ASM-1

[Stopp,Gene]

Allright Kevin! I could give you a hard time but.... naaaaaah.

When 2N4391's are used look out for slightly positive offset sawtooths
as the VCO cap may not discharge all the way to ground. But then again
you used a 33pf instead of an 18pf, so it may be all right after all
since the FET should be on longer (I think). Let me know if the high
frequency track is OK, I'd be interested to hear.

I can't remember what I used for these caps. Maybe I had 18pf's. I think
I also used 33pf's instead of 30's. I can check when I'm back home.....

I used sockets for my two prototypes but after that I just soldered them
chips in. Wish I didn't now, I've seen some strange EG problems on just
one of my boards and I suspect either the 4002 or the 4053. Amidst all
this talk of CMOS maybe I should add that I've seen the 4053 do things
that were in TOTAL CONFLICT WITH THE DATABOOK but I didn't take notes. I
remember some analog switch path did not behave when a certain voltage
was on another totally separate switch pin but I never took notes. I
*did* check that everything was within operating limits, at the time.
Like I said, didn't take notes, so I have no details. Of course the
envelope generators on the boards with sockets behave themselves
wonderfully. Of course.

Funny that your current draw numbers are higher than mine were - I got
about 80ma on each rail. Hey, I have an idea - did you use 100K trimpots
for the ones across +/- 15 volts? Like the VCO initial frequency, or the
VCF offset trimmers? If you used lower values then that would explain
it. Or maybe my meter wasn't calibrated at the time. Or maybe yours
isn't! :) :) :) Kidding. 

I have one unit in the music setup, rackmounted with a MIDI-CV
converter. With the tempco's installed it is just perfect. I turn on the
power strips and blammo - the VCO's are still in perfect tune.

Anyway, good to hear that you got it going finally.

 - Gene

p.s. how are your hit-counters now that your web page URL has made it
into the magazines?

 ----------
From: Kevin Lightner
To: synth-diy at mailhost.bpa.nl
Subject: ASM-1
Date: Monday, March 02, 1998 5:04AM


I've just finished assembly on my first ASM-1. (Sorry it took so long to
do, Gene!)

First off, I'm very happy to say that it all worked upon it's first
power
up!  Yeahhh!:)

However, if some of you already experienced ASM-1 folks don't mind , I
have
a few questions to ask.... :)

First a descriptive-
My ASM-1 uses 2N3904s (instead of the MAT02) and KRL 1.87K 3% tempcos
(similar to Arp).
The pairs and tempco are bonded to each other for each VCO.
The FETS are 2N4391's.

I didn't have any 30pf caps for the VCF or 18pf caps for the VCO's.
Instead, I used 33pf caps for both.

It's about 80% 1% metal film resistors (the vco summers and other
criticals
are 1%), but the rest are 5% carbon film.

Standard sockets (not machined) were used. (Generally, I use machined
but
this is a LOT of IC's :)

Board is wholly defluxed (and gorgeous!)

My current draw is 103ma (+15volts) and 118ma (-15volts).
(Strange for me to see the negative rail drawing more than the
positive.)


Everything appears to work fine. Waveforms are of great shape, noise is
good, VCF works, etc.
The VCO's seem very stable too. :)

I haven't really hooked up pots and used or played the unit.
 I've just gone through each "module" functionally.

Any thoughts / ideas / tips on the above? Bad choice on caps, resistors
or
3904's?

Thanks,
KL