Neo CD Sound Levels Varies

I have a USA Toploading Neo Geo CD. Last night for the first time I discovered the music from the games or audio cd goes loud for a few seconds (roughly 3-5 seconds) then goes quiet for roughly the same time and then goes louder again. This doesn't stop and swaps between being load and quiet.


I have tried several games and does it on all of them. I have tried audio cds and it does it with those as well. Games load up fine its just the audio from the game/audio cds that is the problem.

I have tried the analogue audio outputs through my digital amplifier and also through my tv via the RGB scart lead and it does it for both.
The machine did reset it self last night, but I don't know if it is related to this problem of blown a circuit.

How can I solve this problem? Is it the laser, spinning of the cd, or a component on the audio motherboard? Or something else?

Please help as this is bit of a pain. I have checked the forum and no one else has had the problem.

I would be grateful for any advice

It's difficult to tell what's wrong here... the NGCD has a small audio pre-amplifier board, maybe there are some damaged parts on it, but really, it could be anything from a dead spot on the audio pcb to a dying pre-amp.

The back plane of the std. top loader CD unit is one of the weak spots of the console, if you use too much force while (un)plugging audio or video cords, the back plane may get bent slightly out of its normal position which may result in broken wires or dead solder points.

To get started with the troubleshooting, switch the unit on and *carefully* try to provocate the resetting by slightly shaking all cords, plugs and the PSU. Next, get someone with a multimeter and measure the output of your power supply unit, it should have no ripples and provide a steady voltage, you could also try it with another PSU just to make sure.

Anyway, good luck.

I am hopefully getting another power supply unit soon. The power supply I have has been opened up before. As the previous owner found it to be faulty, but should have been fixed. So maybe the problem has been caused by the faulty power supply. Sometimes the machine resets itself, but I never play the machine for over a hour at a time as I am scared the powers supply will overheat. If I replace the power supply will the fault disappear or is it more likely the circuit has blown up?

Thanks for the advice

How do I measure the output voltage of the power supply if it is connected to the neo cd? I guess the voltage should be constant. I have a american power supply that can be used at 110V or 240V with a shaver adaptor to fit into the uk 3 pin mains wall socket

For taking voltage/resistance measurements, you'll need a so-called multimeter, like this one here:

Digital Multimeter

Perhaps a friend of yours could lend you his if you don't have one, but it comes in handy for all kinds of household repairs so it's a good idea to get yourself one of the cheaper models if you don't need advanced features. A lot of electronics supply shops offer them for bargain prices so don't let them talk you into buying one of those expensive models by Fluke or HP.

If you want to measure the voltage/current of a running NGCD PSU, you just have to plug it in and take measurement on the plug that normally goes into the console. It should output a steady DC 5V 2A on the upper of the three pins and DC 10V 1A on the lower right pin. The lower left pin is for grounding. Most multimeters come with a manual that will show you all the basics you need, if not, you'll find plenty of info on the Web about it.

Anway, just a friendly advice, be careful with what you do, never touch the inner parts of a PSU with anything but the (insulated) measure sticks of a multimeter or an insulated screw driver - even if the PSU is not plugged into the wall outlet, the capacitors still may contain enough voltage to provide you with a nice electrical shock if you touch the wrong parts...