[time-nuts] Tektronix TM500 Series Help

[David C. Partridge]

Isn't the pinout of the MJE3055 (BCE) different from the SJE924 (ECB).

Dave 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Don @ True-Cal
Sent: 02 January 2010 20:33
To: time-nuts at febo.com
Subject: [time-nuts] Tektronix TM500 Series Help

Happy New Year to all!

In working on my TM501 which serves as the power supply for my AM503B
current probe, I had to dismount the 2 series pass transistors from the TM
case (heat sink). After repair (filter caps) and during remounting the
circuit board, Q12 transistor TO-127 case fractured while bending the leads.
This transistor is one of the two series pass transistors that some
TM-Series modules use as external mounted power devices. These two
transistors are used mostly with PSxxx power supply modules. They are not
actually used as active components of the TM501 and fortunately for me, not
used with the AM503B module so I am up and running again. I would like to
fix this situation so I could use this TM501 with any/all modules.

The manual (and device) says Q12 is an NPN, SI, Selected, TO-127 SJE924. For
completeness, the complementary Q10 is a PNP, SI, TO-127 SJE925. These
transistors types are the same across any TM-Series mainframe.

I can't find any SJE or MJE 9xx reference. Does anyone have a cross
reference or know of a substitute device for these transistors? I tried a
MJE3055 which is very general purpose and it does not work with a PS503A
power supply module. This, plus the word "Selected" in the manual, says to
me that something (Hfe?) must be fairly critical. Another alternative is
someone with a junker TM mainframe that would be willing to pull one or both
of these transistors.

Regards...
Don
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