Hey Guys,

Was in the process of replacing the caps on my Data East sound board. Everything seemed to be ok until I turned on the machine and started getting a really nasty and loud popping, crackling, and fizzling noise from the left speaker. Lasted a few seconds went away, along with the sound. Power cycled a few times just to try to figure things out and the lout crackling noises seem to always be different each time, and sometimes I get sound, sometimes I do not.

I also noticed the center amp on the board for the left speaker got very very warm. The right and cabinet speakers are both fine, and their amps were cool to the touch.

Checked all the caps...the joints and polarity all seem to be ok, not the cleanest solder job but nothing seems to be touching anything it shouldn't.

Is this a bad amp? Could I have screwed something without realizing it? Any ideas? Seems more than just a bad speaker, yes?

Thank you,
Jim

So I replaced the amp, and that did not seem to do the trick. After turning the game on and leaving it sit for just a minute or 2, it still gets extremely hot...I know I said warm before but now it’s so hot I can’t even leave my finger on it.

It gets hot even when I unplug the speaker. I was hoping to just unplug the left and right speaker and just use the cabinet speaker, but the left channel amp is still getting hot. I have a multimeter but not the most knowledgeable on how to test circuitry.

I’m assuming it’s getting too much voltage somehow and wondered how I could check with a multimeter. Any input or links to resources would be great.

Yeah I have this and Have gone through it and almost know it by heart lol. I know where the problems may be, I just don’t know how to proceed with testing my theories.

This all happened after I replaced all the capacitors on the sound board. But I’m trying to see if I can narrow it down to which ones it could be in case I made a bad solder or a cap was just bad.

I agree...I don’t solder too often and I’m not the best at it so it’s very possibly I have a bad solder connection somewhere, I’ll have to poke around.

Thanks!
Jim

One thing I noticed... I have an aux power supply wired in to power the sound board. I have a data East machine with the plagued 60hz hum and this ‘hack’ fixes that.

When I power the sound board from the aux power supply the amp gets extremely hot almost immediately. When I hook back in the original power from the transformer, it still gets extremely hot, but it does take a little bit longer to do so. Seconds vs minutes...

Does this help troubleshoot anything?

How would I measure this? I do have a multimeter but I’m pretty new to how to test specific things like this...

I was able to test the voltage on each of the 3 amps (MB3730A) and was getting 10 volts on average for each.

Yes everything worked fine before I started messing with it. All I was trying to do was alleviate the 60hz buzz coming out of the speakers so I replaced all the caps on the power board and sound board.

After firing up the machine, things were ok for a few games, then the left speaker started making loud noises and pops then stopped working. So I replaced the left speaker amp. Fired up the game again and it was ok for a few games, then I noticed the amp getting extremely hot.

And that’s where I’m at now...only thing that was done between it working and not was the replacement of the sound board caps. The power board caps were done awhile ago and all was fine.

For the measurements you mentioned I wanna measure ohms? What what contact points do I use?

Oh, and speaker now does not work again. I have another amp laying around, but it seems like something is causing it to go bad...

At the moment yes, again just kinda getting into all of this so it’s all I had laying around at this time. I shouldn’t have messed with anything, everything was fine until i replaced the caps...

On to learning more!

So here are some pics. As far as the capacitors, I only replaced the radial ones, but I replaced all of them. The only one I question the polarity on is C29 as the cap didn’t have the white stripe in any side so I just went with the short leg being the neg.

Here are a few pics of the board. The amp in question is the center one for the left speaker. This is the second amp I am trying which gets extremely hot. (Screws are our because I was just about to desolder it from the board but holding off for now in case someone can help me pin point my issue.

Nothing “looks” fried or damaged. Not the nest solder job (and maybe this is my problem) but the solder doesn’t seem to be touching anything it shouldn’t.

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Negative lead of the C37 capacitor. You probably think it’s touching the trace? It’s not it’s just an optical illusion. New angle attached.

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No, no compound on the pins. I completely cleaned off the old stuff and apply new thermal paste I had lying around from my computer building days.

Interesting new development...

I went out an got a new soldering iron to reflow my solder joints of the caps in hope I just had a weak connection. And boy, I wish I had this the first time around!

Anyways...Here is where it got interesting.

I hooked up the board back in the machine, turned it on and no sound and amp was HOT. I turned off the machine and waited for the amp to get cool and turned it back on and went into test mode specifically to test the sound. I was actually able to get sound through that speaker just fine, through all the voice and music roms, no issues. And...it didn't even get hot, at all!

