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midi modules using 12v instead of 15v? or 9v for 10v?

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First post, by OriginalDan

Posted on 
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gday, I've bought a few yamaha midi modules from japan but didn't realize how unusal the psu requirements would be and since I'm in aus a 230v country i need to buy replacements
Yamaha TG100 and Yamaha CBX-T3 both originally used a Yamaha PA-1505 PSU 15v 500mA c+
pa1505.jpg
generic replacements for the pa-1505 on ebay are listed as 12vdc 2A , what would the recommended amperage be for a 12v when using it on these 15v modules? locally 500mA, 1.5 and 2.5A multiplug VDC psus are common but the 2.5A due to the larger size can often block neighbouring power plugs
Kawai gmega 10vdc 1A c+ i think originally used PS-101 or PS-102 only image i could find is for the ps-102u
kawai2.png
and Akai SG01k 10vdc 800mA i think is L1038 last letter is the region?
akai.png
would 9v be better for these 10v modules or would 12v be better?
weirdly the gmega is the only one that specifically says not to use other voltages in the manual, I'm not sure if it's just overzealous liability requiremnts or does that module really only work with that specific voltage?
kawai.png

Reply 1 of 1, by mkarcher

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If a MIDI module contains internal voltage stabilization using linear regulation, it requires a minimum voltage for the regulator to be able to provide a stable output voltage. Going lower will cause more noise in the synthesized music. As linear regulators are converting the excess voltage into heat, going higher will cause the regulators to get hotter, which is also not a good thing. So staying close to the original voltage is recommended, but -0.5V/+1.0V is unlikely to cause issues.

You do not just need to look at the voltage, but (especially for Japanese equipment) also at the polarity. The Kawai GMega supply has center negative output, which is not common in Europe/US. If you connect a center positive supply, and there is no series diode for protection, damage to the equipment might occur. If you intend to replace the original supply with a generic supply, make sure you can configure the supply into center negative configuration. Being able to select 10V or 10.5V would be nice, too.

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