Re: 110V 60Hz / 220V 50Hz power supply

----- Original Message ----- 
From: "Didier Derny" <didier@aida.org>
To: <cbm-hackers@musoftware.de>
Sent: Saturday, February 04, 2012 2:44 PM
Subject: RE: 110V 60Hz / 220V 50Hz power supply


> After the failure of the 9090/9060, commodore had to redesign a part of
> the power supply to sell them in Europe.

Well, since they were 110V power supplies I imagine that they _would_ have
to redesign them for Europe and elsewhere ;-)

> They all failed the same way when powered with 50Hz.

"All" being an unknown number >= 2 ?

> When we checked the drive, we had 7.5v instead 5V

Presumably a failed pass transistor but 7.5V sounds a little low, perhaps
suggesting excessive current draw elsewhere.

> I don't know how many were affected, the failing one were 2 pre series.
> It was not officially sold when we received them.

So these were production US models that Commodore had shipped you for
evaluation?

> I don't remember very well, but a chip in the power supply was working
> fine at 60Hz And failing at 50 Hz.

Do we _know_ that some of  these early drives did not also occasionally fail
at 60Hz and it was just a design/quality issue?

I guess we will never know exactly what the problem was, but in any case I
still think that in general you're pretty safe running this sort of
equipment through a step-down transformer of decent quality and appropriate
rating as long as you keep in mind that the transformer in a _linear_ supply
will  run a little warmer; if it is marginal to begin with, has no thermal
protection and is loaded to or beyond its limit it may indeed overheat and
fail but unless there was a primary to secondary short I don't see how that
could damage the regulators. Interesting though.

A switching supply is of course completely unaffected by line frequency.

m

-----Message d'origine-----
De : owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] De la part de Gerrit Heitsch
Envoyé : samedi 4 février 2012 17:59
À : cbm-hackers@musoftware.de
Objet : Re: 110V 60Hz / 220V 50Hz power supply

On 02/04/2012 05:38 PM, Rainer Buchty wrote:
> On Thu, 2 Feb 2012, Groepaz wrote:
>
>> nah. the fact that many PSUs actually contain transformators that can
>> be used for both 110/220v mains (and thus 50/60hz) simply by rewiring
>> should tell you that there is no such problem :)
>
> That doesn't contradict Gerrit. The point here is that the transformer
> was designed to work in both modes, therefore not being designed to just
> (or, today, barely...) fulfill its task.

You just need to use a 50Hz Transformer and design it so that it will be
able to deliver enough power when run at 60Hz. Problem solved.



> (But, yes, I'm running quite some 120V/60Hz equipment from 240V/50Hz
> mains with a 240V/120V transformer in between, and so far never
> experienced any problems.)

So do I, but I always keep in the back of my mind that there could be a
problem, especially if the transformer in question is loaded close to
its specified maximum output.

  Gerrit


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