Crack propogation to inside an IC

N

N_Cook

Guest
Dropped Yamaha XR800F mixer amp, numerous problems mainly around a cracked
board. Crack mechanics dealt with and trace bridges function. But the crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect . Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin 6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?
 
hr(bob) hofmann@att.net <hrhofmann@att.net> wrote in message
news:dcb91d0f-9939-41e6-af36-f2bcdb87c1fe@z4g2000yqa.googlegroups.com...
On Mar 11, 8:41 am, "N_Cook" <dive...@tcp.co.uk> wrote:
Yamaha EMX640 that should be
Click to expand...
Can you encapsulate the whole area with silicone rubber to shield the
area from future shocks (mechanical that is)??


If the trouble returns I'll desolder it , solder in a turned pin socket ,
plenty of height available, and try HY62256 or TMS62256, same pinning as the
original
 
On Thu, 11 Mar 2010 12:44:51 -0000, "N_Cook" <diverse@tcp.co.uk>wrote:

Dropped Yamaha XR800F mixer amp, numerous problems mainly around a cracked
board. Crack mechanics dealt with and trace bridges function. But the crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect . Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin 6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?
Click to expand...

There is nothing common about damage from g-forces.
 
On Mar 11, 8:41 am, "N_Cook" <dive...@tcp.co.uk> wrote:
Yamaha EMX640 that should be
Click to expand...
Can you encapsulate the whole area with silicone rubber to shield the
area from future shocks (mechanical that is)??
 
N_Cook wrote:
Dropped Yamaha XR800F mixer amp, numerous problems mainly around a cracked
board. Crack mechanics dealt with and trace bridges function. But the crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect . Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin 6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?
Click to expand...

Replace it now. The case is cracked, and at least one bonding wire
is damaged. It's not a matter of if it will quit, but when. The
damaged case will let moisture into the die, and it will oxidize.

--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
 
<Meat Plow> wrote in message news:3j7vt4.pqo.17.3@news.alt.net...
On Thu, 11 Mar 2010 12:44:51 -0000, "N_Cook" <diverse@tcp.co.uk>wrote:

Dropped Yamaha XR800F mixer amp, numerous problems mainly around a
cracked
board. Crack mechanics dealt with and trace bridges function. But the
crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect .
Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin 6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or
perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the
pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?


There is nothing common about damage from g-forces.
Click to expand...
g-forces, without localised schock waves, leads to solder breaks of inertial
items, large caps, chokes, transformers etc. This problem is just the one
pin of 28 on the IC the crack ended at. I don't see how it could have
started there. I suppose in some future case where unobtainable IC and
nothing to loose then ties and wedges first, then Dremmel and small centride
mill down to the bond area and silver loaded paint may be worth a go
 
Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:4B9936DF.81CDB454@earthlink.net...
N_Cook wrote:

Dropped Yamaha XR800F mixer amp, numerous problems mainly around a
cracked
board. Crack mechanics dealt with and trace bridges function. But the
crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect .
Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin
6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or
perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the
pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?


Replace it now. The case is cracked, and at least one bonding wire
is damaged. It's not a matter of if it will quit, but when. The
damaged case will let moisture into the die, and it will oxidize.

--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
Click to expand...
Its a balance of probabilities type thing. If/when the problem returned the
amp was useless then yes but the problem is just in the echo section, easily
switched out using the front panel sw. Owners were using sans echo and only
one pa chanel functional for some tome until a problem emerged on the other
pa ch. If I knew for certain that a TMS62256 or other common SRAM would
replace the W24257-70LL then I would go ahead replacing now. The process of
desoldering the original is more likely than not, I would suggest, to make
the original non-functional by any amount of surface pressure applied to the
IC casing
 
I suppose you've already checked to see if there were any broken circuit
traces under the IC.

That would've been my first suspicion where a circuit board crack was
present.
With a small high intensity light (like a 1W LED), it's often possible to
see things on a pcb that normally wouldn't be seen.

High stress mechanical shock can be similar to lightning damage sometimes,
ya never know if ya found all of the damage.

--
Cheers,
WB
..............


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hnaop7$ibu$1@news.eternal-september.org...
Dropped Yamaha XR800F mixer amp, numerous problems mainly around a cracked
board. Crack mechanics dealt with and trace bridges function. But the
crack
ended at pin 6 of a 28 pin SRAM Winbond W24257-70LL associated with the
Yamaha YSS234-F digital effects generator. Unless I press the IC case at
pin 6 there is a weird uncontrolled sci-fi echoing howl around efect .
Cable
ties thru pcb and around the IC and wooden "folding" wedges to that pin 6
spot have "cured" it. If it does return they will have to switch off the
effects and then a matter of trying to find a replacement W24257 or
perhaps
a 62256 would work there. I'm assuming the shock wave propogated up the
pin
and disrupted the first bond point inside, is this a common occurance in
such circumstances?
Click to expand...
 
N_Cook wrote:
Its a balance of probabilities type thing. If/when the problem returned the
amp was useless then yes but the problem is just in the echo section, easily
switched out using the front panel sw. Owners were using sans echo and only
one pa chanel functional for some tome until a problem emerged on the other
pa ch. If I knew for certain that a TMS62256 or other common SRAM would
replace the W24257-70LL then I would go ahead replacing now. The process of
desoldering the original is more likely than not, I would suggest, to make
the original non-functional by any amount of surface pressure applied to the
IC casing
Click to expand...

The probability is very high that it will come back. I would never
return something to a customer with a defect like that. Of course, that
is why my callback rate was always under 1%. It's also why I never
needed to advertise my shop.


--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'
 
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