I did a conversion on a Holophane Bantam 2000 to 39w CMH at one point. I made a small bracket to adapt the existing medium base lampholder mounting holes to a G12 lampholder. As for the height, I made it so it roughly matched the arc tube on the 175w MH it was originally designed for.

Note that there also exist E26 to G21 screw in adapters. However the plastic on mine wasn't suitable for the heat of a 150w CMH lamp

I am looking to convert an AEL series 315 to run 150w G12 base CMH lamps with an electronic ballast. It should be pretty easy to mount the ballast on the power pad and rewire everything, but how should I go about making a CDM-T lamp compatible with the existing (FCO) optical assembly? Should I make a bracket that extends the lampholder out or maybe at an angle?

Any help will be appreciated.

I have been running a 175 watt MV Westinghouse RMA dusk to dawn for a couple years. It has a 120 volt NPF HX ballast. What I was wondering is this. Does the inefficiency of the NPF ballast severely affect the electric bill? Like versus a CWA running on 240 volt or a HPF HX ballast? And also I have wondered, versus a HX, how lossy is a single coil reactor ballast? And yes of course a reactor would be running at 240 volts, and I have been led to beleive that operation at 240v makes any light cheaper to run.

In my area a lot of the older lights from the mid 70s onwards were factory HPS, before the advent of LED there was stuff like Unidors, OV-15s, and B2255s which were factory HPS. There were some older lights such as Unistyles and M-400s, those were more likely to be factory MV here.

The oldest HPS install here was from 1967, it used GE M-400As.

Exactly what I was thinking guys . Plus , a lot of older fixtures had long enough production runs to have been made in multiple lamp types (Silverliners , M-400A , M-1000) As for NEMA tags , even they can be replaced so as mentioned above , unless one physically sees the original label inside , there's really no way to tell unless the fixture in question pre-dates MH or HPS such as a clamshell .

@BT25 - Yep, that's how I think too. Especially if the light doesn't have a NEMA tag.

For city streets I base the light source of the light on the lights that surround it. An AE 113 surrounded by other M-250R2s that are HPS? Must be HPS. A Westinghouse OV-25 in a city that I know has mostly GE lights that are HPS and I've never seen it before? Must be MV (I've seen this a few times). Of course you should gather info on whether the lights are city-owned or utility owned, and whether or not they've retrofitted lights, and of course what lights they've bought and their light sources; this also applies to private property too.

For shopping centers/strip malls/malls, it's hard to tell, since unless you've seen the inside of the light and the catalog number, you can't tell if they're original or not. Private owners are also more likely to retrofit their lights, unlike city/government entities. Of course, if the light has a NEMA tag, then that makes your job of determining the light source easier.

Today, I found my childhood graphics card, the nvidia geforce 7200 gs. I got the card brand new but was kept in an storage container for a year. Due to this, the VGA pins broke off and the fan support broke (if fan used it will hop around loosely). So little me taped another fan on and used adapters. Even today, it still works.
The only reason I got it during that time was not to play games, but to get aero theme on windows 7.
I am still waiting to find more of my old computer stuff .

As was discussed here recently, it is not the best idea to run CWA ballast with seriously reduced capacitor as the impedance becomes closer to pure capacitive, which is harsh for a lamp. Not the thing you probably want to do to a rare/collectible lamp.
 

I think that assumption comes from the dominance of mercury vapor back then...I've also seen old catalogs mention HPS and MH options too.

So, in this case, would the 425W H40 mercury vapor lamp still be overdriven on a 1000W M47 probe start metal halide CWA ballast even if the series capacitor value is near zero microfarads or could the ballast suffer possible overheating?

Alternatively, it may seem that a last resort for running these lamps could be to source a step up transformer with a 480V secondary and possibly do a series of trial and error tests of series choke ballast combinations until the lamp is running at the proper 1.7A operating current and 265V arc voltage drop?