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@vacuumtubes.com
636-939-9190
SND Tube Sales
105 N. Division St.
Bonne Terre, MO 63628
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