Turned the game back off and on again and got a really loud crackling pop sound from the left speaker (all speakers have a little pop to them, but this was louder and more crackly than the others). However, I still got sound and the amp was not hot at all (it would usually get hot within a few seconds). It sat in attract mode for a few minutes without getting hot...however, after I left it for a few more minutes I returned to the amp being scorching hot again

I thought I may have had it...I wonder if this helps trouble shoot it any more specifically.

Thanks for the help thus far...
Jim

Another update...I power cycled the machine one last time and did not play a game, just let it sit in attract mode for about an hour. Attract music came on about 5 times in that time period.

I got full sound form the left speaker and the amp never came close to being hot. Slightly warm, but just as warm as the other 2.

Problem is I have no idea what this means.

After that hour of letting it sit in Attract mode I played a few games and everything was just perfectly fine. I had audio, the amp was not hot at all. However, I finally narrowed it down to the amp only getting hot when the left speaker makes a loud crackling popping noise. When it does this the amp IMMEDIATELY gets so hot I cannot touch it. So as long as I never heard that pop crackling noise, everything is fine, but the moment I hear that noise...its time to shut er down...

Just don't know why

Agreed. I used really thin rosin core 60/40. The contacts are MUCH cleaner after I reflowed with a much better iron. C3 was not replaced. I only replace the radial capacitors. But C3 seems to be connected to the cabinet speaker...I am no having issues with that one. Should I replace C27 for the left speaker do you think?

It’s not leaking or even looks damaged (I understand it still could be).

However, for whatever reason the game has been just fine today...I haven’t had any crackle in the speaker, amp hasn’t gotten hot, and I’ve played quite a few games on and off throughout the day.

Not sure what’s going on here. Still worried something isn’t quite right but I have had zero issues today...

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I may not have. It’s for DE BACK TO THE FUTURE. goodnight! Thanks for your help this far.

So believe it or not...its been almost 2 days and I am having zero issues with my left speaker. I am no longer getting any crackle popping, and the amp is not getting hot at all...and Im getting full normal sound. Game has been on and off several times, sat in attract mode for a bit, few games played...everything seems to be ok (but i dont know why and that has me concerned).

I still have the attract mode buzz and some white noise, but those are from all speakers and not really my concern at this point (thought I do want to try and clean up the white noise if i can).

Jim

Well that's just it...I finally narrowed it down to the amp getting hot ONLY when the speaker would crackle. As long as there is no apparently crackly, everything is. And it has been for 2 days...but yes, I need to keep an eye and ear on it for sure...

So about 3 weeks later I am getting this issue again. I have used the game pretty extensively the past 3 weeks with zero issues, playing every single day. Then all of a sudden out of no where I got the distinctive and loud speaker crackle/pop that causes the amp to get extremely hot. And now it seems the left speaker that’s giving me the issue is now at a much lower volume than the right when it does work...

I have done nothing to the machine other than play it. No mods, no tweaking anything, just regular game play. This is very much puzzling me. I mostly notice it when I first turn the on the game...it makes the loud popping crackle and the amp gets extremely hot. However, it doesn’t happen every time, it’s happened many times to me today, After being fine for 3 weeks, but not every time. And when it doesn’t happen the game plays fine.

I did seem to notice that when it does happen and I immediately turn the game off...I adjust the volume knob a bit and when I turn back on it seems to be ok. But then It will eventually happen again....

Is it something with the volume possibly? I will say that the noise it makes is not dependent on the volume level. It sounds the same whether the volume is turned up or down.

Still getting the issue, though still intermittently. I’m going to try replacing that C3 equivalent .15uf cap and the similar ones around it and see where that gets me.

I just hate that it's intermittent...cause if i do replace components, I will have no idea if that actually fixes it lol.

Yes...ordered and on the way.

Yeah. I’ll see what Happens. Thanks!

So that cap...when I was installing it I realized there was no white stripe to indicate the neg lead so I went by the longer leg being the positive lead. In my order of the much smaller MLCC caps, I did get a replacement for the one you circled that clearly is marked.

Haha yes, this pic was taken mid repair. Here is a current pic.

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I appreciate that! So far so good..i guess...I ordered a few replacement ceramic caps to have one hand. However, I have not had the issue in awhile. So until the issue happens again, I am not going to worry about it. But, I do have the caps on hand to give them a try if it happens.

Thanks for the help!
Jim