There is one problem with all comments  above  ubcant combime output on a 2 lamp lead lag magnetic outout ballast .
   Even our auto transformer ballast would not handle this such low arc voltage  for very long.


   This lamp due 15 arc  volt and high current  it goijg need lot of iron and lot more turns to soak up most of that 120 volt here in the US.     Only ballast that I can think of that it would work
 Is  3  x 70 watt HPS 3 wire chioke ballast wired  in series to soak up most of that 120 volt OCV  while lamp  is running

  Or about 9 x crappy GE 320 mA preheat chokes that on once home depot sold .   Reason why 9 preheat ballast  because  it wired  in series- perallel configuration to lamp it current need and ballast to handle such low arc drop..  in 240 volt country
  U would need do same but with 9 x  40  watt fluorescent
chokes  to soak uo all that 240 volt  wires in 3 each in series
  Then parrallel the 3 sett of series choke . 

There were several different implementations of the heaters, one was to integrate the heaters into the LED signal modules, like what GE did with their GT-X Heated shell lineup (discontinued?) and another was to fit them into the visors.

I think in my area LED traffic signal modules are generally group replaced every 10 years or so. The first and second generation LED signal modules were changed out around around 6-8 years ago, replacing the original ones installed in the early 2000s, which themselves replaced incandescent signals.

I don't see too many issues with dirt accumulation here, even with the LEDs. I suppose back in the incandescent days, they were relamped annually so they were probably cleaned then too, not sure about them now though.

Why in green MH lamps, the electrodes barely glowing during run-up, compared to blue and other colors MH lamps?
Green MH lamps often glowing greenish during starting, while blue lamps glowing very yellowish during starting.
Why is this?

Hello,

My first try would be a leak transformer for an 90W SOX lamps.

Regarding the ballast of an 80W fluorescent, I suspect that RRK means the soviet 8ft fluorescent tubes and balasts?

I certainly think that these ballast are overloaded at such a low lamp voltage drop, however id need the exact ballast data to tell anything about how quick in would catastrofically fail. However I personally and this is my opinion you shold be fine with runnig that for short times / testing purposes.

Please be careful in knowing that a F40T12 ballast, a European 80W mercury vapor ballast, a North American 75W H43 mercury vapor ballast, or a North American 100W H38 mercury vapor ballast WILL QUICKLY OVERHEAT AND CATCH FIRE IN A MATTER OF MINUTES WITH THE ND20 low pressure sodium lamp due to the lamp’s extremely low arc voltage drop. THESE BALLAST SUGGESTIONS ARE EXTREMELY DANGEROUS AND MUST BE AVOIDED AT ALL COSTS.

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No issues with LED traffic lights here, except after 10 years in service a couple chips may go black which is acceptable considering the number of hours they rack up. No snow but plenty of dirt and rain.

I am unaware of any heating systems being built into the traffic lights. But i've never seen snow accumulating on them.

@LightsoftheWest: Thanks, makes sense. If my theory is correct, the evolution goes:

15-000 -> 25-000 -> Series 25 -> Series 125
13-000 -> 23-000 -> Series 13 -> Series 113 -> Series 115

-223 was a variant of the 23-000, with external leveling bolts.
-Later models went one numeral up if they lacked a PC receptacle.
(This does not include PowerPad versions.)

I texted the owners phone and still haven't heard back yet. I haven't really been active there for years but I would like to. If it gets back up and running I'll start posting more again.

The biggest problem I've seen with the LED signals is dirt accumulation on the top half of the module blocking almost all light from the upper half .