Could I hook this amp up to my PC

[Dannymh]

Hi,

I am in the process of re-wiring my arcade to JAMMA, it was hacked apart by previous owner to almost work with MAME. I got it working with MAME whilst I slowly rewire to JPAC/JAMMA.

Anyway there is a stereo amplifier in there (see attached photos) I plug it all in and I can get the starting "pop" on the speakers as they come online, but I can not see how I can get a "line in" to the amp.

There is also an Audio Isolater.

The original Jamma set up was

2 Speakers either side of monito
1 subwoofer

(this is an old LAI 38 inch)

It looks like the left and right speakers are wired into the isolator, which then connects over to a volume pot (there is an additional volume pot wired inside the coin door too)

The woofer plugs directly into the L & R output.

The isolator plugs into the L & R input on the amp

So it looks like speakers >> Isolator >> Input on AMP >> Output of Sub

Is there anyway that I could wire this to get sound from the PC sound card, or am I up for buying one of those mini amps on ebay

Cheers
Dan

[bkenobi]

I don't know about this board in particular, but it appears to have inputs and outputs pretty clearly labeled on the board.  I guess I'm not sure what you are asking. 

As near as I can figure, you have 3 ways to hook up your computer to this. 

• If you want to "plug" your PC into this, then you need to buy a pair of RCA surface mount connectors and solder them onto the board where it says "RCA".  Then, you need to get an 1/8" stereo -> RCA cable and plug it in.
• If you want to connect them with the original connectors (the posts that say "L In" and "R In"), then you will need to get the correct type of connector and build an 1/8" stereo -> connector wire and plug it in.
• If you just want it to work, take a pair of RCA cables and cut the ends off.  Figure out which is signal and which is ground (I can't remember) and solder them to the posts that are labeled "L In" and "R In".

[Dannymh]

The L and R in posts are already connected up to the isolator though, which seems to be how the Left and Right speakers are actually wired to the amp.

The sub seems to plug onto the OUT though.

Probably easier to just buy one of those amps I guess

[Kevin Mullins]

The L and R in posts are already connected up to the isolator though, which seems to be how the Left and Right speakers are actually wired to the amp.

That's the part that doesn't make sense.... the IN posts are just that ... the INPUT from your source. (i.e. in this case would be the PC)
No idea why they would have the speakers themselves routed to those posts.

That's a pretty easy setup, you just need to make sure what you have connected where first.

Throw a pic of this "isolator" up here for us.

[Dannymh]

Ok here is a wide pic and a close up pic of the isolator. You can see the PCB feet where the AMP was fixed to before I took it out for photos

1 - The speakers apart from the woofer go into the isolator (the molex connector on the right of the pic)
2 - The isolator ground wire (black I assume) goes into a clip that joins up with a single white wire I wasn't able to trace through the bundle. This was connected to the Input of the amp
3 - Interestingly the wires for the input and output only sit on either the left or right output/input chanels (my assumption is the Cabinet was wired for Jamma Mono sound at some time in the past, even with a stereo amp.

I cant see how the speakers get any volume unless that black wire is actual and input that is looped over to the isolator which then puts out it's own sound.

As such I assume I need to wire an RCA to the black and white "input" wires and then pop the jack into the PC output?

[Dannymh]

I left the sub hooked up and then touch an rca jack to the input pins and got distorted noise but some noise from the sub

This gives me some hope. I just need to figure out which is the line in to the sound insulator and hopefully I can strip it back and try to connect to that. If it fail, I can just buy a small amp or go back to the PC speakers I already have in there.

If you have any thoughts though please let me know

[Kevin Mullins]

JAMMA by itself is ONLY mono.
So if this machine had a stereo speaker setup it would have come from the game board itself.
What game was in it previously ?

You can use every bit of that stuff in there for.

[Dannymh]

The game that was in there was "Star Gladiators" however there is a "speaker" part on the game board but nothing hooked up.

I cant tell you how absolutely mangled the wiring is in this thing. I have been tracking wires back and forth all over the shop and there were looms for up to 4 players plus a multitude of everything else. I essentially need to strip the whole thing and re-do it but if I can get it up and running I will at least know where the main important wires etc are.

Another thought I just came up with was I looked at the volume pot just inside the door, it is a stereo volume pot and all wired back, though I start losing the wires in the loom somewhere near the power supply.

