In article ,
Dominique wrote:

Hi, I have a digital rackmount synthesizer (Korg Wavestation AD) which
reboot after being ON for a while, sometimes many times in a row (fast)
making a sound like knocking on a door. (When I turn it on it makes "toc"
in the speakers so booting many times in a row makes this knocking sound).

I think it is a power supply issue because when computers have a reboot
problem it's usually caused by the PS. I am unable to get a new PS because
of the age of the thing so I thought replacing the electrolytic capacitors
on the PS board since I heard that those degrade with time.

Am I wrong about that? What other components might cause such behavior?

It might be a power supply problem. Excessive ripple or voltage sag
could lead to the device resetting itself. These might also lead to
the synth making other sorts of odd sounds - humming or buzzing.
Inspect the electrolytic filter caps - see if they are bulging at the
top or sides, or leaking fluid. If so, they're bad and need to be
replaced.

Before you actually start ripping out components, I'd suggest doing
some actual diagnosis and testing. If you have (or can borrow) an
oscilloscope and a good digital voltmeter, I'd suggest checking the
actual power supply voltages (with the meter) and looking at the
supply lines with the oscilloscope to check for excessive ripple,
noise sudden jumps in voltage, etc.

The reset/reboot problem you're experiencing could come from plenty of
other faults, too. Loose wires, loose or oxidized/corroded
connectors, bad solder joints on the PC board (possibly cracked due to
repeated thermal cycling), a transistor or IC gone bad, an IC which is
loose in its socket, etc.

You might want to try one of the oldest diagnostic techniques in the
book. Open it up, turn it on, wait for a while for it to warm up, and
then start tapping on the wires, connectors, and PC board and
components with an insulated stick. See if you can find an area
which, when poked or tapped, causes the synth to reboot or misbehave
in some other way. If so, that's probably near where the problem
actually lies.

I also thought trying to fit a computer power supply. I managed to get the
service manual for the synth and it uses +12V, -12V and +5V, but the synth
only puts a load of 0.15A at +12 and -12 volts and a load of 0.8A at +5V. I
read somewhere that PCs power supply can be unstable if the load is too
low.

Yeah, PC supplies tend to need a minimum load. They may also be
noisier, electrically, than you'd want in an audio component.

Stick with a linear power supply, or a small switcher designed for
those sorts of loads (with good filtering).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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