Hey dudes.
I was planning on making a cheapo dummy load like following:
Two 3.9 ohm 50W wire wound resistors in series, installed on a large heat sink taken from a scrapped 100W mono amplifier.
This would make a nice 8 ohm 100 W dummy load, I think.
I'm planning to make two sets, and connect them in parallel, for a 200W 4 ohm dummy load.
But here's the kicker... I need 250 W. So I was thinking of submerging the bottom halves of the heatsinks in water. No risk of shorts or anything like that.
What do you think? Could it work?
I was planning on making a cheapo dummy load like following:
Two 3.9 ohm 50W wire wound resistors in series, installed on a large heat sink taken from a scrapped 100W mono amplifier.
This would make a nice 8 ohm 100 W dummy load, I think.
I'm planning to make two sets, and connect them in parallel, for a 200W 4 ohm dummy load.
But here's the kicker... I need 250 W. So I was thinking of submerging the bottom halves of the heatsinks in water. No risk of shorts or anything like that.
What do you think? Could it work?
$10 and it doesn't have to look cheap.
9 of these is series / parallel gives 8ohm 225w load. Mount on a beefy heatsink or side of an old discarded aluminum cooking pot filled with water for heat sink and you can probably push quite a bit higher than 250w.
https://m.aliexpress.com/item/32627435854.html
I just got these - they are nicely made.
9 of these is series / parallel gives 8ohm 225w load. Mount on a beefy heatsink or side of an old discarded aluminum cooking pot filled with water for heat sink and you can probably push quite a bit higher than 250w.
https://m.aliexpress.com/item/32627435854.html
I just got these - they are nicely made.
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For free if you have some... Three 2KW 240V Watercookers/Cooking plates/whatever give a nice 8.x Ohm dummy load too.
PS: The look is a bit wired and its not a precisision load...
PS: The look is a bit wired and its not a precisision load...
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I'd use mineral oil contained inside a gallon paint can.
at least that was what Heathkit used to offer in their 'Cantenna' RF load.
I'm pretty sure you can easily purchase the can at a paint store and add your own jacks.
I think water is problematic when it bubbles near the hot surface.
at least that was what Heathkit used to offer in their 'Cantenna' RF load.
I'm pretty sure you can easily purchase the can at a paint store and add your own jacks.
I think water is problematic when it bubbles near the hot surface.
Right, right... 😀 I will use four 15 ohm resistors in parallel then. 3.75 should be good enough as a 4 ohm dummy load I think.
Two 3.9 ohm 50W resistors in series does yield a 7.8 ohm 100W resistor as each 3.9 will handle 50W.
3.9 ohm handling 50W will have 13.964V across it , 2 will have 27.928V in total and 7.8 ohms handling 27.928V gives 100W .
3.9 ohm handling 50W will have 13.964V across it , 2 will have 27.928V in total and 7.8 ohms handling 27.928V gives 100W .
No, it would be 100 watts total as the voltage is shared between each resistor.
Considering the Low resistance of this Load, you could immerse the whole Assembly in a Tub of water with good results. Shorts...Not really significant. Get that Water Boiling !!!
I made a dummy load for my SMPS and just used lots of 50 watt resistors in a tub of water. Worked very well.
And if using commercial resistors, why are we using 15 ohm and 3.9 ohm and "coming close" when dead on 8 ohm and 4 ohm resistors are available off the shelf and cheap. For example, 8 ohm 1% 50w heatsink body with mounting tabs:
http://www.mouser.com/ProductDetail...Nd0dY0KymzjQZdWkJqzrBWtgCUMzOAeNATfj4sAIvqQ==
http://www.mouser.com/ProductDetail...Nd0dY0KymzjQZdWkJqzrBWtgCUMzOAeNATfj4sAIvqQ==
I totally agree which is why I proposed the 25w 8ohm anodized aluminum body resistors with tabs in post 3. The mouser ones are well priced - a lot less than I seem to recall another major brand one.
If you want cheap, the large (8in) stove element is about 27 ohms. Three of those in parallel and you don't need to mess with water cooling or heat sinks. Make a tea while you're testing your amp too. People throw out stoves all the time.
Maybe they are not commercial resistors and are just some he has on a shelf. I have coffee cans full of oddball stuff and these 25 ohmers made me a 400 watt dummy load for free.
There are guys building PCs with the entire motherboard submerged in mineral oil.
Forget liquid cooling; give your PC an oil bath | PCWorld
Soak Your PC in Mineral Oil: Puget Systems Announces DIY Aquarium Cooling
I gave those gold resistors from Aliexpress a test last night. They were not bolted down to the heatsink yet so got kind of hot. They held up to a 120w test though (measured 10ohms when hot vs 8ohm nominal rating). Here is 34.5v ran for 15 minutes using FH9 HV amp:
Next step is to bolt down to heatsink with thermal paste.
Next step is to bolt down to heatsink with thermal paste.
There are guys building PCs with the entire motherboard submerged in mineral oil.
Forget liquid cooling; give your PC an oil bath | PCWorld
Soak Your PC in Mineral Oil: Puget Systems Announces DIY Aquarium Cooling
Good luck servicing this - what a mess...