Bad Part from TI and Avnet: 74LS368AN

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SN74LS368AN. Date code 43AD7HM

In a Pac board at 8B, gives Matrix-like green lines and weird static on
screen. Putting the old part in made it go away. New socket. Put these in
loosely, pushed them in tight, etc. nothing worked to make it go away. Tin
double wipe sockets. Game play is unaffected.

Old part worked fine under every circumstance.

Ordered from Avnet Mar 10, quantity 11. I tried 5, all the same more or
less, amount of static varied.

Shame on you TI. :)

If you would like one, send me a self addressed stamped envelope. :)

Don't ya just love bad parts right out of the box new?

--
"Quality is the enemy of production."
Homepage - http://members.cox.net/rcbullock/ 'It's lamer than Spaeth's!'
** Replies to rcbullock '"AT"" cox.net ** Sorry, I detest spam.
 
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In rec.games.video.arcade.collecting Robert Bullock <rcbullock@_remove_cox.net> wrote:
: SN74LS368AN. Date code 43AD7HM
:
: In a Pac board at 8B, gives Matrix-like green lines and weird static on
: screen. Putting the old part in made it go away. New socket. Put these in
: loosely, pushed them in tight, etc. nothing worked to make it go away. Tin
: double wipe sockets. Game play is unaffected.
:
: Old part worked fine under every circumstance.
:
: Ordered from Avnet Mar 10, quantity 11. I tried 5, all the same more or
: less, amount of static varied.
:
: Shame on you TI. :)
:
: If you would like one, send me a self addressed stamped envelope. :)
:
: Don't ya just love bad parts right out of the box new?


They're probably not bad parts, just not fast enough to be used in the
clock oscillator circuit. Was the original an LS? Did you pull the
TI datasheet and see if that chip is spec'd at 18MHz?


--
Mark Spaeth mspaeth@mtl.mit.edu
50 Vassar St., #38.265 mspaeth@mit.edu
Cambridge, MA 02139
(617) 452-2354 http://rgvac.978.org/~mspaeth
 
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The original was also an LS. The PCB component placement guide had an LS368
shown. Both were made by TI. I doubt TI lowered their spec. Feel free to do
the math on the switching characteristics though. This shouldn't be that
cosmic. I would suspect a batch of parts slightly out of spec perhaps. They
worked, just not well.


"Mark C. Spaeth" <mspaeth@plancherel.mit.edu> wrote in message
news:4241b7c6$0$569$b45e6eb0@senator-bedfellow.mit.edu...
> In rec.games.video.arcade.collecting Robert Bullock
> <rcbullock@_remove_cox.net> wrote:

> They're probably not bad parts, just not fast enough to be used in the
> clock oscillator circuit. Was the original an LS? Did you pull the
> TI datasheet and see if that chip is spec'd at 18MHz?
 

Vaxx

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or the chips feeding the inputs are slowly fading away.......
"matt" <gamefixer@gmail.com> wrote in message
news:eek:KCdnQYfKswti9_fRVn-rQ@starstream.net...
> The part might not be all that happy with the +5 being too low. The newer
> part might have less tolerance for voltage fluctuations.
>
> --
> Matt
> M and M Electronics
> 6661 Stanford Ranch Road
> Suite F, PMB 105
> Rocklin, Ca 95677
> 916-275-5871
> "Robert Bullock" <rcbullock@_REMOVE_cox.net> wrote in message
> news:1Fj0e.3191$Dz4.1036@okepread01...
> > The original was also an LS. The PCB component placement guide had an
> > LS368 shown. Both were made by TI. I doubt TI lowered their spec. Feel
> > free to do the math on the switching characteristics though. This
> > shouldn't be that cosmic. I would suspect a batch of parts slightly out
of
> > spec perhaps. They worked, just not well.
> >
> >
> > "Mark C. Spaeth" <mspaeth@plancherel.mit.edu> wrote in message
> > news:4241b7c6$0$569$b45e6eb0@senator-bedfellow.mit.edu...
> >> In rec.games.video.arcade.collecting Robert Bullock
> >> <rcbullock@_remove_cox.net> wrote:
> >
> >> They're probably not bad parts, just not fast enough to be used in the
> >> clock oscillator circuit. Was the original an LS? Did you pull the
> >> TI datasheet and see if that chip is spec'd at 18MHz?
> >
> >
>
>
 
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Speculations. The voltage was at 4.98 or so, and I still don't see where one
part from one manufacturer that was old as the board would work where new
ones would not. frankly, don't care.

