titan 425, 
excess idle current, the fix was
an open diode, in the B- bias line to the tubes.  I am not familiar with 
the centurion bias circuit, but
check to see if TT also used a diode in series with the B- line causing 
a loss of bias to the tubes.  73, Jim


On 2017-11-20 18:09, Michael Marx wrote:

> Guys,
> 
> I just posted a message about my Centurion with a bias problem.  As I 
> stated I replaced the bias transistor which did not fix the problem.  
> Here is something interesting that I don't understand.  I bought 5 of 
> them from Mouser.  When I measure the transistor junctions with my 
> Fluke 87 meter in the diode function, one junction seems normal as it 
> measures .5 V in one direction and open in the other.  Normal, right? 
> Now the other junction measures open in both directions.  It also 
> measures open in ohmmeter mode.  Could I have bought 5 bad transistors? 
>  Is that even possible?  What am I doing wrong in testing these 
> transistors?  They are just an NPN bipolar transistor, right?  FYI it 
> is an MJ15001G by ON.  This is exactly what Ten Tec sent a few years 
> ago when I had to replace the transistor.
> 
> Very confused.
> 
> 73
> Mike WB0SND
> 
> Michael Marx
> sndtubes at vacuumtubes.com
> 636-939-9190
> 
> SND Tube Sales
> 105 N. Division St.
> Bonne Terre, MO  63628
> 
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