[SOLVED] Korg SP250 with only one working speaker?

Thread Starter

Alan3666

Joined Jul 22, 2021
15
At least I found the datasheet for the LA4728 easily. Farnell , RS, or Mouser don't stock them but I found this one on ebay

Les.
Good shout. No harm in holding off a few days. I've ordered the one from Ebay. It says delivered by 20th August but if they stick it in a jiffy bad and post I might have it by the end of the week.

Cheers

Alan
 

Thread Starter

Alan3666

Joined Jul 22, 2021
15
Another sourced Amp Board arrived this morning. I plugged it in and now have sound from both speakers although the left hand speaker is quite raspy. I suspect that it has been damaged by the faulty board. Something connected to the loud pop and the speaker membrane expanding on power up, I'm guessing.

I've found a replacement speaker on line and will replace when it gets here.

Meantime i'm waiting on the new LA4728 chip to arrive. When it does I'll install in the faulty amp board and see if I can get that one going. I'll leave the raspy speaker in till I've completed that task. I don't want to risk damaging another speaker.

The fellow who sold me the second Amp Board gave me the logic board that sits under the Amp Board, the one with the midi connections. I'll check that out too.

Alan
 

Thread Starter

Alan3666

Joined Jul 22, 2021
15
Final update.
LA4728 chip arrived this morning. After installing everything working fine. I replaced the raspy speaker and that's now good.

One thing I noticed, and some might think this significant, The repair shop who had a go at fixing this board and I'm pretty sure they had this chip off the board, hadn't used any heat sink compound between IC2 and it's heat sink. I applied a lot.

There's no way of telling if they actually replaced the chip, they might have just put it back in.

I suspect there was a bad solder connection or maybe a short on a couple of pins. I was careful to meter out all the pins to nearest component and checked for shorts between adjacent pins after I'd installed.

So I now have a spare working Amp board and also a logic board which checked out fine. I left the module I repaired in place as it has a higher spec amp chip.

If I have no other issues I might sell as a pair to recover some of the costs of this repair.

Now looking for next project.

I've just been stung for £50 customs clearance for an old Alessi drum unit. I've not had to do that in the past. Is this Brexit again.

Cheers

Alan
 
Top