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Old 6th April 2005, 10:52 PM   #1511
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Thanks!

Ding-Ding, Round 2...

First cut, driver board.
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Old 6th April 2005, 11:15 PM   #1512
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Excellent job, you ought to be doing this professionally! Let me know when you order some and I'll Pay Pal some $$ to you for a dozen or so boards. Perhaps a group buy may be in order for this version too.

I think that if you just make a second smaller board for the driver stage that you'd be all done with it. I feel it would be best to keep them seperate from the output stage. There may be some that just don't have much space available on their air tunnels (the original KSA-50 or 100 didn't) to mount them. This would allow mounting the driver board in any convenient location near the output stage as Krell did with the KSA-80 driver board, or just attach the drivers to the chassis some place. This would also allow you to expand to a higher power version by also adding more driver boards to each bank of outputs as in the KSA-100.


Added after seeing driver board.....

Can you go back to the main board again and add two more V+/- pads in front of C-105,6, just extend the rails foil up to in front of those caps? This would allow for straight over jumping of the V+/- rails to the driver board. Its best to keep the pads lined up pad for pad a straight jump over from one to the other. Makes wiring alot easier, if this is possible. Also, need to have the backs of the devices right at the edge of the pcb so there is no pcb edge in the way when attaching it to a flat back sink. Multiple pads for V+/- are also a good idea to have there. This could actually end up being the rail tie points.
Mark
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Old 7th April 2005, 09:36 PM   #1513
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Mark, I saw your first post but missed the edit. Probably a good thing as I have had 24 hours to chill, and now I'm not going to cry!

Power pads, no problems. Is it worth sticking optional pads in for another set of rail caps?

As for the position of the transistors, I was thinking of bottom mounting them, then bending them parallel with the pcb. It just gives a bit more room to run power rails, y'know?
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Old 7th April 2005, 09:41 PM   #1514
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Al, how you can fit heatsink to this board ? Only by screwing with transistors ?
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Old 7th April 2005, 09:57 PM   #1515
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A picture is worth a thousand words

(and a big thanks has to go for tonight's stand-ins, making this picture possible, let's hear it for the MBR20200 twins!)
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Old 7th April 2005, 10:25 PM   #1516
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To Al : It's OK, but by my opinionis this heatsink is redundant for this application - power dissipation at drivers isn't so high.
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Old 7th April 2005, 10:31 PM   #1517
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Pavel

The guys that have built it say that the drivers run at about 65C with a normal T0220 type heatsink. Everyone is currently moving them off the main pcb and bolting them to the main one.

Mark

V10.2. Happy now?
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Old 7th April 2005, 10:46 PM   #1518
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What do you mean by " normal " heatsink for TO 220 ? If you mean typical " small " one, it will be thruth. But I was meaning some square metal sheet cca 2.5 mm thick. Think logical : if you will have output transistors with beta cca 50, you will need only 1 W for driwing ( for output 50 W ) and it is not so much.
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Old 7th April 2005, 10:57 PM   #1519
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You may be right, but I'm going by Mark's experience, he found these heatsinks too small. Aaron has also moved his drivers onto the main heatsink, and reports more stable results.
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Old 7th April 2005, 11:12 PM   #1520
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You know, all is relative - if you take in your arms pot with 50 C warm watter, you can't hold it, but all will be OK - semiconductors can work by much higher temperature, remember at some 3 GHz processor. Good night
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