[Coco] Coco in France

Joel Rees joel.rees at gmail.com
Mon Feb 18 23:26:15 EST 2019

2019年2月11日(月) 21:06、Carlos Camacho さん(idevgames at gmail.com)のメッセージ:

> Well, it looks like his power transformer only steps the voltage down to
> 110V but doesn't alter the frequency. So that remains at 50hz.

Inductive transformers never alter frequency.

It may be that some marketroid is marketing a frequency converting
switching power supply as a transformer, but that could be grounds for a
mislabeling lawsuit.

The easiest way to do that would be to use a switching power supply to
convert to DC, then use an inverting switcher to produce 120V at 60 Hz from
the DC.

There will be coils in there, and one or more may be transformers, but the
device itself is much more than a transformer.

Refresh my memory... the CoCo needs 60hz in order to generate it's NTSC RF
> video correct? And as I tap into the video signal just before it goes to
> the RF modulator for composite out, that would explain why no video there
> too.

I had thought, back when I lived where my coco is now stored, that they
were pulling the 60 Hz off the secondary through some zener circuit, but I
don't recall actually seeing the necessary circuitry to do that, and it wss
probably cheaper (and maybe safer) to synthesize it from the video divider

He says a transformer that converts to 60hz is expensive so is wondering
> about replacing the internal transformer. Frankly, for me, I'd prefer
> spending the money on a good external transformer and not risk my retro
> gear.

Maybe I'm being pedantic, but please call that a frequency converter, not a

Interesting that he is using same transformer with C64 and other retro
> machines without issues.

Anyhow, I just need confirmation on 60hz power requirement.

Gene knows what he's talking about. Transformers have inductance and
reactance, and reactance is the largest piece of the efficiency equation.
Reactance varies with frequency and so does efficiency, and, as he says,
inefficency produces heat.

If I were wanting to run a coco in the Kansai area, maybe I'd risk the
reduced voltage at 60 Hz. Not in Kanto, where they run at 50 Hz. I fried a
programmable TI calculator taking it to Tokyo 40 years ago.

For Kanto, I'd probably do a power supply transplant, put a switching power
supply designed to handle the full range of power input in it.

More information about the Coco mailing list