[sdiy] Advice?: Powering up a vintage keyboard after several years

[rsdio at audiobanshee.com]

That 10ohm resistor is a really bad idea. If you have a 500 mA 15 V supply and connect it to a 10 Ohm resistor, you'll be pulling 1.5 A out of the supply. That's 3 times what it's rated for. It will surely burn out. If you're lucky, the resistor will burn out first, but if it's more than a 20 W resistor then the supply will burn out first.

I'm sure there are many 1.5 A power supplies out there, but if you test a Doepfer supply with a 10ohm resistor then you're asking for trouble.

Also, don't run your power supply for 15 minutes with no load (disconnected from everything). Not every power supply can operate for extended periods with no load.

Brian


On Oct 11, 2016, at 11:43 PM, Roman Sowa <modular at go2.pl> wrote:
> First of all, dust it off inside, remove all spider's nets, spider nest remainings, dead bugs and in extreme cases - mouse poo.
> 
> Disconnect everything from power supply, turn it on and let it run for 15 minutes or so. Capacitors will reshape then by rebuilding oxide layer. Then't it's good time for checking voltages. If this is not far away from nominal, leave it, otherwise you'd have to recalibrate entire synth. If it fails at this point, close the case and stuff it somewhere for another 10 years till you have time to fix it.
> Then maybe check PS under some load, like 10ohm resistor.
> 
> Next, connect power supply back, turn it on and quickly check if voltages do not drop considerably, which would indicate some short or unussual heavy load (like shorted tantal) somewhere and possibility of big blast coming in few seconds. If OK, check if it plays at all and all works as expected. If so, leave it on for next 15 minutes.
> 
> Roman
> 
> W dniu 2016-10-11 o 14:13, Barry Klein pisze:
>> I am going through the stuff in my garage.  I have several vintage
>> synths – some worth quite a bit now – and they haven’t been powered in
>> at least 5 years.
>> What would you recommend – advancing on a Variac, or just plug it in?
>> 
>> Barry