Tek TDS3000 series and Dallas NVRAM

[MarkL]

I was performing a minor repair on a TDS3054 (not B or C version), and I noticed a "Dallas DS1742W-150 Timekeeping RAM" soldered onto the main board.  The date code is 1999, and the Dallas datasheet claims a minimum of 10 year life expectancy for the battery.

Does anyone know if the cal data or other critical information is stored there?  Is there any known backup procedure besides unsoldering it and reading it out on a programmer?  Perhaps via the GPIB?

Has anyone seen any TDS3000 NVRAM go bad?

Given the actual lifetime reported on other Dallas NVRAM parts in other scopes, I probably still have many years left before I have to deal with it, assuming I keep the scope that long.

And a side note... The repair was to replace the CCFL tubes on the display which was getting very dim.  There are two CCFL tubes and they slide out as modules.  It's a trivial repair, although getting to the display itself requires a bit of disassembly.  Display is part #NEC NL6448AC20–06, CCFL modules are 65LHS–3L.  You can also get bare CCFL tubes (2.6mm x 153mm) and solder them in the modules yourself for much less.  FYI.

[voltsandjolts]

I replaced the NVRAM in my TDS3034 as a precaution - I didn't know if there was any critical info in there.
Turns out there isn't, so its safe to let the NVRAM battery die before replacing it.
The only difference I could see by fitting a new blank NVRAM was the "number of powerups" in scope diagnostics was reset to zero.
I think the NVRAM just stores scope setups, timebase, volts per division etc.

Thanks for the display and CCFL PNs, hopefully I won't need them!

[David Hess]

Wow, that is good to know.

Earlier Tektronix oscilloscopes stored the calibration data in the NVRAM leading to a difficult or costly problem if the contents were lost.

[HighVoltage]

I replaced the NVRAM in my TDS3034 as a precaution - I didn't know if there was any critical info in there.
Turns out there isn't, so its safe to let the NVRAM battery die before replacing it.
The only difference I could see by fitting a new blank NVRAM was the "number of powerups" in scope diagnostics was reset to zero.
I think the NVRAM just stores scope setups, timebase, volts per division etc.

Thanks for the display and CCFL PNs, hopefully I won't need them!

I also have an older TDS3034 and may be I should replace the NVRAM.
Did you replace it with the same "Dallas DS1742W-150 Timekeeping RAM" or are there alternatives?

Thanks for this great information.

[David Hess]

I also have an older TDS3034 and may be I should replace the NVRAM.
Did you replace it with the same "Dallas DS1742W-150 Timekeeping RAM" or are there alternatives?

Thanks for this great information.

You can use a faster one to replace a slower one.  I see plenty available at Mouser and Digi-Key although they cost more than $20 each.

I am not aware of any third party equivalent replacements.  I know this issue has come up for older Dallas Timekeeping RAMs which they no longer produce.  In those cases, the Timekeeping RAMs were replaced with standard NVRAMs and the oscilloscope still worked but without the time and date functions.

[MarkL]

Thanks for the info on the NVRAM, voltsandjolts!

It's good to know design mistakes of the past don't always repeat themselves.

[voltsandjolts]

@HighVoltage
"Did you replace it with the same "Dallas DS1742W-150 Timekeeping RAM" or are there alternatives?"

Yes, I used that Dallas part. Not cheap.

[prot_brot]

Will DS1642 work? it has the same 2k x 8 ram and pinout as the DS1742 at half the price

[Jwalling]

I was performing a minor repair on a TDS3054 (not B or C version), and I noticed a "Dallas DS1742W-150 Timekeeping RAM" soldered onto the main board.  The date code is 1999, and the Dallas datasheet claims a minimum of 10 year life expectancy for the battery.

Does anyone know if the cal data or other critical information is stored there?  Is there any known backup procedure besides unsoldering it and reading it out on a programmer?  Perhaps via the GPIB?

Has anyone seen any TDS3000 NVRAM go bad?

Given the actual lifetime reported on other Dallas NVRAM parts in other scopes, I probably still have many years left before I have to deal with it, assuming I keep the scope that long.

Had an opportunity to read out the contents of the Dallas chip in a TDS3014B
Is it possible that there is a back-door into these? I'm no hacker, completely clueless even. 

I've attached the binary as well.

EDIT: Typo. Always a friggin' typo!
Jay

[CNsam]

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