HP 3457A replacement battery - Page 1
Forum section: electronics / testgear

author: radioFlash
author_rank: Regular Contributor
timestamp: August 24, 2014, 11:50:05 pm
content: I recently got an HP 3457A. Looking inside, the latest IC date code I found was early 1986. Although the battery measures 3.04 V, I think I should go and replace it. In my meter, the battery is marked as 3V, but would the Tadiran TL-5155 or TL-4955 be suitable? They're rated at 3.6V. Or, would it be preferable to stick to a 3.0V battery such as the Panasonic BR2/3? The NVRAM chip is marked as a Toshiba TC5517APL-2. The attached datasheet shows that the data rention power supply voltage can be between 2V and 5.5V.Tadiran Tl-5155 datasheet:http://www.tadiranbat.com/pdf.php?id=TL-5155Tadiran TL-4955 datasheet:http://www.tadiranbat.com/pdf.php?id=TL-4955Panasonic BR2/3 datasheet:http://www.mouser.com/ds/2/315/Panasonic_Lithium_BR1-2AA_BR2-3A-348820.pdfI've already replaced the IEC inlet filter as several others have reported the Shaffner filter has a tendency to self destruct. Instead of drilling out the rivets, I used a soldering iron with a blade tip to melt the plastic by the rivets and used diagonal pliers to cut the rivets.

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2014, 06:46:31 am
content: I have an HP 3478a that I need to do this with. The Tadiran 2155 would be my first choice. It not only has about the largest capacity for the price but is the correct size.

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2014, 04:01:34 pm
content: I usually start off with a pricing and availability search at my favorite distributors like Mouser and go from there. That automatically excluded Sonnenschein and SAFT for me.

author: radioFlash
author_rank: Regular Contributor
timestamp: August 25, 2014, 11:17:15 pm
content: It looks like the TL-4955 is the replacement for the TL-5155 and TL-5955 is the replacement for the TL-2155.Looking at the datasheets, it looks like the 4955/5155 is designed for lower current applications than the 2155/5955. They are all the same size and chemistry (lithium-thionyl chloride). I think the TL-4955 would be the best choice, if one could find them. They're not stocked at Mouser and you have to buy 500 of them from Digikey.Tadiran Products to be discontinued:http://www.tadiranbat.com/index.php/products-to-be-discontinued

author: David Hess
author_rank: Super Contributor
timestamp: August 26, 2014, 02:11:45 am
content: The Tadiran 2155 is available from Mouser now. There may be better batteries but cost and availability matter.

author: schopi68
author_rank: Regular Contributor
timestamp: August 26, 2014, 08:36:34 am
content: According to the service manual the replacement battery for the 3457A has the same hp stock no. than the replacement battery for the hp 3478a. But the service manuals description seems to differ in the data - 2,9V vs 3V and 0,72Ah vs. 0,95Ah.A common replacement for the 3478a Battery has been the panasonic BR-2/3A-K (this is the one i've just used as a replacement several time ago). This ones pinout and size fits perfectly into the place of the original battery. Also the nominal Voltage is the same (3V) - the capacity is slightly higher (1,2 Ah). The TL-Batteries have a higher rated Voltage of 3,6V (but this should not be a problem).

author: radioFlash
author_rank: Regular Contributor
timestamp: September 07, 2014, 12:37:12 am
content: I ended up using a Tadiran TL-4955 battery. I also added a battery holder (Keystone 1029). The battery holder was a few mm wider than the original battery, so I had to bodge in a wire to fit it in. I had the meter powered on using a UPS while I changed the battery so that the my grounded soldering iron wouldn't short out the battery.Attached are photos of the old battery and the replacement.

author: radhaz
author_rank: Regular Contributor
timestamp: September 07, 2014, 12:53:20 am
content: I just did this on my 3468A. I used mains power and a butane iron. I also used the Panasonic battery.

author: idpromnut
author_rank: Unknown
timestamp: September 07, 2014, 01:23:10 am
content: @radioFlash: did you in-line a battery pack or just rely on the UPS?As a broader question, I need to replace the battery on my 3478 as well (picked up a Panasonic BR-2/3A) and I was planning on using the AAx2 battery pack (diode OR'd with the battery) as the primary source of backup power while I replace the battery. I don't have easy access to a UPS nor do I have a butane soldering iron. This should work OK providing I don't short anything, correct?

