Synthesizer reboot

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?

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.

Any thoughts or comments?

TIA

Reply to
Dominique
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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.

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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Reply to
Dave Platt

Dry joints on the Power Supply regulators are very common since they get hot.

I would resolder everything on the power supply PCB, it won't take very long. Clean all the connectors throughout the module you can find by gently removing and reinserting them whilst you are at it. If all this doesn't cure it you can then start wondering about faulty components.

Gareth.

Reply to
Gareth Magennis

If you are concerned that the problem is in the PS, grab a voltmeter and verify first that the PS is putting out the correct voltage.

If it is off by more than 15% then buy a generic supply. Most Korg rack mount synths of that era use a standard sized barrel connector so you shouldn't have any problem finding a replacement if you need it.

Reply to
Meat Plow

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Reply to
onetwoandyou

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