SergeModular

I received the Ed-lab digital lab via USPS yesterday and am getting
familiar with it now, but I do have some things to report on it. For those
who question the relevance, this is a 25 year old digital logic trainer
that uses banana jacks and TTL logic, making it it a potential logic
expander for any banana modular (Serge, Fenix, ModCan, Synton.)

Before I get into this, however, a plea: Can anyone point me to data sheets
for the following chips: MC845 (JK flip-flop), SN7480 (gated full adder),
and SN7496 (shift register)? I don't recognize a lot of the jacks on these
things. Also, what's a good cleaner for banana jacks?

A couple of pictures of the unit can be seen at
ftp://ftp.technotoys.com/pub/Misc. It's about 23"x13", in a 2600-like
wooden box, covered with Tolex, and has a matching cover. There's a
built-in power supply (yay!) and a fold-out wire stand for adjustments.
Amazingly, the bonehead who shipped this didn't even put it in a box - he
just used clear tape to wrap it and cover the hardware, then taped on an
address! It's amazing it survived.

Internally, this thing is all handwired, with very simplistic PC boards
directly soldered to the front panel jacks. Fortunately, all the chips are
socketed and exposed, so repair at that level will be easy. One switch is
broken, one flip-flop is dead, many jacks are corroded and intermittent,
and a few are cracked, but overall it's in good shape.

This thing is loaded with logic.

5 x flip-flops
1 x Full Adder
1 x 4-bit shift register
1 x BCD to 7-segment driver and display
1 x 16-jack expansion board slot
7 x multiples (4 or 5 banana jacks each)
4 x 4-input AND gates
3 x 4-input NAND gates
3 x 3-input NAND gates
2 x 4-input OR gates
1 x 2-input NOR gate
4 x 2-input NAND gates
1 x momentary X/Y switch
8 x toggle switches (high/low outputs)
1 x variable frequency clock (with complementary pulse outs and 2 ranges)
1 x line clock (60 Hz)
1 x 4-bit D/A convertor
1 x comparator
5 x inverters
5 x LEDs
ground, +v, and reference voltage jacks

I did some measurements and ascertained that the levels used are 0v and 5 v
(4.59v, actually), so this will trigger my synths. As to how it will handle
overvoltage inputs.. good question: I need to look at my TTL texts. There
is no buffering anywhere in the system; this is all raw ICs, with some
additional support circuitry.

I have not yet hooked it into the synths, primarily because I need to make
some room for it, but so far everything looks good.


Jim Johnson
Metaphoric Software
-------------------
Makers of Techno Toys
Software for Electronic Music
http://www.technotoys.com
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