Korg SP300 Volume Issues

[coleslaw456]

I'm having issues with the volume level on the Korg SP300. Both the left and right volume levels are very quiet, with the right being more quiet than the left. From what I can find online, this seems to be a known issue with certain SMD capacitors going bad. But I can't seem to find a schematic or service manual to tell me what capacitors to look at and what values they are. If anyone knows where I could find some documentation or what capacitors to replace, that would be a huge help.

[The Dude]

I don't have a service manual, but the 10uf/16V SMD caps are a known issue in those keyboards. I usually just ESR test all of the SMD electrolytics and replace any that are bad.

[coleslaw456]

Are all of the SMD caps 10 uf? I don't want to replace a cap with the wrong value. Also do you have a recommendation for a cheap ESR meter? I only have a multimeter.

[The Dude]

I have a Sencore LC75, so not much advice to offer on a standalone ESR tester. You certainly don't need anything expensive just to ESR caps. Maybe someone else can recommend something. There are lots of them on eBay at reasonable prices, but I can't recommend any because I haven't used them. Not all of the SMD electrolytics are 10uF, but my experience is that those that are not, will likely be good in this keyboard. I recall that the cap usually causing your symptom was in the muting circuit, but I can't say where it is located as I haven't been inside one of those keyboards for a while. If you can find and post a schematic, I might remember which one it is. As I said, it's a good idea to test them all anyway- as long as you have the thing opened up.

[Delta362]

I have one of these, in addition to a few others such as the GM328 (very inexpensive tester). Not sure if it's in your price range or not.

https://anatekinstruments.com/produc...esr-meter-besr

[coleslaw456]

I ordered one of these from Amazon, so once it arrives in a few days I'll test and update what I find. Thanks for the help so far!

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[8rz27pkzn@mozmail.com]

Just for the record, in case anyone with the same problem finds this post:

We have successfully repaired such volume issues by replacing all eleven 10uF/16V SMD capacitors on the main board (logic board, on top, not the power board). Since the piano is old (20 years?), we did not individually test the capacitors, but just replaced them all. After desoldering it turned out, that *all* of the caps were dead (0F, open circuit). Due to its age, inside the piano we discovered that the speakers bead (round rubber at the edge of the membrane) was disintegrating. We replaced the speakers aswell. Piano repaired, volume problem solved.