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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 3rd Nov 2018, 4:16 pm   #1
buggies
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Default Temporary load for power supply testing

Needed to test a 5 volt 20 amp power supply was working at full current and had no suitable resistive load. Google lead me eventually to a 3 minute youtube video:-
https://www.youtube.com/watch?v=WECW88rJYrE

Using some scrap 0.7mm O/D (and some 0.4mm) enamelled copper wire I was able to dump the 20 amps and later 35 amps as a test of a transformer.
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Old 3rd Nov 2018, 6:41 pm   #2
Herald1360
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Default Re: Temporary load for power supply testing

Somewhat more sophisticated is a length of stainless steel thin wall tube between a couple of hoses with water flow through. Electrical connections can be via big crocodile clips or a bit better, worm drive hose clips.

Don't forget to turn on the water..... hoses blowing off red hot tube in a cloud of steam is a bit lairy

5l/min water and 60C rise is good for 20kW.
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Old 4th Nov 2018, 4:57 am   #3
M3VUV51
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Default Re: Temporary load for power supply testing

In a similar vein I needed a high wattage resisistor for the current sense input of a 723 based PSU I'm homebrewing. I needed 2 ohms, in the end I used part of an old electric fire element. I just bolted a wire to one end then used a hose clip with a wire attached and slid it up and down the bar until I got the resistance I needed. It works perfectly, also heat proof and easy to mount.
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Old 4th Nov 2018, 5:34 pm   #4
G6Tanuki
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Default Re: Temporary load for power supply testing

Cunning!

In the past I've used a coil of galvanised-steel agricultural fencing-wire to make a 48VDC dummy-load; dunk it in a (plastic) bucket of water and it can dissipate a few hundred Watts for quite a long time (I ran it overnight and only a bit of the water boiled away).

Old car headlamp bulbs are also good - I get H4 (main/dip beam) bulbs with one dead filament for free from my local friendly garage. Wire a bunch of these in series/parallel and you can easily get to 500 Watts dissipation.
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Old 4th Nov 2018, 5:51 pm   #5
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Default Re: Temporary load for power supply testing

6V car bulbs (not easy to find, but they do exist) make good dummy loads for 5V power supplies. I've used 1 or 2 6V headlamp bulbs with the fillaments in parallel as a dummy load on a minicomputer PSU I was rebuilding.
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Old 4th Nov 2018, 7:49 pm   #6
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Default Re: Temporary load for power supply testing

6V bulbs persisted a lot longer in the world of motorcycles.
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Old 4th Nov 2018, 11:10 pm   #7
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Default Re: Temporary load for power supply testing

Still very much available.

https://www.mandp.co.uk/motorcycle-s.../standard.html

Probably even halfords too but you'll need to order them these days.

A.
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Old 6th Nov 2018, 2:58 pm   #8
Andrew2
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Default Re: Temporary load for power supply testing

Quote:
Originally Posted by TonyDuell View Post
6V car bulbs (not easy to find, but they do exist) make good dummy loads for 5V power supplies. I've used 1 or 2 6V headlamp bulbs with the fillaments in parallel as a dummy load on a minicomputer PSU I was rebuilding.
I use the same method. And they light up when 'on' which is always handy.
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Old 7th Nov 2018, 6:40 pm   #9
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Default Re: Temporary load for power supply testing

One bit of advice I'd give if you're using lamps as a load is it's a good idea to have them switched so you can bring them on one or two at a time because the inrush current might make the PSU shut down because the cold current is many times greater than the hot current. Just an extra precaution worth taking especially with some picky SMPSUs.
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