My audio amp isn't toast....But

[Ummon]

There's an audio amp in my Capcom Impress. It looks fine, though as we know that doesn't necessarily mean anything when it comes to electronic components. With the Tetris board that came with it, there was no audio. I'm assuming it was mono, as the rca connectors weren't being used. I connected my computer audio out to those and no audio, either. I did have the main switch inside the cab on. What else can I do to troubleshoot this?

[SirPeale]

First, check to make sure it's actually getting power.  Check the fuse as well *with*a*meter*.

Assuming those requirements have been met, I'd bet on the amp transistors being toast.

[Ummon]

I'm not used to checking fuses with a meter, but I got no readings when I touched the leads to either side. I made sure the cab was on. (Incidentally, I noticed the monitor has to be plugged in to the PS for anything else to turn on. Is this what's meant by a switching PS?) I also tested what I thought were the hot and ground(s) that connect at the back of the board, behind that big heat sink, and nothing there either.

[DJ Infinity]

I have a coupla NAOMI sound amps. They look similar. If Ya want one you mave have it. I have no need for it. My cab(s) use powered speakers. 

[SirPeale]

I'm not used to checking fuses with a meter, but I got no readings when I touched the leads to either side. I made sure the cab was on. (Incidentally, I noticed the monitor has to be plugged in to the PS for anything else to turn on. Is this what's meant by a switching PS?) I also tested what I thought were the hot and ground(s) that connect at the back of the board, behind that big heat sink, and nothing there either.

Ai...that's not how you check a fuse.  Pull the fuse, set your meter to ohms.  Probes on both sides of the fuse, but make sure you only handle one side with your hands, otherwise you will be reading your body, not the fuse.

[protokatie]

Ai...that's not how you check a fuse.  Pull the fuse, set your meter to ohms.  Probes on both sides of the fuse, but make sure you only handle one side with your hands, otherwise you will be reading your body, not the fuse.

Don't forget the add-in of "check to make sure the battery in the multimeter is still good". As Ohm (resistance) metering requires that the multimeter has a small (but still working) power supply of its own. (Should just be something like a standard 9-volt battery)

Edit: All of you "hip cats" these days use digital meters, so I guess my suggestion to check the battery is moot... 

[Ummon]

I have a coupla NAOMI sound amps. They look similar. If Ya want one you mave have it. I have no need for it. My cab(s) use powered speakers. 

Dude, that would be mondo awesome. I'll PM you promptly.

Edit: All of you "hip cats" these days use digital meters, so I guess my suggestion to check the battery is moot... 

That's what I was feeling might be the case. I have a digital meter.

Ai...that's not how you check a fuse.  Pull the fuse, set your meter to ohms.  Probes on both sides of the fuse, but make sure you only handle one side with your hands, otherwise you will be reading your body, not the fuse.

What, you can't measure the fuse while it's still in there? However, I was thinking I needed to measure volts, not resistance. Still, I did measure voltage at those connections at the back of the board, and shouldn't there have been some if it was getting power?

[Blanka]

I have a coupla NAOMI sound amps. They look similar. If Ya want one you mave have it. I have no need for it. My cab(s) use powered speakers. 

Wow!, this amp looks like its capable of things way beyond your 'powered speakers'. This thing must be able to do 2x80 watt stereo on pretty audiophile levels if I look at the components. Is there a big torroid to supply the power? What a waste you chose powered PC speakers instead! Get some serious drivers for it.

[DJ Infinity]

Powered Speakers are cool enough for me thanx. Easy to setup and they sound great especially if you have some car speakers. You can adjust Bass etc. 

[Ummon]

I have a coupla NAOMI sound amps. They look similar. If Ya want one you mave have it. I have no need for it. My cab(s) use powered speakers. 

Wow!, this amp looks like its capable of things way beyond your 'powered speakers'. This thing must be able to do 2x80 watt stereo on pretty audiophile levels if I look at the components. Is there a big torroid to supply the power? What a waste you chose powered PC speakers instead! Get some serious drivers for it.

Well, you could. But I likely wouldn't mess with it either if I didn't already have (what I think are) good speakers in the candy already. It's far easier to just get some decent PC speakers, which are plenty loud enough for me.

[Blanka]

Can you do a thing Ummon? Can you give the type-numbers of the 2 amp-chips on the heatsink? Wonder what they used for that.

[Ummon]

Can you do a thing Ummon? Can you give the type-numbers of the 2 amp-chips on the heatsink? Wonder what they used for that.

Is the picture I posted sufficient to show me exactly where you mean?

[Blanka]

I was able to brighten things up a bit, but the text stays unreadable:

So can you post the numbers in the red circles?

[Ummon]

Those are what I thought you meant, but I don't know such things so wanted to be sure. It'll be a little bit before I get it out of the cabinet, but I'll do it then.

[Ummon]

Here's a video of my latest experience on this matter. By the way, I missed showing the audio cables in the first part of the vid, but essentially I manipulated the wires above that ferrite ring thing, and nothing happened. Every time it made the clipping sound was when I manipulated the cables between the ring and the rca plugs, and only on the white side, so maybe the white and black wires that go to that plug are shorting? (Also, regarding the led behind 'the big capacitor on the amp', refer to the first picture above, top-left of the image.)

[Ed_McCarron]

That toroid is probably a filter, not a transformer.  Seems small for a transformer in the power supply.

You can check a fuse in circuit and under power by looking for voltage ACROSS it.  If you see the power supply voltage across it, its open.

Got a schematic?  Got power?

Get another small amp.  Tie the input grounds together.  Feed audio into the amp under test.  Trace the audio through the circuit until it stops.  The component  before that point is probably bad.

Its a lot of work for something thats fairly easy to replace.  An amp is an amp, no?

[Ummon]

I got another amp from somone, but the coupling was way different. I didn't want to hack the harness if I didn't have to. And that ring I mentioned I said was a ferrite ring, so I guess a filter like you were saying.

Anyways, I think it's likely the power supply is bad, which is what I should've concentrated on a long time ago and yanked the ---smurf--- out. Now I've lost my security bit so I have to go get one just to do that. Sheesh.