Hi guys. Just bought and am fixing a Williams Space Shuttle. I got the main CPU back from being refurbished and all is well. I've moved onto the last few things that need to be worked on.

Regarding sound, it appears that I have sound. At first I didn't think I did. But then traffic outside dropped for a bit and I heard some pulsating noises. I got close to the cabinet speaker and heard the test sounds rotating while in diagnostic mode, but it was at a volume that was nearly inaudible. I have to stick my ear into the backbox to hear anything and it's hard to really make out what I'm hearing since the game is mostly bloops and bleeps.

What should I begin to look at? I've read it could be the amplifiers, or the ribbon cable, or the volume potentiometer. I haven't worked on a System 9 game before so this is quite new.

Any help you could provide, I'd be grateful. Thanks.

The volume of the humming/buzzing gets louder yes, but the sounds do not.

Jumping W10 doesn't seem to help in any way. The sound is still inaudibly low when pressing the sound diagnostic button on the CPU board.

I've scoured the googles for this issue for quite some time and it's quite rare. Usually, there's no sound at all. And although I can work around a little bit, I definitely don't have the expertise to interpret the wiring schematics on my own.

I don't want to shotgun the boards if I don't have to. But I also don't have oscilloscopes or logic probes either.

So I swapped out C32, C53, C52 and the large capacitor on the speech board. No change. The output is still inaudible. [The hummmm is gone when the speech board is disconnected, but returns just as bad when connected]. Jumping W10 shows no difference either. Sound is still barely existent at all out of the speakers. Adjusting the cabinet volume pot doesn't crackle anymore, and there's no indication that it's getting louder (because there's no hum to judge by).

Any thoughts?

How do I easily check the 12V? Also, I've checked for continuity between the cabinet pot and the board and they're solid. What's the easiest way to check the pot as its turned?

I'll check the voltages in a bit. Thanks for the info. I've jumped W10 and removed the speech board and still only get a faint whisper of sounds.

Could it be related to the TDA2002 amplifier? Do you know how it works in conjuction with all this? So far, what you've described above is exactly how I've interpreted other posts about the sound system on System 9.

C26 Voltage reads between -12.8 and -14 depending on which attract mode it's in.
C7 only reads -.81V when the ribbon cable is attached to the sound board.

My dilemma is that even when W10 is jumped and the ribbon cable disconnected, I have sound playing, but at an extremely low level. C7 shouldn't matter in that case.

The volume pot reads between 4800Ohms and 30Ohms of resistance when it's maneuvered through its range which seems like it's working.

What would be the situation if the main volume pot wasn't connected? Would it be ultra loud or ultra quiet? I ask because the board does have some acid damage from battery leakage around that area. Perhaps the volume pot isn't actually being 'detected' in circuit properly.

The System 9 Williams Guide says Q51 rarely goes bad. Can I test this transistor in circuit? Pretty easy if I can figure out which is the base and collector. I'd suspect that if they didn't, one would work and one would not, but they both produce the same output at the same volume with the same noise.

According to this: http://www.pinwiki.com/wiki/index.php?title=Leon_Borre_WMS_System_9_Repair You can jump pins 1 & 2 on the volume pot which would essentially be "maximum volume due to no resistance". When jumping W10 and jumping 1 & 2 on J16, and removing the ribbon cable, I get the same result. Extremely low sound volume.

I measured C26 again and had 13.05V. Must have had the leads backwards last time.

Sorry, I was measuring the wrong C7 last time (the one on the sound board). Unfortunately, I cannot get my probes underneath C7 to measure it.

I did some measuring of the resistors because they're exposed and easy to do.

Resistor        Value in Schematic       Measured Value
----------          -------------------------       ---------------------
R75                          1K Ohm                    .70K Ohm
R74                          1K Ohm                    .70K Ohm
R72                          220 Ohm                   200 Ohm
R73                          2.2 Ohm                    2.2 Ohm
R71                          1 Ohm                       1 Ohm
R77                          3.3 MOhm                2.4MOhm  <--------- problematic?
R78                          3.3 KOhm                  0 <---------------- Never registers a value
R79                          3.3 KOhm                 3.3 KOhm
R70                          3.3 KOhm                 3.3 KOhm

I cannot get a resistance value to show on the DMM for R78. The leads are clean but the resistor seems dead. R77 also shows 2/3rds the resistance of what it should be.

Capture.PNG

Hope this doesn't sound like a silly question, but on my other machines, there are dedicated ground test points on the boards. What do I use for easy ground on this board? I don't see any dedicated terminals like that. (Still learning how all this circuit stuff works.)

So I went ahead and did the following:

• Replaced the sound board with a PinballPCB.com sound board.
• Tested U48 pin 3 against grounds
  • Tested against the screws which hold the board in and got .71V.
  • Tested against the braided wire in the backbox and got .71V.
• Made sure braided wire throughout the cabinet was secured and not frayed.
• Removed both speakers and used a known working speaker.
• Removed the volume pot wires and jumped pins 3 & 4 on the headers to simulate no resistance (full volume). Same effect as if the pot is full blast.
• Adjusted the mixing pot on the new speech board with no effect.

Here's what happens with the new PinballPCB board. I have louder sounds, and I believe all sounds, but NO speech. Sounds are significantly lower than expected though. When a game is full blast, I expect it to be ear piercing. Since it's in my kitchen, it should be well above tolerable levels. However, even when the volume pot in the cabinet is at full blast, the game is still quite quiet. Since there were no instructions with the board, does anyone know if the ROMs shipped with the PinballPCB board are indeed full speech ROMs and not just placeholder chips waiting for me to put my own back in?

Pressing SW2 plays ONE sound only, the first one. It loops endlessly only playing the first sound.

Sound diagnostics in the menu play 01-06 but nothing afterwards.

Starting a game has no speech at all. Airlock closing says nothing. No ready pilots. No countdown. Nothing at all.

So I measured the voltage at pin 8 of IJ17 and get -15.07V. I am not seeing the full voltage getting through to U48 pin 3 though. I'm only seeing -.71V.

Is there anything between IJ17 and U48p3? From the schematic it doesn't seem like it. If C7, C8, or C30 or C31 were nonfunctional, the voltage to U48p3 should still be -15, right? [Attempts to remember my last physics class.]

sndcircuit.jpg

So I changed out C7 with no change. Volume still incredibly low, and no speech at all. (New PinballPCB speech board)

I measure -15V at 1J17(pin8) but only measure .7V at C8, C30, C31 and U48(pin3). What on earth would cause the loss of voltage across that line? There's continuity as far as I can tell at the solder points all across the path from 1J17(8) to C8 and C7, and to that small dot next to 1J16 up to C30, C31 and U48(3).

As a result, I only measure .7V at pin 2 of the J20 ribbon cable.

I'm about to give up.

Capture.PNG

Oh, sorry. Yeah I changed it out. The caps I changed out on the main board were C7, C32, C24, C53 and replaced the entire speech board with a PinballPCB Kohout board.

So here's something I noticed today when checking the sound system trace resistances.

I left the game on for two to three minutes (something I really haven't done) and the voltage on the -12V line at 1J17(8) climbs from -14V to -20V. At that point I turned the machine off. This type of change would be on an issue on the power board, correct? Would point to the bridge rectifier or one of the large capacitors (C9 or C10)?

neg13v.jpg

The issue here has been resolved. Turns out that all of the components on the board are fine, as is the power board. The 1J17p8 push-in pin connector had failed, green and corroded into two halves. Replacing that solved the issue. Lesson learned - check the simplest parts first.

Thanks everyone for the help, by the way!