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Old 23rd December 2008, 02:06 PM   #11
Tea-Bag is offline Tea-Bag  United States
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Quote:
Originally posted by jims
Great looking board, I am in for 4. One suggestion though: Can you space three of the transistors to match the spacing of one edge of Peter Daniels F4 board? I hate drilling, tapping and buying heat sinks, this way one could just drill and tap a couple of new holes, and swap the boards on the same heat sink/chassis that they use with their F4, which is also compatible with the spacing of Peter's new F5 board. Just an idea.


Thanks

JimS

Breaking taps and drill bits in heatsinks is kind of a DIY rite of passage.
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Old 23rd December 2008, 02:14 PM   #12
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Well I have passed at least the first stage of DIY audio. I can count at least 2x 4-40 and 1x 6-32 broken taps in just the last 4 heat sinks. I know this is off topic, but anyone have a good source for almost unbreakable taps for aluminum?

JimS
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Old 23rd December 2008, 03:05 PM   #13
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Quote:
Originally posted by jims
Great looking board, I am in for 4. One suggestion though: Can you space three of the transistors to match the spacing of one edge of Peter Daniels F4 board? .... Just an idea.

Thanks

JimS
Hi Jim,

Actually it's a very good idea, kind of a DiyAudio standard. I thought of doing just that. The one issue I have with Peter's boards is the mosfet spacing. This board generates a solid 100 watts and it's better to have the mosfets spread out over a wider area of the heat sink. Peter my make them this way to work with board restrictions in his CAD tool or to reduce board costs. Just a guess on my part.


Quote:
Originally posted by jims
I can count at least 2x 4-40 and 1x 6-32 broken taps in just the last 4 heat sinks.
JimS [/B]
I have a drill press in the garage for making the holes, along with a very good carbide tap set from my local hardware store. The drill press was a Delta 16'' from Amazon.com bought over a year ago for only $169 on sale. A drill press ensures the holes are straight and to a constant depth. Also use Cutting oil to lubricate the tap and help push out the cutting debris.

Getting the right feel or touch to not over wind the tap is also important. If the tap is turned farther than the hole, you wind up with an eruption or mound around the hole. This stretches the threads and creates additional stress on the tap and the aluminum.

Just some thoughts that have helped me make clean tapped holes.

-David
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Old 23rd December 2008, 03:13 PM   #14
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How many of Peter's PS boards will I need to complete stereo unit?
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Old 23rd December 2008, 03:18 PM   #15
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Quote:
Originally posted by vonfilm
How many of Peter's PS boards will I need to complete stereo unit?
Peter is not offering F1 boards. I'd ask Peter in his F3/4/5 GB threads if you are interested in those.

EDIT: I thought you were talking about the amp boards. I see now the question was regarding PSU boards. 1 Peter Daniel F3 PSU board will work for this F1 board for two channels.

-David
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Old 24th December 2008, 10:41 AM   #16
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Thanks David

What is the spacing of the FETs on your board? Maybe look at a multiple of Peter's spacing. I am away from my bench and can not measure the spacing of the transistors on Peter's board.

Is your tap solid carbide? Do you know the brand? Also do you tap through the heatsink between fins, or do you use a bottoming tap and try to place you FET directly behind a fin? I see possible advantages for heat dissipation for either method. What do you think? I have been using a through hole between fins and tapping using plug taps, purchased at HD and Lowes. Although I have had some problems, after buying a good tap wrench, using aluminum cutting oil, and taking my time, I am getting better at it- but it still takes forever.

Thanks

JimS
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Old 24th December 2008, 03:53 PM   #17
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Hi Jim,

Measured from the left side of the board to the middle pin of the mosfets, the distance in inches is:

Q1: .645
Q3: 2.2
Q7: 4.44
Q4: 6.68
Q2: 8.29

There is a small amount of latitude within the hole to shift the mosfets.

The carbide taps where purchased from OSH, a local hardware chain here in Northern California. I also bought the specific sized drill bits for the taps. It does take a little practice. I buy taps with a cross bar built into the top of the tap. It really helps in keeping consistent pressure without any lateral movement, since taps can be turned from the top like turning on a faucet. Practicing using a piece of aluminum scrap to get the technique down really helps. If the tap is breaking, then they are being over tightened or lateral pressure is being applied.

Regarding where to tap... there is no advantage to tapping over a fin, unless the base is thin and longer screws are required. Mosfets should be mounted fairly evenly across the heat sink and about half way up the height of the heat sink. The heat sink will have good convection flow of air through the fins if the mosfets are mounted near the middle vertically. Taking this approach with my amps, a person can hold their hand near the top of the heat sinks and feel a slight movement of air through the fins.

Merry Christmas and Happy Holidays,

-David
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Old 24th December 2008, 04:17 PM   #18
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Default Fins and bits

Dave,
Thanks for discussing this OT bit.

I use the easy to find IRWIN taps. I find as long as I use them by hand, I am okay. I wonder if there is a recommended tap brand to use other than Irwin.

Another thought on heatsinks. I have some large ones I plan on using for the F1. (12 X 12 X 4" fins). I am considering mounting them horizontally. (think a pizza box with fins) I dont think they'll be as effective in cooling, but actually may get them closer to 45-50c. With an F2 channel on them, I could only get them a little warm.

Mike
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Old 24th December 2008, 04:39 PM   #19
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Hi Mike,

NP on the OT, it's an important topic. Thanks for the recall, I'm using Irwin taps with the built in handle. I've cut tons of 4-40, 6-32 taps with them.

Also if heat sink fins are horizontal rather than vertical, the thermal efficiency is reduced about 10-15%. Just something to keep in mind for c/w calculations.

-David
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Old 24th December 2008, 05:11 PM   #20
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One thing to think about for those of you who are having trouble with broken taps is that "forming" taps are a little harder to break that cutting taps. They essentially re-flow the metal rather than cut out chips and are great for softer materials like aluminum. They just look like standard screw threads that have a little cam or lobe shape, without the cutting flutes of a standard tap

As always whit taps, be sure to drill the exact right size hole, which is different for a forming tap than a cutting one. Best to use number drills. And there is a specific lubricant made for tapping aluminum, although most any lubricant is a lot better than none.

In my experience carbide is a terrible material for taps, unless you are tapping abrasive materials like fiberglas. DW8083, are you sure they're carbide and not cobalt? Big difference. Murder to get a broken one out, too. With HSS taps you can just fill the hole with acid and wait for the tap to rust out.

--Buckapound
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