2465A battery backup


mosaicmerc
 

Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?

--- In TekScopes@..., David <davidwhess@...> wrote:

C2470 at the corner of the battery closest to the center of the board
would be a good place to apply power while changing the battery. The
voltage should be between 3.5 and 5.0 volts.

The original batteries are still made and sold although I would
probably use a less expensive replacement. The last version of the
7854 uses the same battery for memory backup:

http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==

On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?


--- In TekScopes@..., "vdonisa" <vdonisa@> wrote:

Yeah I Hakked freely around there :-)

Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.


J. L. Trantham
 

I’ve been following this thread as I have a two 2465B’s for the past 2 or 3 years, each last calibrated by Tektronix about 3 years ago, one with S/N B05xxxx and one B01xxxx that I have been thinking about replacing the battery/NVRAM and looking at the need to replace the capacitors.  I have never opened them and they work great.  

 

I have three comments/questions.

 

1.        Is it possible to read the contents of the STATIC RAM on the units with the external battery?  The Dallas chips (that I believe to be installed in the S/N B05xxxx unit – or do I have that reversed?),  can be removed, allowed to cool, install a socket, read the contents, then reinsert the chips, and therefore have a ‘backup’ copy of the calibration data and a way to easily replace the chips.

2.       If there is no way to read the contents of the RAM or write data to the RAM on the units with the external battery, and the batteries seem to last > 10 years (IIRC), why go to the trouble of making an alarm circuit, that might also fail or deplete the backup battery faster?   It seems to me that the more critical issue is protecting the calibration data in the most reliable way for the longest time possible then establish a schedule to routinely replace the battery. 

3.       That being said, does Tektronix have a recommended time to replace the external battery or the Dallas chips?  HP recommends replacing the Dallas chips in the 3458A every 10 years.

 

Thanks.

 

Joe

 

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of mosaicmerc
Sent: Tuesday, May 07, 2013 7:19 AM
To: TekScopes@...
Subject: [TekScopes] Re: 2465A battery backup

 

 


Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?

--- In TekScopes@..., David <davidwhess@...> wrote:
>
> C2470 at the corner of the battery closest to the center of the board
> would be a good place to apply power while changing the battery. The
> voltage should be between 3.5 and 5.0 volts.
>
> The original batteries are still made and sold although I would
> probably use a less expensive replacement. The last version of the
> 7854 uses the same battery for memory backup:
>
> http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==
>
> On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
> <mosaicmerc@...> wrote:
>
> >Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?
> >
> >
> >--- In TekScopes@..., "vdonisa" wrote:
> >>
> >> Yeah I Hakked freely around there :-)
> >>
> >> Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.
>


rpoz28cam
 

Greetings,
I have been following this thread for some time now. 
Wouldn't it be just as easy to determine the load path from this battery ie., the battery backed up circuitry then simply using ungrounded variable power supply set to +-1% of the specified battery voltage applied to the said backup system and then simply remove old battery installing new battery in place while power is appled via this external power supply.  Remember this must all be done with everything not commonly grounded.. solder/desolder workstation and power supply.  Thankfully I have a 2467B and just replaced the NVRAM (Dallas Part) without any difficulties.  I'm not sure your not going overkill with the smt100 and diode for a simple battery replacement, just check your work / settings twice before doing the final application of supply and removal of old battery.  One other note, I personally am not a fan of mounting any chemical cells directly on a pcb, just a recipe for future disaster.  I have seen / repaired the damage on some unobtainium devices, not Good!

JLM
 



From: mosaicmerc
To: TekScopes@...
Sent: Tuesday, May 7, 2013 7:19 AM
Subject: [TekScopes] Re: 2465A battery backup

 

Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?

--- In TekScopes@..., David wrote:
>
> C2470 at the corner of the battery closest to the center of the board
> would be a good place to apply power while changing the battery. The
> voltage should be between 3.5 and 5.0 volts.
>
> The original batteries are still made and sold although I would
> probably use a less expensive replacement. The last version of the
> 7854 uses the same battery for memory backup:
>
> http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==
>
> On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
> wrote:
>
> >Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?
> >
> >
> >--- In TekScopes@..., "vdonisa" wrote:
> >>
> >> Yeah I Hakked freely around there :-)
> >>
> >> Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.
>




 

I considered something similarly complicated when I changed the NVRAMs
in my 2440.

The 2465A already has the ability to directly measure the backup
battery voltage and I assume it gives a warning at power on if it is
low.

