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Re: [Amps] Transformer question

Subject: Re: [Amps] Transformer question
From: Geert Jan de Groot <>
Date: Mon, 09 Jul 2007 23:22:43 +0200
List-post: <>
I'm obviously no expert in the American electrical code
(other than some of the stunts I see posted would be definite
no-go tricks over here). On the other hand, 230 volts is all 
we have, we do get the odd American device that needs to be
modified for 230 volts, so..

>> That's correct and not just for appliances.  Here's one real world potential 
> > problem:  If a 120V blower is used in a 240 VAC amp (e.g., older Alpha & 
> > Henry), and one lead of the blower is connected to chassis as the neutral +
> > ground connection -- and if the neutral opens, current for the blower will 
> > find its way to the load center through your grounded RCA, SO-239, BNC, or 
> > any other chassis-grounded connector.

Typically, a transformer has a centre tap (so both windings can be
put in parallel for 110 volt service). I would connect the blower
between one of the leads and the centre tap. Voila - 
the magnetic coupling of both windings (on the same code),
will make sure that the blower will get the right (half)

The amps you talk about would be connected with 3-wire service
(L, N, G) over here. Plugs are symetrical, so you don't know
if L and N is reverted. Running single-pole power switches is
still OK: the only way to service these units safely is by
*pulling the plug* instead of flipping the switch (a double-pole
switch doesn't matter - would you depend your life on 
both contacts working, always?). I made a habit of standing on
the power plug when working on these.

Keeping N and G separate is neccessary, as for one, N and L
may be reversed (remember, symetrical plug, see above),
secondly, 30 mA through the ground line (i.e. 30 mA difference
between L and N) will trip the GPF switch - end of story.
Which also means that if there's any way that 30mA of current
is leaking towards the ground cable, things *will* be switched off.
I feel very safe about this.

The Dutch use a slightly-modified version of the German Electrical Code.
We know the Germans about their thoroughness, and believe me,
they've done a good job on this.


Geert Jan PE1HZG
(now, that 3+ kV anode voltage on these amps, well...)

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