For awhile now, several members have been on a quest to run incandescent lamps in their packs, instead of LEDs. With the reference from Ken’s pack in this thread, the discussion evolved into running the lamps using this circuit. That then turned into “if we’re going to use the correct circuit, why don’t we wire wrap it and get it as original as possible?”
As it turns out, amongst these members, I’m the only one with the tools and (slight) experience to do wire wrap. I identified the parts needed:
ULN2004, 4015, 4047 chips
Capacitor and Potentiometer
Wire wrap sockets
Wire wrap socket tags
Bulb sockets (these are the replacements for the originals, which are near impossible to find)
7328-type bulbs
Perfboard (the salmon colored boards are a material that hasn’t been used for years and is difficult to find)
I started with the strip of 15 lamp sockets. I cut down the correct size strip of perfboard and glued it to a second piece of perfboard, cut to size. Now, I tinned and soldered a length of stripped wire to the common pin on the sockets (this is VCC, or positive power). Some wire wrap gave me the following (I used solder on each of the lamp socket wire wrap joints, as it appears in the reference photos):
3 sockets with wire wrap tags and 15 bulbs later, and I wound up with this:
Now came the fun (and frustrating part) of deciphering the driving circuit. Knowing how 4047 and 4015 chips function was a boon, but layout still had issues, most notably the lack of a good power supply. Each lamp is rated for 200mA at 6V, and the circuit itself draws additional voltage and current. Off-the-shelf batteries that can be used to drive LED circuits don’t allow for the 3A of power this circuit ideally needs. Using an old ATX power supply, I was able to supply the circuit with 5V and plenty of current. Since lamps care more about amperage than voltage to light well, and CMOS chips are 5V, this worked very well, as you can see here:
https://www.youtube.com/watch?v=vcgzAABQibg
The issue I found with this circuit is, it’s upside-down. After looking at it closely, there is no way the circuit can’t NOT be upside-down, given the outputs of the 4015 chips. After looking through Ken’s thread, I noticed that the lights were all apparently set to be static, and one of the 4015s on the powercell appeared to be broken, which explains why no one to date has seen this behavior.
Since the goal is to use these circuits in packs, I’m going to simply invert the wiring from the 4015s, which is probably what they did in GB2 for the other semi-hero pack electronics, and this one was left intact. Since most of these packs are seen in pairs, rather than all four in one scene, there would be no benefit to making another circuit or fixing this one.
Next step; hours of wire wrapping.
