Topics

Easy method for NVRAM battery replacement

Szabolcs Szigeti
 

Hi,


While fixing a 2430A, it turned out that it has two DS1235 NVRAM, with built in battery. I could have replaced it with DS1230, as that is easily available, but this would not have been economical at all. So I looked into how to add an external battery. As these chips are potted, it's pretty hard and messy to get to the original battery. All methods that I have seen on the web involved grinding the potting, and potentially risk damaging the part.


So after some trials, I have found a method that enabled me to quickly and easily add a battery.
All you need is a heat gun with a thin nozzle. Heating the potting will make it soft and more importantly, make it release from the battery. Fortunately the battery is at the bottom of the part (not all such similar devices are like this). First I heated it at about where the battery is and when it became a bit soft, it was easy to scrape it off with a small screwdriver. Then the the negative tab could be pried off the battery. Next comes the hard part, remove the battery. Make sure that the potting is removed all from the area of the battery, and at the edge of the device, remove it at such a depth that you see the whole thickness of the battery. It's not very thick, and there is a PCB underneath, so be careful. I then drilled a small hole into the battery, so it would not explode, when heated and used the heat gun, to heat the battery. When sufficiently heated, you can simply pry/flip it out from its place from the side, by putting a small screwdriver under it. Be careful, as the positive tab is spot-welded to it under, wiggle a bit and then it's possible to snip off the tab.
There are two batteries, but it is enough to do this with one, as the circuitry in the NVRAM will use the battery with the higher voltage.
Then I simply soldered some wire and a battery holder for a 2032 lithium battery to it. I used some epoxy to fix the wires in the cavity, where the old battery was. Originally, I planned to place the new batteries somewhere where there is place inside the scope, but it turned out that actually there is just about enough height, so i epoxied the battery holder to the top of the NVRAM, put some quite ugly looking kapton tape on the top, just in case it would touch the PSU cover. I could probably shorten the wires, but that is ok. It now works fine. Hope this can help someone with similar needs.


Here are some pictures:


https://goo.gl/photos/6u7veVp1usNe4MmQA https://goo.gl/photos/6u7veVp1usNe4MmQA



Szabolcs

ArtekManuals
 

Sounds interesting
The link to pictures is busted?

Dave

On 5/6/2017 2:33 PM, szigszabolcs@... [TekScopes] wrote:

Hi,


While fixing a 2430A, it turned out that it has two DS1235 NVRAM, with
built in battery. I could have replaced it with DS1230, as that is
easily available, but this would not have been economical at all. So I
looked into how to add an external battery. As these chips are potted,
it's pretty hard and messy to get to the original battery. All methods
that I have seen on the web involved grinding the potting, and
potentially risk damaging the part.


So after some trials, I have found a method that enabled me to quickly
and easily add a battery.
All you need is a heat gun with a thin nozzle. Heating the potting
will make it soft and more importantly, make it release from the
battery. Fortunately the battery is at the bottom of the part (not all
such similar devices are like this). First I heated it at about where
the battery is and when it became a bit soft, it was easy to scrape it
off with a small screwdriver. Then the the negative tab could be pried
off the battery. Next comes the hard part, remove the battery. Make
sure that the potting is removed all from the area of the battery, and
at the edge of the device, remove it at such a depth that you see the
whole thickness of the battery. It's not very thick, and there is a
PCB underneath, so be careful. I then drilled a small hole into the
battery, so it would not explode, when heated and used the heat gun,
to heat the battery. When sufficiently heated, you can simply pry/flip
it out from its place from the side, by putting a small screwdriver
under it. Be careful, as the positive tab is spot-welded to it under,
wiggle a bit and then it's possible to snip off the tab.
There are two batteries, but it is enough to do this with one, as the
circuitry in the NVRAM will use the battery with the higher voltage.
Then I simply soldered some wire and a battery holder for a 2032
lithium battery to it. I used some epoxy to fix the wires in the
cavity, where the old battery was. Originally, I planned to place the
new batteries somewhere where there is place inside the scope, but it
turned out that actually there is just about enough height, so i
epoxied the battery holder to the top of the NVRAM, put some quite
ugly looking kapton tape on the top, just in case it would touch the
PSU cover. I could probably shorten the wires, but that is ok. It now
works fine. Hope this can help someone with similar needs.


