Agilent 34970A, Battery replacement and repair

[HighVoltage]

This Agilent 34970A Data Acquisition unit I bought used in broken condition very cheap.
After opening it up, I found the problem right away with a loose ribbon cable.
Then I took it completely apart and cleaned it all and replaced a ribbon cable.

It seems to work perfect now.
But I measured the battery and it has only 2.6V instead of 3V
So, I would think it needs to be replaced.

Does anyone here have experience with replacing this battery?
Do I need to keep the unit powered up or at least plugged in, during the exchange of the battery.
Anything else to watch out for?

Here are some pictures:

[nfmax]

Yes, I have replaced the battery in the unit I bought second-hand a few weeks ago. You should disconnect the unit from the mains supply, calibration data (including relay operation cycle counts) is not dependent on the battery. The procedure is described in the service manual and it's pretty straightforward.
My unit had a cylindrical, through-hole tag mounted battery, not a surface mount button cell like yours. I think these have a larger capacity: if you look at the PCB you will see there are three holes for the battery tags so presumably you can use either. Be careful to choose a battery with the correct pin spacing at the 2-pin end, and with the correct polarity - all possible variants are made and only 1 of the 4 is right!
It sounds as though your battery, while dying, is not quite dead yet. When it finally dies, you will get an error indication each time you power up the unit & 2 codes - clock lost & memory lost. But no harm in replacing the battery now while you are working on it anyway!

[magnehh]

I believe the HP 34790A's had the "long" cell and the old, horrid FRAM. While in the Agilent version, they changed both of them.

I do have two multimeter modules for these if you're interested. Only problem is, they loose the cal data when you unplug them from the main board. :-P

[HighVoltage]

Thank you both for the feedback.
Now I just have to find the right battery with the solder tabs at the right spot.

The original Panasonic number is BR2477A
That one seems not to be available.

[PA0PBZ]

http://www.digikey.com/product-detail/en/BR-2477A%2FVAN/P030-ND/273650

[HighVoltage]

Thank you for the link, PA0PBZ

[nfmax]

Thank you both for the feedback.
Now I just have to find the right battery with the solder tabs at the right spot.

The original Panasonic number is BR2477A
That one seems not to be available.

The battery I fitted was a Varta, Farnell part number 197-2505. This has two pins at the positive end, spaced at 7.5mm. The dead battery was reading about 0.65V (!), and I was seeing error codes 202 and 204 at each power on. I don't think this was the original battery though as there was uncleaned flux on the PCB. My unit is an Agilent labelled one, as are the plug in modules.
I have a spare copy of the (English) service guide - PM me if you are interested

Max

[HighVoltage]

PM sent,
I ordered the original battery from Digikey and I will post again, once the replacement battery is installed.
May be a full calibration will be required afterwards.

[Jwalling]

PM sent,
I ordered the original battery from Digikey and I will post again, once the replacement battery is installed.
May be a full calibration will be required afterwards.

FYI: I've found that these units will accept a standard horizontally mounted CR2032 battery holder like you would see in any PC motherboard. Sure the battery doesn't last as long, but when you need to replace it, it's a snap.

Jay

[HighVoltage]

FYI: I've found that these units will accept a standard horizontally mounted CR2032 battery holder like you would see in any PC motherboard. Sure the battery doesn't last as long, but when you need to replace it, it's a snap.

Jay

Thank you for this information, great idea!
I will get a CR2032 holder and take a closer look.

[Jwalling]

FYI: I've found that these units will accept a standard horizontally mounted CR2032 battery holder like you would see in any PC motherboard. Sure the battery doesn't last as long, but when you need to replace it, it's a snap.

Jay

Thank you for this information, great idea!
I will get a CR2032 holder and take a closer look.

You're welcome. Note that the pins of the holder don't go in the same holes as the original battery, they go in the larger holes between the original pin holes. You'll figure it out using a DMM on continuity - just watch out for polarity. You'll also need to scrape away a bit of the solder mask before soldering it in. I use a bit of scotch tape to hold in the battery holder since you have to solder it in upside down.

Jay

[dom0]

Yes, I have replaced the battery in the unit I bought second-hand a few weeks ago. You should disconnect the unit from the mains supply, calibration data (including relay operation cycle counts) is not dependent on the battery.

The battery powers only the RTC?

In my olde 3478A there was one of these large (thicker but shorter than a AA mignon) lithium cells, over 30 years old, still had 2.95 V or so on it :-)

[nfmax]

The battery powers only the RTC?

In my olde 3478A there was one of these large (thicker but shorter than a AA mignon) lithium cells, over 30 years old, still had 2.95 V or so on it :-)

The battery also supplies the SRAM used to hold the measured data - this is really useful as you can take measurements on an experiment in the lab, then bring the datalogger back to your desk to download & analyse the data. The one I bought recently was for home use, but we have used dozens of these dataloggers at work since I bought us the first one back in 1999!

