05R/W module... dying?

[harmand]

I own a Korg 05R/W module I bought back in the early nineties, which I used frequently for a few years (at home) before starting to use virtual instruments. I remember having turned it on once, some 15 years ago, just to hear its (beautiful) sounds again, but after that I left it always on the shelf, with its (disconnected) power supply on top of it.

Last week, having to meet with some friends for some "jamming", I thought I could bring it with me and connect it to the keyboardist's equipment, just to hear it again.
But the unit, unexpectedly, did not come to life. The display switched on but nothing appeared on it, a part from a series of... pixel rectangles (one for each displayable character) only on the first line of the display.

I was really surprised, because the previous time the module worked fine and had been regularly switched off. Moreover, it has always been stored in a safe and dry environment, with no harm at all. And I really did not think that an instrument like that could fail... on its own, even while NOT being used and not even connected to anything.

I opened it and, as I expected, I did not see any sign of stressed capacitors or leaks or burns or whatsoever; everything looks neat and in perfect conditions. I then thought that probably the backup battery was gone (although this should not actually prevent the device from working); so I removed it and checked it with a tester, finding out that after almost 30 years it is still charged, with its regular 3 volts!!
Anyway I also tried installing a brand new battery, but the result did not change.

So I thought to ask here:
has anyone in the forum experienced such a kind of... sneaky fault?

[voip]

The first port of call would be to check the internal supply voltages and their quality, using a multimeter and scope.

15 years is a long time to leave something before switching it on. It could be that the electrolytics need reforming. This is best done by gradually increasing the mains supply voltage, over a period of hours to days.

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[harmand]

Thanks for your reply.

... It could be that the electrolytics need reforming.
This is best done by gradually increasing the mains supply voltage, over a period of hours to days. .

As you can imagine, I don't have the necessary equipment to do such a thing.
What about leaving the unit "normally" switched on (for hours or days), while connected to its own 12V power supply?
Could this be helpful, dangerous or just... useless?

[voip]

Leaving the unit switched on for a while is a possible approach, but stay near the unit during this process and be ready to turn the power off pretty sharpish, as capacitors can have a habit of letting out their magic smoke. It is more likely to happen with capacitors in higher voltage circuits, but just be aware. The other thing to try is a system test, initiated by turning on the power whilst pressing the +1 and -1 buttons simultaneously.

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[harmand]

Leaving the unit switched on for a while is a possible approach ... The other thing to try is a system test, initiated by turning on the power whilst pressing the +1 and -1 buttons simultaneously.

I tried the system test you suggested but, as I feared, nothing happened at all. I think the problem lies... upstream, because probably the system does not start at all and so no software is loaded.
I already tried also to leave the unit switched on for 20 minutes or so, but then, seeing nothing happen, I turned it off (also because I was afraid that things could get worse).

Later today I will try to leave it on longer (how long would you wait, before giving up?). I'll remove the lid and makesure, as per your advice, to always have the appliance in sight (even if this prevents me from leaving it on for more than a few hours straight).