(Topic ID: 252755)

Speaker Amp Getting Too Hot? - Noisy Speaker Static?


By jimgravina

50 days ago



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  • 46 posts
  • 5 Pinsiders participating
  • Latest reply 13 days ago by jimgravina
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#1 50 days ago

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

1 week later
#2 42 days ago

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.

#3 42 days ago
Quoted from jimgravina:

... Any input or links to resources would be great.

Here's the manual to get you started, schematics towards the end: https://www.ipdb.org/files/126/Data_East_1990_Back_to_the_Future_Manual.pdf

#4 42 days ago
Quoted from mbwalker:

Here's the manual to get you started, schematics towards the end: https://www.ipdb.org/files/126/Data_East_1990_Back_to_the_Future_Manual.pdf

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.

#5 42 days ago

I would suspect something with the original capacitor replacment work, since that sounds like where the issue began presenting itself.

Caps all happy polarity?

Through holes damaged, bad connection to component side trace/pad?

Replacment caps were good? Faulty? Correct part?

Needs more info...

Try checking the original caps that were replaced, their instalation. Ohms test with meter from capacitor lead pad on the Solder side - to a Component side pad, that is accesible but should be connected to the capacitor lead on the Component side. Looking for Continuity here, ideally 0 ohms.

#6 42 days ago
Quoted from razorsedge:

I would suspect something with the original capacitor replacment work, since that sounds like where the issue began presenting itself.

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

#7 41 days ago

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?

#8 41 days ago

I'd try and figure out what signal the amp is supposed to see and compare that to what it's getting.

Maybe take measurements with the game off. How does resistance to ground differ between the two working amps (are they both used?) and the problem amp? What provides the signal to the working amps? Are those components different than the source for the problem amp?

The Pinwiki didn't seem too relevant but it may give you clues for further troubleshooting.
http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega

#9 41 days ago
Quoted from YeOldPinPlayer:

How does resistance to ground differ between the two working amps (are they both used?) and the problem amp? What provides the signal to the working amps? Are those components different than the source for the problem amp?

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.

#10 41 days ago
Quoted from jimgravina:

How would I measure this?

Looking at the assembly drawing, the three amps are the MB3730 chips on the left side. Are they all the correct chips? (Did they work before you 'fixed' them?)

The schematic shows them at the upper right. Looks like they have seven connections. #4 goes directly to ground, do all those measure the same? #1 all go to ground through resistors R10, 26, & 28, do those all measure the same? #2 goes to ground through 22 µf, 16v capacitors C?3, 35, & 54. All those caps good with good path to ground? Similar measurements?
Check the other pins in a similar manner.

#11 41 days ago
Quoted from YeOldPinPlayer:

(Did they work before you 'fixed' them?)
Similar measurements?
Check the other pins in a similar manner.

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...

#12 41 days ago

So if you really want to dive into fixing this, the first thing I would do is to measure the current going into the IC. Yes...easier said than done, but that will give you a big answer about heat. According to the data sheet, it should be 80 to 200mA w/no audio. 12V x 0.2A = 2.4W. That's how much power it dissipates just sitting there, worse case.

For now, let assume the power supply is not an issue since you tried two. And for now, let's also assume the circuitry driving the 3730 is OK, but could be the culprit too - but one thing at a time.

Also look at C3 (or whatever it is on your specific IC you're focusing on). That keeps the amp from oscillating, according to Fujitsu. It could be oscillating and you would never hear it, but it could be going full bore w/o you even realizing it. Ironically, it looks like DE used a 0.15uF, whereas Fujitsu shows what appears to be a 1uF. Check C2 and C4 too. Just guessing those provide a high(er) frequency termination. Just a WAG, but that might also lead to an instability too. Fujitsu recommended a mylar cap. C14, if leaky, could be causing a DC offset. I wouldn't discount that either.

Another simple thing, but very important - clean up the heatsink and apply new thermal grease. Not much, just a thin layer. That helps wick away heat from the IC into the heatsink. Is the heatsink soldered to the board (I don't have a clue if it should be). If it is, check those solder joints too because the heatsink will xfer the heat into the board (usually a bunch of ground plane). The amp could be fine, but if the heat has no place to go - then that is an issue.

Hope this helps. Not much to wrong w/the chip - not a lot of parts involved. Just looks like high power op-amps. But I tossed out a lot of comments, hopefully you can start to narrow it down.

here's a link to the 3730 data sheet: https://www.datasheetarchive.com/pdf/download.php?id=3bb4dd06dc8fa38fc4bd4c8a5c4e0e19205382&type=M&term=mb3730

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#13 41 days ago

What test equipment do you have, just a multi-meter?

#14 41 days ago
Quoted from mbwalker:

What test equipment do you have, just a multi-meter?

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!

#15 41 days ago

As Razor mentioned, did you check the polarity of the caps? The C3 I mentioned above, did you replace that by chance? Was there thermal grease on the heatsink?

Mind posting some pictures of the area in question, both sides of the board? Lots of people here willing to help, someone might spot the issue right away.

On the bright side, things should be fairly straight forward. You just need to eliminate one thing at a time and move on to the next possible culprit.