On Tue, 07 May 2013 12:19:22 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?


mosaicmerc
 

Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.

--- In TekScopes@..., J <rpoz28cam@...> wrote:

Greetings,
I have been following this thread for some time now. 
Wouldn't it be just as easy to determine the load path from this battery ie., the battery backed up circuitry then simply using ungrounded variable power supply set to +-1% of the specified battery voltage applied to the said backup system and then simply remove old battery installing new battery in place while power is appled via this external power supply.  Remember this must all be done with everything not commonly grounded.. solder/desolder workstation and power supply.  Thankfully I have a 2467B and just replaced the NVRAM (Dallas Part) without any difficulties.  I'm not sure your not going overkill with the smt100 and diode for a simple battery replacement, just check your work / settings twice before doing the final application of supply and removal of old battery.  One other note, I personally am not a fan of mounting any chemical cells directly on a pcb, just a recipe for future disaster.  I have seen / repaired the damage on some
unobtainium devices, not Good!

JLM
 




________________________________
From: mosaicmerc <mosaicmerc@...>
To: TekScopes@...
Sent: Tuesday, May 7, 2013 7:19 AM
Subject: [TekScopes] Re: 2465A battery backup



 

Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?

--- In TekScopes@..., David <davidwhess@> wrote:

C2470 at the corner of the battery closest to the center of the board
would be a good place to apply power while changing the battery. The
voltage should be between 3.5 and 5.0 volts.

The original batteries are still made and sold although I would
probably use a less expensive replacement. The last version of the
7854 uses the same battery for memory backup:

http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==

On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
<mosaicmerc@> wrote:

Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?


--- In TekScopes@..., "vdonisa" <vdonisa@> wrote:

Yeah I Hakked freely around there :-)

Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.


vdonisa
 

By the time you add the price of all the additional parts, the additional work and the inconvenience of installing some contraption that isn't a perfect mechanical fit, you may notice that the price of the direct replacement LTC-7P is not such a bad deal :-)

--- In TekScopes@..., "mosaicmerc" <mosaicmerc@...> wrote:


Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?




--- In TekScopes@..., David <davidwhess@> wrote:

C2470 at the corner of the battery closest to the center of the board
would be a good place to apply power while changing the battery. The
voltage should be between 3.5 and 5.0 volts.

The original batteries are still made and sold although I would
probably use a less expensive replacement. The last version of the
7854 uses the same battery for memory backup:

http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==

On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
<mosaicmerc@> wrote:

Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?


--- In TekScopes@..., "vdonisa" <vdonisa@> wrote:

Yeah I Hakked freely around there :-)

Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.


 

Reading the contents of the battery backed up SRAMs directly would
certainly be a challenge. If I had to do that, I would attach power
to the DIP leads and a resistor from GND to CE2 and then try to remove
the SRAM from the board.

Maybe it could be done via the GPIB port if the oscilloscope has that
option.

On Tue, 7 May 2013 08:08:00 -0500, "J. L. Trantham" <jltran@...>
wrote:

I've been following this thread as I have a two 2465B's for the past 2 or 3
years, each last calibrated by Tektronix about 3 years ago, one with S/N
B05xxxx and one B01xxxx that I have been thinking about replacing the
battery/NVRAM and looking at the need to replace the capacitors. I have
never opened them and they work great.

I have three comments/questions.

1. Is it possible to read the contents of the STATIC RAM on the units
with the external battery? The Dallas chips (that I believe to be installed
in the S/N B05xxxx unit - or do I have that reversed?), can be removed,
allowed to cool, install a socket, read the contents, then reinsert the
chips, and therefore have a 'backup' copy of the calibration data and a way
to easily replace the chips.

2. If there is no way to read the contents of the RAM or write data to
the RAM on the units with the external battery, and the batteries seem to
last > 10 years (IIRC), why go to the trouble of making an alarm circuit,
that might also fail or deplete the backup battery faster? It seems to me
that the more critical issue is protecting the calibration data in the most
reliable way for the longest time possible then establish a schedule to
routinely replace the battery.

3. That being said, does Tektronix have a recommended time to replace
the external battery or the Dallas chips? HP recommends replacing the
Dallas chips in the 3458A every 10 years.

Thanks.

