8 Nov
2006
8 Nov
'06
7:42 p.m.
I'll have to look. But, I don't think this board has sockets.
I believe it has 4 banks of soldered in 64k chips.
Thanks!
And if you re-read my message. The RAM board is UNPOPULATED. It has NO
CHIPS.
I was going to scavenge some from somewhere...
Al
Date: Wed, 8 Nov 2006 14:55:28 -0600
From: "Julian Wolfe" <fireflyst at earthlink.net>
Subject: RE: Need Docs for XT RAM Board...
To: "'General Discussion: On-Topic and Off-Topic Posts'"
<cctalk at classiccmp.org>
Message-ID: <001501c70378$38e29240$3c0718ac at CLCILLINOIS.EDU>
Content-Type: text/plain; charset="us-ascii"
What's your XT got in it now? Most non-IBM boards you could populate to 640K
anyway so there was no point in those cards. If it's got 41256 chips on it,
pull them from the card and install them in the motherboard banks, and then
set the switches properly on your XT motherboard and you should be OK.
I have an IBM XT motherboard in my 5155, so I went ahead and did the 640K
upgrade and put the chips in. It freed up a slot on my machine, so I
installed an AST RAMpage/2 in it. It's now got 2625KB of usable RAM
(Windows 3.0 loves it!)
I've done a bunch of work collecting utilities that will correct certain
issues with old hardware or enhance certain capabilities (like get rid of
snow and speed up scrolling on CGA and EGA cards, and stabilize/speedup NEC
v20 chips) Let me know if you need my help.
Julian
9 Nov
9 Nov
3 p.m.
I'll have to look. But, I don't think this board has sockets.
I believe it has 4 banks of soldered in 64k chips.
If this is a real IBM XT mainboard (with 8 slots and no cassette port),
that would be most unusual (note that the modification I described only
applies to real IBN XT mainboards).
But if that is the case, I'd just grab a solder sucker and desolder banks
0 and 1 and fit turned-pin sockets in place of them.
-tony
4:58 p.m.
But if that is the case, I'd just grab a solder
sucker and desolder banks
0 and 1 and fit turned-pin sockets in place of them.
-tony
It occurred to whilst perched atop a big fat rock
that placing a circuit board in shallow tray of cool
water, component side down would probably eliminate
the possibility of smoking a chip while desoldering,
with a wick or whatever. Sound reasonable?
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6:25 p.m.
On 9 Nov 2006 at 16:58, Chris M wrote:
It occurred to whilst perched atop a big fat rock
that placing a circuit board in shallow tray of cool
water, component side down would probably eliminate
the possibility of smoking a chip while desoldering,
with a wick or whatever. Sound reasonable?
Completely unnecessary. Use a good soldering iron (temperature
controlled) and a sucker, such as a Soldapullt Sometimes adding a
bit of solder to a joint while heating helps conduct heat a bit
better.
If you've got access to a good desolering station, even better.
Cheers,
Chuck
10 Nov
10 Nov
4:40 p.m.
But if that is the case, I'd just grab a
solder
sucker and desolder banks
0 and 1 and fit turned-pin sockets in place of them.
-tony
It occurred to whilst perched atop a big fat rock
that placing a circuit board in shallow tray of cool
water, component side down would probably eliminate
the possibility of smoking a chip while desoldering,
with a wick or whatever. Sound reasonable? from the PCB.
-tony
15 Nov
15 Nov
12:22 a.m.
Tony Duell wrote:
In any case, you should be more worried about damaging
the PCB (for
example the through-hole plating) than the chips. 64K DRAMs are not hard
to get, after all. In fact, if I wasn't sure of my abilities to desolder
the ICs, I'd cut the pins off them and then desolder them one at time
from the PCB.
Been there, done that, repaired the resulting mess with blue wire. Not
nice.
A really hot temperature-controlled iron is the way to go. Either that
or as you say, snip the chip and pick the pins out one at a time.
I'm dreading removing the 30-pin thick film module that's wedged tightly
between other thick-film modules in one of my synthesizers.
Gordon.
3:36 p.m.
A really hot temperature-controlled iron is the way to
go. Either that
or as you say, snip the chip and pick the pins out one at a time.
