I have a problem with my RA-9808X. A guy I know tried connecting some small speakers from a car with it, and he probably did something wrong. Now it doesn't light up when I plug it in and turn it on anymore. What may be wrong?

Then you probably have something wired wrong, or have the wrong ohms rating speakers attached to it. There may also be a switch on the amp set wrong ohms rating for your speakers. Make sure your speakers are not wired across channels or if its bridged (1 sub speaker for more power) make sure it is connected to the proper terminals and the ohms rating of the speaker(s) matches what the amp can handle / is set for.

The first question I have to ask is: Are they automotive speakers? Home stereo speakers are typically 8-ohm impedance whereas automotive speakers are typically 4-ohm. If you try to put home speakers in a car, your car stereo head unit may not may not have the power required to overcome the higher impedance. If that's not the case, check your wiring to the speakers (I assume this is an aftermarket system?). If there is nothing apparently wrong with the wiring, try connecting a couple of known good speakers to the wires. If they work, your existing speakers are bad. If they don't work, you probably have something wrong with your stereo head unit. Good luck.

on bridge mode the speaker impedance should be 8ohms, less than this clipping will happen. try bridging two 4 ohms in series.   
if this happens without speaker connected, u have a power amp section that is trying to draw more power than it can handle. 
as for the second check connections first, otherwise i suspect u have a defective power amp for the right channel.

Probably.
Do they connect to the computer via USB or mini plug?
If mini plug, make sure you have the right jack on the back of the computer (there's two)
Then go into System Preferences ... select "Sound" and see if you can select something other than "Internal Speakers" - the computer may just not be aware that you want to use the external speakers ...
Are the speakers powered? Is there a volume control on the subwoofer, or an external fob with a volume control on it? You probably know this if you used them previously with your Compaq computer ...

Good luck!

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it is the problem of ur cable there must be a shorting between the cable try changing ur cable.

Yes, the connector next to the speaker connector is for the power adapter. It's different from the speaker plug so you can't put it in the wrong place. Hopefully you got the right power adapter with the monitor.

Here's the page at HP's site where you can download the User's Guide for this monitor. Hope this helps.

check the all power lines and regulator .is any of them overheating?
then check the power amp ic or transistors.

nuwan.

The speakers need some kind of amplification, if you have something like a set of computer speakers connected and they are not powered they won't work, try connecting them to the headphone jack.
Let me know the set up, what kind of speakers, audio settings from the tv menu.

lone99star

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Instead of replacing you can try and clean it. There are a lot of good contact cleaners out there.

I'd suspect that one of the two output transistors on that channel has gone bad. If you are unsure how to test or troubleshoot this, then you might try replace both the NPN and PNP outputs and catch the bad one that way. If your amp uses an output module then you would of course have to replace the module which would replace all the output transistors on both channels. Good luck. Another thing to look out for, is the emitter bias resistors. They are the large white ceramic ones near the outputs. Sometimes one of those will open up too. They will be of a very small resistance value like .5 ohms (point five ohms) or something in that general ballpark, and have a wattage value of typicaly 5 watts. So they are pretty big resistors. Be sure to check them all even if you do find a bad output transistor. They will often go out with the transistor. Good luck.