1-slot sound prob

[Arakon]

I have a MV1ACHX here (same size as a MV1FZ, but with different layout and non-socketed bios chip).

sound was supposed to be defective, and it is..

I already tried to get sound out of the unamplified/input pins of the amplifier, there's no sound there either.

I found soldering near the yamaha chip:

the red circles show where soldering was done.. not sure for what purpose. I checked to make sure that the traces are still ok.

after messing around with a speaker on the yamaha pins, I managed to get continuous beep sounds out of some of the pins shown in the blue rectangle, although I'm not sure that has anything to do with it. the unibios does NOT report any errors, games work flawless except for the total lack of sound.

what could be fried, where else to check, if it's the yamaha chip, is there anywhere to get a replacement? if not new, any cheap systems that contain one to salvage it?

according to another posting here, if the interrupt line is low, the chip is fried.. however nightmare tony just says "the one from the ym2610 with the pullup resistor".. I see a total of 8 resistors hooked up to the ym2610, which pin is it exactly?

btw, an interesting fact I noticed.. this board uses a TA8201AK amplifier, unlike most others that use a HA13001.

 

[Amano Jacu]

A bit off-topic, but I find strange your MV-1A has a non-socketed bios... I have a MV-1A that is like the FZ (except the lay-out), and the bios is socketed. I think your model should be reported to hardmvs and Razoola.

 

[Arakon]

I actually had one of these before, the bios is in the free area of the plastic (accessible without removing the casing), and was not socketed.. it's still a normal chip, not surface mounted. I socketed mine by now, but I can take pics of it later.

 

[ttooddddyy]

Just a shot in the dark.
It may be a Z80 problem, usually the Z80 watchdog will report an error to the main proc, ie Z80 ERROR on screen, but in some cases it only causes no sound (I dont know which cases). In the process of putting a schematic/block together of the audio circuit for a MV-1 from cart to speaker- but dont hold your breath

 

[Arakon]

well, the thing is, there is no z80 on these boards. there isn't one on the 1fz or 1B/1C either.

I'm assuming the YM2610 is fried, cause there was soldering done to it (prolly fried by shorting or something).

 

[ttooddddyy]

well, the thing is, there is no z80 on these boards. there isn't one on the 1fz or 1B/1C either.

I'm assuming the YM2610 is fried, cause there was soldering done to it (prolly fried by shorting or something).

I thought all versions of mvs boards had Z80s ???

 

[Arakon]

apparently not.. or at least it's integrated into another chip in the smaller models.

in fact on the 1B, the bios has the z80 check and soundcheck removed entirely.

 

[Arakon]

argh.. after a shitload of work, I replaced the YM2610 with one I salvaged from a football champ PCB.. and it still doesn't work. no sound at all, no error.

any more ideas? especially lines to measure etc.

 

[ttooddddyy]

argh.. after a shitload of work, I replaced the YM2610 with one I salvaged from a football champ PCB.. and it still doesn't work. no sound at all, no error.

any more ideas? especially lines to measure etc.

I guess if there is no Z80 there will be no error.
Are you sure the problem is around the sound proc stage. The previous solder work around there may well be a red herring. What happens if you touch the output pins of the YM3016 DAC, seems to be pins 10-15 on a stereo board (looking at a MV-1FS), 6-8 inputs ?
Do you get a buzz from the speakers.
If not one of the 4558 op-amps may be faulty. If you do then it confirms everything from the DAC to the output stage is OK.

 

[ttooddddyy]

Here is a link to the YM2610 data sheet.( thanks MKL)
http://www.ylw.mmtr.or.jp/~hosino/ma-net/sndgen/japanese/ym2610.htm
Its in Japanese but you can get an idea of the pin out.

 

[Arakon]

when I touch the speaker to pins 10 or 11, I get a squeaking noise that gets louder and higher pitched, then gets quieter again and completely dies and remains silent.. also, the amp gets very hot when I do that, so something can't be quite right.

z80 errors still occur on the newer slots, btw, EXCEPT for the 1B and possibly 1C.
funny fact: a normal bios will give a z80 error on a 1B because there's no z80. only the asia bios (which doesn't check the z80) will work flawless on it.

I even got a z80 error earlier when I accidently shorted 2 pins on the YM2610.

 

[ttooddddyy]

I wouldnt be connecting speakers to anywhere other than the output stage. What happens when you put your finger on the YM3016 output pins. Is there a buzz from the cab speaker ? This would possibly confirm if the problem lies before or after the DAC.

 

[Arakon]

I get a noise when I touch all 3 pins of the volume control, but not otherwise.

what are the PAL chips labeled SNK1A and SNK1B for? one of them looks like it might be damaged.

 

[ttooddddyy]

So nothing from the speaker when you touch the output pins of the DAC with volume up full ?

What type of op-amps are being used, 4558s ???

It all sounds a bit wierd to me.

MV1ACHX
TA 8201 (thought they all used HA13001)

Some strang variant.

 

[ttooddddyy]

Check the 5 volts on the op amps, the voltge may be derived from the 12 Volt rail via a 7805.

 

[Arakon]

only found one op amp, and it's a C8440.

the amp is a toshiba, I removed the heatsink to verify.

the op amp has 5V on 2 or 3 pins, so I assume it gets power fine.

here's 2 more pics.. one is a closeup of the amp area, the other a full shot of the board.

when putting my fingers to the YM3016 with the sound on the tv turned up all the way, I do hear various humming/buzzing sounds depending on which I touch.

http://pirate.sparkhost.com/~arakon/amparea.jpg
http://pirate.sparkhost.com/~arakon/board.jpg

 

[ttooddddyy]

Wowww- Arakon. I didnt realise SNK manufactured mvs mother boards up to late 95 (who knows maybe later ?) First time for me to see anything like this, a total, well almost, surface mount mvs mobo. The board will be multi layered, 3,4 layers or more !
Briggs may be interested in adding this to the list.
From what you say on the analog signal from the 3016 DAC it seems the problem is definately in the digital processing. From the pic of the main board on top of the YM2610 there is the SM1 on board sound rom, ram9 and cpu2 (Z80 alternative I guess, whats the IC type ?) Are there smds on the under side of the board ?
As you have eliminated the Yamaha it may be a problem with cpu2, or associated ram or rom chips. Vague I know

 

[Arakon]

ugh..

I have this stupid feeling that cpu2 IS the z80.. "T84C00Am".. I have seen the newer models of the z80 refered to as something with a 84 in the model number too.

there's only resistors, caps etc at the bottom, no chips.

 

[ttooddddyy]

cp2 may be a good start