For this pattern generator I need the dump of the main prom (D313). It's a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

On Wed, 13 Jul 2011 00:07:21 +0200 "H.den Boer" wrote in Message
id: l:

For this pattern generator I need the dump of the main prom (D313). It's a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the data
from it with a lowered VCC?

For this pattern generator I need the dump of the main prom (D313). It's a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

On Wed, 13 Jul 2011 11:41:19 +0200 "H.den Boer" wrote in Message
id: :


For this pattern generator I need the dump of the main prom (D313). It's a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably won't
help. Did you actually measure the short right at the pin with a DMM, or
just assume it was shorted to VCC from the data pattern?

For this pattern generator I need the dump of the main prom (D313). It's
a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably won't
help. Did you actually measure the short right at the pin with a DMM, or
just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway, it
gets warm and consumes
too much power. It's a wonder I can read it at all, but without bit 6 it is
no good.

On Wed, 13 Jul 2011 12:34:27 +0200 "H.den Boer" wrote in Message
id: :




For this pattern generator I need the dump of the main prom (D313). It's
a
27C256 with PLCC32 housing in a socket, located in the right corner on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably won't
help. Did you actually measure the short right at the pin with a DMM, or
just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway, it
gets warm and consumes
too much power. It's a wonder I can read it at all, but without bit 6 it is
no good.

If I had one, I'd be willing to read the binary for you. You could try
these groups, lots of very helpful folks the

http://tech.groups.yahoo.com/group/TekScopes/
http://tech.groups.yahoo.com/group/h...ent_equipment/
http://tech.groups.yahoo.com/group/Fluke_DMM/

If anyone on those lists have a PM5418, I'm sure they be willing to get
you a copy. You could also try Fluke, the last time I dealt with them they
were pretty helpful.

Good luck.

For this pattern generator I need the dump of the main prom (D313). It's
a
27C256 with PLCC32 housing in a socket, located in the right corner on
the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the
data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably won't
help. Did you actually measure the short right at the pin with a DMM, or
just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway, it
gets warm and consumes
too much power. It's a wonder I can read it at all, but without bit 6 it is
no good.

If I had one, I'd be willing to read the binary for you. You could try
these groups, lots of very helpful folks the

http://tech.groups.yahoo.com/group/TekScopes/
http://tech.groups.yahoo.com/group/h...ent_equipment/
http://tech.groups.yahoo.com/group/Fluke_DMM/

If anyone on those lists have a PM5418, I'm sure they be willing to get
you a copy. You could also try Fluke, the last time I dealt with them they
were pretty helpful.

Good luck.

Thanks!

H.den Boer wrote:



For this pattern generator I need the dump of the main prom (D313).
It's a
27C256 with PLCC32 housing in a socket, located in the right corner
on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the
data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably won't
help. Did you actually measure the short right at the pin with a DMM, or
just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway,
it gets warm and consumes
too much power. It's a wonder I can read it at all, but without bit 6 it
is no good.

Does the supply current vary during read depending on the stored data?
If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it
should be, but if you stick a sense resistor in the VCC supply (maybe
with two diodes across it to prevent excessive drop while switching) and
scope that and the read signal while reading the chip, you may find you
can tell the difference when the lower MOSFET in the D6 output stage
switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with
a tristate output controlled by the read signal) may be enough to build
a 'gimmick' jig to let your programmer read it.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

IanM wrote in message
...
H.den Boer wrote:



For this pattern generator I need the dump of the main prom (D313).
It's a
27C256 with PLCC32 housing in a socket, located in the right corner
on the
back of the instrument. Can anybody help me?

What's wrong with the one currently in it? Have you tried reading the
data
from it with a lowered VCC?

I can read it, but databit 6 is always '1' the pin is shorted to Vcc,

Ouch. Well, reading an EPROM at a lower VCC will sometimes allow you to
get all the data off a flaky device, but in your case, it probably
won't
help. Did you actually measure the short right at the pin with a DMM,
or
just assume it was shorted to VCC from the data pattern?

It measures under 25 ohms, so no luck there, the prom is fried anyway,
it gets warm and consumes
too much power. It's a wonder I can read it at all, but without bit 6 it
is no good.

