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Old 14th July 2005, 03:18 PM   #201
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Brian said:
Quote:
- The 3886s mount ever-so-slightly in from the edge of the board. I mounted my heatink so the bottom is flush with the bottom of the board, and needed to convince the pins they wanted to go into the holes in the board. Perhaps mounting flush with the top of the board would be better.
I don't have the parts in front of me. This is speculation. I think I want to mount the chips just a little higher on the sinks. I intend to use the sinks as part of the strucure of the enclosure & I want clearance below the PCB for this reason. After getting the parts I will look into sawing a shallow rebate across the sink to clear the PCB. This is a good point to consider for V.2

Brian said:
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- When soldering the 3886s, do one row of pins on each chip, then the second row. This give the chip a little time to cool down from the first row of soldering.
After the first pin is soldered the alignment of the chip should be checked and adjusted if required. Consider soldering the first 2 pins on opposite corners.
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Old 14th July 2005, 03:24 PM   #202
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Quote:
I will look into sawing a shallow rebate across the sink to clear the PCB.
This is a good idea. I will do this to mine tonight.

Another alternative, if you haven;t already mounted all the components, is to rip 1/32" off the edge of the board on a tablesaw.

For the drill guide, I will place some markings denoting "Flush with top of board", "flush with bottom of board". From there you can measure to obtain the desired position.

For those interested, and who know how they want it mounted, I could drill and tap 4-40 or 6-32 holes in the heatsink prior to shipping. Only takes me about 5 minutes per heatsink. The trick will be knowing where you want the holes before seeing everything.
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Old 14th July 2005, 03:32 PM   #203
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I will probably cut a 1/16" deep 3/32" slot in the heatsink to mount my PCB. I have done this in the past and it makes a very stable install. with no chance for stress on the chip pins.

The hight of the mounting holes is relative to the spacers/standoffs you are using. So you couldn't really create a "universal" template except for width.

One other option is to use a belt sander to eliminate the overhang.
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Old 14th July 2005, 06:20 PM   #204
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I could cut channels in the heatsinks as well if anyone is interested. I'll be running mine across the tablesaw tonight anyway.
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Old 14th July 2005, 06:24 PM   #205
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Brian I suppose then you would need to know how high the board will be on the heatsink. I mean you would need to know what height standoffs are being used if the heatsink is to be mounted directly to the bottom of the case.
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Old 14th July 2005, 06:27 PM   #206
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I have had 5 or 6 people email me about boards. I still have some, so its not too late to jump in.
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Old 14th July 2005, 06:27 PM   #207
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That is correct. Funny, I went with flush to the board because, while I want to go with 3/8" standoffs, someone keep outbidding me on them on EBay
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Old 14th July 2005, 06:33 PM   #208
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Incidently, the reason I recommend mounting the ICs to the heatsink before mounting them to the board...

I placed the ICs on the board (dry) and measured the height from board to mounting hole. Right around 20mm. I then used the 20mm height to mark the mounting hole locations on the heatsink (exactly 20mm).

If you solder the ICs in first, you will a) be very lucky to get both mounted at exactly the same height, and b) both heights will likely not be the one you drilled for.

By mounting first, you will be dead on.

[EDIT]: Also, by mounting to the heatsink first, you can seat them in the heatsink compond with a slight twisting motion to eliminate any air pockets and squish out extra compound.
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Old 14th July 2005, 06:45 PM   #209
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Excellent tip Brian!
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Old 15th July 2005, 06:22 AM   #210
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I'd just like to say that my PCB arrived today and it looks just wonderful. I couldn't see from the pictures, but I'm glad to see that all the connectors are well labeled, so that I don't have to figure out what everything is from the schematic then read it wrong and blow the thing up .

I'm getting antsy waiting for parts now...Don't rush yourself though Brian.
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