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ISX 18-P SOX ignitor Thanks to Ria for sending this 10w SOX parallel ignitor for investigation. There is very little I can find online about this device. The label states it is suitable for 10w and 18w SOX lamps. Shown here with its radiograph to determine what’s inside. From the image I can say there are just two components. The larger looks like a capacitor and it is wired in series with another device. I am not sure from the image what the second device is. It is possibly a MOV (Metal Oxide Varistor) These can drop to a low resistance when a sudden high voltage is present, so could generate a pulse across the lamp. I’d be interested in any other suggestions. Keywords: Gear

ISX 18-P SOX ignitor


Thanks to Ria for sending this 10w SOX parallel ignitor for investigation. There is very little I can find online about this device. The label states it is suitable for 10w and 18w SOX lamps. Shown here with its radiograph to determine what’s inside. From the image I can say there are just two components. The larger looks like a capacitor and it is wired in series with another device. I am not sure from the image what the second device is. It is possibly a MOV (Metal Oxide Varistor) These can drop to a low resistance when a sudden high voltage is present, so could generate a pulse across the lamp. I’d be interested in any other suggestions.

QL_85.jpg ISX18P_ignitor.jpg starter.jpg D2e.JPG
Lamp/Fixture Information
Manufacturer:Whitecroft lighting
Model Reference:ISX18-P
File information
Filename:ISX18P_ignitor.jpg
Album name:Tuopeek / Gear
Keywords:Gear
Filesize:361 KiB
Date added:23 Jan 2026
Dimensions:990 x 1782 pixels
Displayed:574 times
DateTime Original:2026:01:23 19:13:11
Exposure Time:1/250 sec
FNumber:f/5
File Source:Digital Still Camera
Flash:No Flash
Focal length:45 mm
ISO:800
Model:NIKON D3400
Software:Adobe Photoshop Elements 2.0
White Balance:0
URL:https://trad-lighting.net/gallery/displayimage.php?pid=1100
Favourites:Add to Favourites

Comment 1 to 10 of 10
Page: 1

Max   [Sat 24 Jan 2026 at 04:57]
That's an intriguing design indeed. That small device next to the capacitor is too small to be a glow starter of any sort, so the MOV hypothesis is definitely not unlikely. Did you take this X-ray shadowgraph by yourself or did you go to your local dentist?
Tuopeek   [Sat 24 Jan 2026 at 10:53]
Interestingly, you mentioned glow-bottle, I tried my own version using a glow-starter, as I don’t seem to have a suitable MOV. I also found gas filled spark gaps work but they tend to trigger lower than line voltage. The best I had randomly fired during the lamp run up, perhaps with back ground radiation. A glow bottle and a 2uF capacitor worked very well and would happily ignite a 35W SOX on 18W ballast, including hot restart.
I have a few x-ray tubes to hand but the image was indeed taken using a dental-head tube with appropriate shielding and a fluorescent screen for instant imaging. The camera was directly behind the screen. If you enlarge the image, you can spot a few hot pixels from direct hits.
Ria   [Sat 24 Jan 2026 at 11:57]
It didn't work when I tried it, so not sure what the problem is Wonder

Just wondering now if I can persuade my dentist to oblige with a few images Mr. Green
Tuopeek   [Sat 24 Jan 2026 at 13:00]
The fault isn't visible in the image but the ignitor appears to be open circuit. I'd guess the mystery component is faulty.
Dentist x-rays are done on very small image plates. These days they are also processed digitally. If you know a Vet they may be able to take larger images for you.
Max   [Sun 25 Jan 2026 at 09:53]
That x-ray shadowgraph is nicely done for a homemade one! At what voltage did you drive your X-ray tube and what is its anode material?
Tuopeek   [Sun 25 Jan 2026 at 10:15]
Thanks, anode target is tungsten and driven at 65kV.
Max   [Tue 27 Jan 2026 at 07:52]
That's some serious business there!
Tuopeek   [Fri 30 Jan 2026 at 21:39]
Mystery solved. The unidentified component in this ignitor is a SIDAC. These are a kind of self-firing voltage dependant two-legged TRIAC. The type used in this ignitor is a K2000F23 which is now obsolete, but there are equivalents. The rating is around 200V 1A. The capacitor value wasn’t identifiable but something around 300nF will does fine. This little circuit, although designed for 10w and 18w SOX lamps can hot start a 35w lamp. However, it will constantly trigger with it while running up.
Max   [Fri 30 Jan 2026 at 23:04]
Interesting details. Have you dismantled the ignitor (or dissolved it in acetone)?
Tuopeek   [Sat 31 Jan 2026 at 19:27]
Yes, I found the potting degraded with the heat of a soldering iron and could be broken up. With a little digging I managed to free the two components, although the capacitor covering detached with the potting material. On test it looks like the capacitor had failed as the solder joints were fine and the SIDAC works with a different capacitor. I have added a bit more to this investigation on video https://youtu.be/diUufz3iuAA

Comment 1 to 10 of 10
Page: 1