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Old 19th March 2014, 06:09 PM   #1
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Talking Wellwyn 12r

Hello, just thought I would bring up a possible resistor for the build of a dummy load. Please comment if you think they would actually be appropriate.

WDBR1-12RKT - WELWYN - RESISTOR, POWER PLANAR, 12R 1 | Farnell UK

They are 12r and 1500w each, look perfect for high power amp testing.
Flat mounting so excellent for heatsinking.
I did use two of these together mounted on a heatsink inside an old pc power supply case with fan. This gave 6r which is fine i think, a nice value between 8r and 4r (I dont think hey do a more usefull r value).

But unfortunatly I blew them straight away as the amp I was using was very faulty, I think it basically shorted the Resistors.

Geoff
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Old 19th March 2014, 07:36 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

1.5kW pulse rating is pretty meaningless for amplifier testing.

If you want a real hi power dummy load > 1KW I
think you can knock them up out of heating wire.

Why on earth you'd connect a faulty amplifier to a dummy
load is beyond me, and you should be using a lightbulb on
the incoming mains to indicate simple short conditions.

rgds, sreten.
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Old 19th March 2014, 08:00 PM   #3
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Reading down I realise that they actually state the 180w heatsinked "real" value.
But checking the Technical Data it still states that the item will do 700w when on a fan cooled heatsink (which is what most other dummy loads are).
That giving a nice 1400w on the above configuration, of course lets go for a more real world figure and say 1000w, thats still pretty good.

To be honest the amp was meant to have been fixed, but clearly not.
And to be honest putting a lightbulb on the mains, well I never really got my head around that. I always assumed with large power amps that the surge current would overpower the lightbulb every time, leading me to think that there would be a fault when this is not necessarily true.
Also im pretty sure you can have problems on the output stage of an amp without triggering issues on the power side.........

Otherwise I would have taken out a class d breaker or fuse not the dummy load.

Thanks for the constructive advice though, what would you suggest wrapping the "resistance" wire around, seems a lot of people have had this issue of finding a suitable material that can withstand adequate heat buildup, without it looking like a house brick wrapped in wire.

Looks like the other option will just be pockets out for some 100w wirewound metal cased jobbies, will need 10 of them, but if needs must. Wouldnt like to go for anything higher in W as they get a lot more pricey and the cheap ones, I just dont trust. Makes for a bit of a bulky box too.

Last edited by sketchyphish; 19th March 2014 at 08:12 PM.
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