(Topic ID: 241511)

Squawk & Talk - Two sounds missing?!

By crazi

11 months ago

Topic Stats

  • 14 posts
  • 6 Pinsiders participating
  • Latest reply 11 months ago by pindel
  • Topic is favorited by 1 Pinsider


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#1 11 months ago

Hi All,

Eight Ball Deluxe LE

This sound board seems to be working in all aspects except for one sound is missing. Speech works great and when you flick all the various switches on the playfield etc a sound happens - except for the yellow round targets behind the drop target. When you push them the background sound goes quiet as if the effect sound should be playing but nothing! There is also no "match" sound at the end which there is a good chance it may be the same sound used on the yellow targets.

I have no idea - what would make just one sound not work???

I have changed all the socketed IC's except for the ROM's

#2 11 months ago

Now Ive just noticed that when you knock down all the drop targets and you are shooting for "Deluxe" then the yellow targets behind start making an effect noise when hit! Weird!

So it's only not working while you are still shooting for the drop targets but hit the yellow targets behind for those drop targets that are down already....hope that makes sense...

#3 11 months ago

The sound should be same on yellow target hits until 1 thru 7 targets and the 8 ball have been dropped, then their sound should change, so you are missing the first sound.

#4 11 months ago

I've just put the ROM's in a working board and everything works ok so it's not the ROM's...

Ive changed U16 on the sound select and still faulty...


So I think it's two sounds missing then - 1-7 targets and Match

#5 11 months ago

The sounds you're missing are produced by the AY3-8912 audio chip at location U12 on the S&T board. So concentrate on diagnosing that section. Make sure the five EE jumpers below U12 are not installed.

#6 11 months ago

Hi Quench

There's no EE jumpers being used.
I swapped the sound chip and no joy
Have pinned out the chip to it's next location - all ok
10KOhm resistors all ok

Measuring inputs while pressing a target:
Sound chip pin11 goes high
D0 pin 28 goes high
U11 Pin 18 CB1 goes low

#7 11 months ago

The input side of the AY3-8912 is working - all commands sent to the S&T from the MPU board go through it.

Move onto the audio output trail of that U11 chip. It goes via test point TP7 through a switched filter and onto an op-amp at U13 configured as a low pass filter.

When you hit those Deluxe standup targets and there's no sound:
- Do you see any audio activity on test point TP7 (i.e. is the AY3-8912 outputting an audio signal) ?
- What happens on pin 19 of U11 (i.e. it activates the switched filter at transistor Q2 and might be causing it to filter too much)?
- Are you getting any audio activity at the input of the op-amp (pin 3 of U13)?
- Are you getting any audio activity at the output of the op-amp (pin 4 of U13)?

#8 11 months ago

Hi Quench

So that was fun...lol

I got the scope out and first took the working board from a Pacman and put the 8 Ball ROM's on and jumpered. Tried to take measurements at those different points you mention and it was really hard as the signals where basically what looked like total noise except for pin 4 Op Amp output that was a great large square wave when pressing the switch. So that I could work with.

On Test point 7 when pressing a working switch you could see a very small change in signal to a little more defined type square wave but almost impossible to get any sort of proper measurement. But at least I knew what to look for from a working board...

So then stuck in the faulty board. Long story short I basically got the same signals at the different locations so moved on a little in the circuit to C36 2uF. Working board back in and measured and the signal was there but smaller from the resistors. Faulty board in and measured and the signal was there but not as defined. Almost just noise. So I figured **** it, it's 5p and needs replacing anyway - replaced C36 with a new 2.2uf 63v (closest I can find these days) and it now works! Both missing sounds are back.

I measured C36 in circuit and got 2.2uf (within 10%) but when I measured it out of circuit it was struggling to get to 1uf. So in circuit the reading may be getting affected by the other two closely situated caps. Threw me off totally as I had checked it early on...

What I don't understand is that with C36 being buggered - how the other sounds were working!!?? Does my head in Perhaps something to do with the different frequencies - who knows. At least fixed though...

#9 11 months ago


If you have an ESR meter, it'll probably tell you the capacitor is bad. There's another 2uF cap on the S&T board - good chance it's going bad too.

Quoted from crazi:

What I don't understand is that with C36 being buggered - how the other sounds were working!!??

The sounds you were missing are generated by that PSG (Programmable Sound Generator) AY3-8912 chip.
Besides the TMS5200 speech chip, all other sound effects are generated through the Digital to Analog Converter (DAC) chip at U10 which in your scenario is working ok.

The capacitor you changed merges the AY3-8912 audio signal with the DAC audio signal.

This is a case where I used PinMAME to find out which chip generates those sounds you were missing. PinMAME allows you to separately adjust the volume of the three sound devices (TMS5200, DAC and AY3-8912) on the S&T. When I adjusted the AY3-8912 to 0% volume I could see the issue you described

#10 11 months ago

Thanks for the post, recently picked up an ebd and the same exact sounds are missing, though I can ever so faintly hear the game over matching sound, I suspected a bad cap. Now I know where to eye ball

#11 11 months ago

Thanks Quench - makes sense when you know it's only those 2 sounds heading down that line - one to remember

shacklersrevenge - good luck - glad it's helped

#12 11 months ago

May I jump in here please? My EBD is doing the opposite. The only sound I have IS the yellow standups! No background sound, nothing from the drops or the slings, just the yellow standups. However, when shooting the standups going for DELUXE, there is NO sound from them. When I say there’s NO sound, there actually is. It’s just very, very faint with the volume turned all the way up. You have to listen real close to hear it. Speech works fine. Anything I can try without having too good a skill set?

#13 11 months ago
Quoted from Xtraball:

May I jump in here please? My EBD is doing the opposite.

So in your case the issue is more likely to do with the Digital to Analog Converter (DAC) sounds that come out of the U10 chip. The respective capacitor used to merge its audio signal is C43 which is a 2uF 25V capacitor. Replace it with a 2.2uF cap which is more commonly available. It's ok to get a higher voltage rated cap, but never go lower voltage. Note these electrolytic capacitors are directional; one leg is positive, the other leg is negative and they must be installed in the correct orientation. The board marks which is the positive "+" side and the capacitors themselves usually mark which is the negative leg.

In fact you're probably better off getting a capacitor kit and changing them all on this board - the caps on these S&T boards are known to go bad. It's up to you.

If replacing the capacitor doesn't fix it, you might have a faulty AD558 DAC chip at U10 or circuitry surrounding it.
Good luck!

#14 11 months ago

Look in the manual for background sound settings. I don't know why would work and the other wouldn't but many of my S&T boards will not play BG sound until I set it. Don't have the EBD manual but for Embrypon it is #18 setting to "03"

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