SOS Lighting Devices? (*NOT* SoundOff Signal!)

[ur20v]

EDIT: The label actually says "SOS Lightning Devices" (not "lighting")

I just received an odd little strobe I bought on fleabay this week. Seller had zero info but said they couldn't get the dome off due to rusted screws. I haven't gone to work on opening it up yet, but I did notice a label under the dome that says SOS Lightning Devices Co, Model 511... Google offers no useful info, no surprise there, buy I found somoething that mentioned the company was located in Philadelphia but is now closed. Not very helpful, but that's all I found. I'm going to try firing it up, but I'm not going to hold my breath as I'm guessing it's from the early 80s.

Anyone have any info on SOS Lighting Devices?

 

[ur20v]

I didn't try applying power to it and I'm glad I didn't after getting it open. Because I'm so manly, I was able to snap 3 of the 4 screws securing the trim ring to the dome with my sheer, brutal strength, but the slot on the fourth was already stripped, so no screwdriver blade would stay in it. My Dremel made quick work of the screw head and I got the light open.

Unfortunately the very first thing I saw was capacitor carnage:


There are four capacitors in total, so I may as well switch them all out, if I can find suitable replacements.




I will also try to find a replacement transistor, just in case:


I'm not sure what this component is... Diode?


The tube looks like it's seen better days as well:


This clear power wire looks almost like lamp cord or speaker wire and it gives me anxiety, even though it appears to be original...But it's quite ambiguous when it comes to denoting polarity, at least to me:


One interesting aspect of this light is the dome. While the optics aren't very sophisticated, the plastic itself is very thick and it's a very heavy piece, especially for it's rather small size. It's weather-beaten and gets quite dull towards the top, but I do believe it will restore nicely. The most interesting feature of the dome is the o-ring seal:


Aside from the power wire, it seems to me that this light was engineered to be very heavy duty and live a long life. Let's see if I can bring it back to life!

 

[Sparky_911]

I'm thinking some sort of aircraft light. The flathead screws are indicators that it's likely older than 80s. Maybe 60s-70s?

 

[NPS Ranger]

Looks like a heavy duty little unit. I don't think there is any authorized use for amber flashing lights on aircraft though. What kind of a mount does it have? The military used a lot of amber pole mounted lights on vehicles back in the day.

 

[ur20v]

It's definitely automotive, and it has 4 substantial bolts that go through the base for mounting. It's very likely this is from the '70s. I just wish there was some kind of info about the light or company out there.

I've been scouring the web for replacement capacitors, and was only able to find one site that claims to have the large gold 40 microfarad 450v capacitors in stock... for something like $38 EACH! The 0.68 microfarad 400v has also proven difficult to locate. And there is just zero information out there for the transistor, a Texas Instruments EP908 A7601, even on TI's own website. Of course there's a wide variety of coiled tubes on octal bases available, and I may get two just to experiment - one horizontally coiled and another vertically coiled - and see which works better, but I need to get it functioning first.

 

[RS485]

Nice find!

That mysterious device you pictured is a "spark-gap". It's a nice down-and-dirty "timing trigger " device as when the voltage across it reaches a certain point (likely ~230V) it sparks, shorting the trigger cap and causing the flash.

Here's a vid of one in an old Whelen PS with one:

Those old TI transistors are frustrating. FWIW, the "A7601" it a production code...I believe the transistor itself was made the first month of 1976 so I'd guess the fixture was made some time after that making a child of '70s.

I'd expect those two 450V 40uF caps to be wired in parallel. Please chime back if this isn't true. If I were tinkering with this, that's what I prioritize for replacement. Those two caps accumulate all the energy to flash the tube and the rest of the inverter circuitry reacts to their impedance accordingly (hence that signature "whirp" sound during the charging cycle).

The .68uf cap is metal foil, not electrolytic. They can degrade over time but I've seen plenty from the '70s still working satisfactorily.

I *assume* the EP908 plays the traditional role of switching ON to short the primary transformer coil to ground, then switching OFF to transfer energy to the secondary coil (i.e. "fly-back converter"). If so, then it would be an NPN power transistor and the TIP35C has worked out for me in strobes of similar design.

If you can't get it working, then if you could get a couple of good clear pics of the top and bottom of the entire PCB, that would help illustrate the design layout for further diagnostics.

 

[ur20v]

Nice find!

That mysterious device you pictured is a "spark-gap". It's a nice down-and-dirty "timing trigger " device as when the voltage across it reaches a certain point (likely ~230V) it sparks, shorting the trigger cap and causing the flash.

Here's a vid of one in an old Whelen PS with one:

Those old TI transistors are frustrating. FWIW, the "A7601" it a production code...I believe the transistor itself was made the first month of 1976 so I'd guess the fixture was made some time after that making a child of '70s.

I'd expect those two 450V 40uF caps to be wired in parallel. Please chime back if this isn't true. If I were tinkering with this, that's what I prioritize for replacement. Those two caps accumulate all the energy to flash the tube and the rest of the inverter circuitry reacts to their impedance accordingly (hence that signature "whirp" sound during the charging cycle).

The .68uf cap is metal foil, not electrolytic. They can degrade over time but I've seen plenty from the '70s still working satisfactorily.

I *assume* the EP908 plays the traditional role of switching ON to short the primary transformer coil to ground, then switching OFF to transfer energy to the secondary coil (i.e. "fly-back converter"). If so, then it would be an NPN power transistor and the TIP35C has worked out for me in strobes of similar design.

If you can't get it working, then if you could get a couple of good clear pics of the top and bottom of the entire PCB, that would help illustrate the design layout for further diagnostics.

Thank you! What a huge help that is, I really appreciate it. For now I will focus on the two main caps (which are in parallel like you surmised). The spark gap is very cool (though I'm sure quite noisy with RF)! I'm intrigued and going to go read up on it.

 

[kitn1mcc]

neat little light

 

[QUICKONE]

EDIT: The label actually says "SOS Lightning Devices" (not "lighting")


Anyone have any info on SOS Lighting Devices?

Here's another SOS Strobe, (and the Maker's label is readable)
SOS Red Strobe