Here are some pictures:


https://goo.gl/photos/6u7veVp1usNe4MmQA
https://goo.gl/photos/6u7veVp1usNe4MmQA



Szabolcs



[Non-text portions of this message have been removed]

--
Dave
Manuals@...
www.ArtekManuals.com

ArtekManuals
 

Never mind I forgot that yahole doubles up on the link when using the
WEB interface ( but not an email client

https://goo.gl/photos/6u7veVp1usNe4MmQA


On 5/6/2017 2:33 PM, szigszabolcs@... [TekScopes] wrote:

Hi,


While fixing a 2430A, it turned out that it has two DS1235 NVRAM, with
built in battery. I could have replaced it with DS1230, as that is
easily available, but this would not have been economical at all. So I
looked into how to add an external battery. As these chips are potted,
it's pretty hard and messy to get to the original battery. All methods
that I have seen on the web involved grinding the potting, and
potentially risk damaging the part.


So after some trials, I have found a method that enabled me to quickly
and easily add a battery.
All you need is a heat gun with a thin nozzle. Heating the potting
will make it soft and more importantly, make it release from the
battery. Fortunately the battery is at the bottom of the part (not all
such similar devices are like this). First I heated it at about where
the battery is and when it became a bit soft, it was easy to scrape it
off with a small screwdriver. Then the the negative tab could be pried
off the battery. Next comes the hard part, remove the battery. Make
sure that the potting is removed all from the area of the battery, and
at the edge of the device, remove it at such a depth that you see the
whole thickness of the battery. It's not very thick, and there is a
PCB underneath, so be careful. I then drilled a small hole into the
battery, so it would not explode, when heated and used the heat gun,
to heat the battery. When sufficiently heated, you can simply pry/flip
it out from its place from the side, by putting a small screwdriver
under it. Be careful, as the positive tab is spot-welded to it under,
wiggle a bit and then it's possible to snip off the tab.
There are two batteries, but it is enough to do this with one, as the
circuitry in the NVRAM will use the battery with the higher voltage.
Then I simply soldered some wire and a battery holder for a 2032
lithium battery to it. I used some epoxy to fix the wires in the
cavity, where the old battery was. Originally, I planned to place the
new batteries somewhere where there is place inside the scope, but it
turned out that actually there is just about enough height, so i
epoxied the battery holder to the top of the NVRAM, put some quite
ugly looking kapton tape on the top, just in case it would touch the
PSU cover. I could probably shorten the wires, but that is ok. It now
works fine. Hope this can help someone with similar needs.


Here are some pictures:


https://goo.gl/photos/6u7veVp1usNe4MmQA
https://goo.gl/photos/6u7veVp1usNe4MmQA



Szabolcs





--
Dave
Manuals@...
www.ArtekManuals.com

Szabolcs Szigeti
 

Ok, an other try, for some reason my message disappeared.

So her is the link, this is to a google photos shared album, you should be able to see it without any login etc.


https://goo.gl/photos/6u7veVp1usNe4MmQA https://goo.gl/photos/6u7veVp1usNe4MmQA



Let's see if ti works now. I was unable to upload it to the yahoo groups.


Szabolcs

ArtekManuals
 

The problem is Yahole doubles the link

Try this

https://goo.gl/photos/6u7veVp1usNe4MmQA


On 5/6/2017 2:51 PM, szigszabolcs@... [TekScopes] wrote:

Ok, an other try, for some reason my message disappeared.

So her is the link, this is to a google photos shared album, you
should be able to see it without any login etc.


https://goo.gl/photos/6u7veVp1usNe4MmQA
https://goo.gl/photos/6u7veVp1usNe4MmQA



Let's see if ti works now. I was unable to upload it to the yahoo groups.


