Keep an eye on your HP 5334A battery

[NoisyBoy]

I have seen a number of HP 5334A with corroded traces due to leakage from the Ni-Cd memory backup battery.  Because of this, I open and inspect my unit every 6 months for signs of failing battery.  In the last month, I notice error 52 and 51.X when I power up or recall settings.  I suspect the battery has failed, when I measured it out-of-circuit, the nominal 3.6V is now at 0V.  When I charged it, the battery no longer accept charge. 

Luckily, I was able to catch it before it leaked.  While the NOS of the original battery is still available, I decided to switch over to NiMH.  The Varta Mempac has an exact voltage and pin layout, and it fixed both error messages. 

When the unit is on, the battery is charged at a constant 7mA through R50.  The battery has a 150 mAh capacity, so the current is well below the 0.1C threshold for the NiMH battery, and the constant charge should not create heat or overcharge issue.

So far so good, you may want to keep any eye on the battery on your 5334A, especially if you start getting these error messages.

[james_s]

It's not even worth checking it, if it's more than 10 years old just replace it. Those on-board NiCD batteries are notorious for destroying the CPU boards in Gottlieb arcade games like Qbert and others that use that hardware. Omega-Race is another one notorious for having severe battery damage to the boards.

I used to replace them with cordless phone battery packs mounted off-board. Sometimes I add a diode and use a lithium coin cell in a holder, CR2450 works well.

[NoisyBoy]

That's a good point, now I keep a label on the back of every piece of equipment on the service it received, so I can better keep track of "consumable" parts. 

[wn1fju]

It never even occurred to me that the HP 5334A counter had a battery.  But it started to throw Error 5.2 (can't find HPIB address) upon startup, so I figured the address must be stored in a RAM that was backed up by a battery.  Opened it up and took a look...

My battery only had minimal leakage that was easily cleaned up with alcohol.  I replaced it with two alkaline AA batteries in a covered plastic holder with a Schottky diode in series to prevent charging.  I've been replacing failed rechargeable NiCds in my test equipment using that approach for many years, and when (not if) the AA batteries leak, at least the sealed holder seems to contain the gunk and the holder survives with some cleaning.

I have a second 5334A, but upon inspection, that NiCd seems perfectly fine.  Go figure.

[theHWcave]

Am I lucky that my HP 5334B does not need a stinkin battery?
But keep an eye on those 4 RIFA caps in the power filter section and look for fine hairline cracks. One exploded quite spectacularly recently

[wn1fju]

I've already replaced the 4 Rifa caps in my 5334B - I know better!

My 5334As use integrated sealed line filters, not discrete suppression caps.  I guess between the 5334A and 5334B you have a choice whether you want leaking NiCd battery juice or exploded Rifa resin all over your boards.

A long time ago I understood all the differences between the A and B models.  If I recall, the B model was engineered to use cheaper parts, particularly in the C-channel prescaler, than the A model. 

Both models are very nice general purpose counters.  But I would only get one that had the ovenized oscillator option.

[james_s]

Those integrated line filters just have ordinary capacitors in them, some use those RIFAs. I haven't had much trouble with them personally, I think I only had one fail and it wasn't very spectacular. It's probably much worse in 240V land.