Cold Cathode Tube Voltage and Speaker Questions

My brother has some cold cathode tubes, some about 6" long, some about 12" or more. I was thinking of hooking them up to my bike, as shown in one of the great Instructables here, but I wasn't sure of the voltage. I don't want to over-power the tube, and bust it. Plus, the two wires coming out of it are in this black connector, so I don't know which is positive or negative. The tubes put out blue light, if that makes any difference.

I have an old sports radio, which works pretty good and could be turned up really loud. I desoldered the speaker, and hooked it up to a pair of wires coming from a head phone jack. I plugged it into my iPod, expecting loudness, but no - I had to hold it up to my ear, on full volume, to hear it. Is it because the iPod isn't outputting as much voltage or current to the speaker as my radio was? The radio used 3 AA. I really wanted a portable speaker that actually put out big sound, so I didn't have to have those buds stuck in my ear.

Thanks y'all!

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Goodhart9 years ago
concerning the speakers, it sounds like you have a very mismatched "impedance". If you can find out the output impedance of you iPod, the speaker "should" have its rating on the back metal guard around the permanent magnet (should say something like 4Ώ , 8 Ώ, 16Ώ etc. )
Bran (author)  Goodhart9 years ago
The speaker says 8 ohms and .5 Watts.
NachoMahma Bran9 years ago
. I'm with Goodhart. I think your speaker impedance is too high.
Bran (author)  NachoMahma9 years ago
Adding to my other comment about giving it more power, I happen to have a pair of computer speakers. I currently use them in my room to play my music, but they have to be hooked up to a wall. Do you think (and how could I do it) I could run them off of DC power, i.e., batteries? If you need a picture, I can take one. I've looked in the main speaker, and it has a pretty big transformer. I don't know what this brings the needed voltage and current down to, though. THanks for your time.
NachoMahma Bran9 years ago
> Do you think (and how could I do it) I could run them off of DC power, i.e., batteries? . Should be able to run them off of batteries. Check the output of the wall wart for voltage and ampacity. If there is a transformer in the speaker, the wall wart may be putting out AC and the rectifier is in the speaker. . If you have a sub-woofer, the "transformer" may be part of the cross-over network. . If you don't have a wall wart (speaker plugs directly into wall), you will need to ID the rectifier/filter output points.
Bran (author)  NachoMahma9 years ago
It has a standard plug; a 2 prong, small plug. No adapter there. The transformer is inside the speaker. The only voltage I saw said 110v, which I'm sure is input from the wall. I don't have a woofer, they are just two small speakers. One thing I've noticed is that the speaker in the main box has a round metal cap on the back end. It stands out because it's silver-metal colored, not the yellow-ish color as usual. I don't know what that is, and it doesn't have any markings on it. Again, thanks.
NachoMahma Bran9 years ago
. The 120V will go to one side of the transformer. The other side of the transformer will go to a rectifier and possibly a filter. Try using a voltmeter to locate the rectifier/filter output (probably be between 5V and 15V DC). You should be able to hook up your batteries there.
Bran (author)  NachoMahma9 years ago
Ok, I think I see where you're going with this, and this is going to sound really newbie-ish, but what does a rectifier look like? I took pictures of pretty much all there is to this speaker that I can't explain, so maybe it's there, I just can't see it. Thanks, yet again. ;-)
Speakers 013.jpgSpeakers 012.jpgSpeakers 010.jpg
NachoMahma Bran9 years ago
. I don't see anything that is obviously the bridge. I think the IC is the amp, but not sure, it may be the bridge.
. Check the labels. Cx = capacitors, Rx = resistors, VRx = variable resistor, Jx = jumper, etc. IIRC, Dx = diodes.
. Where do the different wires go? I can't tell which is 120VAC (top right?), speakers, etc. The red/black pair looks promising - common color combo for DC.
. Diodes come in several forms. Most I've seen in similar applications are tubular with axial leads - like the resistors in your pics. Some are clear glass (usually very small), some are black with a silver band (or cone-shaped) on one end.
. Four diodes to make a rectifier bridge. Sometimes they are packaged in one small IC.
. Do you have a VOM (volt-ohm-milliammeter)? If not, you can pick up a "cheap but good enough" one for $5-10 at most auto parts stores, electronics stores, Wal-Mart, etc.
Bran (author)  NachoMahma9 years ago
Labels - I looked at all of them, and here's ones that you didn't mention - LDx, which is just a green "power is on" LED; Ax, which are holes, bigger than ones wires would go through, and there is nothing in them. Some have a small amount of solder around the edges on the bottom of the board, but that's it. In the last picture above, in the south eastern region of the board, right below the two capacitors, you can see one, A12. Under the transformer it says SP-1700, which might be a number. The wires - If you are looking at the middle picture, you are right on the wall cord; the red/black pair lead to the speaker which is housed in the main box. The southwestern wire leads to the auxiliary jack. The southeastern pair leads to the other speaker. Diodes - I have the black w/ silver band type. Wouldn't you know it - 4 diodes together. Yes, I have a cheap meter which measures volts (AC and DC) and amps. It has an Ohm symbol on it, though I do not know if it measures them (seems as if it would, though.) Thanks yet again.
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