Hey all you modders... I'm hoping someone can help me with a CCFL question. I bought some 12" UV CCFLs for $5 at fry's a while back, just stumbled across them, and they were exactly what I needed. One of the tubes appeared a little dimmer than the other, but I wasn't too worried about it, as I'm still experimenting with a bunch of stuff, and couldn't really be bothered to get it perfect. These are the first ones I've ever owned, let alone seen in person, so I'm really not sure what to expect, besides equal glow! Not too long ago, in a rage of wiring and UV reactive stuff testing, in a room far far away (ok its just upstairs), I somehow pulled the power cables out of the plug, and reversed them without realizing. Blam, fuse in the CCFL powersupply/transformer blew. Next time I plugged it in no lights. I figured that out pretty quickly and was able to reference some pics I'd taken previously to figure out which wire went where. Got a replacement fuse (of sorts) and wired it up and it works, but one tube is much more noticeably dimmer than the other and more than before. I haven't tried swapping where the tubes plug in to see if the it's the tube or the socket, but I'll do that in a few. (I'm in the garage, cutting plexi at the moment.) So, my question to you all is, have you experienced this before? Is it normal for one tube to be dimmer than the other? Is it an electronics circuit thing, or a tube thing, in your opinion? What can I do to equalize these CCFLs? For those that like circuit pr0n, here's a few pics of the process. Naked Circuitry: Closeup of original fuse (note the now labeled connector to prevent future mishaps): Replacement fuse (1amp... electronics shop lady couldn't tell me specs on the original, but figured an amp would be good enough): Soldered in (closeup): Replaced: Testing (can you see how one is much brighter than the other?): I made a cool short video of a test with some neon paint i put on an old fan, you'll have to add your own sound effects. (may I suggest a whoosh? Since I'm thinking of it, I've gotta go upstairs and check out if its one dim tube all the time, or just the circuits.
You mean buy a new set? umm... I'm trying to save my pennies here. Petra's does have some cool stuff though (not to mention replacement 12" uv tubes, which are currently out of stock.) I'll have to check em out some other day when my pockets are full. Thanks for the answer. I'm thinking its the tube too. However it seems to even out after they've been on for a while. I've got em running now, and both appear almost the same. One tube does seem dimmer, no matter which socket I plug it into.
What happens if you swap which port the tubes are plugged into? Is it still the same tube which is dim?
Good question (and he did answer it). The inverter is just a two-transistor oscillator feeding a high frequency into a step-up transformer. It looks as though the transformer only has a single secondary with the two tubes sharing the output. One is maybe taking the lion's share.
thanks cpemma. what's a secondary? is there a way for me to even it out? so, since the tube behaves the same no matter which inverter socket its plugged into, is there anything I can do to the tube? could it just be a bad connection on the tube itself, & maybe fixable with some tighter connections on the tube?
okay, the solution to this is actually really simple... I ran into the same trouble myself, i see you've sleeved the ccfl cables! thats a big no no, the ccfl invertor pumps out an insane amount of voltage and if you bring the two wires together the EM fields generated by each interfere with each other (very basic explanation)... The CCFls come with both wires seperated for that exact reason. and often the best technique for ccfls, is to have a different return path for the cable to the invertor. (i.e. the path to the ccfl from the invertor is not the same as the one back)... I sleeved my ccfls and the one tube would only light up half way, took off the sleeving and the problem is solved, this problem is especially prevalent with longer ccfl cables...
Interesting. It seems hard to believe though. I think even before the sleeving happened there was this difference in the tubes, which was more noticeable after the fuse blew and was replaced. But before that, I'd sleeved the wires and only had the minor difference as when I got it and used it unsleeved.
Ummmmmm that "fuse" looks like a resistor to me. Check with a multimeter whether it has a 1K resistance.... it would explain anything not working or being dimmer [note: i'm an electronics noob... i'm probably wrong...]
Omit "probably" and I'll agree. It's not the voltage so much as the way a CCFL appears to a high-frequency power source as a capacitative load. The recommended wire is kynar-insulated.
hmm @coldon - I think ilve seen your previously quoted post before... at least I remember reading about the difficulty of changing out the wires length. I still find it odd that since both are sleeved, one has a different brightness. shouldn't they both be affected? I'll have to try it out later, but I really liked the sleeved look. and thanks to all for the responses (even the noobs, since I'm a noob as well.)
at the end of the day what i ended up doing was throwing the ccfl's away... I went to an electronics shop and bought some circuit board and some led's, made myself a uv strip using 15 UV leds (kinda like those led lazer light just using 5 times as many LEDs). Its insanely bright, also runs off 5v power... no high voltages or dangerous invertors in the case (i dont know how many of you have been shocked by a ccfl invertor, but man it hurts!!!!) oh mod minded, take the sleeving off, and try separate the two wires and see if that helps... then sleeve each wire seperately.... as for that fuse, its looks like a 22ohm resistor to me and not a fuse... fuses are meant to break with certain paramters and also need to visually show when they have done so..
Coldon, didn't you see my sig? I don't throw anything away if I can help it! (I'd take Cheapskate's name, but he got it first and deserves it even more than I do!) I have purchased a UV Led to try it out, and liked the results, and you make good arguments for using them. I plan on using them as a spotlight on key things later on, but for me at least the UV leds are fairly expensive. I have noticed a whine coming out of the CCFL inverter, which is another reason not to use them. BTW, it's definitely a fuse. I know its confusing... but that's a certainty. plus, cpemma said it's so... http://en.wikipedia.org/wiki/Fuse_(electrical)#Packages
It's deffo the tube. But for having a choice with "pr0n" in the poll, I just had ti pick it instead of the right answer.
So it sounds like people agree that the problem is just in how that particular tube was manufactured? I don't want to remove the sleeving if I don't have to, and since the other one works great with the sleeving, it seems like a moot point.
Having cut, clipped, extended, shortened, and done all kinds of things to cold cathodes--I have to agree with the general sentiments thus far. That being that mod shop cold cathodes are finicky. I've got a few more tricks you might wish to try. First, fire up the cold cathodes and leave them lit for a long time. Sometimes they equalize by themselves. Sometimes they stay equalized later. Sometimes, they take a few minutes every time you turn them on to equalize. Second, and be very careful or you will get shocked, with both cold cathodes fired up, unplug one or the other. Or at least definitely see if it is the socket by only having one plugged in. Any small differences in resistance (even as little as 2 cm difference between wire lengths or slightly damaged traces on a pcb) can result in in-equalizations. Third, you could try adding a little resistance to the brighter cathode, by extending its length a few cm, and seeing what happens. navig
Thanks for the great troubleshooting tips navig. I have noticed them equalizing over time, but not fully.
