[ARC5] Transformer questions

[Kenneth G. Gordon]

On 15 Aug 2014 at 10:05, Andrew Kopke wrote:

>  Hello , I have a heath 54-179 power transformer used in heath HW-16 and i think
>  SB-220 . The ratings are : 
> Red wires 248V NT .15A                                                                               
>                                                                              
> Brown wires 105V NT 30ma                                                    
>                                                                                
> yel, yel-green wires 6.3V NT 5.5A

OK.

> I was wondering if
> this sounded like anything that could be utilized for a ARC -5 transmitter
> supply I think it can produce 700 volts @ 250 -300ma when used with a voltage
> doubler.

Yes. But STEADY current capability would still be 150 mA. For SSB and CW 
you can draw up to twice that intermittantly.

But 700 VDC is too much for an ARC-5 transmitter.

If I had that, I would use a bucking transformer or a big variac to drop the 
output voltage to no more than 195 V, since I would be using a separate 
transformer for filament voltage. 

You would be getting around 5 VAC out of the 6.3 VAC winding.

A voltage doubler on that 195 V winding would then give you 550 VDC, 
which is what you want.

The 105V at 30 mA winding is for a bias supply.

Bucking the HV down to 195 V would leave you with 82 V out of the 105V 
bias winding, which would still give you over 115 VDC from a full wave 
rectifier for bias.

Sounds good to me.

Ken W7EKB