Joe


rpoz28cam
 

Not sure why you need rev voltage protection in the first place, some attention to detail when working with this device should fill the bill.  I would be more concerned with keeping up with your cal data, not dropping that backup voltage with any shorting, de-soldering activities etc.   As far as LiCl or any other source, I wouldn't trust any of them period.  They all can fail in time!  Look what happen to the new Boeing jetliner.  One more suggestion, I wouldn't use anything on that pcb or any sensitive test equipment for that matter except a esd protected soldering rework station.. such as a Weller WRS3000 series or similar.  I know they are expensive but there is no substitute for quality and performance. 

JLM



From: mosaicmerc
To: TekScopes@...
Sent: Tuesday, May 7, 2013 9:47 AM
Subject: [TekScopes] Re: 2465A battery backup

 
Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.

--- In TekScopes@..., J wrote:
>
> Greetings,
> I have been following this thread for some time now. 
> Wouldn't it be just as easy to determine the load path from this battery ie., the battery backed up circuitry then simply using ungrounded variable power supply set to +-1% of the specified battery voltage applied to the said backup system and then simply remove old battery installing new battery in place while power is appled via this external power supply.  Remember this must all be done with everything not commonly grounded.. solder/desolder workstation and power supply.  Thankfully I have a 2467B and just replaced the NVRAM (Dallas Part) without any difficulties.  I'm not sure your not going overkill with the smt100 and diode for a simple battery replacement, just check your work / settings twice before doing the final application of supply and removal of old battery.  One other note, I personally am not a fan of mounting any chemical cells directly on a pcb, just a recipe for future disaster.  I have seen / repaired the damage on some
> unobtainium devices, not Good!
>
> JLM
>  
>
>
>
>
> ________________________________
> From: mosaicmerc
> To: TekScopes@...
> Sent: Tuesday, May 7, 2013 7:19 AM
> Subject: [TekScopes] Re: 2465A battery backup
>
>
>
>  
>
> Thx for that advice:
>
> Here is my plan :
> Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.
>
> Replacement Battery:
> http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941
>
> I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
> http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999
>
> and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).
>
> Then to direct mount the pcb as a replacement for the LTC 7P by
> 1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
> 2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
> 3) I'll have to unplug the Scope for this as my iron is grounded.
> 4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
> http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf
>
> At least that gives an alert (upon pwr up) if the battery backup becomes weak.
>
> Sounds good?
> If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?
>
> --- In TekScopes@..., David wrote:
> >
> > C2470 at the corner of the battery closest to the center of the board
> > would be a good place to apply power while changing the battery. The
> > voltage should be between 3.5 and 5.0 volts.
> >
> > The original batteries are still made and sold although I would
> > probably use a less expensive replacement. The last version of the
> > 7854 uses the same battery for memory backup:
> >
> > http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==
> >
> > On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
> > wrote:
> >
> > >Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?
> > >
> > >
> > >--- In TekScopes@..., "vdonisa" wrote:
> > >>
> > >> Yeah I Hakked freely around there :-)
> > >>
> > >> Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.
> >
>




 

The 2465A battery circuits already include reverse voltage protection
in the form of diode CR2770 and a 10K series resistor to limit the
current.

On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.


mosaicmerc
 

A custom pcb is hardly a contraption.But I get your point. 8)

--- In TekScopes@..., "vdonisa" <vdonisa@...> wrote:

By the time you add the price of all the additional parts, the additional work and the inconvenience of installing some contraption that isn't a perfect mechanical fit, you may notice that the price of the direct replacement LTC-7P is not such a bad deal :-)


--- In TekScopes@..., "mosaicmerc" <mosaicmerc@> wrote:


Thx for that advice:

Here is my plan :
Topic: Replacing/upgrading the LTC 7P Lithium battery backup for the 2465A STATIC RAM.

Replacement Battery:
http://www.newark.com/jsp/search/productdetail.jsp?sku=24C8941

I plan to make a small PCB ( matching old LTC 7P pinout) for it with this .16Vf SMT diode:
http://www.newark.com/vishay-general-semiconductor/mss1p2u-m3-89a/diode/dp/63R5999

and a SMT 100 Ohm resistor in series ( to protect against a hi current short and reverse supply V).

