[sdiy] Buchla Easel sequencer & CMOS output short circuit protection

[Aaron Lanterman]

I need to go into Buchla PCB layout rehab. The first step is admitting  
you have a problem.

Anyway, having finished laying out a board for the Easel's Pulser,  
I've moved on and have the schematic for the 5-Stage Sequencer in  
Eagle. I've included the sequencer output summing circuitry, which is  
on a different board in the Easel, on this board.

The schematic is at

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_1_200.jpg

Two questions:

1) There's a +15 V and +5 V brought to this board, along with a note  
about "eliminating the +5 V" supply by changing some things and using  
a +12V supply for the LEDs.

Anyone know what the chips are actually powered off of? It's a bit  
ambiguous. If the +5 V volt supply was really _just_ used for the  
LEDs, I wouldn't see any reason to change R9 and R19... which makes me  
suspect that the rest of the circuit is powered off the +5 V (or +12  
V)... but I really don't know.

2) In the easel, the various NOR gate outputs at the top of the  
schematic all go to other parts of the Easel. Here, I want it to be  
able to operate as a stand alone module, so I'm bringing all those  
outputs to outside jacks (if the user wants them).

Anyway, is it safe for me to do that, or should I put some sort of  
short-circuit protection resistor at the output?

- Aaron