[Re: [Back again/Thermal considerations o]

[Harry Bissell]

The Aries modules I have look like someone built a dam of plasticine clay
around the expo converter (right on the pcb) and then back filled it woth
epoxy, and removed the clay when the epoxy set... maybe it was Dennis Colin
himself. I must have a pretty early rev. It's ugly as sin (but still ticking
after 25 years so....  I have what I think is inside the 317 filter block
(judging from the circuit traces I can read and ohmmeter readings, but I find
a weird 3k resistor with a long spacing, maybe its the elusive Q81 tempco
part, but 3K? I'm not sure of that value, 1K is a lot more common. I'll get a
copy up to the mailbox as soon as I acquire the technology to scan prints
(hey, if I still play with analog I'm at lest fond of the past, if not living
in it.)  ;-) Harry

tim.cockram at RedDragonFM.co.uk wrote:
Of course Epoxy is/was used to hide "ripped off" or simplistic circuitry. 
 In the pro-audio world both Aphex and Orban encapsulate strategic lumps of 
circuitry with great marketing names eg dynamic verification generator, 
which when you check out the patents contain a couple of op-amps and a few 
passives.  Ok so the epoxy blocks discourage circuit hackers but not many 
companies.

With regard to the Aries expo convertors I have to admit that I have never 
actually seen one but it looks very similar to a a third party part that was 
described (with schematic) in Electronotes.
 ----------
From: harrybissell at netscape.net
To: synth-diy at mailhost.bpa.nl; Tim Cockram
Subject: Re: [Back again/Thermal considerations o
Date: Wednesday, February 10, 1999 6:49AM

I always had the impression that the epoxy-potted boxes (like aries) were as
much to keep out the curious as to give "thermal stability". While it sure
does that, I note that in the case of Aries they also blocked out that 
portion
of the schematic, I'm sure that was also for "thermal stability". Oh maybe 
I'm
just too cynical... why would they want to hide the hardest part of the
circuit for the simple hacker to duplicate? I'll have the Big Mac, 
please....
:-) Harry Bissell

owner-synth-diy at mailhost.bpa.nl wrote:
After a few months of being incomunicado, it's good to be back.  It's nice
to know that people still care about analogue stuff (sorry I've had to
become very digital at work).

Back to business.

Appologies if I've missed this but there seems to be potential for the
scourge of circuit hackers,  epoxy or silicone potting of the converter
circuit.  Whilst this doesn't change the additional damping caused by the
thermal loss through the connections  it is a little more elegant than the
"Big Mac" box enclosure.

Many electronics supply houses sell potting compound and potting boxes that
are just the right size for the 3046 and support circuitry.

The idea of having a few ready to go, stable exponential convertors appeals
to me (similar to the Arp units in the 2500, the unit used in the Aries or
perhaps the  726 replacement offered by Moog Music UK (ú20ea I believe).

Regards

Tim



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