[R-390] OT: Pass Transistor Question

[Barry]

>A few weeks ago, I mentioned I wanted to build a regulated, low-voltage 
>power supply that uses an LM317 with some pass transistors to enable it to 
>handle a larger current than the LM317 can handle.  The circuit uses a 
>2N2905 to drive a 2N3055 in a "pass transistor" configuration around the 
>LM317 and the circuit description states it's capable of delivering up to 3 
>amps in this configuration.
>
> I have a transformer with a 6-amp capacity and I would like the power 
> supply to deliver up to 5 (maybe all 6 amps) if I want.  Is it possible to 
> put another 2N3055 in parallel with the one in the circuit allowing thus 
> allowing the pass transistors to deliver the extra amperage.  Will this 
> work?
>
> I ran across something like it here:
>
> http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm
>
> (Scroll down to the middle of the page).  The two 2N3055s are paralled and 
> have 0.1-ohm resistors in the emitter lines.  Not sure what these 
> equalizing resistors do, but perhaps that's all I need to add?
>
> By the way, the original circuit is on page 127 of the 1978 ARRL handbook.
>
> Thanks guys for the OT help.
>
> Barry

Thanks for all the replies, guys.  I knew you all would be a big help.

The supply will normally coast along at 600mA to 800mA, but since I found 
such a nice tranny and a set of stud-mount rectifier diodes to boot, I 
thought I'd make it capable of at least what the tranny can supply.

I really appreciate the help (transistors are just weird to me...)!

Barry - N4BUQ