I also try to reduce the number of wirenuts in my cobraheads by making use of the terminal block and using spade connectors to splice wires when needed. I usually use the unused voltage taps zip tied up too. My M-250 CF was the exception, I wired the unused taps to the unused positions on the terminal block.

Interesting that the M-400 used a completely different terminal block compared to the M-250. I wonder why did GE use this odd one with integral socket shrould.

I'm not sure. The socket mounts directly to the black thing. To adjust the socket, you adjust the bracket that holds the terminal block in place and the whole thing moves. The original M-250 (M-400 for 175 and 250W lamps) used a terminal block with a double-length black thing to attach the socket so the lamp would be centered. I've never gotten to see one of them in person though. Such an overkill for a 175W lamp lol. HUGE fixture.

Normally with a PC socket, the far left would be PC black, 2nd would be PC red and ballast input, and far right would be common. In this case with no PC, the far left would be ballast input, 2nd empty, 3rd empty, and far right common. The only time all four terminals would be used is with a 240V ballast with 120V PC, in which case PC hot is far left, 2nd is PC red and ballast input, 3rd is ballast line connection, 4th is PC neutral. I like to use the empty block when present for a ground connection. So far, any 240V lights I've gotten I've converted them to 120V PC sockets. I do this to make it all uniform across my collection so I don't inadvertently stick a 120V PC on a light wired for straight 240V. I did this to my AE 13, OV-15, and two M-100s, which were all straight 240V.

Very interesting. Seems kinda odd compared to modern fixtures to adjust the socket by moving the terminal block lol. Hmm, I've always wondered what the original M-250 looked like inside. I always wondered why GE offered it instead of continuing to see the Form 175 Powerpack until the M-250R was ready. Seems kinda a waste to have a 400w sized fixture with a 175w lamp lol.

Ahh, I think my Crimefighter more or less follows that convention. For the grounds I either use a empty block or install a grounding lug



to a tapped hole on the housing and then attach the ground there. If a fixture has the neutral tied to ground like my R47, I remove it before adding a real ground. The PC I always wire to the same voltage as ballast voltage since all my lights are 120v only or multi tap wired for 120v. If I get a 240v light I might rewire the PC socket for 120v since almost all of my PCs are 120v only. I think I have a 120-277v PC somewhere. If I ever get something like a 277v, 347v, or 480v single light I'd probably just replace the ballast to a 120v one lol.

I think they did continue to offer the Form 175, at least in remote ballast. The Powerpacks were a pretty short-lived thing though. The M-250 might have just been a "new" alternative. They did continue making the Form 400 (remote ballast only, not the powerpack) until I think the mid-60s. After that they just started selling "empty" M-400s for remote ballast.

Ah yeah my preferred method is to run a pigtail from the terminal block to a screw in the fixture but if there's no free terminal block position I just connect the ground right to a screw in the housing or connect a loose wire to the screw and wirenut the ground.

Ahh, when I connect a ground to a screw, I'd like to use stranded THHN wire and a crimp on ring terminal to ensure the wire is snug under the screw. I'll use solid core if I'm wiring up a ground in a fluorescent though.

Ahh so they made the Form 400 until the mid 60s. I guess this explains why in old pictures of Toronto I see clamshells installed well into the 60s. Toronto had a lot of remote ballasted mercs in the suburbs back then.

The same terminal block arrangement shown is also found on M-1000 luminaires up until 1971 when GE revamped its BASIC line of luminaires (non Powr/Door) to include the M250R1, M400 Split Door, and M1000. I have a mid-60s M1000 and two 1970 M400s with this block arrangement.