Slightly OT: Anyone want to swap CEMs for SSMs?

[Jim Patchell]

    When I looked at the block diagram for the CEM3340, the biggest mystery to me
is the internal temp compensation for the exponential converter.  Everything else
looks pretty straight forward to reverse engineer.  Perhaps if one were to make a
compromise and use a tempco resistor for the temp compensation one could make
something that would be pin compatable, but not nessesarily and exact duplicate of
the original.

    -Jim

"Gavin R. Muir" wrote:

> Hi Rob,
>
> > hmm, maybe ripe time to start making SMD replacement modules for these
> > units...
> > If I only knew EXACTLY what the heck is in these suckers, I could prlly make
> > it small enough to be just ever so slightly larger than the actual CEM
> > chip..
> > Anybody know whats on the die?
>
>     This is an excellent idea, even if we could get Mr. Curtis'
> co-operation. I've heard that short of an order for 25,000 to 50,000 units,
> he won't stamp a new run, and no manufacturer in their right mind would
> design a synthesizer which required a run this big. Basically, SMD
> replacements shouldn't be seen as competition to OnChip, even though they
> own the designs.
>
>     I think that these 4 chips are the ones which are really worrisome
> (although there still seems to be a large number of 3020s around). I wonder
> how the chip hoarders out there charging nearly $100 a pop will feel about
> this though! :-)
>
>     This would be ideal for my purposes, as I (along with any other CEM
> based synth owners) could rest somewhat easier that their investment is not
> wasted if the silicon goes bad. All this without having to a) spend hundreds
> of dollars for something that COULD happen, but may not, or b) ravaging a
> poor, totally functional synth for parts. Neither of these are very tempting
> to me.
>
> Cheers and Thanks,
> Gavin.