Does the supply current vary during read depending on the stored data?
If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it
should be, but if you stick a sense resistor in the VCC supply (maybe
with two diodes across it to prevent excessive drop while switching) and
scope that and the read signal while reading the chip, you may find you
can tell the difference when the lower MOSFET in the D6 output stage
switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with
a tristate output controlled by the read signal) may be enough to build
a 'gimmick' jig to let your programmer read it.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:



Have you had personal experience of this work-around ?

Does the supply current vary during read depending on the stored data?
If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it
should be, but if you stick a sense resistor in the VCC supply (maybe
with two diodes across it to prevent excessive drop while switching) and
scope that and the read signal while reading the chip, you may find you
can tell the difference when the lower MOSFET in the D6 output stage
switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with
a tristate output controlled by the read signal) may be enough to build
a 'gimmick' jig to let your programmer read it.

I can try that, interesting thought, thanks.

Does the supply current vary during read depending on the stored data? If
so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it should
be, but if you stick a sense resistor in the VCC supply (maybe with two
diodes across it to prevent excessive drop while switching) and scope that
and the read signal while reading the chip, you may find you can tell the
difference when the lower MOSFET in the D6 output stage switches on to
attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with a
tristate output controlled by the read signal) may be enough to build a
'gimmick' jig to let your programmer read it.

I have succesfully retrieved bit 6 with a pnp transistor, some resistors and
a inverter directly at the output pin. Then came the weird part, I had to
invert it a second time to get it right. So this problem is solved.

Thanks all who contributed!

H.den Boer wrote:
Does the supply current vary during read depending on the stored data?
If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it
should be, but if you stick a sense resistor in the VCC supply (maybe
with two diodes across it to prevent excessive drop while switching)
and scope that and the read signal while reading the chip, you may
find you can tell the difference when the lower MOSFET in the D6
output stage switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly
with a tristate output controlled by the read signal) may be enough to
build a 'gimmick' jig to let your programmer read it.

I have succesfully retrieved bit 6 with a pnp transistor, some resistors
and a inverter directly at the output pin. Then came the weird part, I
had to invert it a second time to get it right. So this problem is solved.

Thanks all who contributed!

Glad you got it to work. Obviously the internal damage was not just a
simple short in the output stage and that you had the genius to try
re-inverting bit 6. Its a neat dodge to be aware of for use as a last
resort. After you have thoroughly tested the result, it would be nice
if you could find somewhere reasonably stable to put the file online.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

H.den Boer wrote in message
l.nl...
Does the supply current vary during read depending on the stored data? If
so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it should
be, but if you stick a sense resistor in the VCC supply (maybe with two
diodes across it to prevent excessive drop while switching) and scope
that
and the read signal while reading the chip, you may find you can tell the
difference when the lower MOSFET in the D6 output stage switches on to
attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with a
tristate output controlled by the read signal) may be enough to build a
'gimmick' jig to let your programmer read it.

I have succesfully retrieved bit 6 with a pnp transistor, some resistors
and
a inverter directly at the output pin. Then came the weird part, I had to
invert it a second time to get it right. So this problem is solved.

Thanks all who contributed!



What sort of differential in the supply current ?

On Thu, 14 Jul 2011 16:36:59 +0100, IanM
put finger to keyboard and composed:

Does the supply current vary during read depending on the stored data?
If so, you *MAY* be able to retrieve bit 6.

It is a little difficult to be certain when you don't know what it
should be, but if you stick a sense resistor in the VCC supply (maybe
with two diodes across it to prevent excessive drop while switching) and
scope that and the read signal while reading the chip, you may find you
can tell the difference when the lower MOSFET in the D6 output stage
switches on to attempt to output logic 0.

If so, a PNP transistor, a few resistors and an inverter (possibly with
a tristate output controlled by the read signal) may be enough to build
a 'gimmick' jig to let your programmer read it.

That has to be one of the best hacks I've seen in a long time. Kudos
and congratulations to both you and the OP.

BTW, I've "repaired" weak output signals in digital ICs by buffering
them with a comparator, but I never would have dreamed of recovering a
PROM in this way.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.