RE: RE: Pac repair

Pretty much exactly what I do with the little pump, but I heat from the chip
side, and suck from the solder side with the board between the knees (don't
wear shorts). Three minuits from decidion to swap the chip (16 pin), to
testing with the new chip in a socket. The problem with the RS red bulb
iron, is the the chip is not clean enough to stuff back in the socket if it
is really not the culprit. With practice this may improve, however.

Mike

> -----Original Message-----
> From: John Robertson [SMTP:jrr@flippers.com]
> Sent: Tuesday, December 12, 2000 4:38 PM
> To: rasterlist@synthcom.com
> Subject: Re: RASTER: RE: Pac repair
>
> I too have settled on the silver Soldapulit as my desoldering tool of
> choice. This one is anti-static as well as a good sucker! I find that I
> can
> be heating one leg, while pumping up the Solda with the other, then by the
>
> time the solder is molten I can place the Solda in place (about 1/8 inch
> to
> the side on the board and canted away from the solder point) then suck,
> now
> move the tip to the next junction and at the same time pump up the Solda.
> Hold up to a light to make sure all the solder is removed at the end.
>
> You can get a nice rhythm going.
>
> You must be careful NOT to let the Solda strike the tip of the soldering
> iron, as this will damage the PCB trace. The tool bounces when activated
> and you must make sure this bounce doesn't let the tool's tip strike the
> hot trace or soldering tip touch point.
>
> After the solder is sucked, I then use a thin screwdriver blade to push
> the
> joint of the pointy end of the leg and feedthrough hole to the opposite
> side of the feedthrough hole on the bottom of the board, and then press
> the
> leg into the chip from the top side of the board at the junction of the
> leg
> and the top of the feedthrough hole. This will normally release the IC and
>
> I can then pull it out with my fingers (NEVER force out with a
> screwdriver!!!). If the IC is still stuck use a pair of expanding jaw
> pliers and grab the ends of the IC, and gently rotate it a smidgen back
> and
> forth to find the stuck leg. Note this rotation is parallel to the face of
>
> the PCB NOT up/down from the board!
>
> I find I can pull a 40 pin IC in about one minute or so from start to
> finish.
>
> John :-#)#
>
> At 02:01 AM 12/14/00, Ranger Mike wrote:
> >Well...
> > A note on desoldering. For years I have used the little solder
> pump
> >in conjunction with my soldering iron with much success. I tried out
> thew
> >big blue soldaput pump here at work the other day, and it does a much
> >cleaner job. I also, recently picked up one of the radio shack red bulb
> >desoldering irons. I have found that the little pump works well for me,
> but
> >is more cumbersome to use. If the chip in question is not bad, it is
> clean
> >enought to stuff back in the socket. The RS red thingy, is way easier to
> >use, but it does not have enough suction to clean the chip up well. The
> big
> >blue, seems to me to be the best of three, while more cumbersome, cleans
> up
> >the chip the best for re-use, should my trouble shooting technique fail
> me
> >and I pull a good chip. I would really like to get a profesional
> desoldering
> >system, but I'm to cheap :-)
> >
> >That's all for now
> >
> >Mike
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: mike_ranger@dofasco.ca [SMTP:mike_ranger@dofasco.ca]
> > > Sent: Monday, December 11, 2000 9:47 AM
> > > To: rasterlist@synthcom.com; TechToolsList@flippers.com
> > > Cc: Paul.Tonizzo@sybase.com
> > > Subject: Pac repair using a chip comparitor
> > >
> > > Hi all
> > > I was working in the shop last night on a pac that has been
> giving
> > > me fits. I tried the "staring at it for hours" approach first, but
> that
> > > did
> > > nothing to fix it :-0
> > >
> > > Weird symptoms. With a standard set up, I was getting a screen
> full
> > > of slashes and zeros, flipping every now and again. I replaced the
> vram
> > > with one of Clay's most excellent products, and the board now went
> through
> > > self test over and over. up to, but not including the cross hatch.
> Self
> > > test showed nothing. Removing the two middle roms changed nothing as
> > > well.
> > > (that was a clue). I tried a special daughter card I have that runs
> MS
> > > pac
> > > with no roms on row 6. booted to currupt screen images, so I felt
> there
> > > was
> > > a problem in adressing the roms, or ram.
> > >
> > > Last night, on a whim, I decided to try out my new HP 10592
> logic
> > > comparitor. I set it up to check 8k becuase I noticed the IRQ was not
> > > firing. The comparitor said it was fine. Since it was my first crack
> at
> > > using the tool, I was not convinced. Going back to the adressing
> issue, I
> > > decided to check the ROM selct lines, by 7N chip, 74ls42. The
> comparitor
> > > showed 3 bad outputs on this. Swapped it and the board came to life.
> > > Even
> > > works with the original vram, so the bad chip could have been messing
> with
> > > the RD signal. No sound yet, but I'll get that working :-)
> > >
> > > On the Logic comparitor. The HP is a nice little unit, but you
> must
> > > get one with the zif card. This was an add on produced in later runs.
> It
> > > allows you to configure your chip with dip switches, where the
> original
> > > unit
> > > shipped with cards you had to phsically alter to match the chip
> > > characteristics.
> > >
> > > Others in the comunity feel he BUGTRAP device is a better
> > > comparitor, but I have no experience with it, so if you are looking
> for
> > > one,
> > > you should investigate those as well.
> > >
> > > The logic comparitor will be pretty much useless on any
> tri-stated
> > > device. It will not make a newbie a guru, and like any test
> equipment,
> > > you
> > > have to understand the it's limitations to use it effectively.
> > >
> > > Too bad I go sniped on that fluke model 90 z-80 thingy last
> friday
> > > :-( Gusee I'm going to have to save up for one of them nifty 9010A's
> > >
> > > Mike
> > >
> > > To UNSUBSCRIBE from techtoolslist, send a message with "UNSUBSCRIBE"
> in
> > > the
> > > message body to: techtoolslist-request@flippers.com. Please direct
> other
> > > questions, comments, or problems to jrr@flippers.com.
> >-------------------------------------------------------------------------
> --
> >** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in
> the
> >** message body to rasterlist-request@synthcom.com. Please direct other
> >** questions, comments, or problems to neil@synthcom.com.
>
> --------------------------------------------------------------------------
> -
> ** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in
> the
> ** message body to rasterlist-request@synthcom.com. Please direct other
> ** questions, comments, or problems to neil@synthcom.com.
---------------------------------------------------------------------------
** To UNSUBSCRIBE from rasterlist, send a message with "UNSUBSCRIBE" in the
** message body to rasterlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Wed Dec 13 10:32:04 2000