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Old 20th August 2005, 02:29 AM   #531
maf_au is offline maf_au  Australia
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Russ,

Will the monoblock PCB be flush with the 3886 at the back, or overhanging like it is in My_Ref?

I didn't realise this until after I had populated the board and my layout is a little compromised because of it and a communication error trying to solve another unrelated issue with the case...

My 3886's heatsink surface hangs below the actual heatsink by 3-4mm. I can rectify this, but not this weekend, and I'm away next week. Do you think it will run ok like this? The chip is temp protected, right? So if it's not thermally happy it will cut out.

Michael
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Old 20th August 2005, 03:46 AM   #532
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Quote:
Originally posted by maf_au
Russ,

Will the monoblock PCB be flush with the 3886 at the back, or overhanging like it is in My_Ref?

I didn't realise this until after I had populated the board and my layout is a little compromised because of it and a communication error trying to solve another unrelated issue with the case...

My 3886's heatsink surface hangs below the actual heatsink by 3-4mm. I can rectify this, but not this weekend, and I'm away next week. Do you think it will run ok like this? The chip is temp protected, right? So if it's not thermally happy it will cut out.

Michael

I have been told that the chip will fail quickly if not heatsinked. The thermal protection has a time delay, it will not shut down quick enough to prevent permanent damage.
Think I read they will blow out the back on failure.

George
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Old 20th August 2005, 03:53 AM   #533
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Quote:
Originally posted by maf_au
Russ,

Will the monoblock PCB be flush with the 3886 at the back, or overhanging like it is in My_Ref?

I didn't realise this until after I had populated the board and my layout is a little compromised because of it and a communication error trying to solve another unrelated issue with the case...

My 3886's heatsink surface hangs below the actual heatsink by 3-4mm. I can rectify this, but not this weekend, and I'm away next week. Do you think it will run ok like this? The chip is temp protected, right? So if it's not thermally happy it will cut out.

Michael
The issue you are dealing with (PCB and chip not flush) is only on the REV A boards (which I did not design). I am not sure if it is an issue with manufacturing or in the gerbers. In any case I am not sure if it was intentional or not...

I built a few of those boards and I did a couple of things to handle the offset:

1) I cut a 3/32 slot the length of the heatsink at the same height as the standoffs. Which works very well.

2) Take the chip end of the PCB to a belt sander until its flush.


The monobloc REVC(A&B) boards that I did design should not have this "feature". They are designed to sit flush to the HS when the back of PCB is touching the HS.

I would get all the HS contact you can, you don't want to fry em.

Cheers!
Russ
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Old 20th August 2005, 04:10 AM   #534
maf_au is offline maf_au  Australia
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Thanks guys, that was what I was worried about.

Good to hear the monoblocks won't have that feature.

I'll spend the time to get everything else sorted neatly, and get the holes adjusted when I get back before I power it on.

Times like this, be nice to have a drill press!

Michael
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Old 20th August 2005, 04:54 AM   #535
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Thanks guys, really looking forward to getting some funds together and building something now
Is there an FAQ or tutorial on here somewhere I've managed not to see? Explaining the purposes of the diff. bits?
I've just been looking at some of the various amp designs and PCBs people have made. Wow, talk about DIY professionalism
I'm certainly very impressed.
Anyways, I'll keep a look out. When I get some money I'll probably be buying some groovy kits.
Cheers guys,
--Nathan
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Old 20th August 2005, 07:26 AM   #536
Franz G is offline Franz G  Switzerland
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Quote:
I have been told that the chip will fail quickly if not heatsinked. The thermal protection has a time delay, it will not shut down quick enough to prevent permanent damage.
Wrong! You can check the termal shutdown for hours, no damaging of the chip.

The thermal protection of this LM chips IS reliable.

Franz
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Old 20th August 2005, 01:18 PM   #537
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For the short term, you could insert a small piece of aluminum in between the chip and your HS to fill the gap. Apply a thin film of HS compond to both sides first.
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Old 20th August 2005, 02:49 PM   #538
maf_au is offline maf_au  Australia
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Ok, that's it from me, it's starting to come together. See pic.

Toroid cabling check question:

I have this toroid:

http://www.altronics.com.au/index.as...=item&id=M5525

On the My_Ref PCB, there are 4 connections:

PL3 Gnd
PL4 Gnd
PL5 24va1
PL6 24va2

The toroid secondaries are paired Red & Black, White & Orange.

I see that PL4 and PL5 (Gnd) are on the same PCB trace. Should I connect:

Red = PL5
White = PL3
Black PL4
Orange PL6

Thanks,

Michael
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Old 20th August 2005, 06:31 PM   #539
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Quote:
Originally posted by maf_au
Ok, that's it from me, it's starting to come together. See pic.

Toroid cabling check question:

I have this toroid:

http://www.altronics.com.au/index.as...=item&id=M5525

On the My_Ref PCB, there are 4 connections:

PL3 Gnd
PL4 Gnd
PL5 24va1
PL6 24va2

The toroid secondaries are paired Red & Black, White & Orange.

I see that PL4 and PL5 (Gnd) are on the same PCB trace. Should I connect:

Red = PL5
White = PL3
Black PL4
Orange PL6

Thanks,

Michael
Michael, you are correct. Wire as you said.

That Toroid should work great.

Cheers!
Russ
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Old 20th August 2005, 06:37 PM   #540
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Hey Michael, thats shaping up to be a sweet little amp. I like it
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