#16 41 days ago

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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#17 41 days ago

What pin is this from photo 2?

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#18 41 days ago
Quoted from YeOldPinPlayer:

What pin is this from photo 2?[quoted image]

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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#19 41 days ago

Thanks for the pics, wont be able to take a close look until tomorrow.

Asking the obvious again, heatsink compound on the IC? We really need to know this before anything else. Ideally, new.

#20 41 days ago
Quoted from mbwalker:

Thanks for the pics, wont be able to take a close look until tomorrow.
Asking the obvious again, heatsink compound on the IC? We really need to know this before anything else. Ideally, new.

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.

#21 41 days ago

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

#22 41 days ago

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

#23 40 days ago

What about the c3 cap? Was that ever replaced?

A word about solder: The lead free you can buy at Wallymart is somewhat hard to deal with since it has a higher melting point. Some decent 63/37 or 60/40 that contains lead is a lot easier for a newbie. Rosin core too. Don't use plumbers solder, not safe for electronics long term.

#24 40 days ago
Quoted from mbwalker:

What about the c3 cap? Was that ever replaced?
A word about solder: The lead free you van buy at Wallymart is somewhat hard to deal with since it has a higher melting point. Some decent 63/37 or 60/40 that contains lead is a lot easier for a newbie. Rosin core too. Don't use plumbers solder, not safe for electronics long term.

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?

#25 40 days ago

Where's C27 on the schematic? I searched for it, but didn't see it.

#26 39 days ago

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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#27 39 days ago
Quoted from jimgravina:

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...[quoted image]

Jim,

Ahh...OK. I was looking at my LAH schematic which is a little different. Hitting the sack now, will look at it Monday night.

Did you by chance mention what pin this is for? Apologies if I missed it.

Thanks.

#28 39 days ago
Quoted from mbwalker:

Jim,
Did you by chance mention what pin this is for? Apologies if I missed it.
Thanks.

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

#29 39 days ago
Quoted from jimgravina:

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

Jim,

Duh, senior moment for me. Back at the beginning of the thread, I even posted the link to the game manual at ipdb.com. LOL!

So rather than having you buy a bunch of parts and replacing all the possible culprits one at a time by educated guesses, consider getting one of these and just test what's in the game. Granted you'll likely have to remove parts to test. It really is slick for $20. Get some decent solderwick, and it won't be that bad. Food for thought.

ebay.com link » B1 Color 1 8 Tft Esr Transistor Resistor Diode Capacitor Mosfet Tester W Hook

C27 - yes, that's the C3 in my LAH. If could be bad, but it won't leak tho.

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#30 39 days ago

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

#31 38 days ago

No doubt, can be hard to chase down an intermittent. I guess keep an eye on it for now. At least you sort of have an idea when it's acting up w/the crackling noise being a indication.

#32 38 days ago
Quoted from mbwalker:

No doubt, can be hard to chase down an intermittent. I guess keep an eye on it for now. At least you sort of have an idea when it's acting up w/the crackling noise being a indication.

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...

2 weeks later
#33 18 days ago

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.

#34 14 days ago
Quoted from mbwalker:

As Razor mentioned, did you check the polarity of the caps? The C3 I mentioned above, did you replace that by chance? Was there thermal grease on the heatsink?
Mind posting some pictures of the area in question, both sides of the board? Lots of people here willing to help, someone might spot the issue right away.
On the bright side, things should be fairly straight forward. You just need to eliminate one thing at a time and move on to the next possible culprit.

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.

#35 14 days ago
Quoted from jimgravina:

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.

Hang in there, it will seem like a wild goose chase - but it's a process of elimination. Lot's of people here willing to help.

#36 14 days ago
Quoted from mbwalker:

Hang in there, it will seem like a wild goose chase - but it's a process of elimination. Lot's of people here willing to help.

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

#37 14 days ago
Quoted from jimgravina:

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

Don't forget the earlier post I did about the parts tester...cheap $20 investment.

#38 14 days ago
Quoted from mbwalker:

Don't forget the earlier post I did about the parts tester...cheap $20 investment.

Yes...ordered and on the way.

#39 14 days ago

Good deal. Still might be hard to spot an intermittent part, but that's a good start.

Let us know when you get it and start to test parts.

#40 14 days ago
Quoted from mbwalker:

Still might be hard to spot an intermittent part

Yeah. I’ll see what Happens. Thanks!

#41 14 days ago

Caps are cheap, easy enough to shot gun it and replace them all and keep your fingers crossed.

Shipping is probably just as much as the caps.

#42 14 days ago

I can't see the negative marking on this cap. It should be visible.

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#43 14 days ago

That cap is polarized, so there is some sort of marking. Keep in mind sometimes the marking is for the +, other times it for the -.

Edit: Oops, didn't know that was you Grumpy posting and not the OP. Apologies.

#44 14 days ago

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.

#45 13 days ago

Just asking the obvious... I assume there's no screws here because you were tinkering w/the board, right?

Sorry - had to ask.

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#46 13 days ago
Quoted from mbwalker:

Just asking the obvious... I assume there's no screws here because you were tinkering w/the board, right?
Sorry - had to ask.[quoted image]

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

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