[Collins] Bucking transformer for 30S-1 finished!

[Dr. Gerald N. Johnson]

You aren't likely to be running both amps at the same time. Wire the 
bucking transformer with a primary on/off switch. Wire two 230 volt 
outlets, one for each final. That one transformer should supply both 
finals at the same time.

The reason for the primary switch is that you don't want to be supplying 
power to the transformer core when you aren't loading it often. You can 
cut the standby current some by wiring the primary to get the output 
voltage with the low voltage windings going up to the high voltage input.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 6/9/2012 2:01 PM, frank hughes wrote:
> Hi,
>
> I have been thinking about how to reduce the line voltage for the 30S-1 for
> some time.
> Variac is the easy way, but for the amps capacity on 240, all the units I
> have found were too large for my tiny shack space.
>
> The recent article about "bucking transformers" in ER caused me to look
> over the piles'o transformers at the
> local electronics surplus place for a candidate.
>
> AC line here runs 253 VAC at low-load times, and drops a little during high
> load periods.
> The 30S-1 manual says "230VAC input", so I tried for that value.
>
> The transformer I found is a Center Tap, so I wired the input for 240.
> The transformer has two 50A 6VAC secondaries, and two 25A 12VAC
> secondaries.
>
> I tried the 12vac first, but it dropped the line below 220vac, which I
> thought too low for the 30S-1.
> The 6vac secondaries were just right, very close to 230vac output.
>
> I bolted the transformer to the ceiling, out of the way of everything else.
>
> Unfortunately, the surplus place did not have another identical transformer
> for me to use with the 30L-1,
> but that just gives me a good excuse to return on a regular basis and snoop
> around for my next project!
>
> 73
> Frank
> KJ4OLL
>
> http://s180.photobucket.com/albums/x257/fish1_07/transformers/
>