[volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) fo...

Sun Jan 24 17:35:06 EST 2016

The 3rd edition service manual shows BT601 on the schematic as 3 Volts,  
however the parts lists in that manual shows it as originally being a 2.9V  
battery with the list of parts changes indicating that it was  later changed 
to 3.4V, and that the new battery is not compatible with the  original 
resistor network.
Just to confuse, an earlier manual shows that same battery in the parts  
list as 3V, and just to confuse further both parts list refer to the battery 
as  BT501 instead of BT601.

These batteries are described in the parts list as Lithium Sulfur  Dioxide.

There's a bit more information here.....

http://www.eevblog.com/forum/blog/eevblog-426-hp-3457a-multimeter-teardown/

The text only version on archive.org of an old SAFT catalog shows this for  
the LX-1634....

LX1634,  2 /3A,  3.0,  0.85,  0.660,  16.8,  1.380, 

 35.1,  0.49,  14.0,  S.GTM.FU.
Sort of bring your own units but it does look like 3 V.
Further searches on LX-1634 might prove beneficial.
Regards
Nigel
GM8PZR

In a message dated 24/01/2016 20:17:54 GMT Standard Time,  
drkirkby at kirkbymicrowave.co.uk writes:

I've got  a HP 3457A 6.5 digit multimeter - S/N 2703A04579. It's working
fine, but  I'm aware the battery must be at least 11 years old, as I first
bought the  meter 11 years ago. I suspect its due for a change.  I'm trying
to  find a *reputable* source for a replacement. I want to avoid eBay, due
to  the number of fakes on there.

Opening the meter up, I see the PCB shows  "BT 601". There's no name on the
battery I can see, but the type number of  LX 1634. The voltage measured on
my 4.5 digit handheld DVM is 3.03 V.  Googling  around

https://groups.yahoo.com/neo/groups/hp_agilent_equipment/conversations/topic
s/48964

would  suggest the battery was made by Saft and is a Lithium-manganese
dioxide  (Li-MnO2). The size appears to be known as 2/3A. One source
suggests a  replacment is the Panasonic BR-2/3AE2SP

Mouser's uk  site
http://www.mouser.co.uk/
says shipping is restricted, so only  available in the USA.

The nearest I've found to anything remotely  suitable is actually a 3.6 V
battery

"CROMPTON ETERNACELL   T32/8AA8F  Battery, Single Cell, Lithium Thionyl
Chloride, 2100 mAh,  3.6 V, 2/3A, Axial Leaded, 16.3  mm"

http://uk.farnell.com/crompton-eternacell/t32-8aa8f/battery-lithium-2-3aa-ax
ial-lead/dp/774017

I'd  rather not fit a higher voltage battery, although given it provides
power  to some 5 V static RAM, I would not expect it to be a problem. That
said, I  believe when on mains power this battery is not needed, so there
may be  some circuitry that would not like a 3.7 V battery. When power is on
the  unit, there is 4.88 V across the static RAM. As mains is reduced, so
the  voltage drops to about 2.8 V. I think there must be a Schottky diode
that  stops the battery being drained when the mains power is on.

The battery  needs to have either very thin pins or wire-ended. Some I have
seen have  tags a 2~3 mm wide, which will not fit in the PCB. Others have 3
terminals,  which stops you putting it in the wrong way around, but they
will not fit  properly on the PCB.

In applications like the 3457A, when the SRAM  needs to be kept alive when
power is off, I wish HP would have put two  batteries in holders and diode
-OR'ed them. If they had done that, one  could just pull out a battery from
holder A, and put a new one in B. Then  when B gets old, put one in A.

My first problem though is finding a  suitable battery. Next problem is
changing it without losing the RAM  contents, but I don't think that's a big
deal.

The 3.6 V Lithium  Thionyl Chloride is very tempting, as it has a higher
capacity than the  Lithium-manganese dioxide and they have a very low
self-discharge  (1%/year). I'm just not overly happy about fitting a higher
voltage battery  than it is supposed to have, but phyysically it fits, and I
can get one  easy enough from Farnell in the UK.

Dr. David Kirkby Ph.D CEng  MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham  Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales,  company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910  441670 / +44 7910 441670 (0900 to 2100 GMT only  please)
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