Is this a sudden new problem, something that always happened, or something that got gradually worse?

The sound board amplifier is supposed to be muted via the cpu reset line and some kind of delay circuit on the sb100. It is muted until the board boots up so you don't hear garbage noise at power up. I would make sure the 32 pin connector is soldered well on the MPU and sound board first.

I agree....connector issue between MPU and sound board. Check those cables.

Thanks for this info as I've had it on an F2K I've been trying to get 100% for a friend. Of course the darned reset circuit still won't work consistently despite changing nearly every component in it. Wish I could find my DS1811 replacements!

I know some of my older Gottleib's screech when turned on. This is a warning noise that could alert arcade attendants or owners that the power switch was being played with. Sort of a screech beep noise very loud though.

Supposedly this is how it's supposed to work but on my Hot Hand (which makes a weird sound on startup too, but not a screech) the reset pin that should be held low until it's started up is actually just tied to 5V. Not a jumper / hack or anything, the schematics actually don't match the real thing.

SB-100 sound board, not sure what Wild Fyre has.

But yeah, find the pin on the connector (pin 25?) and the chip it (hopefully) goes to, jumper it to ground, see if the screech (and all other sound) goes away.

Interesting... i will have to double check this next time i have one to fix. I have seen up to 3 different sb-100 versions.

As far as I was aware, only system 3's made a loud beep on power up. I don't recall any other Gottlieb systems making noise at power up.

I'm aware of three different versions (a-c) because each dealt with chimes differently. Mine was a 'c', which had no chime hardware at all, just synthesized sound.

My Barbara Wire makes the loudest screech at power up, sounds like a new Stern knocker. I watched a Todd Tuckey video and he said they added the screech so the operator would hear it if someone was messing with a game.

I have fixed quite a few of these sound boards and i don't remember any sounds until attract mode hits... Once attract mode starts it plays a short jingle.

i vaguely remembering having a problem on one that would sound like it was playing every sound effect at one time right at boot up and it was something i fixed on the sb100 itself, but I can't remember exactly.

For the solenoids. I would first suspect the enable pin is floating for the decoder on the driver board then. Check the solenoid enable line at MPU j4 and driver j4.

solenoid bank select is the enable for the decoder. The 74154 is selected when that pin is low. So what i would do is... Game in solenoid test. unplug driver j4. check with a probe the enable connector pin of driver j4. See if it is floating (logic probe will make a god awful noise). If you have a low at the j4 connector, plug it back in then check right at the pin on the decoder.

Remove the connector and testing with a logic probe can help isolate to the MPU or driver where the signal is lost at. The driver board probably has a pull up resistor to keep this line high when J4 is not connected.

Similar issue just started occurring on one of my classic Sterns. Did you come up with the problem/fix?

Which machine / sound board?

Oops - sorry.....F2K SB300 & VSU100. All caps have been replaced.

Looking at the F2K sound board schematics, it doesn't seem very similar to the SB100

Have you verified the interconnect cables are good?

Yes, continuity checked for each strand and board re-pinned. This one has me scratching my head. Thanks for the ideas tho', please keep them coming!

If it helps, I blew a cap on my SB100 and now it gives a little static screech at startup?

This one is a short, LOUD screech at power on. I'm starting to think that maybe one of the new caps I put in might have been bad. I'll have another look at it over the weekend.

No pull-up resistor on the solenoid enable on the SDB. It's interesting, even back at the MPU just goes through a 470ohm resistor & then right to CB2 on U11 6821. So I guess the 6821 is doing the job.

Found this out with this project: https://pinside.com/pinball/forum/topic/checking-interest-bally-sdb-output-tester -- which btw may help anyone fixing up more than one or two machines with working through issues of missing solenoid signals from the MPU.

What happened for me is the SDB I was using for testing had a 74L154 in it (from factory). Worked fine with the prototype design of the DIP switch tester manually simulating solenoids during development. I just got the actual tester pcbs in & tried them at the bench, all was good. Connected in a machine & solenoids were being activated as soon as you flipped the dip switches. Should have to press the momentary button for that to happen. Well here the SDB had its 74L154 replaced with a 74HCT154. I didn't dig deep in the datasheet but I'm thinking that's the cause. Somehow a floating input to the 74L154 didn't matter, but it does on the 74HCT154. Simple enough fix, but it's kind of surprising they wouldn't have just added a weak pull-up at the SDB to begin with. I suppose technically if you don't have the wire harness at J4 on the SDB connected, the solenoid lines are all pulled high which doesn't correspond to anything on the 74L154's output. But still..

This is relevant to this thread a bit I think -- but I've always noticed a low hum on the SB-100 that has the chime circuitry. Kind of a static sounding noise.. and it changes in intensity as you adjust the volume up/down. The "C" revision of the board (without chime circuitry) didn't seem to have that. Does that sound normal? One board in particular was pretty bad and I changed caps & also tried changing a few other ICs, but it still had the "normal" hum that I've experienced with most chime boards.

I spent a while about 5 years ago trying to figure out these boards.. a good solid week or so learning and playing around -- AFAIK one of the first people to document much on them over at http://www.techdose.com/projects/Stern-Pinball-SB100-Sound-Board/346/page1.html

The reason I'm asking is I still have a handful of boards that I need to clear out of here! My original plan was to offer repair services on these and that didn't happen because I never could figure out if some level of background hum was normal for the chime boards or not.

My Rev C has a hum all the time, low in the background. The techdose article mentions the hum as a way to check if the LM380 is disabled or not, so I assumed they're always supposed to have it? It's never loud enough for me to notice if I don't look for it though, not much louder than the hum of a transformer...

