>Date: Fri, 1 Nov 2002 10:00:42 -0800 >From: Gamba <[EMAIL PROTECTED]> > ><http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html#NoPointer> >There's a schematic for network shown there, as well as a Bourns >replacement part number and a link for the Bourns' data sheet. > >Should be makeable because the 20 pin DIP socket allows a lot of space. >A homemade circuit board with surface mount parts sounds interesting.
I whipped up a little design in Osmond PCB using 0805 size resistors and capacitors. It might make more sense to use a pair of eight resistor networks such as DK part # 4816P-1-270-ND. It might also make sense to use something besides 0805 size, because you can't fit two of them across the width of the thing, so the parts must be offset some and that makes it messy. The design is at http://www.io.com/~trag and look for files Discrete_00 and Discrete_01. The only difference between them is that the latter has an outline of .028 holes on a .035 grid surrounding it. So if you wanted to do a step and repeat with it at one of the commercial shops, you could then break/cut the boards yourself, rather than paying them. They usually charge a lot for many tiny boards as opposed to one big board with lots of holes. The problem is, I can't figure out a convenient way to copy and paste the design in about three bazillion times. The traces don't go with the copies. I used .035" holes for the pins but I'm not sure what metal to use for pins. Standard 0.100" header strips are too thick I think. They're 0.025" square and the pins on the original RC network DIP are only 0.019" wide. Advanced Circuits https://www.4pcb.com/33each.asp has a $33/board special but there's a minimum of 3 so it's basically $100 plus shipping and $10 handling. Maximum board size is 10" X 15" but it says there's an extra charge for step and repeats, so I don't know if they'd charge extra if one laid out the repeats onself, or if that's only if they have to do the step and repeat for you. You could get about a million of this board in 10" X 15". Alberta Printed Circuits http://www.apcircuits.com has an inexpensive Proto service. It's not as nice, as you don't get solder mask and silk screen and minimum trace is 8 or 10 mils, I can't remember which. But they're pretty cheap for their proto service. The board is 1.100" X 0.400". Will that fit in the space in the SE? Digi-Key doesn't list 200 pf SM caps, just the 220 pf and the difference shouldn't matter, given that the original part has a 30% tolerance on the caps. There are several of them. For 50V rating one Part number is PCC221CGCT-ND and price is $.62/10 or $4.17/100. For 100V rating another is PCC1981CT-ND and the price is $1.62/10 or $11.40/100. There also don't appear to be 25 ohm surface mount resistors. There are 24 ohm and 27 ohm resistors. Again, the original part has a 10% tolerance, so it shouldn't matter too much if one uses a 24 ohm 5% part here. I think P24ACT-ND is the part number, with pricing being $.80/10, $2.15/50, $4.93/200 or $17.20/4000. Osmond PCB is available at: http://www.swcp.com/~jchavez . It's a nice little PCB tool for the Mac. Feel free to use the designs above in any way you wish. Jeff Walther -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> The FAQ: <http://macfaq.org/> --> AOL users, remove "mailto:"; Send list messages to: <mailto:compact.macs@;mail.maclaunch.com> To unsubscribe, email: <mailto:compact.macs-off@;mail.maclaunch.com> For digest mode, email: <mailto:compact.macs-digest@;mail.maclaunch.com> Subscription questions: <mailto:listmom@;lemlists.com> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
