VC Trigger Generator PCB

The VC Trigger Generator is a bit like an LFO, I suppose, but for generating triggers (these are the S-Triggers I was writing about earlier).  It has pads to allow for V-Triggers too; I've installed all of those parts, for completeness (they may help for any debugging, too!), but I'll be using the S-Triggers.

Yep, that's a LOT of transistors! 17 of them! (And only 2 are for the V-Trigger add-ons.)  Two SSM2210s have been replaced with discrete pairs. Note also the 2N4891 on the left (the little tin can)... hard to find, but I got 10 from Nikko in the UK. That should be plenty for what I may eventually build: they're only used here, the Sequencer, and the S&H.

There's a 2M resistor printed on the board; it should be 100k. It is well-documented on the schematic, etc., but just make sure you take note of it.

Another resistor is listed as "SELECT" - this is the resistor for the LED. I put a 1k resistor in there, which should be fine for the yellow LED I plan on using (Mouser 78-TLHY5401). There's not many LEDs in the Synthasystem: just here, the Peak Selector, and the Sequencer... this is the only one where you need to select a resistor value, though. In case you don't remember:

R_LED = (V_cc - V_f) / I_f , where:
V_cc is the source voltage (here, per the schematic, +12V)
V_f is the forward voltage drop of the LED (look this up on the datasheet or Mouser page, 2.4V for mine)
I_f is the forward current of the LED (look this up on the datasheet or Mouser page, 10mA for mine)

So mine calculates out as (12 - 2.4) / .01 = 9.6 / .01 = 960R, and I rounded up to 1k.