Star castle sound issue

Hex92

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I have a couple of Star Castles that I am working on and one has multiple sound problems.

The Background sound is a little wonky (maybe higher pitched). It doesn't sound like my other one (which sounds like I remember).

There are no explosion or thrust sounds.

Shield bounce is BARELY audible

Fireball seems about 1/2 volume

Star sound and Fire work and have the correct volume.

I replaced all the electrolytics and IC 4, 5, 15 and 26. There was no change.

Suggestions as to my best bet for my next replacement?
 
Are you working on multiple sound boards, or multiple cabinets? If you're testing in multiple cabinets, you may want to try just swapping the sound boards, since things can sound different with different voltages, if a speaker has been eaten by mice, etc.

But, beyond that... the schematics are very clear for troubleshooting sound problems. There are only a few active components per sound, and looking at the sounds that you say have problems, a couple things that look common across all of them, but not to the sounds that are working, is the 2.2V voltage from Q2, the Noise from IC14 and IC15, and the 60Hz from IC16.

Since you say Fireball and Shield have some audio, and Explosion and Thrust have none, my best guess would be that your Noise generator circuit isn't working. Fireball and Shield have a mix of 60Hz and Noise, while Explosion and Thrust only use Noise.

Do you have an oscilloscope? You should be able to very quickly check whether those are good. IC14 pin 3 should be approximately 12Vp-p (between 3V and 15V)... IC15 pin 6 should be 12Vp-p (+/- 6V). IC15 is a TL081 op amp, which fairly commonly fail, so that would be my first guess.

DogP
 
The laser and background sounds are each clocked by an LM566 VCO (voltage controlled oscillator). My experience is that these chips vary in frequency output quite a lot from part to part. It is quite normal to be able to hear a slight change in overall pitch in the sound when changing these chips or from board to board. There's nothing wrong with them and there's no specifically correct pitch other than what you might call the average mean value resulting from sampling a lot of chips.

One big problem with buying the noise chip and vco chips these days is that they are expensive and there are tons of fake ones being sold. The sellers that sell fake chips often sell under many names across many sites, i.e. eBay, AliExpress, and lots more that you probably never heard of. They make their living deliberately selling known fakes to the unwary. If you test parts received right away and file a dispute, you'll usually get your money back but if you just stick them into a drawer then your refund window times out and they have your money. Bad sellers make their living based on this scheme. I was able to recently purchase some working LM566 from Alltronics.com but 30% of the chips (3 of 10) that I got from them were bad. When I complained, they shipped 5 more for free and all of them happened to work. All LM566 chips that I bought on eBay and AliExpress were bad, like 30 of them purchased 10 each from 3 sellers.

Bill B.
 
I have two complete cabinets but I am doing all the testing in one since the other cabinet has a 4 ohm speaker installed.

Unfortunately I don't have an oscilloscope. But I will try to replace Q2(since I have some of those. I tried replacing IC15 hoping that was the problem, but looks like I need to find a noise generator....

Are you working on multiple sound boards, or multiple cabinets? If you're testing in multiple cabinets, you may want to try just swapping the sound boards, since things can sound different with different voltages, if a speaker has been eaten by mice, etc.

But, beyond that... the schematics are very clear for troubleshooting sound problems. There are only a few active components per sound, and looking at the sounds that you say have problems, a couple things that look common across all of them, but not to the sounds that are working, is the 2.2V voltage from Q2, the Noise from IC14 and IC15, and the 60Hz from IC16.

Since you say Fireball and Shield have some audio, and Explosion and Thrust have none, my best guess would be that your Noise generator circuit isn't working. Fireball and Shield have a mix of 60Hz and Noise, while Explosion and Thrust only use Noise.

Do you have an oscilloscope? You should be able to very quickly check whether those are good. IC14 pin 3 should be approximately 12Vp-p (between 3V and 15V)... IC15 pin 6 should be 12Vp-p (+/- 6V). IC15 is a TL081 op amp, which fairly commonly fail, so that would be my first guess.

DogP
 
Is there an easier way to test these chips than on a board? I always install sockets, but don't want to have to keep swapping chips if there is another option.

One big problem with buying the noise chip and vco chips these days is that they are expensive and there are tons of fake ones being sold. The sellers that sell fake chips often sell under many names across many sites, i.e. eBay, AliExpress, and lots more that you probably never heard of. They make their living deliberately selling known fakes to the unwary. If you test parts received right away and file a dispute, you'll usually get your money back but if you just stick them into a drawer then your refund window times out and they have your money. Bad sellers make their living based on this scheme. I was able to recently purchase some working LM566 from Alltronics.com but 30% of the chips (3 of 10) that I got from them were bad. When I complained, they shipped 5 more for free and all of them happened to work. All LM566 chips that I bought on eBay and AliExpress were bad, like 30 of them purchased 10 each from 3 sellers.

Bill B.
 
But I will try to replace Q2(since I have some of those.
Q2 is easy to test... it should just be 2.2V DC, which you can check with your multimeter.

DogP
 
Q2 is easy to test... it should just be 2.2V DC, which you can check with your multimeter.

DogP
It wasn't q2. Looks like I need a noise generator....i got lucky on the other sound board. This one is going to be more difficult.... and expensive
 
Not sure if it helps, but I believe the MM5837 would be a suitable replacement (you should check the datasheets to confirm).

DogP
 
Datasheet for the S2688 says that it is an alternate for the MM5837. Which I can get on Ebay for ~$8 from China.....Hopefully it works.


Not sure if it helps, but I believe the MM5837 would be a suitable replacement (you should check the datasheets to confirm).

DogP
 
Fixed.

I bought 3 MM5837 chips from China to replace mine. They were supposed to be NEW. They were all definitely used.

BUT one worked out of the bunch. So I now have a second set of working boards. New T-molding in on the way. Hope to have a one completely assembled game by the end of the weekend. Still need to source a new speaker for the other.

Going to file a dispute on the others...and they fact that they were definitely NOT new.
 
I bought 3 MM5837 chips from China to replace mine. They were supposed to be NEW. They were all definitely used.

BUT one worked out of the bunch. So I now have a second set of working boards. New T-molding in on the way. Hope to have a one completely assembled game by the end of the weekend. Still need to source a new speaker for the other.

Going to file a dispute on the others...and they fact that they were definitely NOT new.

Which vendor?

I purchased an IC from Ebay asian vendor once. Large 40pin type. I found pins were tinned already (i.e. not new). I inquired and they blame a sub-contractor supplier for it. Really hit-miss with them. :(
 
Background still not right

The 5837 fixed most of my issues, but I was playing both machines back and forth to see if there was a difference. This one has a background sound issue still. It doesn't reverb...or oscillate.... not sure what you want to call it. If it's oscillation it could be the 566 chip (how can I get so lucky to have the 2 hardest chips to find go bad)...

Video demonstrates the issue better than I can describe it.

https://www.youtube.com/watch?v=5c7qx2XFWWo

What do the experts think?
 
No improvement

I bought 3 of the 566 chips from a US seller. None of them fixed the problem.....So I am at a complete loss now.
 
Fixed

The "wawa" effect is made by the 74LS163 chips. I replaced both of them and now my sound is 100%....other than a bit of static. Will try to replace a few more caps to see if that clears it up.
 
Info Helped Me

My background drone was high not low but after seeing mentioned to replace the 74ls163an I did just that and it fixed me right up. Thanks for the info!
 
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