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Old 10th March 2008, 10:45 AM   #11
Tarzan is offline Tarzan  Belgium
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Right Bonsai, but I like to know what these particular resistors cost.
I'm thinking about another use...
Thanks,
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Old 10th March 2008, 11:31 AM   #12
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Quote:
hi, What do these resistors cost?
I bought mine surplus from Skycraft in Florida a few years back for $4 ea.

I just finished checking and they don't carry them now.
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Old 10th March 2008, 11:52 AM   #13
acid_k2 is offline acid_k2  Italy
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My "small" dummy load:

http://it.geocities.com/fabiobonotto.../DummyLoad.htm

(page in italian only, but schematic is "universal" )
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Old 10th March 2008, 12:55 PM   #14
TheMG is offline TheMG  Canada
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Quote:
Originally posted by acid_k2
My "small" dummy load:

http://it.geocities.com/fabiobonotto.../DummyLoad.htm

(page in italian only, but schematic is "universal" )

Why do you have that parallel diode in there? The way your schematic is right now, if you turn the pot until the wiper is towards the top in reference to the diagram, you're shorting out half the output wave right through the pot and diode!
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Old 10th March 2008, 03:49 PM   #15
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Here is my small (50W) DIY Speaker Dummy Load. With this config, you can also hook up a speaker to monitor your test. Capacitance and inductance can also be added to the test using the binding posts.
Attached Images
File Type: jpg diy-speaker-dummy-load-u.jpg (52.6 KB, 597 views)
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Old 10th March 2008, 05:00 PM   #16
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Quote:
Originally posted by Bonsai
You can also use electric kettle elements. Typically about 2 2 Ohms, so is you wire 3 in parallel you get 7.3 Ohms.

Good for about 6KW when immersed in Water


You don't mean that, do you? Should be SERIES connected.
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Old 10th March 2008, 05:18 PM   #17
AndrewT is offline AndrewT  Scotland
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220Vac & 22r gives about 2kW.
Three in parallel will be around 7r3.
Might be a bit lower if you only push in 200W though.
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Old 10th March 2008, 05:49 PM   #18
Nordic is offline Nordic  South Africa
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Question... bear in mind speaker's impendance fluctuations....

Can one use a 50W loudspeaker in parallel with say a 50W resistor to tesst for outputs above 50W?
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Old 10th March 2008, 06:19 PM   #19
djQUAN is offline djQUAN  Philippines
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Quote:
Originally posted by mag
Depends on which resistance you need and how much power you need.

For instance I am using 14 resistors in parallel, every resistor is 56ohm 10W to give me a load of 4ohm 140W.

When I use it for really high power I put the resistors in a can full of water. When you use 300W or more you see the water boiling

It is good for short power tests but of course not for continuous load at more than 50W.

same thing as I did but I used 2 sets of 15x56R so I have two 3.7R loads. if an amp survives 3.7R, 4ohms would be easy. besides, resistance goes up when the resistors heat up.

Click the image to open in full size.
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Old 10th March 2008, 06:25 PM   #20
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Quote:
Originally posted by AndrewT
220Vac & 22r gives about 2kW.
Three in parallel will be around 7r3.
Might be a bit lower if you only push in 200W though.
I used to have a similar setup years ago, with a dual network for 2x8R or 1x4R in a large plastic keg full of water.

I need a new test load capable of high power, so I think I'll use conventional high power resitors, heatsinks and a fan as the old fashioned jug elements aren't as conventiently available as in the past.
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