I picked up a Yamaha Su-10 little music sampler for cheap because it was sold as 'not working'. Now Ive fixed a few pieces of musical equipment before with no issues but this ones stumped me. I put batteries in and turned it on which I know I shouldn't have in hind sight but it sat there a moment before releasing magic smoke. now I thought OK blown caps. there's no sign of any magic smoke release inside the unit at all. Here are the pics I took of the power input area. The taller cap is one I replaced because the multi meter showed it as NC. Then I checked the shunt. It gets power across it just fine. The voltage regulator seems to drop though. The voltage will start high at the 9v of the power supply but quickly drop to half a volt. Could this be a fault in the regulator or something else? It doesn't do it all the time. Other times I cant read a voltage on it at all. Is there a way to test this with out ordering a replacement regulator and hoping that fixes it?

 

you can procure a service manual from Yamaha at http://faq.yamaha.com/us/en/article/music-production/tone-generators/su10/4486/5846

 

Well I got one but can you give any more help? Still learning all this. What do I look for, where should I test, what do I look for in the manual?

 

Where did the smoke originate?

You have your choice of using a 12V supply or the six batteries. If there is a short in the system, you might want to get MORE batteries.

before you energize it again, you can use your phone and make a movie ... then you can review the movie to narrow down the smoke source.

 

It was first powered on with batteries, Ive since gotten a power supply. When it first came on and smoked it came out near the switch where I took the photos. However Ive looked at both boards and haven't seen any signs of smoke damage. Ive smelled magic smoke before but this was almost sulfurous. It hasn't done anything since.

 

Sulfurous smells could originate in the battery, although that typically occurs when charging and gas escapes.

Some claim flux smells sulfurous. I can't recall using that much solder flux to cause that smell.

Follow your nose ....

Do you have a picture of the schematic you are using to troubleshoot?

 

Not yet, waiting on the service manual to show up so Im kinda probing blind. I couldnt smell anything at first because the unit came from a smokers house so it was just cigarette smell. I also cant feel anything get hot when under load

 

Ok I got the manual. Can you still help me?

 

Start by looking at the diagram in the manual, where the power supply is, mains battery input,it would help others to give you better replies if you can take a photo of the psu circuit in the manual, and post it, ...

 

Start by looking at the diagram in the manual, where the power supply is, mains battery input,it would help others to give you better replies if you can take a photo of the psu circuit in the manual, and post it, ...

Sorry, holidays have me busy at work. So I dont have the best camera or a scanner so let me know if you need anything else.
Voltage regulator section




The Vreg chip and transistor used


and the reset circuit




So when I first turned it on I smelled sulphor and saw smoke from around the switch area. however I saw no smoke damage to the board or the components. Ive replaced a few capacitors that looked suspect but otherwise hadn't vented. Ive noticed the voltage regulator voltage drop from 5 to 0 volts after powering up. My oscilloscope is broken so I'm just down to my multimeter but I don't think it would help in this case anyway. I just don't know. Its throwing into question what I thought I knew about electronics. Could it be something else in the device?

 

Hello people can helping me one off you guys i need the full discribtion off this ic12 thanks regards