Can you record the sound issue? Is it analogue hum? Or is it digital errors?

Digital errors, you likely have mismatched speeds of 5101 rams. That causes sound problems. Cgeck / replace u8 and u13 with a matching pair or RAMs. Get 150ns ones PCD5101.

Yes I think Barakandl is spot on. Check those 5101's. Everything else sounds like an easy fix.

The 5101s are the bottom two chips on the MPU.

Your description matches what happens with a mismatched speed RAMs. U8 and U13. Look at those two chips and check the markings on top and let me know what they say. You likely need to get PCD5101P quantity 2. Great plains electronics i think sells these as well as arcade chips.

Another check is to go through all the audits and see if any is stuck on an erroneous number. Typically with mismatched RAMs you get one or more audits that will not store correctly and get stuck on some random garbage number.

That is a mismatched pair and def cause problems.

At least get a u8 that matches your u13. I would buy two and replace both.

Removing the RAM removes the credits, high scores and clears audits. You add credits by pressing the coin chute switches at the bottom of the coin door. You can probably add credits by going into the audits section of the test menu and adding them with the credit button. There is no free play on this era of Stern machines. I set low replay values to add credits at 50,000 points or something. Sounds like you have other issues going on with connectors and the MPU and not just sound issues. You need to get all that other stuff straightened out first.

When you swap the rams, all stored data gets scrambled.

Open the coin door you will see two buttons. One button cycles the test mode which you have found, the other button will clear the audit.

Go through and clear all your audits to zero, or use the manual to set them to what you want. When the game was making "knocks" you hit a replay score and it awards a free game. Since the audits got scrambled the replay score changed. Set one replay score to 10,000 pts so you can rack up free games quickly.

Manually push a coin switch to add some credits.

Yes as long as your connectors are up to snuff. You probably need to repin the connectors due to age and corrosion. J3 and J4 are a must.

Connector problems are pretty common. Not a bad idea to rework them and that marco kit appears to have everything you need. Might be a bit overpriced compared to buying individual pieces.

woo hoo. have fun. meteor kicks ass.

My Meteor had the same problem but it was stranger, was working fine then started making the weird noises. Swapped in new 5101s and fixed it. Mine were matched and working then the problem started.
Maybe the matched 5101s decided to break up?

I am pretty sure it has to do with the read / write speed of the RAM. Perhaps as the RAM ages the time it takes to write/read increasted. If the two are not matched up speed wise, you get errors that show up in the sound effects. Why sound is the symptom, can't really say, but super common. Usually when sound effects are off, there is one or more audits that also refuse to save properly.

Typically you can still use both of these RAMs in other situations that need just a single 5101.

mine just makes the rocket explosion sound, no other sounds at all. my chips are mismatched, would this solve my problem?

It is in the realm of possibilities. In my xp, mismatched RAMs just makes some sounds odd, not missing.

Your issue sounds more like problems on the SB-300 sound board itself. Getting a matched pair of RAMs is a good non invasive first step.

do you see any issues here? or what should i look for?IMG_0405.JPGIMG_0403.JPGIMG_0404.JPGIMG_0401.JPG

just ordered the chips. hope this helps out....

Hi Lysurgeon, if you are concerned your RAMs are not compatible. Take a picture of them or read me off the imprint. I am very familiar with this IC and matched pair compatibility.

i can do this when i get home. thank you for all the help!

IMG_0446.JPGIMG_0448.JPGIMG_0447.JPGIMG_0450.JPG

Those 5101 rams are not compatible with each other. The top one is 450ns and the bottom one is 150ns. this causes problems.

i figured that might be the case. cant wait to switch them out.

OK, I have the same issue with my sound. So far, I have replaced all the caps on the sound board and have brand new ribbon cables going to the MPU.
I thought it might be the 5101 IC's mentioned, but I put in my new Alltek MPU and the sound issue remains. I'm not sure what else to check next. Please Help!!

The SB-300 is typically not an easy board to fix. The 6840 timer creates squre waves Q1, Q2, Q3. To fix this board you need to be able to trace signals through the circuits while the game is in cycling solenoid test. Understanding a logic probe, schematics, and basic TTL chips is needed at the minimum.

Only real non invasive thing i can recommend is checking the noise generator test point. It is like a clock circuit and is always running. TP5 should always be 2-3 volts dc. If it is 0v or 5v, u10 or u13 is bad.

Test point 5 = 2.69 volts

Any other things I can check?
If it is in fact the sound board is the issue, I will just send it out to be tested/repaired.

Any other suggestions?

If you can't follow along with this, i would send the board out.

http://www.pinball4you.ch/okaegi/rep_soundsb300.html

i have repaired probably 20+ of these sb-300 sound boards. I can do it for a flat $45 shipped back.

Andrew

Great quote. That would be the only suggestion I would need.

Thanks! I will try those tests this weekend to see if I can locate the issue. I will pm you when I give up.

I ended up sending the sound and MPU board out to Jerry Clause. I got it back in a week and everything works now!

I may have to send my sound board out to get repaired. Tried an altek mpu and sound issue remains. Send me a pm with all the info Andrew. Tiered of not having sound...

I have a Meteor with the Ultimate MPU from Alltek Systems and was experiencing the same audio issues and random resets too. I have cleared the memory of the MPU and then the audio start working and no more resets.