[Collins] 516F-2 Lowering Voltages

Dr. Gerald N. Johnson geraldj at weather.net
Wed Jan 25 16:09:45 EST 2012



On 1/25/2012 11:32 AM, Byron Tatum wrote:
> Hello-
>      Thanks to everyone for their advice regarding my desire to lower my 516F-2
> voltages. After studying the aspects of using filament transformers as
> autotransformes to lower the supply voltages my final questions are:
>         1.  What is preferred - To use the fil windings of 516F-2 itself as
> autotransformer function or to use a separate fil transformer in front
> of 516F-2?

Its hard to say. The external transformer takes more heat out of the 
516F-2 transformer by not having any power losses in the 5 volt 
windings. But it takes up space at the power supply location. Though I 
know an electrician that used a bucking transformer for his whole house 
to make lamps last longer. Either takes heat out by backing off on 
saturation of the core that causes high peak primary currents.

>         2. If I use a separate fil transf in front of 516F-2 what should be its
> ratings?

The 516F-2 has a 4 amp line fuse. Conservatively, then the transformer 
should be rated for 4 amps, though 3 will probably do and survive. 
Probably 12 volts secondary at 4 amps, or 50 VA for a buck/boost 
transformer with 120/240 primary and 12/24 volt secondary. There are 
several on epay this week with that 50 VA rating. They have enclosed 
wiring boxes to make inserting them in a bit of extension cord between 
the wall outlet and the rigs easier to make neat than an open filament 
transformer which is not commonly made these days, though Hammond and 
most ham fests will have them. In the latest Mouser catalog Hammond 
filament or low voltage transformers have prices similar to the 
buck/boost transformers on epay.
>                                                          Thank you, Byron WA5THJ
> ______________________________________________________________
>
73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association


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