[time-nuts] Tektronix TM500 Series Help

Charles P. Steinmetz charles_steinmetz at lavabit.com
Sun Jan 3 04:17:06 UTC 2010


Don wrote:

>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?

The only thing special about the SJE924 (and 925) is the package (now 
long and truly obsolete) and the fact that it's a Darlington.  Any 
transistor of the appropriate voltage and dissipation ratings can be 
used, form factor permitting, if you add the second (driver) 
transistor externally.

My Tek manuals say the transistor in question is Tek P/N 
151-0349-00.  The following source sells TO-127 transistors marked 
"034900" for $6.50 each:

http://www.sphere.bc.ca/test/tek-parts/tekparts2.html

These should be direct replacements; however, the source identifies 
them as MJE2801, which -- if correct -- I do not believe is a Darlington.

Best regards,

Charles 






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