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Old 25th January 2012, 08:08 PM   #501
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Heck, with the bulbs, it's 600W worth

The more of them you run, the hotter the heat sink can safely be... Also, the heat sinks I'm planning to use are large, but not very thick, having more resistors will make it easier to spread the heat out on the sinks.

Besides, they're cheap, and non-inductive, so how can you go wrong?

Roscoe
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Old 25th January 2012, 08:35 PM   #502
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What's wrong with bulbs? They're cheap, don't need a heatsink and, as a bonus, give light.

Sure, some resistor-based solution might sound better, but really, the amount of heatsinking required will be ridiculous.
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Old 25th January 2012, 08:36 PM   #503
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with resistor ,we have a lot of heat ...I thinks is better use a fan, like Noctua....

or lamp from US
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Last edited by nicoch58; 25th January 2012 at 08:39 PM.
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Old 25th January 2012, 08:41 PM   #504
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Bulbs are huge, and fragile.

Maybe we don't want the light.

Heat sink size isn't that bad since the resistors can safely operate at much higher temperatures than the JFets....

Roscoe
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Old 26th January 2012, 05:01 AM   #505
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Default Option....

Quote:
Originally Posted by Roscoe Primrose View Post
I plan to use 4 of these in parallel per channel: MP9100-50.0-1% Caddock Thick Film Resistors - Through Hole

Roscoe

Hi Roscoe!

I found Caddock: Power resistor 20 Ω 100 W here at my delivery!

Two of the in paralell gives 10 ohm and then you take 2 pc 2ohm/50 watt to give you 300 watt with 14 ohm.
Or something like this which will keep cost somewhat lower - and the heat acceptable???

Best

Olav
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Old 26th January 2012, 05:31 AM   #506
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Quote:
Originally Posted by ra7 View Post
What's wrong with bulbs? They're cheap, don't need a heatsink and, as a bonus, give light.

Sure, some resistor-based solution might sound better, but really, the amount of heatsinking required will be ridiculous.

sure you re right but bulbs are not a good idea with a daughter playing football in the living room
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Old 26th January 2012, 05:36 AM   #507
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Quote:
Originally Posted by OlavHaal View Post
Hi Roscoe!

I found Caddock: Power resistor 20 Ω 100 W here at my delivery!

Two of the in paralell gives 10 ohm and then you take 2 pc 2ohm/50 watt to give you 300 watt with 14 ohm.
Or something like this which will keep cost somewhat lower - and the heat acceptable???

Best

Olav
not a good idea you will have 35 watt dissipation on a 50 watt resistor , too short , try to find minimum of 100W or use 4 20 ohm , remember i use 1 800W 10 ohm resistor and my heatsink is still very hot with 75W off dissipation on it
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Old 26th January 2012, 06:18 AM   #508
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Quote:
Originally Posted by juanitox View Post
not a good idea you will have 35 watt dissipation on a 50 watt resistor , too short , try to find minimum of 100W or use 4 20 ohm , remember i use 1 800W 10 ohm resistor and my heatsink is still very hot with 75W off dissipation on it

Hi Juanitox!

Yea - I know very well - but with 2 in parallell = 2x 100= 200 watt plus 2 50 watt (or make it 100 watt) = 200 + 100(or 200)= 300watt (or400watt).

So you get really close with this - I believe.

Have to run - my helicopters to shore will leave soon

Olav
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Old 26th January 2012, 08:13 AM   #509
generg is offline generg  Germany
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Quote:
Originally Posted by OlavHaal View Post
Hi Juanitox!

Yea - I know very well - but with 2 in parallell = 2x 100= 200 watt plus 2 50 watt (or make it 100 watt) = 200 + 100(or 200)= 300watt (or400watt).

So you get really close with this - I believe.

Have to run - my helicopters to shore will leave soon

Olav
I have a case for the F5 or F4 with adequate heatsinks and these are sufficient for the SK and the resistors.

Olaf I think your values are o.k. regarding the heat, I have the same wattage combined, only difference, I used four 10 Ohm/50W to make the ten Ohm as a starting point for the resistor chain.... so the heat is still a bit more diversified...
but I do not think this is necessary....

Juanitox is your machine ready and sounds.....?
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Old 26th January 2012, 08:17 AM   #510
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i 'm finishing mounting the Rifa and power choke , and R-core transfo in my little chassis ... it will sounds or not this weekend
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