[time-nuts] Tektronix TM500 Series Help
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Jan 4 01:00:58 UTC 2010
Mark wrote:
>The problem with ordering from Sphere is the prices. Their parts
>tend to be expensive and the shipping is a killer ($22+ last time I
>ordered) for a simple transistor. You can buy suitable replacements
>for under $0.50 each.
Suitable in the sense of Pd, Vceo, Hfe, and Ft, yes. However, there
can be good reasons for wanting an exact-fit part. In this case,
mounting transistors in other packages upside-down creates
heatsinking issues, and mounting them normally with crossed wire
leads creates potential reliability issues for equipment that will be
subject to shock and/or vibration.
Both sets of issues can be dealt with (the latter more easily than
the former, IMO), and I'm not averse to improvising -- but for
someone who has already decided, for whatever reason, that only an
exact-fit part will do, the only currently-available TO-127s I'm
aware of (other than the Sphere parts) are the ECG/NTE 182/183s, and
remaining stocks of those seem to be selling for around $30 each from
the sources I checked.
Best regards,
Charles
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