Hi All,

I bought an old security light fixture (the old classic die-cast aluminum sort that you see on garages/barns) that I believe used to be mercury vapor, but it is so old that the informations on the bulb are gone and the transformer is rusted. Probably the old owner took it down because it stopped working, but I got the fixture for $10 off of marketplace so I figured it would need new hardware anyways.

I'm considering keeping the fixture as MV and putting it up in my yard using a metal halide ballast, as I understand that you can run MV lamps off of the next-size-down probe-start MH ballasts. I may also just convert to HPS since I have some 70W HPS lamps already.

Regardless, I am wondering: What is a good, reputable brand for ballasts? I would like to buy a variety of 120V ballasts all at once to have in inventory, and one potential website selling ballasts sells "Keystone" ballasts. What are some brands that you all prefer for 120V ballasts?

In the search for ballasts I am also seeing the distinction between magnetic and electronic ballasts being made from potential vendors. What are the key differences between magnetic and electronic as it pertains to reliability, and which do you all prefer?

MV Bulb -> MH Ballast compatibilities are not as simple as one wattage size lower. For 175W, 250W, 400W, and 1000W* lamps are completely compatible with MH ballasts of the same wattage. For wattages below 175W, it becomes more complicated, but those are rarely used for yard lights (175W and 250W are most common as far as I have seen). If you are considering using 100W MV or below then we can cross that bridge when we get there, in my opinion it's more effort than it's worth (I bought a 100W MV lamp and running it is a pain). HPS lamps are very uncomplicated in this regard as their ballasts are still widely available. 70W should be just fine if you decide to go the HPS route.

As far as brands go I am not very familiar with that, I am sure some are better than others but I am not sure which ones.

For HID lamps, almost all ballasts are magnetic, meaning resembling a transformer instead of a circuit board. Electronic ballasts start to pop up more often in wattages below 100W, and they are probably more expensive and not worth it. Reliability with these I would assume is much more variable, though I don't have anyu experience with them. Also never heard of them even existing for probe start lamps, though I could be wrong.

What is your goal with having multiple ballasts on hand? Just wondering cause if you want to be able to just run some lamps every once in a while I have a ~perfect solution for that.

Also uploading a picture of the lamp and fixture will help determine what it would have been, these types of lamps are very easily identifiable usually.

I think that post light conversion project would be cool. Indeed 175W can be kind of a lot for a post light. I think for this application a 50W HPS, 70W MH, or 100W MV, which are all roughly equivalent in brightness. They are decently brighter than your 35W HPS porch light but a good step below 175W MV. Now to choose which one...

50W HPS:
- Light will obviously match the color of your HPS porch light.
- Ballasts are easy to find.
- Bulbs commonly available in medium base so you won't have to change the socket in your post light.

70W MH:
- White light, which may or may not be desirable for you.
- Ballasts are also very easy to find.
- Bulbs pretty much only available in medium base, again no need to change the socket.

100W MV:
- White-ish light if coated, or if clear a teal that will contrast the HPS porch light which may or may not be desirable (I think it'd be cool).
- Ballasts are very difficult to find, and when you do find them they invariably aren't 120V. You can use a 70W MH ballast which will underdrive slightly, or a 100W MH ballast which will overdrive slightly.
- Commonly available in mogul base, though you can shell out some extra to get an A23 shape one with a medium base. Depending on your fixture you may or may not have the necessary space to fit a mogul socket.

You mentioned having 70W HPS lamps on hand, they are roughly as bright as a 175W MV but if you want it to be real bright that is another option. They are also available in medium base and ballasts are of course easy to find. No right or wrong answer to be honest, these are just my suggestions