Then to direct mount the pcb as a replacement for the LTC 7P by
1) soldering it with pig tail wires to the nearby tantalum C2470 to maintain pwr during installation.
2) Remove the old Lithium and then direct mounting the new PCB as a replacement using thru hole leads snipped from old parts.
3) I'll have to unplug the Scope for this as my iron is grounded.
4) Optionally use a high impedance OPA/comparator (pwred by the 5V supply) to monitor the new batt. voltage and drive an onboard mini beeper if the backup voltage (@ circuits output) drops under 2.5V (1/2 Vcc).
http://ww1.microchip.com/downloads/en/devicedoc/21733j.pdf

At least that gives an alert (upon pwr up) if the battery backup becomes weak.

Sounds good?
If it works out...I'll make a step by step image seq. I can publish the pcb layout and the guide in the files section?




--- In TekScopes@..., David <davidwhess@> wrote:

C2470 at the corner of the battery closest to the center of the board
would be a good place to apply power while changing the battery. The
voltage should be between 3.5 and 5.0 volts.

The original batteries are still made and sold although I would
probably use a less expensive replacement. The last version of the
7854 uses the same battery for memory backup:

http://www.mouser.com/ProductDetail/Eagle-Picher/LTC-7P/?qs=MQ89PJz411eJdMnu%252btznWw==

On Tue, 07 May 2013 04:43:05 -0000, "mosaicmerc"
<mosaicmerc@> wrote:

Ok, so i need to apply power to where the tantalum is next to the lithium during the swap??...Are the lithium batts available?


--- In TekScopes@..., "vdonisa" <vdonisa@> wrote:

Yeah I Hakked freely around there :-)

Assuming that all you want to do is replacing the battery and nothing else. The problem is that it is rigid and has 4 strong pins at quite some distance from each other. You cannot remove it by wiggling while heating the pins in turns. And there's not enough clearance to cut the pins from the component side either. You don't want the hand pump due to recoil / splattered solder. Which leaves you with solder wick or the Hakking tool as possible options. If you go for the solder wick take care of overheating, lithium batteries are known to be good at exploding / starting fires.


mosaicmerc
 

Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap.

No custom PCB req'd.!


As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine?

--- In TekScopes@..., David <davidwhess@...> wrote:

The 2465A battery circuits already include reverse voltage protection
in the form of diode CR2770 and a 10K series resistor to limit the
current.

On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.


 

I am not sure about the details of ESD safe soldering stations.

What is required in this case is that the tip not share a low
impedance ground with the instrument to prevent inadvertent shorts of
the applied battery and backup power but the tip also must not
accumulate static charge.

I would use my existing grounded soldering iron, run it from an
isolation transformer to break the ground, and add a resistance from
the soldering iron ground to the instrument ground.

On Tue, 07 May 2013 15:50:26 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap.

No custom PCB req'd.!

As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine?

--- In TekScopes@..., David <davidwhess@...> wrote:

The 2465A battery circuits already include reverse voltage protection
in the form of diode CR2770 and a 10K series resistor to limit the
current.

On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.


rpoz28cam
 

Yes, pretty much like that! that is,  provided you don't lower or reduce the backup source voltage  to less than the minimum specified voltage of that Static Ram chip, probably around the 3Volt range.  Just be sure your equipment is off, unplugged from mains and totally isolated from any other test gear you may have.  As far as your 10K esd provision.. if it were mine, I wouldn't trust it!  I know we all at times think oh there's no static on my soldering iron / or me.. my solder in my hand.. just be careful.  In effect the potential on your soldering tip should rise to your old battery voltage while your 'patching' in the new battery in original pcb location while the variable power supply (very low current setting) is providing the backup power to that Static Ram.  The key to success in doing this is making sure your equipment chassis or grounds are  not grounded common with your soldering iron or solder.. or anything at 0 volts potential.  If your not real sure about this, maybe someone else in the group can offer some more advice!

JLM




From: mosaicmerc
To: TekScopes@...
Sent: Tuesday, May 7, 2013 10:50 AM
Subject: [TekScopes] Re: 2465A battery backup

 

Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap.

No custom PCB req'd.!

As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine?

--- In TekScopes@..., David >
> The 2465A battery circuits already include reverse voltage protection
> in the form of diode CR2770 and a 10K series resistor to limit the
> current.
>
> On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"
> wrote:
>
> >Thx for your input!
> >
> >Look @ this..
> >http://www.eaglepicher.com/images/commercial/ltc7p.pdf
> >
> >I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.
> >
> >The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.
> >
> >I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.
> >
> >The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.
>




vdonisa
 

My advice is to use a battery pack with 3 AA(A) batteries as the temporary power supply, and apply it at such location on the board that it would power just the RAM (not the whole board).