I took a photo and from what I can gather the following wires are the same colour as those coming from the speakers

left: red and Green, Green and brown (no idea which is positive and negative
right: white with black stripe and blue with white stripe

Anyway I was wondering if anyone could look at the photo attached and tell me the pinout of these, i.e. which is ground and which should be the signal from the PC, because I should be able to splice a wire to this theoretically.

From looking at the photo and comparing to http://scarvell.net/wiki/index.php?title=VOLUME_CONTROL_MOUNTING_AND_WIRING it looks like the two pinouts on the bottom  of the photo should be wired to the left and right channel coming from the PC, I might strip back the wire and splice in single channel to see and test it with a crappy speaker I have here.

What do you think and what may the potential issues be?

Dan

[Dannymh]

I am going to try splicing one of the wires on the bottom of that pick to the PC and see if I get any results. Will let you know how it goes.

Dan

[Dannymh]

So as it stands I can get sound to the sub only by going straight to the amp in.

Wiring to the volume pot had no effect.

Nearest I can tell it looks like the audio isolator has all the input and out for the other speakers that wire into the amp for the sub, but I can't see how to get any volume to the left and right speakers.

Worse comes to worse I am going to have to just wire a pot to the sub and go from there.

Any other ideas, or does anyone have the LAI 38inch booklet or any information on the isolator

[Dannymh]

I bypassed the isolator and wired one speaker straight to the output, well I actually took the wire that was going into the isolator and put that and a ground into the output, the funny thing is this brought both speakers on so it looks like i am going to have to trace back all the wiring and figure out what has been done here and simply re-wire it without the isolator.

The one problem I am getting with this method is the volume pot does not turn the volume all the way down so I can not get the volume to turn off if the pot is down (kind of the reason I wanted to get it going in its current form)

Anymore ideas. The amp obviously works its the isolator that has my noodle baked

[Dannymh]

Righto this makes no sense but here we go

volume Pot is wired as such

Channel 1 - Bw is ground to Jamma speaker ground
Channel 1 - Is gets input from Jamma
Channel 1 goes from Jamma into the isolator

Channel 2 - goes straight through to isolator

Isolator has a loop of white which also goes out to a 2 point input with a black ground so again a single channel

All good I have no problems with having a single channel and I can wire this up I just need the pot to actuall turn the sound down when I turn it all the way down. My thoughts are that it either doesn't have the right resistance or is faulty or this isolator somehow comes to the party and would otherwise have an effect.

Really what I need is an isolator expert this is really starting to make me go 

All

[BobA]

That thing you are calling an isolator looks like an amp board.  The heat sinks on the ICs indicate power not isolation.

[Kevin Mullins]

That thing you are calling an isolator looks like an amp board.  The heat sinks on the ICs indicate power not isolation.

He's referring to this piece.....

[lkench]

Are there any numbers at all on the chips on the "isolator"?  If we could figure out what the chips are, we would have a better clue as to what that board is actually doing.  I do agree though, that if it really is just osolating a signal, it probably wouldn't have those heatsinks.

-lkench

[Dannymh]

I popped it off the other day and it says

"Audio Isolator" on the back of it.

It also looks a lot like this but without the jacks
http://solorb.com/elect/musiccirc/stereoiso/index.html

I will pop it off again now and get any numbers that are on the back. One discovery I figured out yesterday is that the way it gets "stereo" is by splitting the mono signal so that explains a little, but I still cant figure out how or why the rest is wired the way it is

[Dannymh]

Ok on th eback of the "isolator" it says

"Audio Isolator PCB"

Next to the Pins where the molex plug in, the top row has "1" on both sides
on the bottom row, one side has "M" the other has "FM"

Then at the bottom it says
"Mega-50"

Cheers

[BobA]

That thing you are calling an isolator looks like an amp board.  The heat sinks on the ICs indicate power not isolation.

He's referring to this piece.....

Ok now I can see the little transformers.  It certainly is some sort of isolation.  Disregard my last comment due to poor eyesight

[Dannymh]

Yup the funny thing is the right hand side set of wires have a looped white wire that goes out to input and a black that comes straight out of the PCB which is obviously ground.

Really it should be going to and output somewhere but then the same problem exists that I can not see how the input ever hits the amp

[Dannymh]

Oh if it helps this is an old LAI 38inch, the Yellow and grey ones (though it had been sprayed with confetti/white hammer finish  ) so that may help. I am thinking I might just have to rewire the amp to a nw volume pot and forget about the rest