Tech: DE Sound board 520-5077-00

[stangbat]

I have a 520-5077-00 Data East Sound board. This is the board used in Tommy, WWF, GnR, and MSF. When the game is powered on, the board puts out static during the short sound clip that is played. It also puts out static when sound data is being triggered from the CPU. It is static similar to when tuned to a dead area on an FM radio. I have found one background sound loop that sounds correct, and two other short sound loops that sound right, but they play very briefly at the end of a game.

If I go into the adjustments menu to set the background volume, it is static with the faint background music underneath while at 100%. When I lower the background volume to 25%, it sounds good with no static. As I increase the background music volume in the menu, the static increases, but the background music stays faint underneath. Keep in mind this is the background music adjustment in the menu, I'm not adjusting the volume with the potentiometer in the cabinet. The test tones in the diagnostics menu sound correct but the test voices and music do not.

If I remove the connector going to the potentiometer in the cabinet, I get full volume static (very loud). This leads me to believe the volume potentiometer is not a culprit.

The voltages into the board from the power supply check out fine (+12v, -12v, and +5v). I have checked the voltages generated on the board at C47 and C49, they are correct at +5v and -5v respectively.

I have checked the data cable and used a known good cable, the cable is fine. I have the latest ROMs. I have done the following with no difference in behavior:
-Swapped in another CPU and BSMT2000 chip
-Changed the RAM
-Replaced the shift registers at U23 and U24
-Replaced C30

The fact that it tries to play sounds at the correct times, plays test tones, and plays some music correctly makes me believe the DAC, RAM, CPU, and BSMT2000 chips are okay.

The board has been repaired in the past. Whoever did the work knew what they were doing based on the desoldering/soldering work. The following was removed and replaced at some point before I got the board:

VR2 - 7805 regulator
U4 - 6264 RAM
U8 - 74LS74A
U10 - 74LS240
U11 - 74LS273
U19 - PAL 16L8
U26 - TDA1543A DAC
U30 - LM833N

I have a logic probe but not an oscilloscope. If an oscilloscope is needed I will make a probe and get software so I can use a computer sound card for diagnosis. I also have schematics and I can scan them and post a copy if needed.

I don't know where to turn next to get this running and if possible I'd like to fix it myself. I'm not expecting to be spoon fed, I'll put in the effort to learn and figure this out. But I need some direction at this point. Thanks!

 

[Lindsey]

Have you tried fresh sound EPROMs?

 

[dc2010]

based on what you've said, seems to me you have either

1 a problem with sound proms

2 a faulty potentiometer/ cold solder joint with said

or 3 a bad resistor on the sound board probably in the amp section

i would also look at your cabinet speaker, has it been replaced with incorrect ohms speaker?
bad connection? is there a capacitor connected to the leads on the speaker itself?

just some ideas off the top of my head...

 

[stangbat]

based on what you've said, seems to me you have either

1 a problem with sound proms

2 a faulty potentiometer/ cold solder joint with said

or 3 a bad resistor on the sound board probably in the amp section

i would also look at your cabinet speaker, has it been replaced with incorrect ohms speaker?
bad connection? is there a capacitor connected to the leads on the speaker itself?

just some ideas off the top of my head...

Thanks for the help. To answer your suggestions:

1) I have a programmer, I've re-programmed them, verified them, and tried them in another board. Doesn't seem to be the problem.

2) Changed it already.

3) I've changed a few of the resistors in the amp section, no change. I've checked the others, they are fine.

Speakers are fine. And they work fine with the other sound board.

Edit: New ROMs are on the way (from China). I'll program them when I get them, but I've already tried a new ROM at U7 and it didn't help.

 

[dc2010]

Thanks for the help. To answer your suggestions:

1) I have a programmer, I've re-programmed them, verified them, and tried them in another board. Doesn't seem to be the problem.

2) Changed it already.

3) I've changed a few of the resistors in the amp section, no change. I've checked the others, they are fine.

Speakers are fine. And they work fine with the other sound board.

Edit: New ROMs are on the way (from China). I'll program them when I get them, but I've already tried a new ROM at U7 and it didn't help.

ok.... im almost certain you have an issue "hiding" in the amp section

you said you have some sound at 25%,and a background loop works at the END of a game

so somewhere between where power comes in from your supply board and the output to your speakers(this includes your dmd panel speakers) your not getting proper juice, and if you are measuring correct volume going in, then its not the psb, im actually having a static issue on lw3 but i didnt even bother with it as it is intermittent and in storage too lol. can you put up a few pics, one of the whole board, and one close up of the amp section?

 

[Lindsey]

You might try poking around the pre-amp and power amp with a speaker. One speaker lead connected to ground and one probing into the circuit. You might be able to figure out where the problem is. For example, if you get sound out of the pre-amp you know the problem is after that in the circuit. If you're getting static even at the input of the pre-amp you know it's more likely a ROM or RAM problem. Even though you've changed them it could still be an open or shorted address, data or control line somewhere. Have you checked the address and data lines of the RAM and ROM with a logic probe? If you got really desperate you could verify continuity of all the address, data and control pins with a meter.

It will be tough to do all this with the board in the machine. Ideally the board would be on a bench and you would use an oscilloscope instead of a speaker. I don't know how tough it would be to get the board generating sound on a bench with that sound board. I've never had to work on that specific sound board.

Something to think about anyway.

