How about a couple of 1 Ohm 1ØØ Watt Dale resistors wired in parallel. They can usually be found at electronic surplus stores and amateur flea markets.
These wire-wound resistors are surrounded by a large heatsink, are cheap on the used market and make excellent loads for testing power supplies.
73,
Jay/AF2C
At 11:32 AM 3/19/06 -0600, you wrote:
"Jim Shorney" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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On Sun, 19 Mar 2006 11:31:20 -0500, [EMAIL PROTECTED] wrote:
>>There are a number of options available to you, but in all cases you will
>>need an Amp meter in series the output of the PS7.
Another option is to build a load tester. It's not as complicated as it
sounds, especially for someone with a well stocked junque box.
Take two or more 2N3055s (good for 15 amps each in theory) and wire them in
parallel on a monster heatsink. Don't forget to use emitter ballast resistors
(I just used a "slinky coil" of some solid wire I had handy). Wire up a
smaller NPN power transistor to drive it in a "Darlington" configuration,
with a pot in the base circuit of the driver transistor to control the drive
current. You'll want some value of fixed resistor in series with the pot to
set the maximum drive level, or you'll end up blowing the transistors.
I built one of these years ago with 2x 2N3055H, and IIRC have had it loaded
up to 20 or so amps with no ill effects. I didn't use an enclosure, all the
parts are aerially mounted on the heatsink. Ugly, but it works. It's a handy
gadget to have around for testing 12v power supplies. Just don't hook it up
backwards or you will let the smoke out of your transistors. The 2N3055
collectors go to +, ballasted emitters to -.
I've used the automobile headlamp method too, but this has the advantage of
being able to adjust the load current.
--
TR7/RV7, TR6/RV6, T4XC/R4C, L4B, NCL2000, SB104A, R390A, GT550A/RV550A - all vintage, all the time!
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