pa1505@sdcc15.ucsd.edu (Barry Brown) (06/16/89)
I have a 20 meg hard drive whose only flaw is a shot 7406D surface-mount
chip. It seems that the only way to cheaply salvage this drive is to
desolder the chip and replace it myself. The PCB is four-layer (two on each
side). Besides telling me I'm stupid to try this (I already know that), can
anyone give me advice on how to do it? Pointers to a mail-order distributer
that stocks SMDs would be great, too.
Thanks in advance
Barry Brown
pa1505@sdcc15.ucsd.edu
-OR-
bebrown@ucsdphil@diablo.amd.com (Phil Ngai) (06/17/89)
In article <465@sdcc15.ucsd.edu> bebrown@ucsd (Barry Brown) writes: |I have a 20 meg hard drive whose only flaw is a shot 7406D surface-mount |chip. It seems that the only way to cheaply salvage this drive is to |desolder the chip and replace it myself. The PCB is four-layer (two on each Just get some sharp cutters and cut the legs off the device. Then you can unsolder each lead individually. Clean it off with solder wick and solder a new chip in. I'm assuming the device is a SO type of package (gull wing) and not a J-lead type. |side). Besides telling me I'm stupid to try this (I already know that), can |anyone give me advice on how to do it? Pointers to a mail-order distributer |that stocks SMDs would be great, too. Sorry, I don't know about this. Digi-Key has surface mount resistors and capacitors but doesn't seem to have many surface mount ICs. -- Phil Ngai, phil@diablo.amd.com {uunet,decwrl,ucbvax}!amdcad!phil "The government is not your mother."
mmm@cup.portal.com (Mark Robert Thorson) (06/18/89)
It may be easier to cut out the old chip, solder 14 little jumper wires to the pads, glue a 7406 in a standard DIP to the board (upside down, use Crazy glue), then solder the jumpers to the upraised pins of the DIP. Unless you have a soldering iron with a very fine tip, you may have trouble making the connections to the pads on the board. What I do in this situation is to get out my old soldering GUN, wrap about 4 or 5 turns of heavy copper wire around the tip, then bend the end of the wire forward to form a tiny tip. The tiny tip should be no more than about 1/2 inch from the regular tip of the gun, because otherwise you lose too much heat to melt solder.
larry@kitty.UUCP (Larry Lippman) (06/18/89)
In article <19590@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes: > [Discussion about replacing SMD deleted] > ... > Unless you have a soldering iron with a very fine tip, you may have trouble > making the connections to the pads on the board. What I do in this situation > is to get out my old soldering GUN, wrap about 4 or 5 turns of heavy copper > wire around the tip, then bend the end of the wire forward to form a tiny > tip. The tiny tip should be no more than about 1/2 inch from the regular > tip of the gun, because otherwise you lose too much heat to melt solder. I'm impressed. You must have both an awfully steady and strong hand in order to position a couple-pound soldering gun (even with a "fine tip") well enough to solder wire to SMD pads! On a more serious note, I would be rather concerned about stray leakage currents from the soldering iron destroying CMOS circuits, since I don't know of any soldering gun which has grounded elements. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"
wiz@xroads.UUCP (Mike Carter) (06/27/89)
In article <3243@kitty.UUCP>, larry@kitty.UUCP (Larry Lippman) writes: > In article <19590@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes: > > [Discussion about replacing SMD deleted] [[ DIscussion about bravery with an iron deleted ]] > On a more serious note, I would be rather concerned about stray > leakage currents from the soldering iron destroying CMOS circuits, since > I don't know of any soldering gun which has grounded elements. > > <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. I have heared a lot of folks say this in the past about working with CMOS and some saying the same thing about TTL...(although they were taken with a tablespoon of salt too..) The only problems I have ever encountered with CMOS are: (1) Don't discharge your 6.5 foot TESLA coil near a CMOS circuit (2) Dont scrape your feet over a 70% nylon carpet and touch a CMOS circuit Other than that, I've desoldered and resoldered miles upon miles of jumperwire, broken traces, component leads on CMOS boards and not once have had any other I.C's die because I worked on the board without a grounding strap. My bench top is grounded....but I.C's dying from AC eddy's from my iron..NO. In fact..if this had any merit to it, all of the major and all of the minor manufacturers and repair shops would be using other means to solder CMOS I.C's into pcb's. SMT chips may be physically smaller in size, but the chips (the working guts within) rarely change in physical size. Just the packaging... The only extra care needed with SMT is the LENGTH of time the iron sticks around...they are more susceptable to heat dammage. .....that and the uncanny ability for the SMT's to jump right out of your hands and find the most conjested waste basket with the deepest and ugliest content array. Of course I'm gonna get flamed by the purveyors of scientific research and the 500 watt soldering iron crowd....(sigh) -- ============================================================================= = Mike Carter N7GYX, Phoenix AZ| Q: Why did the Chicken cross the road ? = = hplabs!hp-sdd!crash!xroads!wiz| A: To ESCape the Main Menu . = =============================================================================