On Sun, 28 Jan 2007 10:37:31 -0000, "Mungo \"Two Sheds\" Toadfoot"
put finger to keyboard and composed:

Franc Zabkar wrote:

I don't think the largest caps are your most likely culprits. Instead
I think that the one near R12 is probably the root cause of your
problems. As a general rule I always check the smaller electrolytics
on the primary side of switchmode PSUs (eg the one near R2) as these
often go high ESR. But as others have advised, change all the caps on
the supply secondary for good measure.

- Franc Zabkar

Thanks Franc.

If you have a minute spare I wonder if you would look at the second picture
again and tell me if you can work out what is next to the capacitor you
recommend I replace; the one near R12?

http://www.arcl40.dsl.pipex.com/roland/roland.html

I know it's difficult to make out but the power board is back in the
keyboard now until I can find a source of capacitors, so I can't take more
pictures yet. It looks to me like another capacitor but it's covered in
moulded black plastic with a pinched top. It looks to me like some kind of
sleeving to protect the component from heat, or interference maybe, as it's
located next to the transformer? I will remove the component when I change
the caps but at present I've no real idea what it is!

Any ideas?

A coil? If so, it will measure close to zero ohms, and there should be
an Lnn circuit reference on the PCB. I'd find out where the + terminal
of the capacitor goes. It will probably go to one of the secondary
outputs at connectors CN1/2/3/4. Actually, upon closer inspection the
capacitor looks to be covered in fixing glue, so it may not be bulging
as I first thought. BTW, when replacing these caps, make sure you use
low ESR, 105 degC types.

- Franc Zabkar
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