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Ash Flash Discoverer II

Ash Flash Discoverer II

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Merry Christmas! This is one of two lighting-related gifts I received this Christmas. The other is from a fellow member which I will upload later.

I bought this on eBay in November, after a several month-long search. Although it's a little rough cosmetically, I'm pleased to report that after cleaning the battery terminals, this lantern works just fine. Steel wool cleaned up the chrome and made it shiny again. It came with an unbranded daylight lamp that I have no doubt is the original. It shows very little sign of wear. I didn't know anything about this lantern except that it was apparently preheat, which is why I've been on the hunt for one. I've since thoroughly examined it, and I have all the details.

It is an electronic ballast, utilizing one transistor. The ballast appears to be an off-the-shelf part, made by NEC. It bears the NEC name and a model number, and the transistor is also NEC. It is indeed preheat, more correctly an odd sort of preheat/rapid start hybrid. Only one cathode is heated, and OCV is applied while preheating. So when powering on you preheat until the lamp reaches a hot-cathode discharge, then let go. When only that end of the lamp is inserted, it can be seen glowing orange when preheating. Sometimes an arc strikes across that end. This is evident that preheating is provided by the ballast itself (perhaps an alternate tap on the transformer), rather than being directly connected to the power source. I've found that you have to be diligent of ceasing to preheat once the lamp has started, as when the batteries are good enough it can cause such high current to travel across the cathode that it damages it.

Notice the white thing on top of the lantern - that is an incandescent warning lamp that lights up if the lantern is powered on, but the lamp has not started. It appears to be connected to the output of the ballast, perhaps serving as a dummy load to protect the ballast when the lamp has not started. When batteries are fresh the OCV is high enough to instant start the lamp with no preheating at all, but usually preheating is required to start the lamp.

This lantern runs off a monstrous 9 D batteries. The output is regulated surprisingly well - lamp current lowers only slightly as the batteries wear. The biggest sign of battery wear is that starting becomes increasingly difficult as OCV and preheat current lower. With fresh batteries, input current is about 0.55A running, and 0.70A preheating. This lantern is able to run on worn batteries impressively well - it's able to start some lamps down to a loaded voltage of 0.8V per battery!

This lantern is very well made - the entire body is metal, as is the reflector and the internal structure that the ballast is attached to. With batteries it weighs 4.5 lb! It's also very easy to completely disassemble. I took it apart while cleaning it up, and took pictures of the ballast, which I will upload later.

Something intriguing I found was that if I connect the lamp in a traditional preheat configuration, using a wire to manually preheat the lamp, the ballast pushes plenty of current through the cathodes, causing an arc to strike across both. It works so well that maybe someday I'll actually modify this to work that way. I wonder why they never did it that way to start with?

Ash_Flash_Discoverer_II.JPG IMG_4972.JPG IMG_4944.JPG IMG_3186.JPG

Light Information

Light Information

Manufacturer:Ash Flash Corporation
Model Reference:Discoverer II
Lamp
Lamp Type:F4T5
Fixture
Fixture Type:Portable fluorescent lantern
Ballast Type:Electronic - single transistor with semi-preheat
Electrical
Voltage:13.5V DC - 9 D batteries
Physical/Production
Factory Location:Japan
Fabrication Date:Possibly 1969

File information

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Filename:Ash_Flash_Discoverer_II.JPG
Album name:themaritimegirl / Flashlights & Lanterns
Keywords:Lanterns
File Size:251 KB
Date added:Dec 25, 2015
Dimensions:2465 x 1848 pixels
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DetroitTwoStroke
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Dec 25, 2015 at 08:07 PM Author: DetroitTwoStroke
Neat!

Pride and quality workmanship should lie behind manufacturing, not greed.

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GoL Solanaceae.Keif.Fitz Keif Fitz bubby_keif
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Dec 25, 2015 at 08:17 PM Author: Solanaceae
This is an amazing find there, Trent.
Now, if the current on the one cathode is so rough, could you wire the two cathodes in series so they both are heated and they don't get stressed?

