For 35A rectifiers, what is maximum without heatsink

[geminni]

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]

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]

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]

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]

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]

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]

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]

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]

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

 

[geminni]

Ok, thanks!

 

[AndrewT]

Hi,
since only 1pair of diodes conduct at a time then the voltage drop is 1.4V.

Peak charging currents are quite high, but assuming an average charging current of 2A, gives an average dissipation of under 3W.

That 3W is easily dissipated on just about any metal plate and allows amplifier consumption of around 200W.

No worries.