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Help Repairing Batrider with no sound

twistedsymphony

twistedsymphony

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I've got a Batrider it's a very clean and untouched board but when booting it displays "Sound Error" and then the game plays normally but with 0 sound.

When I first got this board it would do this occasionally and would usually resolve after a reboot or two, now it just does it all of the time.

Looking at MAME source for clues it had this note about Truxton II
Code: 
	// Bit 0x01 returns the status of BUSAK from the Z80.
	// BUSRQ is activated via bit 0x10 on the EEPROM write port.
	// These accesses are made when the 68K wants to read the Z80
	// ROM code. Failure to return the correct status incurrs a Sound Error.

So According to that the error occurs if there's an issue with the Z80 or EEPROM

Anyone have experience with this error or suggestions on non-destructive ways to work out the failing component?

Normally with something like this I'd just shotgun replace stuff but given the value of these boards I'd like to do all I can before I put an iron to it (that and my soldering station hasn't been working right)
 
Only since you said it used to fix itself, does it do this error booting with a different power supply?
 
Does it work if you switch it on, then off and on fairly quickly? Intermittent boot time issues are often things like the reset cap. Also of course, reseat the sound rom and verify the data with a reader.
 
Maybe check continuity between the 68K, Z80, and sound rom? If you have a rom checker, verify the sound rom, and see if the Z80 is alive?

There's a basic block diagram to guide you here.
 
Thanks for the tips everyone.
I've already dumped and confirmed that the sound Rom is good. I suppose I could try writing a replacement. I will also try another PSU

I have tried the "warm boot" to see if it's a failing T518A or associated cap but it doesn't seem to help. I suppose it could be too far gone now to work.

That block diagram is great, it looks like I should see if the RAM next to the Z80 is faulty also...
 
I checked all of the roms again and they all checked good. Installed a new sound Rom just incase and no change there.
it's worth noting that this game does a ROM test on boot, including the Z80 ROM and it passes everytime without issue.

I tried on 3 different cabs (3 different model PSUs) Also tried with voltage a little hot and a little lo and no change.

tried multiple times to do a quick off and back on and no luck getting sound to work at all ever.

I tried putting pressure on some of the surface mount chips, notably the OKIs and the SUB_DEC1 custom since they're part of the sound section and tied to the Z80... no results there.

I did go into service mode and poked around there.
I noticed that entering into service mode also produces the sound error message. Also exiting out of the sub menus back to the main menu triggers the message as well. To me this implies that the program is essentially restarting when this happens which would essentially rule out the T518A and cap as a problem I think.

one interesting thing in service mode is that there is a "Sound test" and an "ADPCM Test". the ADPCM test menu I can enter but no sound ever plays. the "Sound Test" screen I can't even enter, it just displays the "sound error" message instead.
 
It sounds to me like a dead or damaged z80. Could be wrong.
 
If you have a logic probe or oscilloscope, you can probe the clock pin on the Z80 to make sure its pulsing, and probe the Reset pin too to make sure the Z80 is getting reset at power on.

If those signals check out but the Z80 isn’t showing much logic life otherwise then, I’d swap the Z80 CPU and/or test its RAM out of circuit. That means desoldering them from the board unfortunately.
 
Doesnt batrider have a debug mode? That lets you see the code as it plays, if so, it might give you an idea of where the error occurs.
 
Would piggybacking a spare, working Z80 on top of the existing one be worth trying to see if that might resolve your sound issue?
 
Derick2k said:
Doesnt batrider have a debug mode? That lets you see the code as it plays, if so, it might give you an idea of where the error occurs.
Click to expand...
If it does I don't know how to access it.

The error comes on immediately on boot, as in it's on the screen as the monitor fades in. After that the title screen actually states "music: off, sound effects: off", it's like the game disables sound because it failed initialization on boot.

GoldenGlover said:
Would piggybacking a spare, working Z80 on top of the existing one be worth trying to see if that might resolve your sound issue?
Click to expand...
good idea! this looks like a Toshiba Z84 which I don't have any on hand to try.
 
ShootTheCore said:
If you have a logic probe or oscilloscope, you can probe the clock pin on the Z80 to make sure its pulsing, and probe the Reset pin too to make sure the Z80 is getting reset at power on.
Click to expand...
ok, this is fun....
I hooked up my pocket scope to the clock pin and... SOUND WORKS. I tried restarting 4 or 5 times, worked every time Played for 15 minutes, no issues, perfect sound.

disconnect the scope.... "sound error" O.o

kind of difficult to troubleshoot when the act of troubleshooting temporarily fixes the problem, but it gives me a lead... sort of.
 
Thinking about this more....
the cheap scope I used has about 500Mohm of resistance across the leads, looking at the wave form of the clock it appeared to fluctuate between 5v and 4v. My assumption is that it was just moving too fast for my scope, but maybe it wasn't? maybe the scope was acting like a pull-down resistor and allowing the clock pulse to actually register?

It looks like the clock is generated by the near by "E68DEC1B SUB_IF2" chip.

Does the TMPZ84C00AP-8 (the specific model Z80 on this board) have an internal pull-down on the clock? if so and it's faulty that could explain the behavior. There doesn't appear to be any issues with the clock trace or solder joints between these two chips
 
What voltage levels were the clock signal peaks reading on the scope? Hopefully close to 5.0V and not much higher.
 
So I received this board today at the request of the new owner for repairs.

Did some readings with pin 24 and used the datasheet table as a reference. The pin ended up being a really cold joint inside between component side and solder side. It took a while to clean up because the solder gone bad and couldn't flow right, but the rest of the IC pins reflowed with ease.

1712872229411.png


Also, I installed a piggyback DIP40 socket in preparation of a new Z84 coming in the mail soon but it looks like I might not need that anymore (maybe)

As of now, it's working 100% with no issues. Been booting it up in several intervals throughout today. Will report again after a cold boot on Monday.
 
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