If the chip couldn't take 4.98 and work with it, it's bad.

"VaxX" <geoff_gunn@hotmail.com> wrote in message
news:4242985b$0$250$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com.au...
> or the chips feeding the inputs are slowly fading away.......
> "matt" <gamefixer@gmail.com> wrote in message
> news:eek:KCdnQYfKswti9_fRVn-rQ@starstream.net...
>> The part might not be all that happy with the +5 being too low. The newer
>> part might have less tolerance for voltage fluctuations.
 
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Archived from groups: rec.games.video.arcade.collecting,sci.electronics.repair (More info?)

In rec.games.video.arcade.collecting Robert Bullock <rcbullock@_remove_cox.net> wrote:
: Speculations. The voltage was at 4.98 or so, and I still don't see where one
: part from one manufacturer that was old as the board would work where new
: ones would not. frankly, don't care.

The simple fact is that that circuit doesn't drive the 74ls368 with
valid TTL input levels. The resistors across the gates in the 368
result in the inputs being stuck at invalid TTL input levels, so the
output levels aren't guaranteed. If the crystal/cap don't provide
enough excitation to get enough feedback to start the circuit oscillating,
it's the circuit's fault, not the chip's fault.


: If the chip couldn't take 4.98 and work with it, it's bad.

Most of my pacs work down to 4.3 (and many below).

--
Mark Spaeth mspaeth@mtl.mit.edu
50 Vassar St., #38.265 mspaeth@mit.edu
Cambridge, MA 02139
(617) 452-2354 http://rgvac.978.org/~mspaeth
 
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Archived from groups: rec.games.video.arcade.collecting,sci.electronics.repair (More info?)

I still don't see how the old chip would work where none of the new ones
would. And the response about 4.98 was to previous speculation. I've seen
them work at 4.3ish too.

I'll try to repost when my new batch of 368's come in.

"Mark C. Spaeth" <mspaeth@plancherel.mit.edu> wrote in message
news:4242c959$0$561$b45e6eb0@senator-bedfellow.mit.edu...
> In rec.games.video.arcade.collecting Robert Bullock
> <rcbullock@_remove_cox.net> wrote:
> : Speculations. The voltage was at 4.98 or so, and I still don't see where
> one
> : part from one manufacturer that was old as the board would work where
> new
> : ones would not. frankly, don't care.
>
> The simple fact is that that circuit doesn't drive the 74ls368 with
> valid TTL input levels. The resistors across the gates in the 368
> result in the inputs being stuck at invalid TTL input levels, so the
> output levels aren't guaranteed. If the crystal/cap don't provide
> enough excitation to get enough feedback to start the circuit oscillating,
> it's the circuit's fault, not the chip's fault.
>
>
> : If the chip couldn't take 4.98 and work with it, it's bad.
>
> Most of my pacs work down to 4.3 (and many below).
>
> --
> Mark Spaeth mspaeth@mtl.mit.edu
> 50 Vassar St., #38.265 mspaeth@mit.edu
> Cambridge, MA 02139
> (617) 452-2354 http://rgvac.978.org/~mspaeth
>
 
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Archived from groups: rec.games.video.arcade.collecting,sci.electronics.repair (More info?)

Maybe I have met this one before, and maybe not. If you can put it in
a socket, instead of directly on the board, and find that it works, I have
met this one before. If not, no.

Jim

Robert Bullock <rcbullock@_REMOVE_cox.net> writes:

: SN74LS368AN. Date code 43AD7HM

: In a Pac board at 8B, gives Matrix-like green lines and weird static on
: screen. Putting the old part in made it go away. New socket. Put these in
: loosely, pushed them in tight, etc. nothing worked to make it go away. Tin
: double wipe sockets. Game play is unaffected.

: Old part worked fine under every circumstance.

: Ordered from Avnet Mar 10, quantity 11. I tried 5, all the same more or
: less, amount of static varied.

: Shame on you TI. :)

: If you would like one, send me a self addressed stamped envelope. :)

: Don't ya just love bad parts right out of the box new?

: --
: "Quality is the enemy of production."
: Homepage - http://members.cox.net/rcbullock/ 'It's lamer than Spaeth's!'
: ** Replies to rcbullock '"AT"" cox.net ** Sorry, I detest spam.



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