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themaritimegirl
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themaritimegirl themaritimegirl themaritimegirl
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Dec 25, 2015 at 08:31 PM Author: themaritimegirl
Thanks guys!

My guess would be no, not the way it's set up anyway. The cathode heating is paralleled with the current going through the lamp itself, so you can't heat both cathodes without redesigning the whole circuit. It's forgivable since you shouldn't still be preheating once the lamp has started, anyway. It's only after the lamp has started that preheat current increases.

As I said though, it appears that the whole thing would work fine wired in a traditional preheat setup, so maybe someday if I'm feeling bold enough, I'll re-wire the switch to do that.

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GoL Solanaceae.Keif.Fitz Keif Fitz bubby_keif
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Dec 25, 2015 at 08:37 PM Author: Solanaceae
Yeah, I would try to conceal the starter, I definitely wouldn't physically modify it. Also noted, I'd see where you come from about redesigning the curcuit. If you put the neutral/positive and the hot output, you'd short the thing out.

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themaritimegirl themaritimegirl themaritimegirl
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Dec 25, 2015 at 08:38 PM Author: themaritimegirl
It would be manual preheat, like it already is. A glow starter doesn't work, anyway - I tried.

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Dec 25, 2015 at 09:20 PM Author: funkybulb
Beside i there one problem it wont run right being heated at both ends. That why u have
anode and cathode for DC. beside a FS 5 or FS2 starter need 80 to 90 volt to fire. A F4T5 only need 30 arc volt to run so OCV only need be in 60 volt range this why a starter wont fire.

No LED gadgets, spins too slowly.  Gotta  love preheat and MV. let the lights keep my meter spinning.

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themaritimegirl themaritimegirl themaritimegirl
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Dec 25, 2015 at 09:57 PM Author: themaritimegirl
It does work being preheated at both ends when wired in a normal manual preheat configuration. I tried it and it worked, as explained above.

The ballast produces way more than 60V OCV. Remember, this isn't a magnetic ballast - there's no inductive kick, so there has to be enough voltage to make the lamp glow, and then heating the cathode allows it to start. I guess in that sense this is really a sort of rapid start ballast, rather than preheat.

The starter does ignite, but the current isn't enough to cause the contacts to close. I think the warning lamp is connected at the ballast output in parallel with the fluorescent lamp, so the resistance of the warning lamp overpowered the starter. I think the switch is wired in such a way that the warning lamp is disconnected while you're preheating (so it doesn't steal the needed OCV from the fluorescent lamp), so maybe if I held the switch in while trying the starter, then it would work.

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themaritimegirl themaritimegirl themaritimegirl
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Dec 26, 2015 at 10:02 PM Author: themaritimegirl
I just found two advertisements for this, both dated 1969! I thought this should be older than the Discoverer V, my example of which dated from 1970.

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themaritimegirl themaritimegirl themaritimegirl
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Oct 22, 2016 at 03:14 PM Author: themaritimegirl
I've done some work on this lantern recently. A while back I was doing a voltage range test on it, and while I had it running at the full 13.5V, I noticed the current started increasing at a visible rate, and I started to smell something. I shut it off, and when I lifted up the lantern I found a red puddle underneath - the paper capacitor had gotten hot and melted all the wax off it! So I replaced it with a mylar film capacitor, and that fixed the high current draw.

Today I went ahead and replaced the electrolytic cap. No change in performance, but good to do, I figure. While I had it open I studied the complicated-looking switch, and figured out how it works. I also discovered why a high-current arc strikes across the cathode, sometimes blowing it, when you preheat. It turns out that in the preheat mode, the cathode is simply directly connected to the power supply, with no ballast circuitry involved. This is a surprisingly lazy design, and I didn't expect it.

I also found that the open-circuit voltage is 120V at 12V input, measured with a true-RMS multimeter I now own. Running frequency is about 18 KHz. The incandescent warning lamp is connected between ground and part of the ballast circuitry. There's about 3V across it when lit.

Now that I know how the switch works, I'm more motivated to someday re-wire the whole thing into a standard preheat configuration, with the cathode heat provided by the ballast itself.

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