This way if you get a power outage / blown fuse / tripped breaker during your work, your RAM will continue to stay powered until mains power is restored.

Remember that the whole purpose of the exercise is to keep RAM contents safe.

--- In TekScopes@..., David <davidwhess@...> wrote:

I am not sure about the details of ESD safe soldering stations.

What is required in this case is that the tip not share a low
impedance ground with the instrument to prevent inadvertent shorts of
the applied battery and backup power but the tip also must not
accumulate static charge.

I would use my existing grounded soldering iron, run it from an
isolation transformer to break the ground, and add a resistance from
the soldering iron ground to the instrument ground.

On Tue, 07 May 2013 15:50:26 -0000, "mosaicmerc"
<mosaicmerc@...> wrote:

Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap.

No custom PCB req'd.!

As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine?

--- In TekScopes@..., David <davidwhess@> wrote:

The 2465A battery circuits already include reverse voltage protection
in the form of diode CR2770 and a 10K series resistor to limit the
current.

On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"
<mosaicmerc@> wrote:

Thx for your input!

Look @ this..
http://www.eaglepicher.com/images/commercial/ltc7p.pdf

I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.

The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.

I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.

The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.


Jerry Barr
 

cud just use a butane solder iron/that wud elliminate the shorts issue
 
Jerry KJ6NTL

From: J
To: "TekScopes@..."
Sent: Tuesday, May 7, 2013 9:10 AM
Subject: Re: [TekScopes] Re: 2465A battery backup
 
Yes, pretty much like that! that is,  provided you don't lower or reduce the backup source voltage  to less than the minimum specified voltage of that Static Ram chip, probably around the 3Volt range.  Just be sure your equipment is off, unplugged from mains and totally isolated from any other test gear you may have.  As far as your 10K esd provision.. if it were mine, I wouldn't trust it!  I know we all at times think oh there's no static on my soldering iron / or me.. my solder in my hand.. just be careful.  In effect the potential on your soldering tip should rise to your old battery voltage while your 'patching' in the new battery in original pcb location while the variable power supply (very low current setting) is providing the backup power to that Static Ram.  The key to success in doing this is making sure your equipment chassis or grounds are  not grounded common with your soldering iron or solder.. or anything at 0 volts potential.  If your not real sure about this, maybe someone else in the group can offer some more advice!JLM


From: mosaicmerc
To: TekScopes@...
Sent: Tuesday, May 7, 2013 10:50 AM
Subject: [TekScopes] Re: 2465A battery backup
 
Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap.No custom PCB req'd.!As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine?--- In mailto:TekScopes%40yahoogroups.com, David wrote:>> The 2465A battery circuits already include reverse voltage protection> in the form of diode CR2770 and a 10K series resistor to limit the> current.> > On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc"> wrote:> > >Thx for your input!> >> >Look @ this..> >http://www.eaglepicher.com/images/commercial/ltc7p.pdf> >> >I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using.> >> >The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking.> >> >I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies.> >> >The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early.>


rpoz28cam
 

Yup.. Jerry that would work too.. as long as you can control the heat to the sweet spot and not damage the board.



From: Jerry Barr
To: "TekScopes@..."
Sent: Tuesday, May 7, 2013 11:17 AM
Subject: Re: [TekScopes] Re: 2465A battery backup

 
cud just use a butane solder iron/that wud elliminate the shorts issue
 
Jerry KJ6NTL
From: J
To: "TekScopes@..."
Sent: Tuesday, May 7, 2013 9:10 AM
Subject: Re: [TekScopes] Re: 2465A battery backup
 
Yes, pretty much like that! that is,  provided you don't lower or reduce the backup source voltage  to less than the minimum specified voltage of that Static Ram chip, probably around the 3Volt range.  Just be sure your equipment is off, unplugged from mains and totally isolated from any other test gear you may have.  As far as your 10K esd provision.. if it were mine, I wouldn't trust it!  I know we all at times think oh there's no static on my soldering iron / or me.. my solder in my hand.. just be careful.  In effect the potential on your soldering tip should rise to your old battery voltage while your 'patching' in the new battery in original pcb location while the variable power supply (very low current setting) is providing the backup power to that Static Ram.  The key to success in doing this is making sure your equipment chassis or grounds are  not grounded common with your soldering iron or solder.. or anything at 0 volts potential.  If your not real sure about this, maybe someone else in the group can offer some more advice! JLM