 

[dc2010]

You might try poking around the pre-amp and power amp with a speaker. One speaker lead connected to ground and one probing into the circuit. You might be able to figure out where the problem is. For example, if you get sound out of the pre-amp you know the problem is after that in the circuit. If you're getting static even at the input of the pre-amp you know it's more likely a ROM or RAM problem. Even though you've changed them it could still be an open or shorted address, data or control line somewhere. Have you checked the address and data lines of the RAM and ROM with a logic probe? If you got really desperate you could verify continuity of all the address, data and control pins with a meter.

It will be tough to do all this with the board in the machine. Ideally the board would be on a bench and you would use an oscilloscope instead of a speaker. I don't know how tough it would be to get the board generating sound on a bench with that sound board. I've never had to work on that specific sound board.

Something to think about anyway.

great point! ............................................................................................................................................................................................................................................

 

[stangbat]

One reason I think the preamps are being overdriven is the 25% sound issue. What I've determined is if I turn the background volume down, what is happening is it no longer overdrives the preamps. Regular sounds effects still do, so they sound like static. As I increase the background music in the menu, it becomes distorted like the effects. So I don't think it is a power issue coming into the board. Plus I've tried another board and it worked fine to the extent it could (it was an earlier version and could only hold two of the three ROMs).

If I remember correctly, I've probed all the RAM address lines as well as quite a few of the ROM lines. I haven't done everything though which means I can't rule this out as a possibility.

A friend has an oscilloscope and I need to get it from him. In the mean time I can poke around with a speaker. That wouldn't hurt.

 

[dc2010]

So I don't think it is a power issue coming into the board.

to clarify i wasn't saying power coming into the board

 

[stangbat]

So I don't think it is a power issue coming into the board.

to clarify i wasn't saying power coming into the board

Okay, sorry. I'm trying to respond to too many posts.

One thing I did was I put an additional 10k ohm resistor on the ground to the pot, which lowered the volume further. I still had the same issues and it sounded the same, just a lower volume. This is another thing that makes me think the problem is before the power amps. I also swapped out the power amps with known good ones and the problem stayed exactly the same.

I've powered the board on the bench, but I don't think there is any known way to get it to play sounds other than the initial start up quote when power is first applied. I'll poke around with a speaker some today and see if I can come up with anything.

 

[stangbat]

I did some poking around with a speaker. The output from the LM833N at U30 seemed really loud. This is the first preamp that is right after the DAC.

 

[Lindsey]

I did some poking around with a speaker. The output from the LM833N at U30 seemed really loud. This is the first preamp that is right after the DAC.

From both op-amps or just one? U30 is a dual op-amp. The resistors at R16 and R17 should set the gain for the op-amps in U30. Might be worth checking those resistors.

Could also be a shorted cap at C48 or C50. I think those are the numbers. The schematic I'm looking at is kind of fuzzy. They're the caps in parallel with R16 and R17.

EDIT: Was it the correct audio or static? If it's the correct audio you can rule out the RAM or ROM issues.

 

[stangbat]

From both op-amps or just one? U30 is a dual op-amp. The resistors at R16 and R17 should set the gain for the op-amps in U30. Might be worth checking those resistors.

Could also be a shorted cap at C48 or C50. I think those are the numbers. The schematic I'm looking at is kind of fuzzy. They're the caps in parallel with R16 and R17.

EDIT: Was it the correct audio or static? If it's the correct audio you can rule out the RAM or ROM issues.

I checked both outputs at Pin 1 and Pin 7. Both seemed too loud. Almost as loud as the amplified sound from the speakers. And this was using an 8 ohm speaker vs. the other speakers which are 4 ohm.

The caps (C48 and C50) measure fine, maybe 2700 pf on my meter. I replaced these caps and it didn't make a difference. I actually got 60 Hz hum after replacing a few ceramic caps so I put the old ones back in and the hum went away. I'm not exactly sure which caps were the problem, but changing them didn't change anything other than add hum. Based on this, I'm thinking that they aren't the issue.

I have checked R17 and R16 on the board and they test fine. I haven't unsoldered them to check them though.

The sound is static like, but I really believe it is because it is distorted from being overdriven. The lower volume music and low volume effects seem to be fine. When the background music level is raised in the adjustments menu, it becomes distorted.

Also, I have the pot in the cabinet turned all the way down and the sound is still rather loud. When I put in the other sound card, with the pot all the way down, the sound is silent. My other DE games behave the same, when the volume pot is all the way down, no sound. So on this board, even with the pot all the way down, there is still sound and it isn't low sound, it is fairly loud.

 

[stangbat]

Also, I think this was in the other thread, my voltages are a little on the high side. +5.6 and -5.6 volts. I've replaced both regulators and tried several different regulators. If I put in the other sound board, the voltages are fine at +-5v. So the problem doesn't seem to be the main power supply or transformer voltages. I don't understand why the voltages for this board are a little high, especially since I've replaced all the caps.

 

[mrgone]

here are some pics. sorry it took so long to get them posted. let me know if you need any more.

 

[stangbat]

Thanks for the pics. From what I can see, nothing looks out of place on mine. I think I'm done with trying to fix it. I did manage to repair the CPU and flipper boards and get the game working except for the sound. So I've actually been able to play it a bit. And I learned a lot in the process. So all is not lost.

 

[FlashbaxArcade]

Old thread here, but I'm havin no sound on a LW3. Did you fix this problem?

 

[stangbat]

No, but playpin35 had it fixed after I sold the game to him. I think I had some bad ICs, probably counterfeit, which was causing my issues.

LW3 uses a different sound board. It is somewhat similar to the one I'm discussing here, but not the same.

 

[playpin35]

No, but playpin35 had it fixed after I sold the game to him.

I sent the board to Rob Anthony(Lock when lit). He said there was 1 bad IC and a bad or missing cap(if memory serves correctly).