Do I need to heatsink if I install 40A Schottky 250V - PS of Rotel RB991 - diyAudio
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Old 30th July 2006, 06:39 PM   #1
dtm1962 is offline dtm1962  Canada
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Default Do I need to heatsink if I install 40A Schottky 250V - PS of Rotel RB991

I have a bunch of On-Semi MBR40250 schottky power diodes in TO220 case style.
My RB991 power Amp (200W per channel) has dual PS (sharing a Common Xformer) and uses 2 BR154 (one for each channel) which are 15A 400V standard Power Diode Bridge.

The DC Rails are 70V and the Rail Fuses are 6.3A SloBlow and the Amp consumes a total of 550W (~750 VA). It has a 1.2KVA transformer.

I was going to make up a bread board using 4 MBR40250 Schottky per channel.

Assuming that the Amp is operating at 6 Amps @70 VDC = 420 VA
at maximum power (assuming the worse case), the diodes have a Forward drop of 0.6 at 6A & 70 C temp which translates into 3.6W of dissipation that the TO220 case has to handle.

Is this asking to much for a non-heatsinked Power Diode in a TO220?

Any help would be appreciated!.

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Old 30th July 2006, 07:14 PM   #2
poobah is offline poobah  United States
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Yes... this is too much without a sink...

TO-220 devices top out at 1-2 Watts for dissispation naked in free air. You do need some heat sink... not alot. Some sort of a clip-on jobby should work for you.

You should also look at surge rating for the old diodes and make sure your new surge rating is comparable.

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Old 31st July 2006, 08:50 PM   #3
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heatsinks are good, use them, your diodes will last a lot longer
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Old 2nd August 2006, 01:29 AM   #4
Leolabs is offline Leolabs  Malaysia
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Originally posted by EWorkshop1708
heatsinks are good, use them, your diodes will last a lot longer

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