From: mosaicmerc
To: TekScopes@...
Sent: Tuesday, May 7, 2013 10:50 AM
Subject: [TekScopes] Re: 2465A battery backup
 
Thx for this... So all I need to do is solder in the new batt, while maintaining power to the RAm during the swap. No custom PCB req'd.! As for ESD on the soldering iron, Won't a 10K from metal tip to gnd be fine? --- In mailto:TekScopes%40yahoogroups.com, David wrote: > > The 2465A battery circuits already include reverse voltage protection > in the form of diode CR2770 and a 10K series resistor to limit the > current. > > On Tue, 07 May 2013 14:47:41 -0000, "mosaicmerc" > wrote: > > >Thx for your input! > > > >Look @ this.. > >http://www.eaglepicher.com/images/commercial/ltc7p.pdf > > > >I am not sure whether the 2465A batts have built in rev. voltage protection. So I thought I need to add it given the commonly available substitute part I am using. > > > >The battery is actual on it's own little daughterboard so the A5 should be buffered for the most part from 'chemicals' . The Lithium Chlorides have a 0.1% failure rate, of which some subset might include leaking. > > > >I wish I could see a guide as to how to read the data form the Static ram. That way i leave the batt alone unless it dies. > > > >The bit abt the alarm is kinda zero cost for me, and I like modding things so ... its my own idiosyncracy. That OPA I linked to has an input impedance of 10^13 so ..power drain isn't the prob. Also, if the batt. leaks its volts will start to fail and the alarm will pick it up early. >



J. L. Trantham
 

David,

Thanks for the info. Can you tell me what the SRAM is? I confess that I have not looked inside the scope or a service manual.

I wonder if you might be able to apply a 'clip' to the chip with wires to a chip programmer, set to the same part number as the SRAM, (with the scope unplugged and backup battery installed) then read the chip.

Might be worth a try, particularly if you have to recalibrate the scope anyway.

Joe

--- In TekScopes@..., David <davidwhess@...> wrote:

Reading the contents of the battery backed up SRAMs directly would
certainly be a challenge. If I had to do that, I would attach power
to the DIP leads and a resistor from GND to CE2 and then try to remove
the SRAM from the board.

Maybe it could be done via the GPIB port if the oscilloscope has that
option.

On Tue, 7 May 2013 08:08:00 -0500, "J. L. Trantham" <jltran@...>
wrote:

I've been following this thread as I have a two 2465B's for the past 2 or 3
years, each last calibrated by Tektronix about 3 years ago, one with S/N
B05xxxx and one B01xxxx that I have been thinking about replacing the
battery/NVRAM and looking at the need to replace the capacitors. I have
never opened them and they work great.

I have three comments/questions.

1. Is it possible to read the contents of the STATIC RAM on the units
with the external battery? The Dallas chips (that I believe to be installed
in the S/N B05xxxx unit - or do I have that reversed?), can be removed,
allowed to cool, install a socket, read the contents, then reinsert the
chips, and therefore have a 'backup' copy of the calibration data and a way
to easily replace the chips.

2. If there is no way to read the contents of the RAM or write data to
the RAM on the units with the external battery, and the batteries seem to
last > 10 years (IIRC), why go to the trouble of making an alarm circuit,
that might also fail or deplete the backup battery faster? It seems to me
that the more critical issue is protecting the calibration data in the most
reliable way for the longest time possible then establish a schedule to
routinely replace the battery.

3. That being said, does Tektronix have a recommended time to replace
the external battery or the Dallas chips? HP recommends replacing the
Dallas chips in the 3458A every 10 years.

Thanks.

Joe


 

I considered that method of reading the SRAMs but the problem is that
the address, data, and control lines are connected in parallel with
other unpowered devices. The ESD protection diodes in the other
devices will short the signal lines to ground and power which are both
at zero volts when unpowered.

If the SRAMs had separate address and data buffers, then you could
remove just the buffers and then read the SRAM in circuit but that is
not the case here.

From the look of it, Tektronix designed the 2465A to accept two
different SRAM pinouts but they only used one in production. It is a
Toshiba TC5564 which has the same basic pinout as a 2764 EPROM. The
NEC part number of uPD4464 is also given. Lots of standard SRAMs or
even NVRAMs should work.

If you are going to recalibrate the oscilloscope, then there is no
need to save the SRAM contents.