Even if you decide to do it a pin-at-a-time, a good iron helps a lot. I
once tried to clear a hole in a PCB using a cheap hobbyist-grade
soldering iron (using the standard method of applying the iron to one
side of the PCB and the solder sucker to the other), and it simply
couldn't provide enough heat to melt the solder. I ended up grabbing my
temperature-controlled iron and had no problems.
I'm dreading removing the 30-pin thick film module that's wedged tightly
between other thick-film modules in one of my synthesizers.
The quality of the PCB makes a big difference. I've had PCBs from
cheap-n-nasty consumer electroncs that shed tracks if you look at them,
conversely I've had PCBs from high-end test gear that will stand just
about anything without problems.
-tony
16 Nov
16 Nov
1:36 p.m.
Tony Duell wrote:
Can't always snip the pins. Generally speaking,
desoldering a chip isn't necessarily catastrophic, but
what if it's old and irreplaceable? And you don't have
access to all that high tech stuph. It just seems to
me that if you flood the chip with cool water, you'll
probably totally eliminate the possibility of smoking
it. Somethings just can't be replaced you know...
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In any case, you should be more worried about
damaging the PCB (for
example the through-hole plating) than the chips.
64K DRAMs are not hard
to get, after all. In fact, if I wasn't sure
of my
abilities to desolder
the ICs, I'd cut the pins off them and then
desolder them one at time
> from the PCB.
2:02 p.m.
On 16 Nov 2006 at 13:36, Chris M wrote:
Can't always snip the pins. Generally speaking,
desoldering a chip isn't necessarily catastrophic, but
what if it's old and irreplaceable?
...then one would assume that your goal was to salvage the chip
rather than the board. In that case, I'd simply cut the board around
the chip then desolder the chip from the board remnants.
Priorities, priorities. Either you want to save the chip or the
board.
But if you're replacing a chip, who cares what happens to the old
one? In severe cases, I've taken a dremel to the chip leads and
simply cut the IC body away for easy access.
Cheers,
Chuck
2:34 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 16 Nov 2006 at 13:36, Chris M wrote:
judiciously. No problemo.
Can't always snip the pins. Generally
speaking,
desoldering a chip isn't necessarily catastrophic,
but
what if it's old and irreplaceable?
...then one would assume that your goal was to
salvage the chip , and soldered it to the pin rather than the board. In that case, I'd simply
cut
the board around
the chip then desolder the chip from the board
remnants.
Priorities, priorities. Either you want to save the
chip or the
board.
Possibly both. What if both were important? And I
have freed a trace or two from a circuit board due to
overheating, and soldered it to the pin judiciously.
No problemo.
I remember a guy who desoldered EVERY chip from his
C64 (?), soldered in sockets, then pressed the chips
back in. Granted though this was at an electronic
facility, with all the proper gear.
But if you're replacing a chip, who cares what
happens to the old
one? In severe cases, I've taken a dremel to the
chip leads and
simply cut the IC body away for easy access.
The tender mercies of the wicked are cruel LOL LOL LOL
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3:14 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 16 Nov 2006 at 14:34, Chris M wrote:
Not necessarily. What if you had 2 funky boards, and
wanted to swap parts between the 2. Aha, gotcha don't
I? ;p
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Possibly both. What if both were important?
Then you wouldn't be trying to separate them, would
you? :)
3:58 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 16 Nov 2006 at 15:14, Chris M wrote:
Probably. But I would have to say the vast majority
of us have resorted to swapping components. You can
make educated guesses, but in the absence of test
equipment, what other "methodology" is possible?
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Not necessarily. What if you had 2 funky boards,
and
wanted to swap parts between the 2. Aha, gotcha
don't
I? ;p
...then I'd say that your powers of diagnosis
requied some honing. :)
4:30 p.m.
On 16 Nov 2006 at 15:58, Chris M wrote:
Probably. But I would have to say the vast majority
of us have resorted to swapping components. You can
make educated guesses, but in the absence of test
equipment, what other "methodology" is possible?
Just so--what's to prevent you from aquiring a used 'scope and
learning how to use it? I'm still using an old Tek 465 that I've had
for a long time that does most of what I need in a piece of test
equipment. I've also got a logic analyzer, but it rarely sees the
light of day.
There is a certain level of tooling required for most fields. I
suppose you could work on your car with nothing more than a pair of
gas pliers and a hammer, but doing things right requires the right
tools.
Cheers,
Chuck
4:41 p.m.
