Help with Sky Wolf repair

[Pflaugi]

I never dared to do PCB repairs ... but now it's time I got further.

Admittedly, I don't have a lot of knowledge and I'm still at the beginning. But I want to try. I get tools one by one.

For this purpose I bought a cheap Skywolf that has no sound, and on the left there is a strange white flickering stripe that is a bit annoying.
It's a bootleg, but I think that's just right for educational purposes.

This is the PCB:



and the status in operation:

https://pflaugis-arcade.de/index_htm_files/skywolf.mp4

To the sound problem:

The PCB is completely without sound.
For this purpose I built active speakers and could hear sound at PIN 1/3 and 5 on the AMP.
I thought the AMP was defective and replaced it.



... but still no sound after that, but I can hear Sound at the AMP on PIN 1/3 and 5, but PIN 3 and 5 are scratchy...

After further tests I found that the capacitor is defective. Then I exchanged it ...



Now I have sound, but very scratchy and also quiet. Has to turn up the volume so that it is reasonably loud. In addition, the AMP is about 75 ° and I have interference ...

Here is the result:

https://pflaugis-arcade.de/index_htm_files/skywolf2.mp4

Because of the temperature and the background noise, I soldered a 100nF capacitor between PIN 1 and 4. Now the temperature is better and the background noise is gone.



But the Sound is still not good. Still too quiet and too scratchy and not clear.

Here is the current state:
https://pflaugis-arcade.de/index_htm_files/skywolf_falsch.mp3

And this is how it should be:
https://pflaugis-arcade.de/index_htm_files/skywolf_richtig.mp3 (Example from MAME)

Well, not bad for a start. But now I need help with the next steps ... Does anyone have any ideas?

 

[ekorz]

what chip feeds the input on the amp? If there’s an op-amp before that, I’d check its inputs and outputs with an audio probe. Before that might be a d/a converter and you could probe the output. You could also check the audio data on the rom.

 

[Pflaugi]

Okay thanks, I check this. As I said, I am a beginner in repairs, but would like to make it

 

[Pflaugi]

The 8910 are responsible for the sound. At some PINS I can pick up the sound clearly and distinctly. The chips seems fine.
There is no OP AMP on this board. The place would have been on R6. Only a resistor was soldered in there...

 

[ekorz]

The 3 analog outputs are marked on the datasheet, if any don’t sound good then it might be that chip. http://datasheet.datasheetarchive.com/originals/scans/Scans-061/DSA2IH0094116.pdf

Before that it’s digital so you could use a normal probe to see if any inputs are stuck high or low but you’ll also need to know if they’re supposed to be high or low. Maybe only a few inputs are connected to a processor and those should be flickering.

worth checking the source data on the audio rom(s) if they’re socketed. I’m not sure which are audio code… https://github.com/mamedev/mame/blo...ca3424bf5103/src/mame/drivers/kyugo.cpp#L1358 maybe the ‘maincpu’ or ‘sub’ ones since the rest are graphics it seems.

Otherwise you have harder work in front of you. I’d also be curious if the clock signal is right, based on how it sounds, but you’d need an oscilloscope or a probe that could show you the waveform for that. Also one thing easy to check, are those chips getting full 5.0v?

 

[Pflaugi]

The 8190 chips seem fine.
The sound on the potentiometer is normal and not overdriven, but quiet.
I have now also installed another AMP because I thought the new one was not okay, but that's not it, I have the same error.

The soldering eyes at the location of the AMP dissolve. Not good quality. Let the AMP loose for now until the sound works.

Here is the sampling:
https://pflaugis-arcade.de/index_htm_files/skywolf3.mp4

What comes to mind ... The capacitor on the AMP was broken, I exchanged it with the same value as the old one ... 16V / 100uF then the sound went again, but with the error. Does it have to be a different value? But that contradicts the old capacitor, that was the same ...

 

[ekorz]

Does this pinout look right to you? http://andysarcade.de/data/electronics/components/upc1181_upc1182.htm

1 input 5 output. Check the voltage going to the amp?

so is the sound content wrong (samples at wrong time? Wrong samples?) or is the sound just poor/muddy? It seems fine on those outputs from the 8190’s but I don’t know the game. Wherever it starts to get bad (input good, output bad) replace that thing!

 

[Pflaugi]

Done! The sound works again ...
In the end it was the defective capacitor in front of the AMP and a bug in the wiring.
The pinout is wrong. The bootleg version I have has 2 x Speaker + (where GND should actually be)...



Now the sound is good:
https://pflaugis-arcade.de/index_htm_files/skywolf4.mp4

Many thanks for your help. Really great forum here ...