[sdiy] Chip Tempcos was RE: Solder paste and toaster ovens

[Peter Grenader]

Harry Bissell Jr wrote:

> There is a kind of "packing peanut" material for
> shipping that is a figure-8 shape of styrofoam.
> 1/2 of this stuff JUST slips over a TO-5 can

This is full of holes (the peanuts, not the idea).  I'm not sure how
effective this would be from isolating the ambient temp fluctuations of it
breathes like it does.  Small cell, maybe.   Epoxy would be best  - but also
a complete real drag.

Here's the thing - I've got a mold that can be used to pot the whole mess.
The expo converter is on it's own little 1 x 1 inch boardlette.  Two
potential problems arise:  ah...is that a 12 volt expo converter or a 15
volt?...hmmm coulda sworn I marked them.  second problem is the weight of
the boardlette once the epoxy is glopped on.  it inserts into the main board
with a socket.  it's fine on it's own, but add some weight and given that
it's mounted vertically, I'm afraid that gigging may jostle these out.  I
could solder them I guess - but they're so COOL as removable modules
(kidding).

I'm thinking that possibly the only thing I'll have to pot is the space
between the base of the tranny and the chip resistor.  Thing is, these VCOs
are real real stable.  the tranny pair I' using makes sure of this.  In
'normal' room conditions you'll be able to set your clock by them.  I
recently ran four of them at rom temp (a room full of drafts, that has a
heater running at night and the door open to the outside during the day) for
three days at 1k hz.  They were still tuned in unison 72 hours later   On
stage though with temp going all willy nilly - this may be another story.
But no one's complained about drift  yet - and they shouldn't ought'a -
again - the LS318.

<<The idea is to keep the tranny from changing
temperature quickly.  Using large mass (like you
suggest) is one way, Isolation is the other.>>

The second idea is to keep the tempco and the tranny at relatively the same
temperature -