Agilent 34401a revisions

[NoisyBoy]

Hey everyone,

I have a couple questions regarding the 34401a that I cannot find any information on the web, I hope you can help:

• I understand the last and final firmware level is Rev 10, for those of you who has it installed in your DMM, what is the three revisions levels when you look it up in the System Menu
• I just ordered a new front display board from Keysight, it upgraded the last revision number (display) to 03 (I had 02 in my old panel).  Does anyone know what are the changes between 02 and 03?  Is it just a hardware revision?  Or is there actually some real firmware changes?

Thanks to all the wisdom shared by this wonderful community, the panel swapped out was a piece of cake.  [/list]

[coromonadalix]

There is a revision 11, but you have to send it at Keysight, they wont sell you directly the firmware chip, i've tried ...  and i dont know how much it cost ..

For the revisions i did not see any paper /document about that, maybe ask Keysight for the changes ??



Brief History  on the   34401A-06     service note

Up to the fw 06-04-01  you will have the old unobtanium display chip,       pcb: 34401-66502

Past the  fw 06-04-02  you'll get the newest more repairable display pcb   pcb: 34401-66512

You can still order the newest pcb version 34401-66512, but the quantity is low ...  and the price is high,  around 200$ in my country, dont know how much you've paid for it ?

There is a version 10 leaked in the attachement, never tried it, it is supposed to work if you reprogram your (U502) fw chip and put the newest display pcb ... never heard of anyone doing it


For the VFD (vacuuum display) pn: 2090-0296 it is not orderable from Keysight anymore, you have to rely on chinesium parts around the web.
Some have success, others dont, I have seen some Samsung and Itron named / printed on them ??
I have ordered 2 vfd's to replace one dimmed at 50% in one of my meter,  time will tell when i have them delivered.
I hope they have protected the pins as i asked ..... they told me yes ...

I will tell my source if it work ... around 30$ usd each ... not from Ebay.

[HighVoltage]

A few years ago, the VFD on ebay from far east were really good quality.
Lately, like in the last 2 years, every single one I bought was not nearly as good as they used to be and I have given up on buying them from ebay.

The VFD with the attached PCB is worth the money from Keysight, as long as we can get them.
 

[NoisyBoy]

Thanks for the info, I was able to order the front display board from Keysight in the US.  It is $150 plus tax, but it saved me the headache of having to deal with the eBay vendors.  I think it is well worth it as it keeps everything original.

My meter now has revision 11-05-03 on it from what it is worth, would be interesting to see if there’s anything more current.

It would be interesting to see if anyone knows what is different about the V3 display. 

Thank you for all the info you shared.

[HighVoltage]

I have on of the last produced 34401A and it is made in Singapore in 2016/2017.
It has 11-05-03 installed.
It seems that 11-05-03 is installed in all Keysight branded models.

But I have not noticed any thing different from older 34401A

[coromonadalix]

Damn i want one badly loll

[NoisyBoy]

Thanks for sharing the version info, as it has been a mystery that I cannot find on the web anywhere.  All I was able to find was the Agilent video from 2014.  Back then the display was still at revision 2.

I do enjoy using the unit, it is a reliable and responsive DMM.

[mr.fabe]

I have an Agilent branded 34401a assembled in Malaysia with the 11-05-02 FW.

Sent from my Moto Z (2) using Tapatalk

[JohnPi]

I have a newer one that is 11-5-2, and older ones that are 10-5-2. All are labelled 'Agilent'.

I'm puzzling over some SCPI commands, but so far the only difference I see is that the '11' one lights the 'Adrs' annunciated while in remote. I'm not sure why.

[Peter_O]

I've just fetched a 11-05-02. Display not brilliant but OK.

I wonder which manual to download and print.
Would the 2014 Edition 10 User's Guide from the keysight website be OK, or do I need to look for a special one?

[jusaca]

I wonder which manual to download and print.

I would say that is wasted paper and ink. I played around with my one for an hour and got almost everything working. Then I skimmed through the manual to understand the last tricks and details.
Regarding which manual to use - I think it does not really matter at all. As far as I can tell, they did not change anything regarding the way to use the meter.

[NoisyBoy]

I think that version is fine. By 2014, it is running on the final 11-5-3 firmware. I have two units, one with 11-5-3, the other with 11-5-2.  The last digit is the display board firmware, I have not been able to detect any operational difference between them.

I also agree with jusaca on the printed manual, I have both set of the original manuals that came with the meter still in shrink wrap, and I have never opened them. I only use the PDF version, much easier to search.  If you are going to go through the effort to print them, you might as well just purchase the real hard copy.

[Neo2199]

Hi, sorry to revive this old thread, but I just got my 34401A and by checking revision it says REV 01-01-01. Does anyone know what it means? Should I attempt to update?

[dorkshoei]

Hi, sorry to revive this old thread, but I just got my 34401A and by checking revision it says REV 01-01-01. Does anyone know what it means? Should I attempt to update?

measurement processor revision -- i/o processor revision --  front panel processor revision

01-01-01 seems suspicious to me.  Did you obtain it from the procedure shown here?   

What is the serial# and county of manufacturer (on rear)?