OK, one more situation where you need to remove a chip,
and do not want to destroy either the chip nor the PCB:
Had an IBM MDP board that had intermittent screen data corruption when
scrolling. On close examination, found that it had originally been
assembled with one pin of one chip bent under, instead of through the
board and soldered. Desoldering the chip, and resoldering it with ALL of
the pins properly connected fixed it.
4:44 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
Just so--what's to prevent you from aquiring a
used
'scope and
learning how to use it? I'm still using an old Tek
465 that I've had
for a long time that does most of what I need in a
piece of test
equipment. I've also got a logic analyzer, but it
rarely sees the
light of day.
There is a certain level of tooling required for
most fields. I
suppose you could work on your car with nothing more
than a pair of
gas pliers and a hammer, but doing things right
requires the right
tools.
Absolutely nothing. Except finding the time and
desire. And I wouldn't need to learn how to use it,
though a brushing up would be in order. Still, my
instincts would be to try a li'l chip swapping rather
then get all hot-and-bothered by a thorough diagnosis.
Besides, as the gnattering off-list respondent has
said, I'm not really all that bright, so a proper
piece of test equipment probably wouldn't do a whole
lot of good :<
I want one of those color HP DSOs I used for a bit in
the late 80's. They were $30Gs back then I think.
Anyone have a clue as to the model #?
Yet I can only wonder what *could* be used to scope
out problems on the uP systems of today. You need at
the very least 2x the sampling rate to effectively
analyze a waveform. I cannot image what an 8ghz scope
would go for.
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5:06 p.m.
On 16 Nov 2006 at 16:44, Chris M wrote:
Yet I can only wonder what *could* be used to scope
out problems on the uP systems of today. You need at
the very least 2x the sampling rate to effectively
analyze a waveform. I cannot image what an 8ghz scope
would go for.
An even better question might be "where is the tradeoff between
simply tossing a non-functional modern uP board and replacing it and
actually trying to repair one?"
Heaven knows, there's probably a whole landfill full of 90's PeeCee
mobos that died from the Chinese Capacitor Disease. One might even
know that a given board died of said ailment. Where's the gain in
repairing one?
On the other hand, if this is a piece of specialized equipment that
simply uses a uP, that's a different matter.
Cheers,
Chuck
5:15 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On the other hand, if this is a piece of specialized
equipment that
simply uses a uP, that's a different matter.
Right. The essence of the question was has the
technology to diagnose kept up with the speeds these
things are capable of. I would have to imagine yes,
but the cost for a piece of "capable" test equipment
for today's electronics has to cost a whole lot more
then it did back when.
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4:18 p.m.
> Not necessarily. What if you had 2 funky boards,
and
> wanted to swap parts between the 2. Aha, gotcha don't
> I? ;p
On Thu, 16 Nov 2006, Chuck Guzis wrote:
...then I'd say that your powers of diagnosis
requied some honing. :)
Howzbout: wanting to insert a sandwich board in between the PCB and the
chip. Such as a Percom Data Separator with a soldered in WD1771,
or a Percom doubler
4:32 p.m.
On 16 Nov 2006 at 16:18, Fred Cisin wrote:
Howzbout: wanting to insert a sandwich board in
between the PCB and the
chip. Such as a Percom Data Separator with a soldered in WD1771,
or a Percom doubler
I think it's a matter of priorities again, Fred. If the board was
the more valuable, I'd scour the face of the earth for another 1771
and destroy the one on the board, rather than destroy the board.
3:47 p.m.
On 16 Nov 2006 at 14:34, Chris M wrote:
You might, if you needed to remove the chip for testing (either to test
the chip, or to be able to force signals that it drove on the board so as
to test other bits of the machine). Or if you wanted to read out the
program from said chip (maybe it's a PAL or a microcontroller, or something).
Yes, you can separate ICs and PCBs without damaging either. I do it all
the time. My original comment was that in the case of removing 64K DRAMs
(very common chips) from a PC/ST motherboard, it was worth sacrificing
the chip if you weren't sure of your abilities to remvoe it in one piece
without damaging the board.
-tony
Possibly both. What if both were important?
Then you wouldn't be trying to separate them, would you? :) 
17 Nov
17 Nov
6:12 a.m.
On 11/17/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Or have a use for the chip, but value the board as well (especially in
the case of being able to restore it to full functionality later).
