Asura Blade & Sengoku Blade - No audio on supergun

[crunchywasp]

I recently sent a supergun I built to a member here and he's having some issues with the audio on Asura Blade & Sengoku Blade.

There's no audio regardless of whether the attenuation's turned on or off, there's just a buzz and background noise.

He's tried other games with the SG and they all work fine with no audio issues.

The SG's one I built about a year ago and used myself since. I've ran a bunch of different stuff on it with no issues, even Cave stuff which I've read can be troublesome with attenuation. I've never however tried either of those 2 boards.

We've checked the following:

+5v & 12v at the JAMMA edge and
ruled that out.

Played both games in 2 cabs - they've no audio issues.

Adjusted the volume pot up on the board with no effect.

...but no joy in diagnosing the problem

Before we arrange a return for diagnosis has anyone experienced any similar issues with these boards whether it be with a supergun or cab, or does anyone have any suggestions?

Apologies in advance if this would be better placed in the supergun section and thanks in advance for any help

[dbstallman]

Check the ground path inside the supergun itself. I've had similar problems when the ground was missing to the speakers in my cab.

I am refering to the ground path after it leaves the PCB, not the ground on the board (which is probably fine).

Brian.

[crunchywasp]

Thanks Brian,

My initial thoughts are that it's a ground issue somewhere. It's difficult to diagnose or investigate remotely and the owner's understandably reluctant to prod around inside. The wires are all bundled and tied down to cable tie bases so without unbundling everything it's difficult to confirm from photos.

This particular SG was a prototype I built (the first with an enclosed PSU) about a year ago but from memory ground will be taken directly from the JAMMA edge to the attenuation circuit where it either terminates or continues to pin 2 of the 8 pin DIN A/V out (Neo Geo pinout). I usually terminate a gnd at the attenuation circuit and run gnd from pin 14 (video gnd) of the JAMMA edge directly to A/V out, then from there via a scart lead to pin 18 of the scart plug.

To confirm, audio is mono from pin 10 of the JAMMA edge > attenuation circuit > pin 1 of the DIN > pins 2 & 6 of the scart plug > TV speakers.

Audio is working on all boards other than these 2.

Cheers

[KmanSweden]

Missing -5V?

[crunchywasp]

I may be wrong but as far as I'm aware neither of these boards require -5v. It's an arcade PSU inside and -5v is hooked up with 18AWG wire in any case.

Thanks though, that was one of my first thoughts too

[meijin]

I'm the one with the evil pcbs, which don't work on Mr. Wasp's splendid SG
And I guess also that it has something to do with the ground path or maybe with the attenuation circuit (which blocks the low sound signal!?)

As far as I know both games don't require -5v and also I checked the -5v line on the SG and it works. So this is not the problem.

[emphatic]

IIRC, I've read somewhere that the ordinary GND is better (more compatible) to use for superguns than Speaker-, however I have no written documentation to back this up.

[crunchywasp]

Thanks meijin & emph

I never use speaker - (Pin L). I always take the ground for audio from one of the grounds at e, f, 27 or 28.

[emphatic]

Thanks meijin & emph

I never use speaker - (Pin L). I always take the ground for audio from one of the grounds at e, f, 27 or 28.

Maybe these games require Pin L then?

[crunchywasp]

You may be right!

Anyone?

[FrancoB]

I use pin L for Speaker- however on the few PCBs I have metered they tend to be the same as GND. I seem to think it's not the case for all PCBs though and maybe this is one of them

mejin, you could try linking pin L to GND at the JAMMA edge with a piece of wire to see it it sorts it

[crunchywasp]

Thanks Franco, I was just thinking along those lines in the car there.

Hopefully it's as simple as that. If that's the case I'll start using pin L

[crunchywasp]

Right, so meijin's tried linking pin L to a connected ground with a short length of wire on the JAMMA edge of the PCB and although the buzzing noise disappears there's still no audio.

He's tried this on both boards with attenuation on and off, and tweaked the volume pot on the PCBs up a touch with still no joy.

Looking at the bottom of the Sengoku Blade PCB it does have a trace at pin L though, and Asura Blade may well have too but I neglected to ask in PM - Bastian, can you confirm please? Cheers

I'm confident I can resolve this if I have the SG & PCB in front of me but any suggestions before he has to pack it up and arrange to have it sent back to me would be most welcome, thanks.

Very grateful to everyone for your help so far, cheers

[emphatic]

Anything for you, sweetie.

[crunchywasp]

x

[meijin]

can you confirm please? Cheers

I just took a photo of the Asura Blade pcb before I went to work this morning. There is a trace, but it goes to nowhere...




Here is also the photo of the Sengoku Blade pcb (solder side).
http://img692.imageshack.us/img692/2341/dscf2847i.jpg"

[cools]

Erm, PIN 10 and L are supposed to go directly to the +/- speaker posts, preferably 10 to + and L to -.

This is how every cab I've ever owned that didn't have an amplifier has been wired. Maybe with a connector or two in between but still, always direct from both pins.

[crunchywasp]

Providing the speaker is getting a signal & ground it should be grand regardless of where the ground's taken from surely?

Like emph I remember reading somewhere ages ago that hooking up speaker- (L) with an SG to TV speakers or whatever can sometimes cause issues so I always just hook up audio from speaker+ (10) and a ground from either pin e, f, 27 or 28.

I use an 8 pin din socket and scart lead (NG pinout, audio via TV speakers) so just run a single ground to pin 2 of that to ground audio & video.

I guess in cases where the PCB's expecting ground at L this is going to cause issues though

If this is in fact the problem then at least it's an easy and straightforward fix.

[cools]

Not sure how the attenuator works, but would hooking up the speaker pins to the attenuator inside the gun before audio is sent to the TV work?

[crunchywasp]

Sorry, my last post is a little misleading - audio from pin 10 doesn't go directly to the DIN but via the attenuation switch.

To confirm...

audio is mono from pin 10 of the JAMMA edge > attenuation circuit > pin 1 of the DIN > pins 2 & 6 of the scart plug > TV speakers.

The attenuation switch is hooked up like this, except where the diagram shows an RCA connector it is in this case a DIN socket...