Upgrading is not as simple as flashing new firmware. 

[NoisyBoy]

Wow, that would be the original edition at launch.  I have never seen a unit in that firmware level either. 

I have never been able to get any detail on the changelog, upgrading firmware requires you to program a new U502 ROM, and I believe it will also require a recalibration.  So unless you have a reason to upgrade, it may not be worth the effort.  Due to the age of the meter, perhaps a full functional test and accuracy check should come first.

Good luck.

[dorkshoei]

There are hardware barriers that limit how far one can upgrade each component.  Service guide has some into but its not complete as,its a static doc.  Keysight may have more info.  Also some upgrades even if hw supportsl can only be done by keysight.

Without confirmation of a very early serial i suspect version reported is not correct

[Neo2199]

Yes, I have followed up the video.
the SN:3146A01412 Made in U.S.A.
Yeah I know the upgrade will be hard, just wondering if it is worth it. The only reasonable version would be 05-01-01. The others require different display board. Also bit worried about difference in the main board HW in respect to firmware.

By the way, looks like xDevs repaired the same version of 34401A https://xdevs.com/fix/hp34401a/

Yeah, my current plan is to replace all tantalum and electrolytic caps, get missing fuse holder then full accuracy and functionality check, then will see.

[coromonadalix]

wow thats a first    

But you have the unobtanium display circuit,  you can not put any type of firmware in it

And you can not put the more modern display in replacement of the unobtanium one,  if you dont flash the main eeprom unit,  there is a note i've read on the manuals

pretty darn clean meter,   looks like a time machine  loll

And yes the accuracy should be checked first,  if it aint broke  dont touch it


The revision 11 of the display firmware was in the past only obtainable from keysight if you did an meter exchange, dont know if that condition changed ??

And their exchange system is pricey as $$$

I would be curious to see their reaction  when you told them that you have the first version ...  and you want to get the firmwares changes / history  if there is one to get

Digikey has the two different fuse sockets and the fuse caps,  beware  they are separated parts  not a kit,  i managed to get theses parts to rebuild one of my 34401a

Even the main ac socket can be found,  not on the keysight parts page, was around 40$   few years ago

I recapped my meters  and worked them with an hot air desoldering station and used kapton tape  to protect the surrounding parts from over heating, and do use anti static gloves and proper grounding

Once recapped, they where sent for calibration  and passed with  flying colors, and one of them received clone VFD from AliExpress at 30$ usd at the time

[Zoli]

Yes, I have followed up the video.
the SN:3146A01412 Made in U.S.A.
Yeah I know the upgrade will be hard, just wondering if it is worth it. The only reasonable version would be 05-01-01. The others require different display board. Also bit worried about difference in the main board HW in respect to firmware.

By the way, looks like xDevs repaired the same version of 34401A https://xdevs.com/fix/hp34401a/

Yeah, my current plan is to replace all tantalum and electrolytic caps, get missing fuse holder then full accuracy and functionality check, then will see.

The fuse holder is Schurter 0031.3558(digikey 0 stock); maybe is cheaper/simpler to order from online distributors then from Keysight, considering the late habits.

[Neo2199]

Thanks for all the advice. All good info.
I will probably stick with if it ain't broke, don't touch it. We will see how the performance testing goes.
I actually got the fuse from Mouser. https://www.mouser.com/ProductDetail/693-0031.3558 have last 4 in stock...

[dorkshoei]

The fuse holder is Schurter 0031.3558(digikey 0 stock);

Are you sure?  I thought it was 0031.3551.      0031.3558 uses the same inner fuse holder and that can be removed and used on the 34401.

3558 was in stock yesterday but gone today :-(

I will probably stick with if it ain't broke, don't touch it. We will see how the performance testing goes.

That would be my advise.

[Zoli]

The fuse holder is Schurter 0031.3558(digikey 0 stock);

Are you sure?  I thought it was 0031.3551.      0031.3558 uses the same inner fuse holder and that can be removed and used on the 34401.

3558 was in stock yesterday but gone today :-(

I will probably stick with if it ain't broke, don't touch it. We will see how the performance testing goes.

That would be my advise.

I can confirm that the removable part is identical, since I've changed it on my HP(worn out slot, otherwise functional; I think that multimeter eated up more then 100 fuses....); I cannot speak for the PCB part, because I didn't changed it.

[dorkshoei]

I can confirm that the removable part is identical, since I've changed it on my HP(worn out slot, otherwise functional;

I know.  I was just saying that 0031.3551 is the actual pcb part and removable part.   If you just need the removable holder (which most people do) 3558 is fine and you can discard the pcb part.

[Neo2199]

Yes, just the removable part. Should be fine. THX

[NaxFM]

I just bought a 34401a made in the USA with the red connectors, It is marked agilent but has the HP symbol on the serial number sticker. However the serial number is the new format (US12345...)
Let's just hope it has the new revision, i'll let you know the serial number and the firmware version when i recieve it.
According to another user on another post, it should have the newer pcb, we'll see...

However, there's something i didn't quite understood. The firmware version is just an academic excercise to determine when it was manufactured, right? Does the firmware matters aside from understanding if it uses the new display board?