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What are these and do you think its toast

shirreff

Apr 7, 2012
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Hi this circuit board is from a music keyboard I bought in a sorry state. It powers up but is not working. So this is the mother board and as you can see the capacitors? are burnt out all the 10v ones.
So wonderful people what do you think, first off are they capacitors and if I need to order some what should I order? I'm guessing it was a power surge that killed it.
Should I bin it or try and fix it?
 

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kellys_eye

Jun 25, 2010
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...not burned out. They have previously been replaced - badly.

The soldering is....... awful.
 

shirreff

Apr 7, 2012
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Oh dear, I did wonder about that. Well I think this board has been miss treated so there's not much point wasting any time on it.
 

Terry01

Jul 5, 2017
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I think they are resistors and wouldn't be very hard to replace. Better wait till someone who knows better than me verifies.
 

shirreff

Apr 7, 2012
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Thanks, it's came out of a Korg M50 which is a great keyboard so I will persevere if possible.
 

kellys_eye

Jun 25, 2010
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Not resistors. 10μF 10V capacitors. The korg is definitely worth fixing though...
 

Terry01

Jul 5, 2017
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Ah I see them now! I was on my tablet and just saw the R###. The resistors it relates to are so small,the small pic on my tablet and my dodgey eyes all added up to me not even seeing the resistors. No knowledge prob played a big part too! Lesson in for today! ☺
 

shirreff

Apr 7, 2012
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Ok, they should be cheap enough so it's just down to my time and skill. I removed a couple and they weren't too bad to remove but one of the pads underneath is gone so that will be my next question. Can it be repaired? I'll send s picture later. I'm pretty sure it wasn't me who pulled it off but it's still missing. My soldering skills aren't the best but I can get by, I'm just used to changing tact switches but I do have a good rework station.
 

kellys_eye

Jun 25, 2010
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Were they dud? Test one to see if they are faulty (poor ESR) and replace if so. They were obviously replaced in the past for some reason, maybe they've gone dud the same way?

You should inspect the PCB tracks too/from the capacitors to determine if you can replace them in situ axs there are often thru-holes that take the track to the other side of the board that may require repairing.

Photos of the cleaned up area will help.
 

shirreff

Apr 7, 2012
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I'll send some pics soon, the resistors look cracked, all 10v that is like they have blown. The others look ok. Maybe they are the wrong rating? I'll see if I can locate the service manual for the keyboard which might help.
 

shirreff

Apr 7, 2012
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I've added some images which I hope helps. You should be able to see the damaged pad which I need advice on how to repair too.
 

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kellys_eye

Jun 25, 2010
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That board has has 'some work' done on it and all the soldering associated with that work is utterly appalling! Note the capacitor orientation before removing (in case it isn't marked on the board) and clean up the pads with good desolder braid then wash with IPA.

Fit new (quality) parts using decent flux.

Can you get a schematic/service manual?
 

shirreff

Apr 7, 2012
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I've been looking for the service manual but no luck yet. What about the damaged pad? When I removed the resistor using my de-solder iron the part came off and no pad was there so I think they have just put solder on top hoping it will work.
I noticed some connections look slightly melted so I'm assuming it's suffered from a power surge?
 

kellys_eye

Jun 25, 2010
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If you clean up the damaged pad and the board around that area you will be able to see where the circuit track should go and make a soldered link from the end of the component to a point on the board where the track is whole again.
 
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