This is a repair log for an early Stern SB100 sound board. As I go through the repair (it's currently almost dead) I'll update the problems. If anyone would like to post to add suggestions, please feel free to.

Repair log #2.

Stern SB100 Sound PCB

Problem #1: No sound, completely dead.

Initial Diagnosis: All test points test ok with voltages. Going to apply some theories learned from my first SB100 repair here: https://pinside.com/pinball/forum/topic/tech-hot-hand-sb-100-no-sound

(Disclaimer: I work quite a bit during the week, so depending on parts needing to be ordered, and when I can get some time away from work to take a look at this, it could be a week or so between updates.)

-Pat

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What's interesting, is this is an SB-100 Rev C-1 just like my other, however this one has a TP9.

When checking U7 pins 3,6,8,11, they are all blipping high when they are supposed to, so that means the board is producing the sounds, and it's somewhere in the mixer/preamp/amp section. Caps look like they're original, if I have the same values here in my parts drawers, I'll replace all of those anyways. Going to do some more tests downstairs.

-Pat

When checking voltage at each amp chip pin #1, it's measuring 7 volts. I thought it was supposed to be around 5, but I know that on arcade game pcbs, it should be 12volts. So I'm not sure what this voltage should be.

I replaced caps C47, C51, C53, C55. Now when I power on the game, I got the power on thump the first time (which makes me believe the amps are working), but 2nd and 3rd time no power on thump. However, in the previous repair, the game isn't supposed to have this thump.

Edit: I recently got a Radio Shack probescope, and was so excited to use it in this particular repair to look at the audio signal, however I can't get it to work. I'm not sure if there is something wrong with it, or I'm not using it correctly (probably the latter). Going to research how to use the probescope to look at the audio signal, and possibly remove U14 and try to put the resistor between pins 1 and 7 to see if I have sound.

I removed U14, placed a socket there, put a 47k ohm resistor between pins 1 and 7, and I have sound. So it seems like U14 is bad on this board also. However, when replacing cap C47, the negative lead wasn't even soldered into the board. I'm assuming that may have had something to do with it too.

I have some parts on order, I will post again after testing to close out the log.

-Pat

Yes, and got the power on thump but no sounds.

-Pat

Sound board is 100% working. When placing the newly arrived MC3340 in, sound has been returned to the game.

I have since moved from Tennessee to Utah, and even changed my name to facilitate a small repair business out here for some local folks. However, my personal Hot Hand is still having sound issues, somewhat. It's not perfect.

When powering on the game, I get a VERY LOUD noise but everything else is ok. I'd like to not have that loud noise anymore, as it's pretty shocking. LOL

The video below shows the game with a hum as well, I have since fixed that as it's a connector/header pin issue. I need to redo the header pins and connectors in the game.

What is causing that initial loud noise upon power up?

-Pat

Here ya go:

I ordered another harness from the mpu to the sound board (there was a lot of corrosion that actually I had to wire wheel the metal insulator inside the head behind the lamp driver and solenoid driver as well), so I have a feeling the actual harness is just almost eaten up. I figured new .100 header pins and a new harness may help a lot.

But I still feel like there is something else on the SB100 itself that isn't muting all of that noise upon power up. Like something is being dumped. However, the poweron melody, game start melody sounds really good. I adjusted all the freqencies to spec earlier in this post.

-Pat

No, I am using an Altek MPU.

I got the new cable today, and same power on noise. Nothing changed.

I did not replace the header pins, as this is the 2nd board that they didn't look bad at all on. I'm thinking it's not the pins on the board, or the lack of the power on muting.

-Pat

Interesting.

I have a Bally -35 that I was going to repair. Maybe I'll get that going instead of using the Alltek. I like keeping the Alltek around to test other games.

bingo, as usual ty Quench. I'll update the thread when I get the -35 working and the issue is resolved.

-Pat

So major necro bump, but I'll explain why.

Finally got moved into a new house in New Mexico (I'll explain a little more below), and finally have a nice 19x11 pinball room, with a workshop in the garage, and a 16x16 metal building going up soon. Hot Hand is the next game on the list to shop, I just have to get the body back from storage, and then , with everyone's baited breath, I will continue and resurrect this thread.

(I used to live in Tennessee, and we went to Southern Utah to take care of my wife's mom with dementia. Southern Utah isn't the greatest place in the world, so I just put up a few games but never really worked out in the garage because of neighbors, but also my mother in law. I didn't have a lot of time to work on stuff. Then, of course, the pandemic happened to everyone, as well as my mother in law taking a real bad turn for the worst. We brought her with us to New Mexico and she is now in an assisted living. So I finally get to work on games uninterrupted for a while, and Hot Hand is first on the list. Thanks everyone for your patience, I know everyone probably gave up on this thread, but it's coming soon!)

-Pat

(Edit: Just a little update though after quench's post 2 years ago. I found my bally -35, but it's not working. So, I think I'm going to make the mods Quench asked about, and finally redo all the header pins on the sound board, and absolutely make sure all of my solder work is stellar.)

When setting up the game today. There is no more loud power on screech. The pop bumper whistle plays, but that's it. So are you saying, it should be completely silent, until it completely powers up?

-Pat

I can't find the techdose article anymore. That was some good info, hopefully someone has it saved.

When searching videos for Stern Games with SB100s, and looking through my old forum posts, it seems to be a hodge podge of the pop bumper sound and nothing (when powering on the game).

I'll see what I have, change the caps and post back.