Unfortunately, some people will retrofit with an "almost drop in" lamp. This would be a LED lamp on mains voltage, and the ballast is just bypassed (and can be left there if removing it is too much work). I would hope to find MH alternatives, but I'm not really hopeful on that one.

That is exacly what i see done. And those LED lamps are exactly what we learned to expect from them, being LED....

One more thing i tried at some point in the past, is using a magnetically ballasted CFL (actually a PL + screw base adapter) straight on the output of the Mercury ballast. Here it works well as the ballast is just a choke, so it goes in series with the choke in the adapter, and its impedance is negligible compared to that of the adapter - so no real difference from using the adapter directly on 240V

In your case, the Mercury ballast when running only light load is basically a step up transformer, with the output voltage being its OCV. Our 240V PL adapters might well be the option that suits your Mercury autotransformer ballasts, if their OCV is around 240V.....



And how abot adding ignitor to the Mercury ballast and using MH lamp of the same wattage ?

Problem is, there are no probe start MH's below 175W and second there are no usable ignitors available in the US. So for some enthusiast showcase lamp you may import some 750V parallel ignitor from Europe, but that way is not usable for any commercial installation (problem with missing UL safety certificates, with the consequences in validity of insurance contracts,...), nor for any work you do as a contractor for someone else (legal responsibility issues).

I have seen 360 watt MH probstart for MV drop in replacement, also there a HPS retrofit lamps out there
But both lamp are expensive to obtain

Any problems using a superimposed ignitor with pulse MH ? Or are they of different spec from probe MH ?

With enclosed lantern, the worst that can happen is destruction of the gear & a lamp explosion. But that happens from time to time with just normal gear failures (shorting out old ballasts etc).... And nobody makes big deal of it, as it cannot cause harm outside of the lantern

I know the retrofit lamps are expensive, and it looks to me like a "close enough" common lamp + normal pulse ignotor may cost less than a special retrofit lamp

Iwasaki (EYE) makes an entire line of metal halide lamps for mercury ballasts. They are the "Clean Ace" line and I have seen a couple installations of these before, particularly in old mercury parking lot fixtures, and in one case, indoor 250w mercury recessed cans in a city hall atrium. They are all rated daylight 6500k, and run just slightly greener than a typical daylight MH lamp. They are all probe start and are an exact drop in for mercury fixtures. I installed one of these a few years ago in a 175w MV "bucket" area light because the customer wanted more light without having to replace the fixture. The color these lamps give off is quite nice, like a halophosphor daylight fluorescent

Cool, didn't know that!

The Iwasaki "Clean Ace" bulbs are popular for aquarium lighting-have them in 250 and 400W Good lamps!Mine are about 10yrs old and still work fine.

Any problems using a superimposed ignitor with pulse MH ? Or are they of different spec from probe MH ?

Probe MH's are made along MV spec's (only need higher OCV, but the same run current and arc voltage), pulse along European HPS specs, so the ballast currents and arc voltages do not match.
There are some 400W lamps rated for both ballasts, but I'm not sure these are sold in the US...

In my country MV bulbs still light up small parking lots and smaller streets. High power HPS took their place first in main streets, then low power ones followed for places with less traffic. What started out as a clever and energy saving effort, soon turned out to be a disaster - low power HPS started failing after 2-3 years and often are either cycling or completely off. They turned out to be a far more expensive technology to maintain, and instead of dimly lit streets we occasionally have complete darkness or repeating sudden switch-offs of light. Mercs were usually replaced here only after they stop working - one parking lot close to me has mercs almost 20years old - all green and with the light output of about 75W incandescent. Low power HPS, however, fail dissapointively quickly - they have nothing in common to high-power ones which (as I witnessed) can last as long as 3 decades!

Truly, mercs' output becomes almost uselessly low after about 3-4 years. I also hate the quartz tube darkening after as soon as couple of starts, but I've found an intricate way to minimize it - using 125W merc on a 40W T12 magnetic ballast! They wear very slow that way, the light output is comparable to 40W fluorescent, light color is warmer and more pleasant, heat output is reduced, and (what I liked most of all) their beautiful run-up takes as much as 5-10 minutes! They can be considered a very usable replacement for a 40W T12 with smaller size, easier to focus beam, and a very pleasant shade.

However, I think I'll miss SBMV the most - I adore that old-tech "hack"!

Will SBMV go away too? It may qualify as a specialty lamp.

Is there reason for the short life of HPS in your area ?

Here, 70W SON /I's (HPS with internal glow starter) tend to last about 5 years with present day Chinese production, and old ones that are still in service after 10 years are not uncommon

I am far not sure that using a 125W mercury lamp on a 40W ballast will make it blacken less. Most of the blackening happens in the starting/early warm up, when the electrodes are cold. With 40W ballast they may be too cold for as long as the entire working time of the lamp

Here for what i know SBMV stays

@Ash
I don't know. Here we even had 50W types if I remember correctly, which happened to last the shortest of all. 5 years is a short service life, since in my country street lights typically get replaced every 10-15 years. Cost of maintenance for low power sodium seems far greater than for mercs - both because of their shorter life and higher cost. And those low power types are an "adaptation" and "development" of original HPS technology for what I know, and seem to have many compromises - that's why they appeared later and are shorter lived.

What I say about 125W MV running on 40W T12 ballast is my own experience. When I bought my first lamp I had no control gear, so impatiently tested it with the only higher power ballast I had. Even after 5-10 startings to full power there was no blackening of the quartz tube, but it did appear rather fast after I purchased and started using it on original MV ballast (it took just 2-3 startings). My theory is that electrodes get less wear, as the emission at 40W is lower, and so are the internal temperatures in the quartz tube. I also tested the same lamp on 20W T12 ballast, but it took ages to warm up (15 minutes or so), warm-up was so gradual it almost appeared still, and the light output was uselessly low.

I adore SBMV, and have quite a few of them - 100W, 125W, 160W, 250W - all E27. I don't use them, just switch them on for fun from time to time. Nowadays they are mostly cheap Chinese OEM, some even so low quality they will probably not last much longer than an incandescent lamp. It surprises me SBMVs are not going to be banned as they are high power lamps with very low efficacy and many replacement options.

I think the biggest use for SBMVs today is for UV production for plants and reptile enclosures. They may stick around just for that reason.

There are compromises, but even with them, 70W SON /I last 5 years with cheap manufaturing and over 10 with good old manufacturing. It is fair enough lifetime for a low power lamp

The Mercury as you said, they may last for 30 years, but modern mercury lamps (without the emitter that leaves white deposit) have quite bad light output drop within just a couple years, then it is time to replace them anyway. If you have to do maintenance anyway, atleast use a more efficient lamp....

The electrode wear is determined by the current but also by the energy of the particles escaping from it. If the electrode is too cold, the voltsge drop is high, and so is the energy of particles escaping from it, then it sputter the electrode. So you have to stay above that minimum current that keeps the electrode sufficiently hot

I have a SBMV from around 2000, back when it was made in Europe. Used it for a while in a 125W Mercury lantern that i have (bypassed the ballast), before i found where to get the proper 125W lamp