FREDS HOT

[jleaman]

Freds Hot

Ok so i Build a Fred brige Rectifier for one channel of my amplifier useing 4 freds and 4 caps that peter daniel gave me.

When powered up it works but starts getting warm on the heat sink and the one channel that it is powering for my small amps HUM.

Any idea's Any one..

Id like to use fred's but if they introduce HUM and lots of un nessasary heat then ill use standard Brige Recifiers

 

[analog_sa]

Id like to use fred's but if they introduce HUM and lots of un nessasary heat then ill use standard Brige Recifiers

Absolute nonsense

 

[jleaman]

yeah i know. Im confused

 

[JOE DIRT®]

give us a schematic on how you wired up the diodes Jason or a pic.....for me personally I use snubber caps on rectifiers similar to those


DIRT®

 

[jleaman]

Peter daniel gave me 8 snubber caps and 8 fred's OUT of the kindness of his heart : O) AWWw brings a tear to my EYE : O )

But ill post a picture of it tonight and stuff.

 

[tbla]

brings a tear to my EYE

...i'm touched......😉

 

[Peter Daniel]

If they hot, use bigger heasink.

 

[jleaman]

there not that hot but the heat sink is warm ill try a bigger one just in case.. But what about the humm..


Peter I have not recieved any emails you regarding the Web-page.

 

[tbla]

what about the humm..

........................humm along......😉

sorry, can't help it - it's friday...

 

[Brian Donaldson]

Teach them the words. Sorry, I couldn't help it.

 

[jleaman]

Ok here is a picture. the heat sink is 5 " x 5" x ( finns 1.75 " )

and the fred's are B1060's

with snubbers MKT1817's On each fred

My amplifiers are 2 x irfp240's each mono block

15,ooomf in this setup up running one channel alone.

And this heat sinks is warm.

Why. do i need a bigger heat sink than the amplifiers??

 

[li_gangyi]

seems to me you might have got the freds connected worngly...can you give a close up?? I use some freds...with snubbers also...and I just use a scrap heasink I found inside one for my broken PC PSUs....and they don't even get warm...warming up slightly when I pull 8A....

 

[jleaman]

here you go

 

[li_gangyi]

hmmm...try this layout...
And did you know you can get these freds for free at On-Semi?? check out this webby at
www.on-semi.com

 

[jleaman]

That is the way i have it.

 

[jleaman]

Here is the first one that i did. Using a small heat sink from a 300watt SMP From a computer psu.

 

[chris ma]

Hi,

This is the way I wired mine. It only get a little bit warm after an hour when pulling 3A.

I may be wrong, please double check again.
Chris

 

[li_gangyi]

hmmm...could it be because of the insualtion?? u gotta make sure the tabs dun touch the heatsink...they are connected internally to K...

 

[chris ma]

Looking at the pic you posted here http://www.diyaudio.com/forums/showthread.php?postid=265117#post265117

Why the blue and yellow wire from the transformer connect to the caps?

Chris

Oh I see it now, you are using dual secondary to connect to the same bridge? I do not understand this...

 

[analog_sa]

Teach them the words. Sorry, I couldn't help it.

Nor could i. I find no explanation for the existence of this thread - it's obvious diodes can't generate hum if correctly wired and not blown, whether freds or not.

Still, the abscence of hum may be an even bigger problem if one's to believe Zappa


I whipped off her bloomers'n stiffened my thumb
An' applied rotation on her sugar plum
I poked'n stroked till my wrist got numb
But I still didn't hear no,

Dinah-Moe Humm
Dinah-Moe Humm
Where this Dinah-Moe
Comin' from