[Test-Equipment] HP-3478A DMM (was "Bench meter recommendation")

[Mike Manes]

The trick I use is to power the gear on and top use an isolated tip
soldering iron to replace soldered-in Li CMOS BBU cells.  In all
the applications I've seen, the Li batt is isolated from the +5V bus
by a diode, so the CMOS RAM is line powered when the gear is on.

Putting the new cell in the circuit before the old one comes out could
drain the new one, shortening its life.

73 de Mike W5VSI

Edward Knobloch wrote:
> Hi
> 
> I have an HP3478A and enjoy it, but am worried about having to eventually
> replace the 3V Lithium battery that powers the calibration memory chip.
> Obviously, i want to replace it before it loses the calibration data.
> 
> The battery is soldered in.  Should I solder another battery  temporarily
> in parallel
> with the existing battery while I unsolder it?  Any pitfalls to avoid?
> 
> Thanks,
> Ed Knobloch
> 
> 
> 
> On Sat, 07 Apr 2007  "Miles B. Anderson, K2CBY" <k2cby at optonline.net>
> writes:
>> I disagree with the most recent post cautioning against used test 
>> equipment.
>>
>> About three years ago I bought a used HP 3478A on e-bay and managed 
>> to pay
>> only about $125 for it including postage. I've used it ever since 
>> and
>> couldn't ask for a better meter. It's probably off cal on the last 
>> digit,
>> but even so it's way more accurate than anything else I have in the 
>> shop.
>>
>> 3478As seem to go on forever, and the labs that replace them do so 
>> because
>> they are switching to automated test equipment rather than because 
>> of
>> defects. They are also in good supply and cheap at the price.
>>
> <snip>
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-- 
Mike Manes    manes at attglobal.net     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."  A. Einstein