Yeah that low hum you describe seems to be what I'm talking about. It does increase with volume though, does yours exhibit that behavior too?

Yep. Does your hum go away (along with sound) if you ground pin 10 of U6?

Have not tried that, but may get a chance over the next month or so as I'm working through some other issues on the only machine I have with an SB-100 in it.. which is a shuffle alley actually lol. It's been acting up with solenoid/sound issues once in a while, so I probably have a cable to replace or header pins to address. Anyway hopefully I can then get through some of these boards and clear some space!

I wonder if there's enough market for repro SB-100s... It seems a lot of people have trouble with them and they're almost impossible to find if you need one

Hard to say -- I think the bigger market would be to replace it with something much more capable. Maybe having the option to go "old school" with the original tones/sounds AND use custom sounds/music. Many of the early Bally/Stern games wouldn't be so horrible to play if the sound was better. Beeps and Boops don't really do much for games like Nugent.

There is great demand for SB-100 boards. I get people responding to my SB-100 sales adds that sold years ago asking if I have more. I am always looking for SB-100 sound boards to buy, fix, and resell. SB-100 sound boards have high failure rates. When i fix them, i find problems in many different areas from logic to blown amps, bad caps, etc... One thing people always overlook is the AC cap used. The says schematic says putting two polarized caps in parallel is OK.... but it is not. You have to put two 470uF in series - + + - or + - - +.

I kicked around the idea of reproing SB-100 next, but the hand assembly is a killer. I did the Bally -51 sound board, prototype works a treat, and have enough parts to assemble 20 of them, just actually doing it by hand sucks. I might be more worth my time to buy dead sound boards and rebuild them.

Also... Bally left TTL gates inputs floating all the time it looks like. I ran across it in the -51 sound board. I guess in most cases it is fine, but bad practice. The 74154 should have pull ups on the driver board since it is selected low, otherwise you are just asking for problems if driver j4 floats. Does 74LS154 have internal pull ups and HCT does not i am guess. Kinda makes sense. The 4000 series stuff needs pulls up/down usually after the nvram nand gate debacle of 2015.

Andrew

It's the cap right above U6, it's not on the schematic... Same with the 37K resistor next to U6

Trouble is, there's probably only, say, six different sound signals coming in? And I suspect most of them are combined, since each is just a basic wave of some type. You could replace the different bloops with sound effects, but it'd still only be those few effects.

People are weird, I love the bloops. Much better than chimes.

Hrm, I bet you could reproduce most of this board using just a CPU. *goes to record the inputs and outputs of each section on the board*

Yeah I don't think it'd exactly be an easy task if you'd keep with stock ROMs and try to do custom sound effects.

True. CPU or FPGA if you're capable would be the way to go, as Andrew said.. too many components, too much labor to just reproduce the board as per the original design.

See this picture

IMG_20160130_154412_(resized).jpg

As you can see, the cap is now desoldered because I fried it to a short. I also had to solder on that blue resistor in parallel to R93, because after I fried the cap R93 was reading 2.5K ohms. I think I remember it being 37K before, but, as I said, it's not on the schematic, so I have no way to check what the value of any of them should have been. Since your board is older, it may not have these, since I'm assuming they're a late addition since they're not on the schematic. R93 is a pullup for pin 10 of U6, which, according to the schematic, is supposed to be connected to pin 25 of the 32 pin connector (RESET). Not sure what the cap is for, probably some RC circuit thing to keep pin 10 low (muting the amp) for about half a second while the MPU boots, as the cap charges it would ground the pin less until it's pulled up enough to unmute the amp, as opposed to having the MPU send a signal when it's ready. If your board actually has pin U6.10 connected to J1.25 as the schematic suggests then you probably won't have either of these components, but if you do I'd definitely replace both and reflow the solder on U6, might fix the screech

Stern calls toggling the power switch mischief. lol. Service bulletin #11 disconnects MPU reset from the sound board that doesn't need it. Couldn't hurt anyway.

IMG_0416_(resized).jpg

My old Stern godawful bootup howl was a MPU-200 with bad 5101 RAM. Did the normal ping sounds then a deafening wail as the cpu ran wild.

Ah, fascinating. So apparently somewhere in rev B and C they must have started doing this from the factory, but not updated the schematics.

Edit: replaced my R93 with a 47K and put a new capacitor in as the service bulletin states, not only is my screech gone, but I now have no noise at startup at all. So if I was getting the same problem as other people have been having, definitely try grounding pin 10 of U6 by jumpering it to TP4 to see if it cuts out the startup screech, and if so, do the mod suggested in the service bulletin / check your R93.

Also drew this up quickly, will throw it in some unused space on my next PCB order...

2016-01-30_19-08-35_(resized).png

Slight error in the text there.... that should be a 3.3uf cap... 3.3 microfarad not 3.3 farad.

A voltage rating higher than 6 volts could be substituted.

Just removing the pin will only possibly make it worse. If pin 10 is at 5V sound is enabled, if it's grounded sound is disabled. Without the resistor pulling it up you've just left pin 10 floating. The part values have some wiggle room, you're probably fine with 20-50K (maybe even 10). I didn't have a 3.3uF cap so I used 4.7uF, 25V.

If you can't find them locally, I'd suggest just ordering an assortment off amazon or newark. I quickly found that it was worth $20 to just have a box full of everything from 1ohm to 100K ohm and .01uF to 250uF

Also just to be clear, you actually have three jumpers right next to U6 instead of two jumpers and a resistor or just two jumpers? And the third jumper just goes directly to pin 25 and nowhere else?

I had the same terrible screech on my Lectronamo start up but then the game played noises fine the rest of the time. I preformed the service bulletin on my Stern SB-100 version B and the screech is completely gone.