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-   -   Bridge rectifier and Aleph 3 (http://www.diyaudio.com/forums/pass-labs/96001-bridge-rectifier-aleph-3-a.html)

Skorpio 9th February 2007 12:41 PM

Bridge rectifier and Aleph 3
 
I have just finished my Aleph 3 (test part) and one think surprised me a bit: The rectifier gets rather hot!

PSU: 800VA transformer, 1 bridge (35A) i metal housing, 2x47000uF/40V caps....no hum/noise....

I have mounted the bridge directly on the secondary windings (for shortest possible wiring)so it is not mounted as normal on chassis.

It ran rather hot after few minutes (still touchable), so I fitted it on a small heatsink. After some hours this heatsink is now rather hot too, but still touchable.....

Will this be a problem? If I must rewire it is a major workaround and amplifier works perfect. My concern is reliability....how rough is this rectifier bridge?

jacco vermeulen 9th February 2007 01:03 PM

The dissipation of the diode bridge rectifier may only be some 3 watts, if you picked the regular bias level.
But 3 watts is still enough to need a 10C/W heatsink if you wish to keep the temperature of the rectifier diodes at 50-55C (20-25C ambient)

The lower the temperature of the rectifier diodes is, the higher their thermal reserve is.
For class A/AB PP amplifiers, that translates into a high thermal reserve, which is necessary for the diodes to pass high peak current levels without choking to death.
Bias on the Aleph/3 is constant, and higher than that it never gets. Means that the temperature of the diodes only affects their life expectancy. At 55C, they may outlive you.
Why anyone would hang a diode rectifier block out in open air, instead of bolting it to the case ? Beats me.

Everything gets hot: cars, women, Aus, class A amps,... rectifiers.

Skorpio 9th February 2007 01:31 PM

Thank you for your good answer.....the reason for the placement is wiring. The transformer is big, 20cm height. Next to it is capacitors in same height. If mounted on chassis buttom an extra 3x40cm wiring is needed...

Anybody heard of failing metal housing rectifiers?

steenoe 9th February 2007 02:13 PM

Quote:

Everything gets hot: cars, women, Aus, class A amps,... rectifiers.
And the worst: beer:D

Steen:)

Magura 9th February 2007 02:16 PM

Quote:

Originally posted by Skorpio

Anybody heard of failing metal housing rectifiers?


Yes, it sounds remarkebly close to a BANG :hot:

Magura :)


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