[sdiy] Tempcos a NoGo

[Tom Arnold]

On Thu, Jun 07, 2007 at 06:20:33PM -0700, dj hohum wrote:
> 1) Tempco resistors.
> A pain to get, and expensive when you do.

Cheap from Digikey in SMD.  Harder to work with of course, but definately
cheap.  Manufacturer is Panasonic, if you're interested I can dig for the
part number or I'm sure someone will volunteer it.  Something I've played
with is making a small board to hold a dual transistor and one of these SMD
tempco's on so that it fits the pinout of the DIP8 LM394.  Put a blob of
thermal epoxy on top and now you have your compensated expo pair.   Hard 
part is finding a dual transistor that everyone can agree on...

> Why are tempcos, in particular Q81 variants no longer produced? Surely
> there were other applications other than music synthesizers? 

The Q81 is actually still available if you know the correct company to order
them from ( Vishay/Ultronix ) and are willing to buy a bunch.  The Tempco's
I currently have ( besides the SMD ones ) are KRL's.  I think another
supplier is Precision Resistor.   When a group purchase is done ( I'll be up
for that in a month or so ) they get fairly inexpensive.

-- 
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