Hi all.

My Roland E-500 has a problem: after ~5 minutes of being switched on it will
turn itself off and immediately switch back on again. It will then do this
every few minutes, or after a longer period of time, or sometimes not at all
and will work normally. There is nothing happening physically to the
keyboard to trigger a restart and the mains lead is good.

It has an internal switching power supply board and a seperate power
amplifier board with a small relay on it which clicks when the power goes
on, and when the keyboard restarts itself.

I found a discoloured and cracked 220ohm resistor on the power board and
replaced it, even though it was still testing at 200ohms, but this has made
no difference. I've also re-soldered any joints which looked suspect.

One other possible symptom is that the main transformer on the power board
hisses. The sound changes if I push on the transformer itself, or on the
board. There are two large capacitors near the transformer, one of which has
a small bulge on the top, which can be pushed back down easily, but shows no
sign of leaking, nor do any of the other caps.

Any thoughts?

I can put some pictures of the power board on the internet if it would help.
It has big "proper" components on it :-)

Simon.