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Old 17th March 2007, 09:17 AM   #1
geminni is offline geminni  Yugoslavia
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Default For 35A rectifiers, what is maximum without heatsink

I couldn't find how many ampers can survive rectifier without heatsink.
I have downloaded datasheet for it but there was nothing about it.
Can i use this 35A for 2x200 amplifier rated at 8 ohm?
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Old 17th March 2007, 10:03 AM   #2
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You will only draw max current on Power On.
While playing the current are reduced to app. 10A for 8 Ohm speakers at full power.

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Old 17th March 2007, 10:07 AM   #3
Netlist is offline Netlist  Belgium
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Hard to tell without more info but an easy solution for cooling a rectifier bridge is to mount it on the chassis. In most cases that will be enough unless we are talking big classA amplifiers.

/Hugo
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Old 17th March 2007, 06:45 PM   #4
geminni is offline geminni  Yugoslavia
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Thanks for the graph, ACD!
So, by the graph i relize that my rectifier, 35A, can be pushed to deliver some 31 amps without any trouble on 40C summer temp
Ok, mounted a small heatsink ofcourse

Other thing about this i want to ask. I have made the amplifier 2x40w runing 6 ohm speaker. Transformer is 2x20V with 4 Amps, for stereo. Rectifier is 35A and does not have heatsink. Is this safe for rectifier? Only 4 amps and no heatsink?
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Old 17th March 2007, 07:12 PM   #5
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The current handling capability depends on the thermal resistance for junction to ambient. I have no idea what you are using, but a Rth of 20 to 30 degrees C/watt wouldn't surprise me. So you could dissapate only 3 to 4 watts without overheating.
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Old 17th March 2007, 08:28 PM   #6
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Please see other diy-constructions here at the forum....
Many "low power" amps (up to 80-100W) have the diode bridge fitted on the PCB without any heatsinking
Above that, I would recommend just to fitt the diode bridge to the chassis to be save
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Old 18th March 2007, 06:15 AM   #7
batee is offline batee  United States
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I tried a GBPC3506 at 25A and no sink (not even chassis), ambient temp was about 35F. It cracked along one side, but continued to function.

Bryan
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Old 18th March 2007, 06:22 AM   #8
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by geminni
Thanks for the graph, ACD!
So, by the graph i relize that my rectifier, 35A, can be pushed to deliver some 31 amps without any trouble on 40C summer temp
Ok, mounted a small heatsink ofcourse

Other thing about this i want to ask. I have made the amplifier 2x40w runing 6 ohm speaker. Transformer is 2x20V with 4 Amps, for stereo. Rectifier is 35A and does not have heatsink. Is this safe for rectifier? Only 4 amps and no heatsink?

it's easier to drill one hole and fit one screw than to write two posts
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Old 18th March 2007, 06:29 AM   #9
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It has to be fitted someway anyway, so just attach it to bottom or back plate of the chassis
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Old 18th March 2007, 11:34 AM   #10
geminni is offline geminni  Yugoslavia
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Ok, thanks!
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