On 16 Nov 2006
at 14:34, Chris M wrote:
You might, if you needed to remove the chip for testing (either to test
the chip, or to be able to force signals that it drove on the board so as
to test other bits of the machine). Or if you wanted to read out the
program from said chip (maybe it's a PAL or a microcontroller, or something). Possibly both. What if both were important?
Then you wouldn't be trying to separate them, would you? :) Yes, you can separate ICs and PCBs without damaging
either. I do it all
the time.
Me, too. The most recent example I can think of is removing an
INS6120 12-bit CPU from a DECmate III board and sticking the chip into
an SBC6120. I needed the chip right away, but I wanted to replace the
soldered 40-pin DIP CPU with a machined-pin socket for the day when I
wanted/needed to run that board in a DECmate chassis.
The entire board cost me $50, what a bare CPU would have cost, but I
wanted to retain two working parts, not just one. For those keeping
score at home, the board is a 4-layer board with internal power/gnd
pins that do _not_ want to let go of a DIP CPU. 38 pins were easy...
the power and ground pins were not. In the end, I managed to end up
with an intact CPU *and* an intact board, but unless you have
pro-grade tools, you'll find it difficult to replicate this effort.
-ethan
6:37 a.m.
Me, too. The most recent example I can think of is
removing an
INS6120 12-bit CPU from a DECmate III board and sticking the chip into
an SBC6120. I needed the chip right away, but I wanted to replace the
soldered 40-pin DIP CPU with a machined-pin socket for the day when I
wanted/needed to run that board in a DECmate chassis.
Be careful when pulling chips - you just can not do this willy nilly
and expect nothing to happen. Everytime a chip goes thru a heat cycle
like soldering (or unsoldering) you damage the chip. There is no way
around this. Even the first cycle, when the chip leaves the tube (or
tape) for the first time, to be stuck to the board, the chip takes a
beating internally. Obviously the manufacturers make the chips to get
thru this first heat, but generally not any (or many) other cycles.
In the real world, a tech that unsolders chips and reuses them tends
to be shown the door quickly by the QC guys.
--
Will
10:29 a.m.
--- William Donzelli <wdonzelli at gmail.com> wrote:
Be careful when pulling chips - you just can not do
this willy nilly
and expect nothing to happen. Everytime a chip goes
thru a heat cycle
like soldering (or unsoldering) you damage the chip.
There is no way
around this. Even the first cycle, when the chip
leaves the tube (or
tape) for the first time, to be stuck to the board,
the chip takes a
beating internally. Obviously the manufacturers make
the chips to get
thru this first heat, but generally not any (or
many) other cycles.
In the real world, a tech that unsolders chips and
reuses them tends
to be shown the door quickly by the QC guys.
so if you presumably (probably? possibly?) eliminate
any heat getting to the ic's innards by the method I
described, you're likely doing no damage to it?
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11:06 a.m.
On 17 Nov 2006 at 10:29, Chris M wrote:
so if you presumably (probably? possibly?) eliminate
any heat getting to the ic's innards by the method I
described, you're likely doing no damage to it?
I'm not sure about this, but it would seem that using water to cool
the body of an IC while needing to apply more heat to the pin to melt
the solder would make for a steeper temperature gradient through the
packaging. Could this in fact be counter-productive by increasing
stresses on the encapsulation?
I really don't worry too much about overheating a chip by desoldering
it. Consider that what destroys a chip thermally during operation is
localized overheating within the die itself. Using a temperature-
controlled iron would seem to elminate most overheating problems.
As another example, consider the use of ovens for mounting SMT
devices. No water there--and the small, low thermal-mass SMT
devices seem to survive just fine.
Cheers,
Chuck
1:12 p.m.
I'm not sure about this, but it would seem that
using water to cool
the body of an IC while needing to apply more heat to the pin to melt
the solder would make for a steeper temperature gradient through the
packaging. Could this in fact be counter-productive by increasing
stresses on the encapsulation?
I really don't worry too much about overheating a chip by desoldering
it. Consider that what destroys a chip thermally during operation is
localized overheating within the die itself. Using a temperature-
controlled iron would seem to elminate most overheating problems.
