Failure of the POKEY chip were likely bonding wire failures. Voltage stress failures are
not likely to self repair.
I would agree, the fix is likely temporary.
Many early chips used gold wire for bonding but later chips used aluminum. Which is better
is always a question. The pads on the die were usually aluminum, while the package was
often gold. These are acoustically bonded.
One wonders if one put a capacitor on the lead with a non-lethal voltage and used such a
heating method, it might be able to arc weld the wire back on. Using the method of heating
might enhance the success as well.
Dwight
________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Pete Rittwage via
cctalk <cctalk at classiccmp.org>
Sent: Wednesday, July 24, 2019 6:24 PM
To: Jeffrey S. Worley <technoid6502 at gmail.com>; General Discussion: On-Topic and
Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: Resurrecting integrated circuits by cooking them.
On 2019-07-24 13:31, Jeffrey S. Worley via cctalk wrote:
Yesterday evening, in the process of refurbishing five
very badly
treated Atari 800 computers I had a hunch and subjected a failed Pokey
chip (Atari Part CO12294 Wikki link
https://en.wikipedia.org/wiki/POKEY
) to high heat by way of the barrel of my soldering iron until
saliva evaporated from it in about 1 second.
The chip, which did not work before in any of the machines now works
perfectly.
Pokey (see wikki link) is common to all Atari 8-bit computers and
common in many Atari coinop video game systems. These chips are
becoming scarce, so much so there is a sort of replacement being
manufactured
https://hotrodarcade.com/products/pokeyone-atari-pokey-chip-replacement-for…
.
The replacement Pokey only emulates the audio portion of the original
chip, leaving the PotKEY part unimplemented. Pokey gets its name from
Potentiometer Keyboard. It also handles the Atari SIO peripheral
signals, so without those an Atari computer cannot use standard
peripherals like serial disk drives, and other common interfaces.
Thus, for Atari computers a true Pokey is a must.
I stumbled upon a fix for this one and wonder if I reinvented the wheel
or if this information may be of use to the group in treating other
sorts of chips.
Reflowing is a treatment for a lot of hardware these days and generally
regarded as a hack which won't last. As modern hardware, CPU's and
video chips in particular run very hot, I can see how this might be,
but Pokey and most of the stuff we work with don't have this
environmental restriction. Most of our gear runs at 40 degrees
centigrade or lower. So I'm guessing the problem with my disused chip
was oxidation within the package and that cooking the chip a bit
cleaned things up? Any advise or observations would be appreciated.
I tried this on another chip the same evening, an Antic. The Antic DID
work for a second or two, whereas it had before given no signs of life,
but then returned to its failed state.
Best,
Jeff
(Technoid Mutant)
I tried this a year or two back with about 30 x SID, VIC, and PLA chips
out of C64's. I heated them in the oven at about 250 for 15 minutes.
None of them showed any more signs of life than before I tried it,
unfortunately.
--
-Pete Rittwage