[Coco] Coco in France

[Gene Heskett]

On Monday 11 February 2019 08:30:19 rietveld rietveld wrote:

> You need to make V/F constant.    France uses 230v.   So 230/50 = 4.6
> You need to keep the V/F = to 4.6 after the 110v step down.   To do
> this you need to keep the voltage slightly higher so that the V/F
> stays at this constant

Dunno where you found that, but by that rule the v/f=2.11666666667 when 
running on the std NA wall plug voltage of 127 volts. I'd like to have 
some of what whoever did was smoking when he/she dreamed that one up, 
its pretty good stuff. That would make you take back stuff you didn't 
sell!

And as I said, raiseing the voltage of a 50 cycle feed that much will be 
harder if not outright destructive to the 60 hz transformer, as that 
would be around 152 volts AC, and its iron would be saturated pretty 
badly at the voltage peaks that high since they would be according to 
the rms math, 215.562938389 volts peak. I might give the poor coco's 
transformer a maximum of 30 seconds if the fuse didn't clear first. IMO, 
wearing my CET hat, the only sensible way to solve the problem is to 
replace that aged 4700 uf with a fresh 6800 uf. It may even be a 35 volt 
cap, and based on its normal operating voltage of less than 16 volts, 
could even be replaced with a 16 volt or 25 volt unit. Operating a 35 
volt rated cap at  12 to 14 volts does not make an electrolytic last 
longer as it will do a chemical deformation over the years, gradually 
reduceing its breakdown voltage to the actual operating voltage, a 
process which also reduces its measured microfarads by a similar amount.

> Sent from my BlackBerry
>   Original Message
> From: Carlos Camacho
> Sent: Monday, February 11, 2019 7:06 AM
> To: coco at maltedmedia.com
> Reply To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] Coco in France
>
>
> 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.

Even that 110 is "slanguage", the wall plug voltage in new construction 
has not been 110 volts since before the REA days right after WW-II. Its 
been targeted at 127 for at least 40 years now.

> Refresh my memory... the CoCo needs 60hz in order to generate it's
> NTSC RF video correct?

No, its 60 hz video is determined by a quartz crystal, which runs on DC 
and as long as the DC is stable, it couldn't care less what the 
powerline frequency actually is.

> 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.

Theres no video there because the coco is crashing from low voltage 100 
times a second, and doesn't have a chance to get booted up long enough 
to start making video before it crashes again.

> He says a transformer that converts to 60hz is expensive so is
> wondering about replacing the internal transformer.

That might help but probably not enough to make it actually run, it would 
reduce its operating temps though.

> Frankly, for me, 
> I'd prefer spending the money on a good external transformer and not
> risk my retro gear.

Sigh, this is getting frustrating, its Zero help.

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

See my previous comment here.
>
> Anyhow, I just need confirmation on 60hz power requirement.
>
> Carlos
>
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Cheers, Gene Heskett
-- 
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