[Amps] What to do about 'Neutral' in HB amp?

[Steve Bookout]

Hello all,

Thanks for the input, so far.

I made a boo-boo on the transformer.  it's 0, 220, 230 and 240 volt on 
four terminals.

Steve, NR4M

On 12/28/2022 9:22 AM, Steve Bookout wrote:
> Hello all,
>
> I'm building a HB amp for 10 meters and am looking for the best 
> solution to a problem I've wondered about for DECADES.
>
> Other than using a 4 conductor plug/outlet (2-120 volt, one neutral 
> and one ground) how should a person deal with the 120 volt neutral?
>
> This would be a concern for the blower, small 12 volt DC power supply 
> and filament transformer, and maybe something else I'm overlooking as 
> I write this.
>
> I know I am guilty of just taking the neutral side of a 120 volt 
> component to ground, but as I understand it, the ground is never 
> supposed to carry current, with the neutral carrying the current from 
> the 120 volt stuff.  The ground and the neutral are connected together 
> at the breaker box, but are treated as different lines in the 
> equipment.  Back in the day, I suppose taking neutral to ground was 
> done, as several times I've been slightly shocked by an old boat 
> anchor with leaky caps.   Also, GFI circuits would always trip, as 
> they should, when that piece of equipment was turned on.
>
> These are things I've thought of, in no particular order.
>
> Using a 240 > 120 step down transformer and run the 120 volt things 
> off of that.
>
> Neutral to chassis ground and ground, ground, ground everything 
> together, and to the 240 ground coming into the power supply.
>
> Use the common connection point between two 120 volt windings, wired 
> in series, on the input of the HV transformer for 240 use.
>
> Looked at a bunch of schematics and some are kinda lacking in detail.  
> Most either use dedicated 120 volt winding off of the secondary of 
> transformer, or a separate 240 volt input transformer,   I'm sure the 
> ones lacking in detail are not doing for nefarious reasons but to keep 
> from cluttering up a schematic. It's combining block diagrams with 
> detailed schematics.  I'm sure they're doing it right, otherwise, 
> would not get UL approval.
>
> I seem to remember from decades ago, seeing where someone had two 
> resistors between the two input lines of a 240 volt input transformer 
> and was using that point as neutral.  Would love to know  how that 
> worked out.  Short the 240 input with two resistors in series and use 
> the point between the two resistors as 'neutral'.
>
> The transformer I have, and will use, is a Peter Dahl, with no 120 
> volt winding, only terminals marked '0', '240', '230' and '240'. 
> Secondary is NOT center-tapped, so will be using a FW bridge.  No joy 
> there.
>
> I guess I'm leaning toward a 240/120 step down transformer.
>
> It would be much more straightforward if I was building with all new 
> parts from scratch.  Actually, as I think of it, my DC power supply 
> will take either AC voltage inputs, and automatically deal with it.
>
> Love to hear what everyone thinks, and to hear if you've ever done 
> anything just a wee bit 'shady', when dealing with this issue.
>
> 73 de Steve, NR4M
>
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