On Tue, 07 May 2013 17:18:34 -0000, "wb4bpp" <jltran@...> wrote:

David,

Thanks for the info. Can you tell me what the SRAM is? I confess that I have not looked inside the scope or a service manual.

I wonder if you might be able to apply a 'clip' to the chip with wires to a chip programmer, set to the same part number as the SRAM, (with the scope unplugged and backup battery installed) then read the chip.

Might be worth a try, particularly if you have to recalibrate the scope anyway.

Joe


rpoz28cam
 

Joe,
I might be able to shed some light on that.  When a employing a SRAM (Static Random Access Memory) such as one used for data / constants retention in this scope, there are some procedures for proper use.  To read the data or enable the part for read/write operations in a SRAM there has to be +V or 5 volts on the Vcc pin to start with.  Then you have to toggle some various lines to their respective 1(hi) or 0(lo) states in order to read  / enable or chip select the part.  When said SRAM is in the power down state with only the backup battery the address bus and data bus are not present and accounted for but the memory is kept in current condition by battery.  Does this help you understand?  Also when the chip is in circuit you can't just seize the bus(s) with - say clip leads . dip chip..remote/external programmer / reader device, etc and control the part, there is a great potential of damage to other parts that drive this part not to mention data corruption attempting to do this.  Highly not recommended at all!  I guess during the era of this design there were not many backup options available to 'download' data from the memory cells in these parts.. but it has been done in the past!

JLM





From: wb4bpp
To: TekScopes@...
Sent: Tuesday, May 7, 2013 12:18 PM
Subject: [TekScopes] Re: 2465A battery backup

 
David,

Thanks for the info. Can you tell me what the SRAM is? I confess that I have not looked inside the scope or a service manual.

I wonder if you might be able to apply a 'clip' to the chip with wires to a chip programmer, set to the same part number as the SRAM, (with the scope unplugged and backup battery installed) then read the chip.

Might be worth a try, particularly if you have to recalibrate the scope anyway.

Joe

--- In TekScopes@..., David wrote:
>
> Reading the contents of the battery backed up SRAMs directly would
> certainly be a challenge. If I had to do that, I would attach power
> to the DIP leads and a resistor from GND to CE2 and then try to remove
> the SRAM from the board.
>
> Maybe it could be done via the GPIB port if the oscilloscope has that
> option.
>
> On Tue, 7 May 2013 08:08:00 -0500, "J. L. Trantham"
> wrote:
>
> >I've been following this thread as I have a two 2465B's for the past 2 or 3
> >years, each last calibrated by Tektronix about 3 years ago, one with S/N
> >B05xxxx and one B01xxxx that I have been thinking about replacing the
> >battery/NVRAM and looking at the need to replace the capacitors. I have
> >never opened them and they work great.
> >
> >I have three comments/questions.
> >
> >1. Is it possible to read the contents of the STATIC RAM on the units
> >with the external battery? The Dallas chips (that I believe to be installed
> >in the S/N B05xxxx unit - or do I have that reversed?), can be removed,
> >allowed to cool, install a socket, read the contents, then reinsert the
> >chips, and therefore have a 'backup' copy of the calibration data and a way
> >to easily replace the chips.
> >
> >2. If there is no way to read the contents of the RAM or write data to
> >the RAM on the units with the external battery, and the batteries seem to
> >last > 10 years (IIRC), why go to the trouble of making an alarm circuit,
> >that might also fail or deplete the backup battery faster? It seems to me
> >that the more critical issue is protecting the calibration data in the most
> >reliable way for the longest time possible then establish a schedule to
> >routinely replace the battery.
> >
> >3. That being said, does Tektronix have a recommended time to replace
> >the external battery or the Dallas chips? HP recommends replacing the
> >Dallas chips in the 3458A every 10 years.
> >
> >Thanks.
> >
> >Joe
>




 

There was no need for the ability to archive the battery backed up
SRAM contents. The backup battery was expected to last for the
intended design life of the instrument just like with the NVRAMs
Tektronix later used.

When I have designed systems that use non-volatile memory in the past
where the contents were important, I have included dual backup
supplies so the battery could be swapped easily or dual EEPROMs and a
way to save and restore the data if necessary.

On Tue, 7 May 2013 10:48:52 -0700 (PDT), J <rpoz28cam@...>
wrote:

. . .

I guess during the era of this design there were not many backup options available to 'download' data from the memory cells in these parts.. but it has been done in the past!

JLM