Hi there.

I was at the metal scrap yard the other day and when I looked in the "dirty cast aluminum" bin and to my surprise I see a vintage Nema head sitting on top of the pile

The PC, bulb and lense have been smashed off but the main body, slipfitter, socket/ballast and smooth style reflector were intact and in good shape.

The fixtrue is dated from 1974 and the ballast is very rusty. My question is, how can I tell what wattage the ballast is? No lables or markings anywhere other than the date of manufacture.

I'm going to assume it's a 175w MV ballast as these seem to be the most common but it could be a 100w or maybe even a 250w perhaps?

I will post pics when I figure out how lol...

It probably would be 175w but it could be 250 if the refractor is twelve inches across. The other problem is voltage. Is it single or quad tapped.

Try 250W lamp, if it does not run up completely try 175 etc

It probably would be 175w but it could be 250 if the refractor is twelve inches across. The other problem is voltage. Is it single or quad tapped.

I believe it's only wired for 120v as I only see two line in connecton points. I will try and post some pics.

Try 250W lamp, if it does not run up completely try 175 etc

If I had a 250w MV lamp I would but only have 175w and 100w lamps. I did try a 175w clear ED lamp made by Globe  and it seemed to run up to full brightness.

Can you measure amps in series with the lamp ?

Can you measure amps in series with the lamp ?

I could do that. I have a good multimeter and how would you go about probing for current measurement tho?

Nothing special, just wire it in series with the lamp....

Nothing special, just wire it in series with the lamp....

Thanks Ash.

Used a multimeter many times on automotive DC electrical systems but never with home A/C current. The danger factor is a little intimidating at first.

Wire it in up ahead, set to AC A, and dont touch while power is on

And use an appropriate multimeter, with the wires in the correct jacks ofcourse.....