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Old 29th December 2008, 03:23 AM   #1001
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If you find any other errors like this let me know. I will contact Joel at Advanced Circuits in the morning and mention this to him. This entire order was not cheap. The last batch of boards was a reorder from the original files. Everything should have been identical. I will let you know if we are due some compenstion. I have both boards on the desk in front of me and they are definately plated on the latest batch. If you look closely you can see that the bores are also plated. Make test with the DMM after mounting to be sure nothing contacts the sink after grinding. Good watching out guys.

I always wondered if the SMD board might be a better choice here because the lower mass would respond quicker to temperature fluctuations. Any thoughts on this?

Tad
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Old 29th December 2008, 05:58 AM   #1002
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Quote:
Originally posted by BobEllis
The first batch of boards did not have pads on the bottom of the diode boards. It sounds like a manufacturing error since Tad just reordered - the first I've heard of from Advanced. Maybe they'll give us a break on the next buy.

I'll grind the pads off with a Dremel. If you have a sheet of mica or some Kapton tape, you can just insulate them.
The Pads are not in the gerberfiles.... but there should be a thermal pad between the diodePCB and heatsink anyway..... just be carefull to remove solder on the bottom side when you mount/solder the diodes. Failing to do this will give too high thermal resistance for the diodes to track the heatsink temperature.

\\\Jens
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Old 29th December 2008, 05:59 AM   #1003
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Quote:
Originally posted by tryonziess
If you find any other errors like this let me know. I will contact Joel at Advanced Circuits in the morning and mention this to him. This entire order was not cheap. The last batch of boards was a reorder from the original files. Everything should have been identical. I will let you know if we are due some compenstion. I have both boards on the desk in front of me and they are definately plated on the latest batch. If you look closely you can see that the bores are also plated. Make test with the DMM after mounting to be sure nothing contacts the sink after grinding. Good watching out guys.

I always wondered if the SMD board might be a better choice here because the lower mass would respond quicker to temperature fluctuations. Any thoughts on this?

Tad
The SMD version is easy to try... I say go for it....

\\\Jens
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Old 29th December 2008, 08:13 AM   #1004
AndrewT is offline AndrewT  Scotland
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I lay the diode side in contact with the heatsink backplate.
With the SMD version I lay a strip of self adhesive tape on the sink and then the SMDs on top of this.
Use thermal compound to transfer heat as quickly as possible.

When do we adopt the Thermal Track ONsemis to this layout?
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Old 29th December 2008, 02:45 PM   #1005
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Quote:
Originally posted by AndrewT
I lay the diode side in contact with the heatsink backplate.
With the SMD version I lay a strip of self adhesive tape on the sink and then the SMDs on top of this.
Use thermal compound to transfer heat as quickly as possible.
Andrew, If you do this, you must also change the connection to the "mainboard" or reverse the diodes on the PCB - right??....

This is important stuff! I recommend to do it the way that I intended the board to be used.

Quote:
Originally posted by AndrewT
When do we adopt the Thermal Track ONsemis to this layout?
Well "we" (I) already have a layout started.... I just never made it a group project....

\\\Jens
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Old 29th December 2008, 03:01 PM   #1006
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by JensRasmussen
If you do this, you must also change the connection to the "mainboard" or reverse the diodes on the PCB -
or connect the little PCB with a twisted pair so that it can be located very close to the output devices.
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Old 29th December 2008, 03:03 PM   #1007
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Quote:
Originally posted by AndrewT
or connect the little PCB with a twisted pair so that it can be located very close to the output devices.
That would work.... I'm just not much for wires.....

My point is that you should give the full details of your - improvements - so as not to confuse the rest of us.

\\\Jens
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Old 30th December 2008, 07:23 AM   #1008
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The diode board should be screwed to the heat sink via the access holes in the main board the way I see the original plan. the diodes are facing the main board. Tape is between the heat sink and the diode board. correct?
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Old 30th December 2008, 09:55 AM   #1009
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You've got it, BP
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Old 30th December 2008, 01:19 PM   #1010
rob3262 is offline rob3262  United States
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Quote:
Originally posted by JensRasmussen
.... but there should be a thermal pad between the diodePCB and heatsink anyway..... just be carefull to remove solder on the bottom side when you mount/solder the diodes. Failing to do this will give too high thermal resistance for the diodes to track the heatsink temperature.
\\\Jens

Quote:
Originally posted by AndrewT
I lay the diode side in contact with the heatsink backplate.
With the SMD version I lay a strip of self adhesive tape on the sink and then the SMDs on top of this.
Use thermal compound to transfer heat as quickly as possible.
I wasn't aware that a thermal pad was going to be used for the diode PCB. I like Andrew's idea of tape and SMD, I bought surface mounts to try both pcb versions.

The though occurred to me... why not just solder 1N4007's to the
bottom of the PCB per the screening, add a dab of compound and mount the pcb with these diodes in direct contact to the heatsink. No reversed leads or anything funny, and no thermal resistance.
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