Gooooood morning! We've got a bit of a long one here as I'm seeking some answers and want to give as much info as possible...
As I am stepping into the space of HID light fixtures, I recently acquired a NOS ITT R175 Yard-Lite.
Date printed on the outer shell states it was originally from Mid-1977. Even came with it's original Westinghouse Mercury Vapor Bulb.
I've been attempting to get this thing up and going for the past few days, but I am getting some odd behavior from it. On first power up using the original packaged bulb, it came up wonderfully. At least, it seemed at first. Upon reaching full brightness, the ballast became unusually loud and the arc began to sputter. I promptly unplugged it and checked for any smoke, shorts, or physical damage, but found none.
I decided to give it another go about a couple of days later. This time, it did the same thing, except the lamp knocked itself out within about a couple of seconds of the arc sputtering.
Out of pure curiosity, I grabbed my only other on-hand MV, a much newer Philips 175w. Lit it up, and...it kept stable for significantly longer than the Westinghouse would. Absolutely no strange ballast noises or sputtering out after a few minutes (whereas the Westinghouse cut out after about 2 minutes). Confused, I threw the Westinghouse back in. Lo-and-behold...it dropped out again. I swapped the Philips back in...and now the Philips bulb is doing the same thing. Pretty thrown-off at this point and based on what I have heard from friends deeper into the hobby, my ballast may be cooked from the jump.
About a couple hours later I decided to plug it in one more time, but on camera so that I could show some friends what it was doing. Except this time...it decided not to do it? With the Philips bulb installed, it ran for a solid 10 minutes with no issues. I even unplugged it, cooled it off, then plugged it back in to see if it would stay. It stuck around another handful of minutes until I unplugged it.
Later on in the night when I was in my room and winding down, I decided to plug it in again and see how long I could get it to stick around. Roughly an hour or so with absolutely no complaints, smells, or sputters.
Lastly, I moved it elsewhere in my room to let it run even longer. Plug it in, runs fine, then...we're back to the sputtering. Except this bulb isn't knocking itself out. Genuinely have no idea now.
Apologies for the long post. This thing has me scratching my head and I cannot for the life of me figure out what is causing this thing to misbehave. Especially since it only seems to do it sometimes. A friend previously suggested I add a capacitor, as this fixture did not come with one out of the box. He later suggested the ballast was faulty after the conundrum with the two bulbs cutting off. Hoping I can get an answer or two. Maybe the 48-year-old ballast really is just bad after all of those years in the box
(and I'm just coping/desperate to not have to hunt down a replacement) 
