[time-nuts] Tektronix TM500 Series Help

[Charles P. Steinmetz]

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