[HighVoltage]

Today I installed the new battery (original replacement from Digikey)
The Battery was out for about 6 minutes and the instrument kept all calibration data.

Tomorrow I will check the calibration on all ranges.
It seems so far, that it was a success.

Thanks for all your help.

[plesa]

I know that it is little bit late, but in my unit fir battery CR14250, it is rotated by 90 degree compare to your picture.

[HighVoltage]

I know that it is little bit late, but in my unit fir battery CR14250, it is rotated by 90 degree compare to your picture.

How can it be rotated 90 degree?
You mean 180 degree?
Can you take a picture of what you have in your unit?
Thanks

[HighVoltage]

BTW, this 34970A has been turned on for a while now and seems to be very stable.
I still need to do a detailed calibration check.

Do you usually check the calibration on all channels of a 901 card to also include the multiplexer card ?

[plesa]

I calibrate only one channel, but before I highly suggest to check the relay card resistance and relay odometer.

Quite funny is the fan placement on side completely covered with enclosure, I'm quite curious what is purpose of this fan, because on another side it is covered by IEC connector assembly.
So It cannot cannot help to flow air inside instrument, like we saw inside Keithley 7510.

[plesa]

What I forgot to mentioned - check the relay counter on internal DMM (if present).
I do not find the way how to check it through front panel, only remotely by DIAG:DMM:CYCLES?
For instance on my unit the DMM relay K102 is almost dead >10M cycles. Probably someone selected different ranges 10V/100V or similar switching problem
For details check "Chapter 5 Theory of Operation - Internal DMM" in service manual.
I needs to desolder relay and replace it by new one Omron G6SU-2-DC3
Because my unit has only one issue ( errors in self test 740/741/748 and etc) all were due to unlocked instrument, when I locked calibration all are gone.Battery has 3V.
Based on the relay counter I expect that unit failed calibration due to K102 relay.

There is another trap - if you checking basic performance of modules put into terminal some wire. Unit has been supplied with two modules. Both as faulty ones with marking which relay is faulty.
So I checked the odometer and maximum was 25 cycles.
DIAG:RELAY:CYCLES? (@101,102, ....)
So I checked them according to service manual and yes they seems to be not working.
So I expect that someone reset relay counter, but modules were almost new. When I measured the relay contacts all were OK, yes the problem was in terminals!!!!!
The guy which has been cheeking the modules make same mistake probably.
If you are measuring the screw, there is ope circuit, when you put there some wire it is OK

[HighVoltage]

Thank you plesa, this was really good information.

One more question,
If you would replace a relay, can you reset the counter to reflect the new relay installation?

[plesa]

Yes, both can be cleared/reset. You needs to unsecure the instrument
CAL:SECURE:STATE OFF,HP034970

and then
DIAG:DMM:CYCLES:CLEAR  (1,2,3 ) depends on which relay counter you want to reset
DIAG:RELAY:CYCLES:CLEAR (@101,102, ...) depends on which relay counter you want to reset

The good document for this is manual for 34972A instead of 34970A manual
http://cp.literature.agilent.com/litweb/pdf/34972-90001.pdf
or old HP manual
http://www.keysight.com/upload/cmc_upload/All/34970-90003_users.pdf

That's pity that this is not possible for bench DMM, or I do not know how.
This can be helpful to predict the relay failure like you have on 34410A.

Which firmware you have and what is response to SYSTem:VERSion?

In meantime I found only service note to my serial number http://literature.cdn.keysight.com/litweb/pdf/34970A-13.pdf related to stability of 400k Vishay UXB thin film resistor which can affects 10M and 100M Ohms measurement.
And another related to connection bwtween main board and DMM http://cp.literature.agilent.com/litweb/pdf/34970A-14C.pdf
Funny is that my serial number is not affected by cover exchange, but in real it does not have proper cover ( so check if your cover has ventholes on righ side and bottom end).


Complete list you can found here:
http://servicenotes.literature.keysight.com/litapp/SearchSN.do?method=openExternalSNSearch&prodNum=34970A

Also interesting document about change FRAM ( when you have 740 errors ) in attachment.

[plesa]

I just found that latest firmware is v13, programmed in U401 ( 27C4096 OTP EPROM). I will really appreciate if someone can post version v12 or v13 for upgrade.

[HighVoltage]

I have two of these Agilent 34970A units.
How do I test what FW version is installed?
Can I do it over the UI?

[plesa]

I have two of these Agilent 34970A units.
How do I test what FW version is installed?
Can I do it over the UI?

Version of FW is in response to *IDN? command, it is first number ( XX-X-X).
Do you have PLCC 44 package programmer?

[nfmax]

I have two of these Agilent 34970A units.
How do I test what FW version is installed?
Can I do it over the UI?

Version of FW is in response to *IDN? command, it is first number ( XX-X-X).
Do you have PLCC 44 package programmer?

Keysight Connection Expert also shows the firmware version from the ident string. My unit returns 12-1-2. Does anyone know what the differences are?

Max