Szabolcs





--
Dave
Manuals@...
www.ArtekManuals.com

Szabolcs Szigeti
 

Argh. Let's try the link again, and see if it works now

https://goo.gl/photos/6u7veVp1usNe4MmQA https://goo.gl/photos/6u7veVp1usNe4MmQA

mosaicmerc
 

Merchison Burke
 

All versions of the link worked for me with Win XP Pro SP3 and Thunderbird 52.1.0 (32 bit) and Firefox 52.1.0 (32 bit).

I download all posts to my computer and read them with Thunderbird. When I clicked on the link, I was able to see the photos with Firefox.

On 2017-May-06 2:55 PM, szigszabolcs@... [TekScopes] wrote:
Argh. Let's try the link again, and see if it works now

https://goo.gl/photos/6u7veVp1usNe4MmQA https://goo.gl/photos/6u7veVp1usNe4MmQA


David Kuhn
 

Wow, great job Szabolcs! Question, what all data is in the Dallas BRams?
Is it just temporary data or do they contain the calibration tables to? If
they to contain those, do you have to have the scope recalibrated (not
certified) after doing this, especially if the battery was already dead?

Dave



On Sat, May 6, 2017 at 23:21 Merchison Burke merchison@...
[TekScopes] <TekScopes@...> wrote:



All versions of the link worked for me with Win XP Pro SP3 and
Thunderbird 52.1.0 (32 bit) and Firefox 52.1.0 (32 bit).

I download all posts to my computer and read them with Thunderbird. When
I clicked on the link, I was able to see the photos with Firefox.



On 2017-May-06 2:55 PM, szigszabolcs@... [TekScopes] wrote:
Argh. Let's try the link again, and see if it works now

https://goo.gl/photos/6u7veVp1usNe4MmQA
https://goo.gl/photos/6u7veVp1usNe4MmQA




[Non-text portions of this message have been removed]

Szabolcs Szigeti
 

Hi Dave,

Thanks. In the case of the 24xx digital scopes, both. It stores saved vaweforms, settings, etc. as well as calibration data. So these are lost. However, for these scopes, it's not that big of a problem, as calibration is quite simple, most of it is automatic and does not require much equipment. For example, to calibrate the 2430a all you need is a DC power supply.
This may not be the case for other scopes. So if there is still data in the nvram, that should be saved.

Szabolcs

Szabolcs Szigeti
 

Hi,

That is a good question. I think the method of using heat to soften the potting would work here too. The only question is where to start. Given that this also has a quartz crystal inside as well as a battery, one needs to be careful.
I did fix a DS1287 RTC/NVRAm chip following he instruction at http://www.auroragrp.com/agi/other/tekmate/tekmate.html http://www.auroragrp.com/agi/other/tekmate/tekmate.html


But that was easy, as one only had to access the bent up pins. On the DS1486, there are no such pins, but for start I would assume that it is similar to the 1287 and the battery and xtal are on the top.But careful removal of the potting should reveal this I guess.


Szabolcs

Chuck Harris
 

Tektronix used these Dallas NVRAM devices as all-in-one RAM
for their controllers. They contain a variety of stack and
internal variable storage, as well as calibration constants
and instrument settings...

One point that may be of interest... The control chip in the
Dallas NVRAM insists on having sufficient internal battery
power before it will allow the chip to be accessed for
reading or writing under normal operating conditions.

It is very likely that the NVRAM can have failed as far as
the scope is concerned, and still have all of the data saved
in the hibernating RAM cells.

Since the NVRAM has two redundant cells in its battery, and
a voting power switch, if you add 3V power to one of the
cells, you should then be able to read the part on your
EPROM programmer, and may be able to save the calibration
data.

Because I calibrate scopes, *I* wouldn't bother, a dead
NVRAM is at best holding thoroughly past any reasonable
expiration date calibration constants.

-Chuck Harris

'Daveyk021 .' daveyk021@... [TekScopes] wrote:

Wow, great job Szabolcs! Question, what all data is in the Dallas BRams?
Is it just temporary data or do they contain the calibration tables to? If
they to contain those, do you have to have the scope recalibrated (not
certified) after doing this, especially if the battery was already dead?

Dave