For 35A rectifiers, what is maximum without heatsink

geminni · 17th March 2007, 09:17 AM

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?

Jan Dupont · 17th March 2007, 10:03 AM

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.

Netlist · 17th March 2007, 10:07 AM

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

geminni · 17th March 2007, 06:45 PM

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?

sawreyrw · 17th March 2007, 07:12 PM

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.

Jan Dupont · 17th March 2007, 08:28 PM

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

batee · 18th March 2007, 06:15 AM

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

Zen Mod · 18th March 2007, 06:22 AM

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

Jan Dupont · 18th March 2007, 06:29 AM

It has to be fitted someway anyway, so just attach it to bottom or back plate of the chassis

geminni · 18th March 2007, 11:34 AM

Ok, thanks!

17th March 2007, 09:17 AM	#1
geminni diyAudio Member Join Date: Dec 2006	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?

17th March 2007, 08:28 PM	#6
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	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 __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

18th March 2007, 06:29 AM	#9
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	It has to be fitted someway anyway, so just attach it to bottom or back plate of the chassis __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

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17th March 2007, 10:07 AM	#3
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	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

17th March 2007, 06:45 PM	#4
geminni diyAudio Member Join Date: Dec 2006	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?

17th March 2007, 07:12 PM	#5
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	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.

18th March 2007, 06:15 AM	#7
batee diyAudio Member Join Date: Mar 2004 Location: Rolla, MO	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

18th March 2007, 11:34 AM	#10
geminni diyAudio Member Join Date: Dec 2006	Ok, thanks!

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