Videobrain computer - power supply?

[carlsson]

Those dual voltage transformers are quite often seen, 9/10VAC + 15/16/18VAC.

[CatPix]

Little bit of advice : usually, AC power is never required inside the computer (the C64 being an exception since the 9V AC was used by the Datasette) so it is absolutely okay to replace the 10 V AC power source by a 9V DC source (the opposite is not true, never replace a DC power source by an AC one. It will not work at all). Same for the odd voltage one. Tests may be required but a 15VDC power source will usually do the job as good.

Internally those tensions are split and turned into the standard (of the era) 12V and 5V (and usually a -5V for RAM).

There are cheap voltage droppers that can feed from 12 to 24 VDC source and drop it to 9V or lower, so make a less clunky power source.

https://www.aliexpress.com/item/32805882664.html?gatewayAdapt=glo2fra&spm=a2g0o.search0304.0.0.48702aeaeamXsn&algo_pvid=8b49e6dc-140a-4824-b142-b17f0cef6287&algo_exp_id=8b49e6dc-140a-4824-b142-b17f0cef6287-28

Note that those circuit can actually do the opposite, that is, feeding from a 9V power supply to provide 15V. Given that, as Carlsson said, that usually the 9V is where you have the most power requirement and the 15/18V the less, it may be a better solution to go that way. High power 9V power supplies are a bit more common that 15V ones, and cheaper.

Edited April 20, 2022 by CatPix

[MattPilz]

Thanks @CatPix that's all great information especially as a novice when it comes to understanding power supply compatibilities. I actually tried to open up one of the original VideoBrain adapters that had only half the power coming out of it, but those things must be mechanically welded in ways that seem impossible to separate compared to a lot of others that can at least be split.

[CatPix]

In addition, something I forgot to mention is that usually, a small voltage difference won't matter (like replacing a 10V requirement with 9V, or 18V by a 15V power supply) but the power requirement in Amperes/milliamperes should be matched, or exceeded.

Replacing a 1.5A power supply with a 2A one will work, but the opposite won't work either.