Soldering cycles cause latent failures - parts of the chip that still
work, but are much weaker. A typical type of latent failure is a
microscopic crack caused by a thermal shock. As long as the crack is
closed, the electrons will probably not worry too much about jumping
it, much like two wires touching. However, the problems of microscopic
cracks in a semiconductor die make for a weak spot that perhaps can
not handle another solder cycle or current surge.
--
Will
12:46 p.m.
so if you presumably (probably? possibly?) eliminate
any heat getting to the ic's innards by the method I
described, you're likely doing no damage to it?
The better option is to heat the chip up reasonably slowly - when I
strip a chip from a board (I use a solder pot), I will just warm the
part in question up a bit. When the solder pot hits the pins, the
internal structures of the chip will not get a big jolt. This is quite
similar to how the big pick and place solder machines work on a
factory floor.
Of course the thing to do is to not need to use a pulled part in the
first place, but sometimes that is not really an option with rare
chips. Just keep in mind that a solder pulled chip is a weaker device
than one factory new, and that latent failures lie within.
--
Will
4:51 p.m.
Of course the thing to do is to not need to use a
pulled part in the
first place, but sometimes that is not really an option with rare
chips. Just keep in mind that a solder pulled chip is a weaker device
than one factory new, and that latent failures lie within.
While heating a chip (e.g. by soldering/desoldering it) will weaken it, I
am not sure the effect is particularly noticeable. I've not noticed that
the chips I've desolderd/resoldered are especially likely to fail (e.g.
if I've removed a few chips from a board for testing, then resoldered
them, future failures on that board may well not involve any of those
chips). I've done it with SMD stuff too -- the manufacturers tell you not
to, but I have never had any problems from so soing. If I was making
stuff where a failure could cause significant loss or injury then I'd
bahave rather differently of course.
And given the choice between a backup of the program in a chip (e.g. on
my PC) and a possibly weaker chip (that is, I've desoldered it to copy it
[1]) and not weakening the chip but no backup (so when it fails I am
really stucK), I'll pick the former every time.
[1] Of course I don't resolder it. I put in a turned-pin socket.
Always. We can debate the reliabilty of sockets ad nauseam, but none of
the classics I own are in 'mission critical' -- if I get bad contacts at
a socket I can rasily reseat the chip without any real problems.
-tony
18 Nov
18 Nov
12:38 p.m.
--- William Donzelli <wdonzelli at gmail.com> wrote:
Well I'm not sure if that's better. Granted there
would be less of a shock, but wouldn't it be even
better to insure no heat gets to the chip at all?
I may have borrowed this idea from the model train
dudes, but it's the basic heat sink principle. If
you're soldering details onto a brass boiler,
essentially a thin hollow tube, you run the danger of
desoldering previous-nearby work. So, between the part
you want to solder and the part you don't want
desoldered, encompass that area with a tissue or
whatever soaked in water.
SO...if you surround the chip (and not necessarily
the whole board) with cool water, and possibly agitate
with a fish tank pump or something, it's pretty
unlikely any heat will get to the chip at all. And if
you fear that heat will be prevented from getting to
the component side of the pins/solder, I was thinking
that dribbling or brushing some wax? onto that side
the pins/board to give the area under it a chance to
heat up (by being insulated from the water). I know I
said that all pretty awkwardly but I'm on 4 hours
sleep here...
Even Radio Shack used to sell these little aluminum
clips that presumably would get clamped onto a pin for
desoldering. That's what I seem to remember anyway.
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so if you
presumably (probably? possibly?)
eliminate
any heat getting to the ic's innards by the
method
I
described, you're likely doing no damage to
it?
The better option is to heat the chip up reasonably
slowly - when I
strip a chip from a board (I use a solder pot), I
will just warm the
part in question up a bit. When the solder pot hits
the pins, the
internal structures of the chip will not get a big
jolt. This is quite
similar to how the big pick and place solder
machines work on a
factory floor.
1:48 p.m.
Well I'm not sure if that's better. Granted
there
would be less of a shock, but wouldn't it be even
better to insure no heat gets to the chip at all?
Heat will get to the chip. You can not stop it travelling up the metal
pins to the die. The thermal resistance of the metal is so much less
than that of the surrounding material (typical epoxy for DIPs) that
heat will mostly ignore anything but the metal - and the metal goes
straight to the die.
