P.S. As I understand it from your description of the FRAM mod, you will be contemplating either:

- reading the contents of the existing RAM and transferring them to the FRAM
or
- recalibrating the whole scope

Neither is an easy task. Calibration in special will require all sort of unobtainium jigs (like the tunnel diode pulser one).

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

Great, then you've already seen it. Just make sure that the AAA batteries are fresh and making good contact in the holder before unsoldering the lithium.

I recommended Allied since they also ship lithium batteries outside US. Mouser generally doesn't. If you're in the US then of course you have a choice.

Assuming that the rest of the circuit is sane, the new battery will surely last for another +20 years. Based on your expectations on the life of the rest of the scope, you may decide on the FRAM mod.

---In TekScopes@... mailto:TekScopes@..., <2465bct@...> wrote :

> Also an illustrated guide to replacing the A5 board battery (for the non-SMD version) is here in the photo section:
>
> https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848 https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1079293848
>
> Click on photos, they have captions explaining what's going on.
>
> The battery is usually available from http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/ http://www.alliedelec.com/
>
> If you have the SMD version it's a completely different (and grim) story.

Thank you.

Yahoo won't let me look at the links. I have seen such a guide before and it
was very clear about how not to lose the calibration (remove the capacitor
next to the battery, solder wires leading to a triple AAA battery holder,
replace the battery, unsolder the wires and replace the capacitor).

As far as the battery is concerned, it is available on Mouser with part
number: LTC-7PN (vendor part number) the same as on alliedelc. The mouser
price is about $8 cheaper ($15.82 vs. $23.92). This is an exact drop-in
replacement for the battery in my scope. Which, after seeing other pictures,
makes me think that my battery has been previously replaced.

However, timb on eevBlog has a modification which replaces the RAM chip with
an FRAM and eliminates the battery. He has applied it to his own early B scope
and is sending me the details. That modification is probably a better choice,
but I won't know until I see it. My understanding is that he replaces the RAM
chip with an FRAM, replaces a diode with a resistor and a link to something
else forming a voltage divider to satisfy the battery voltage monitor.

Since the A5 board is easy to take out, that modification will probably be the
last thing that I do. If I do timb's modification, I will probably lose the
calibration data. However, I plan on a calibration so that may not be an
obstacle.


Mike