neogeo aes 3-3 no sound, where to start?

lherre

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No, I mean I tried to replace the bios yesterday, I put a socket and then when I installed the new bios I don't have signal, and checking for example the bios pin, 1 (5V) and 2 (GND) have continuity.... so something is not right. I have to check it because right now the machine doesn't boot at all.
 

DaisyAge

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Yeah I'm asking if when you tested continuity on the pins, does the multimeter beep once or make a long tone? My multimeter alwayts makes a short beep between 5v and gnd but that does not mean they're shorted.
 

lherre

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I’m checking resistance (with the biggest valué in the multimeter) between points, 0 value it has continuity / 1 it is not connected directly.

I don’t have logical probe with sound yet.

but I’m not sure if I affected some traces changing the bios so I will use the jame’s bios pinout to follow the points and fix the short. Not sure if I will be able to bring back to life the machine.
 
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Should be fixable. Make sure you don't have any bridged solder points on the socket.

This video gives a really clean view of how to do the bios install without fancy equipment. I really like how efficiently he checks for damaged traces at 8:22.

 

lherre

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Should be fixable. Make sure you don't have any bridged solder points on the socket.

This video gives a really clean view of how to do the bios install without fancy equipment. I really like how efficiently he checks for damaged traces at 8:22.



I will check in an hour or so, thanks!!!!
 

lherre

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I checked bios pins and apparently continuity is good except one trace to the pin 55 from the 68k but GND and 5v are still shorted/give continuity so the console doesn’t start or show anything. I’m crazy looking for something but I can’y find it. But i provoke it when i changed the bios yesterday.
 

DaisyAge

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If you're measuring resistance between ground and 5v you're gonna find it. Does your multimeter have a continuity mode? It's usually an arrow with a line on the end or like a sideways wifi symbol
 

lherre

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Thanks for the tip!!! Yes it has a continuity mode (but no sound).

the 5v gives 001 value with them and between pin 1 and 2 that is 5v and ground it gives 2XX, if I check ground with ground is 001 too. So as you said there is continuity but not total (value 001 as a direct point) although I think it is still more than it should.
 

lherre

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I manage to recover the machine (no sound) and passed the diagnostic bios.
I hear the “tones” so something about the audio works. Not sure what I have to check with this error. Replace sound ram? The z80 is new so it can’t be dead... i will check traces but I’m sure I checked the traces from the sound chips.
 

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lherre

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Besides I have a problem with the D button, it appears pressed all the time
 

ack

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I manage to recover the machine (no sound) and passed the diagnostic bios.
I hear the “tones” so something about the audio works. Not sure what I have to check with this error. Replace sound ram? The z80 is new so it can’t be dead... i will check traces but I’m sure I checked the traces from the sound chips.

Its pointing to an issue with the sound ram chip or the traces to it.
 

lherre

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Is there any pinout and where the BR6116 traces go?

I saw some from de neo-D0 chip ( sda2-3-4 and 6116CS) but i don’t know the rest. This 4 point where good.

Besides i have to look for a BR6116 chip to replace the current one.
 

ack

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I would check the traces between the z80 and the sound ram chip. If there was an issue with the traces to the NEO-D0 it should have made it impossible for the z80 and 68k to exchange data to indicate there was an error.
 

lherre

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I fixed one trace from the z80 to the ram (sdd1 signal- z80 pin 15 to ram pin 10).

Now I haven’t beeps at all or the ram data (00) error.
I simply have the expected-value error .
The actual value changes between resets. Sometimes is FF, FE, 00, D2, etc
So replace BR6116? Or could be other component now?
 

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ack

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I would double check you didn't create a bridge when fixing that trace.
 

lherre

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I joined the pins directly with a cable under the board so very unlikely but I will check all the points later again to be sure.

Thanks a lot ack for your help!!!
 

ack

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I dunno something happened. It really shouldn't have gone from playing its sound jingle and reporting an error to nothing by fixing that bad trace. So it makes me think either of the bridge situation or maybe you miscounted pins when doing the bodge wire? If you don't find anything I would try removing the bodge wire and see if goes back to the older behavior.
 

lherre

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Good news!! I checked all the points again and I didn’t find anything out of place. I run again the diagnostic bios/cart and all the tests passed ok. Changed bios and it sounded fine!! I imagine that the other day the cart wasn’t making a good contact or something and giving me a false positive.

Now I need to fix the D button that appears always pressed. Any guess? The CR3/4/5 with 10 pins or the one with 8 pins above or the blue ones marked as BFX15?
 

ack

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I would use a logic analyzer starting at the controller port and working your way towards the neo-c1 and see where it stops mimic'ing your D button presses.
 

lherre

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Thanks, I will check today with the multimeter in which point the reading change. I found the D button signal after the resistances before the neo-C1 chip and there when I connect the controller change from 5V to 0V (rest of the buttons are 5V without pressing them). So the problem is before that point since if I don't connect the controller the value is fine, 5V, only changes when I plug the controller (I imagine it closes the circuit). I tested with 2 different controllers to be sure.
 

lherre

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For now I measured values of the CRE401 resistances for all the arrays and the values are correct (1k or 330 ohm depending on the pins). The one that is connected to button D is the middle one (second pin starting from the left is the one connected to Neo-C1). I compared values (continuity, resistances, etc) with other buttons (right, C, etc) and are the same. Continuity with Neo-C1 is correct, so, maybe I have a faulty Neo C-1? (I hope not...)
 
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lherre

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Measuring better and comparing with other button when I press “right” (the stick) the voltage on the array or other points connected to the “right” signal are all almost 0 (0.05V) but in the button D is slighty higher (0.3V) when is not pressed but if I really press the D button it shows the same value as the others (0.05V).

Maybe is the capacitor inside the array?
 

ack

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Its possible. I've replaced a couple of them because of similar issues to what you are seeing.
 

lherre

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I'll try to replace the one responsible to the D button, I hope it works. I have a non functional mvs that have some of them.
 
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