Remember that we are talking about tiny parts here with tiny
tolerances, so even a tiny force can have a big effect. The big effect
that can happen is the hairline fractures I mentioned earlier. Warming
up a chip first and slowly (obviously do not go overboard) will give
all the internal parts a chance to expand easily, and when the heat
from the solder operation hits those parts, the shock
will not be as
bad.
Even Radio Shack used to sell these little aluminum
clips that presumably would get clamped onto a pin for
desoldering. That's what I seem to remember anyway.
Heat sinks are good as well, just most IC packages can not accept them
well, and when they do, they often get in the way. About the only
place you can really use them is on the old TO- cans - and there it
would be better to just clamp on a normal thick heatsink for the case.
The advantage to using these is twofold - the heatsink is designed for
the case so it works well, and it gives you something to grab hold of.
--
Will
QA auditor U S Robotics circa 1996
17 Nov
17 Nov
11:16 a.m.
New subject: separating rare ICs from boards/ was Re: Need Docs for XT RAM Board...
Ethan Dicks wrote:
Or have a use for the chip, but value the board as
well (especially in
the case of being able to restore it to full functionality later).
but I wanted to retain two working parts, not just one. For those keeping
... had a similar situation with two pieces of equipment based on the 4004
processor, both of which I wanted to keep functional. Both use 4201's (clock
generator specifically for 4004/4040 systems, a rather obscure little IC) but
one of the 4201's had failed. Fortunately the remaining good one was already
socketed so there was no problem moving it over after replacing the bad one
with a socket. I've since been able to replicate the functionality of the 4201
with 3 SSI CMOS ICs so I don't have to keep swapping the good 4201 back and forth.
(...cracked the bad 4201 open and actually managed to find the fault under a
microscope - a blown trace in a metalization layer ... not that I can do
anything about it.)
18 Nov
18 Nov
12:42 p.m.
New subject: separating rare ICs from boards/ was Re: Need Docs for XT RAM Board...
--- Brent Hilpert <hilpert at cs.ubc.ca> wrote:
(...cracked the bad 4201 open and actually managed
to find the fault under a
microscope - a blown trace in a metalization layer
... not that I can do
anything about it.)
No chance at all? lol
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2:17 p.m.
New subject: separating rare ICs from boards/ was Re: Need Docs for XT RAM Board...
Chris M wrote:
--- Brent Hilpert <hilpert at cs.ubc.ca> wrote:
Nah. Tony Duell, on the other hand...
Gordon
(...cracked the bad 4201 open and actually
managed
to find the fault under a
microscope - a blown trace in a metalization layer
... not that I can do
anything about it.)
No chance at all? lol 
19 Nov
19 Nov
7:18 a.m.
New subject: separating rare ICs from boards/ was Re: Need Docs for XT RAM Board...
Gordon JC Pearce wrote:
Chris M wrote:
It is possible to repair this, it is just not economical.
What you need is a focused ion beam machine.
Most of bigger IC design centers have them.
IIRC somewhere around 600USD/hour operating costs, probably higher by now.
Jos Dreesen
--- Brent Hilpert <hilpert at cs.ubc.ca>
wrote:
Nah. Tony Duell, on the other hand...
Gordon
(...cracked the bad 4201 open and actually
managed
to find the fault under a
microscope - a blown trace in a metalization layer
... not that I can do
anything about it.)
No chance at all? lol 
9:43 p.m.
New subject: separating rare ICs from boards/ was Re: Need Docs for XT RAM Board...
From: Jos Dreesen / Marian Capel <jos.mar at
bluewin.ch>
Gordon JC Pearce wrote:
Hi
Even if you replace the trace, it may still not work. The trace
most likely blew because a transistor shorted. Unless they put a
few extra transistors on the die, it would be hopeless. Most
current uP's have extra gates and flops but these are intended
for last minute mask changes that always seem to happen.
Dwight
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Chris M wrote:
It is possible to repair this, it is just not economical.
What you need is a focused ion beam machine.
Most of bigger IC design centers have them.
IIRC somewhere around 600USD/hour operating costs, probably higher by now.
Jos Dreesen
--- Brent Hilpert <hilpert at cs.ubc.ca>
wrote:
Nah. Tony Duell, on the other hand...
Gordon
(...cracked the bad 4201 open and actually
managed
to find the fault under a
microscope - a blown trace in a metalization layer
... not that I can do
anything about it.)
No chance at all? lol
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