author: radioFlash
author_rank: Regular Contributor
timestamp: September 07, 2014, 02:39:07 am
content: Quote from: idpromnut on September 07, 2014, 01:23:10 amI just relied on the UPS. The 3457A consumes only about 10 W while on, so I didn't worry about the UPS shutting down before I was done. I made sure nothing else was on the UPS while I was doing this. In retrospect, I probably should have tested how much power on time the UPS provided.The spec for the Toshiba SRAM (see datasheet in the first post of this thread) specifies a minimum of 2 V for the data retention voltage. I would measure your 2xAA pack with the diode to make sure it's > 2 V. If you're going to rely on it, I would solder it in place rather than rely on clips which might come loose. Look at the schematics to find an appropriate place to solder your pack.Have a solder sucker handy to remove the solder from the hole after you remove the old battery.

author: radioFlash
author_rank: Regular Contributor
timestamp: September 07, 2014, 01:51:33 pm
content: For reference, attached are the schematics and board diagram for the NVRAM and battery backup.

author: David Hess
author_rank: Super Contributor
timestamp: September 07, 2014, 05:07:18 pm
content: I wonder what kind of diodes they used for CR505 and CR517.The schematic shows schottky diodes but I think U511 had a standby current of 1 microamp (typical? maximum?) which is low enough that leakage through the schottky diodes could be much greater than the SRAM standby current. The parts list says or at least implies that the TC5517APL-2 SRAMs was even selected and it would not surprise me if they were selected for low standby current.Ah, the HP 5082-200 diodes (similar or the same as a 1N5711) have a reverse leakage of about 5 nanoamps at 5 volts. HP thought of everything.

author: schopi68
author_rank: Regular Contributor
timestamp: September 08, 2014, 10:30:17 am
content: Folks... Please keep in mind that working in this devices requires an ESD protected workplace.If your soldering iron is ESD-proof it does not have a low resistance connection to mains earth. If it is grounded directly, it should not be used to do any soldering in this device. Just opening this devices on an non ESD safe workplace makes it prone to get some damage.It is not necessary to touch a part to move large amounts of the electrons (Electrostatic Induction).http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Electrostatic_discharge.html(and yes - even at the end of the 1980's ESD-protection and working in ESD-protected areas had been HP-standard. They kew what they had to do to build devices that will last for decades)

author: radioFlash
author_rank: Regular Contributor
timestamp: September 08, 2014, 11:52:09 pm
content: I used a Hakko FX-888 which had a measured .5 Ohm resistance to the ground connector on the plug from the soldering tip. It claims to be "ESD Safe".

author: schopi68
author_rank: Regular Contributor
timestamp: September 09, 2014, 10:59:22 am
content: Strange thing. I've taken a look into the literature and it seems that i had to correct myself.Actual state of the art ESD control only says that the resistor is only a recommendation for (electrical) safety. The ESD Association standard for grounding recommends a hard ground without a resistor (to ground devices, not humans).This is a little bit contrary to my previous knowledge, because this told me that the resistance also limits high (circuit destroying) discharge currents.

author: David Hess
author_rank: Super Contributor
timestamp: September 09, 2014, 12:16:56 pm
content: There may be so much capacitive coupling in most cases that the difference between high and low resistance is insignificant. A high ground resistance would still be useful to prevent catastrophic shorts when a ground loop is present.

author: bronson
author_rank: Regular Contributor
timestamp: December 11, 2014, 08:37:39 am
content: If you use a solder sucker, make sure you use it better than I did... I went mains powered with a butane iron. Even though there's barely any room to get a solder sucker and iron over the holes, I managed to suck a big blob of solder, which fell right out and splattered over U603. The unit beeped and reset, then froze while booting.I swept up the mess with the iron and figured I was boned... Finished with wick, which was WAY easier anyway. Forget the sucker for this job.Turns out I got lucky... After a power cycle, this thing still works and looks as calibrated as before.Incidentally, my controller board looks totally different from RadioFlash's... Mine has solder mask or conformal coating, and all the refdes are in the 600 range instead of 500. The manual on both Agilent's site and BAMA is dated 1986 and doesn't match at all. Most recent datecode that I saw here was 1987. Some web searching turned up a 1988 manual athttp://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%203457A%20Service.pdfthat seems to fit perfectly.Mildly irritating that they redesigned it so thoroughly but didn't bump to 3457B. I guess since they didn't improve it, that didn't merit a change.Well, all's well that ends well. Be more careful than I was. Also, once you've snipped the battery lead, make sure to hold it in the air. I had a close call where it sprung back down and tried to touch metal-cased C642.