[time-nuts] Tektronix TM500 Series Help

Charles P. Steinmetz charles_steinmetz at lavabit.com
Sun Jan 3 20:55:17 UTC 2010


Mark wrote:

>The mainframe power transistors are NOT darlingtons.  They are plain 
>NPN/PNP power transistors with non-standard pinouts.

The TO-127 pinout is ECB -- most other plastic power transistor 
packages are BCE.

I just pulled the cover off a TM503, and the 151-0349-00 (and 
151-0373-00) devices in it are NOT darlingtons.

At least some Tek manuals say the 151-0349-00 devices are SJE924s, 
and the information I have on those (which I copied from a now long 
lost Motorola databook of the era) indicates that they are 
darlingtons (there is some corroboration for this on the web, but I 
have not found a web datasheet).  However, a current source of Tek 
parts (see below) says that its 151-0349-00 devices are MJE2801s, 
which I believe are not darlingtons.  So, either Tek was incorrect in 
stating that P/N 151-0349-00 = SJE924, or the Motorola datasheet I 
copied from was wrong that SJE924s are darlingtons, or I copied 
wrong.  (Surely it couldn't be the third?   ;-)   In any case, it 
does not appear that the transistors in TM5xx frames are darlingtons.

If anyone wants original form factor TO-127 transistors (presumably 
Tek old stock, marked "034900"), they are available from:

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

Best regards,

Charles








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