Do I need to heatsink if I install 40A Schottky 250V - PS of Rotel RB991

[dtm1962]

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!.

Thanks,

[poobah]

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.

[EWorkshop1708]

heatsinks are good, use them, your diodes will last a lot longer

[Leolabs]

Originally posted by EWorkshop1708
heatsinks are good, use them, your diodes will last a lot longer

Agree