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Old 4th January 2013, 12:54 PM   #81
6L6 is offline 6L6  United States
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On an amp at this power, discrete diodes might not be the best bet.

Get a pair of 200v 35A Vishay bridges and mount them with a little thermal grease under them.
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Old 4th January 2013, 04:14 PM   #82
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That's what I was thinking would be my next step. Is there any benefit to "double" rectifying? Trying to decide if I should remove the old ones or leave them there. I assume no negative effects at least?
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Old 4th January 2013, 04:17 PM   #83
6L6 is offline 6L6  United States
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A bridge for each winding gains you a few things -

More current capability on the bridges

Distributed heat compared to a single bridge

A reduction in transformer physical hum when current draws change

Can you link to the PSU board you are using? I would like to see a closer photo of it.
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Old 4th January 2013, 04:32 PM   #84
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Here's the link: Heavy Duty CRC Power Supply Kit for Class A Ampllifier | eBay

So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board? That makes sense to me if I'm going to go through the trouble of doing this in the first place. Just need to make sure i wire to the board properly.

I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?

I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.
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Old 4th January 2013, 04:33 PM   #85
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6L6. it is a e-bay board. clone of the aleph PSU board from chipamp.com
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Old 4th January 2013, 04:37 PM   #86
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just pull them out. then you short the pads for 2 of the 4 rectifiers.
like this:


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Originally Posted by oneplustwo View Post
Here's the link: Heavy Duty CRC Power Supply Kit for Class A Ampllifier | eBay

So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board? That makes sense to me if I'm going to go through the trouble of doing this in the first place. Just need to make sure i wire to the board properly.

I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?

I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.
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Old 4th January 2013, 04:48 PM   #87
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Got it. And the outputs of the rectifiers just go to the AC pads as such?

(+) of two of them to the left AC0 pad
(-) of those same to the right AC0 pad
(+) of the other two to the right AC1 pad
(-) of those same remaining to the left AC1 pad
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Old 4th January 2013, 04:52 PM   #88
6L6 is offline 6L6  United States
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Quote:
Originally Posted by oneplustwo View Post
So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board?
No, you only need 2.

Parallel 2 of your windings two times, to get the transformer connected as intended.

Now you should have (2) 18v windings of 400VA each. Put a bridge on each.

Quote:
I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?
No. Remove them.

Quote:
I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.
It's worth a shot, but 15A diodes will not last long in that circuit even if cooled by submersion in a mountain stream...
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Old 4th January 2013, 04:53 PM   #89
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yes. on AC0 it is (-)(+) and (-)(+) on AC1. you need to confirm that your board is the same. but i suspect it is
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Old 4th January 2013, 04:59 PM   #90
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@6L6 - Ah, gotcha. That makes sense. I was confused by "a bridge for each winding."

@AudioSan - your description is much simpler!

Thanks to both for your help! Much appreciated!

Now... to decide which rectifiers to get. Not sure I'm a believer in the super fancy ones, but then I haven't tried them before. I'm inclined to just the cheap 35A fairchild ones. Open to suggestions. Even the expensive ones aren't all that expensive I guess compared to the dollars I have in heat sinks alone!
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