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Sega Model 3 (Blast, NVS4000, etc) no JAMMA sound / buzzing fix

I think you’ll have a hard time confirming a specific I resistor. Pretty sure when I did this I just grabbed one from the bottom of my workbench drawer. The 10ohm one rated for 1w that Nem shared should be perfect for this
 
I have a question about the wiring for mono sound pcb boards to use with that psu. My friend has this ground loop plug in the sound in connector. Mono sound actually works like this. But is it ok to use or damage incoming?
 

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I'm super late to this party, but I am pretty sure that loopback wire is supposed to be in there. It's how you get mono sound.

You only remove it when you want to use the amp for stereo sound. You connect to line level output using a 4 pin to RCA harness. See here.
 
kazuo said:
I'm super late to this party, but I am pretty sure that loopback wire is supposed to be in there. It's how you get mono sound.

You only remove it when you want to use the amp for stereo sound. You connect to line level output using a 4 pin to RCA harness. See here.
Click to expand...
Cool. Thanks for the information. I will try that loop then.
 
I’ve never had sound and came across this post.

Wires plugged in speakers
4 pin to cpo
4 pin from cpo to bottom Door.

Test: put loose wires from this speaker loom to jamma edge connector= sound
.& Speakers and speaker wires work.

Next:
I notice jamma wiring goes into:
Dc out 1?
Then a female 4 pin comes out of there too.
And this has a jumper wire.
7978FD5F-1497-41AA-B51A-87ED4E7F3679.jpeg


So I assumed that’s mono jamma going into amp (dc port) and also
Mono coming out, that I plugged the speakers into?

Is this correct, with nothing in speaker in/out?

I assumed using the rca to 4 pin,
Is for stereo line level to go into amp, and then you would have to use the speaker out to the speakers

Is this correct

Or does mono also use speaker in/out?

We pulled the amp and r1 blown

Replaced and it blew immediately when I have jamma board on and also test rca from tekken to speaker in.

Does this mean I did mono and stereo at same time and it blew it?

Since replaced r1 again but not tried anything before asking
 
Per this post on page 1, it sounds like you may be feeding line level and amped mono at the same time, which is what is blowing the resistor.

You may need to check your wiring configuration against the service manuals (or compare to other user photos) and ensure everything is hooked up correctly. I'd provide more specific advice, but I don't have access to my cab with this power supply at the moment and I don't remember off-hand how it is hooked up, other than having the loopback in the SOUND IN port, and then (possibly) SOUND OUT hooked up to what I can only assume are the speakers (see this post, seems to suggest my memory may be correct).
 
I’m going read that fully but keep getting confused, maybe I have a cable missing.

By loopback in SOUND IN do you mean the cable with the jumper?
Because this is female and so is sound in port.

So that’s why I think I’m missing a male to male adapter.

Then the bottom cable (coming from speakers) that’s plugged in in my circle on photo, I assume speaker out.

So
jamma to dc out
Dc out jumpered cable to speaker in
Speakers to speaker out, is the config for mono.

And stereo would be rca to speaker in, and speakers to speaker out, only with no jamma board on harness?
 
hardyhell said:
I have a question about the wiring for mono sound pcb boards to use with that psu. My friend has this ground loop plug in the sound in connector. Mono sound actually works like this. But is it ok to use or damage incoming?
Click to expand...
So is this plug standard that goes in speaker in?
While using mono?

And the plug coming out of dc in, the 4 pin with jamma wire, is never to be used?
 
You might be missing the jumper, yeah.

I'm not 100% sure about how it's supposed to be wired, just going off memory. I can't check how my cab is wired, since I don't have access to it right now. Best advice I can give you is check the service manuals, or try and parse out what's happening in this thread versus how your cab is wired up. My feeling is you need to connect the stock cabinet speaker wiring to sound out, then run the loopback into sound in. Should solve all your problems, but it's entirely possible I am wrong.
 
I agree it seems that way.
I’m sure I tried that, but used a wire and no sound.

Perhaps it wasn’t connected properly, it was a bit messy:

I’ve since blown r1 again.

I really don’t understand the logic tho.
When taking apart.

Speaker in- is rca 4 cables direct to amp
Jamma is 2 cables direct to amp

Amp to volume
Then amp to speakers (4 wires)

I have no idea why jumping. + and - on a amp input does anything.

Unless it acts as a switch to trip the rca in/ so can’t be used. Or to switch amp into mono mode.

The most confusing bit is that from the dc port a 2 wires come out, with a loop cable also - with a 4 pin connector.

Internally, I have no idea, because only 2 wires from psu go to the amp, which is from the jamma speakers, so god knows where they come from
 
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