Finding the cmos battery

My guess is that it is a 2032 button cell - which have been popular for that function for a long time. Are you able to apply about 3V at the appropriate polarity and see if the memory comes back? Or even 1.5V as proof-of-concept?

After which comes the question of whether it is rechargeable (LIR2032) or not (CR2032).

Peter Wieck Melrose Park, PA

I was thinking *if* it is rechargeable, I *could* (could I not?) replace with an equivalent non-rechargeable in series with a diode to prevent it from taking a charge it's not designed for?

Look for a 1/2 to1 farad electrolytic capacitor. Probably near the upc.

Caps were used to retain voltage to a circuit. Some telephone systems I worked on used them.

KenW

What? Are you guys saying there may be no actual battery at all? And they've used an electro in place of one?

At that value it would be a supercapacitor I'd imagine. Were they installing those in new equipment 10 years ago?

I remember several consumer electronic items using a "supercap", something like 0.47F. They did go bad certainly.

Very possible

KenW

Cursitor Doom Wrote in message:r

The .47 to 1F caps have been used for 30 years in stereo receivers.

I'm suitably amazed. Mind you I've never had much to do with them.

Sure for memory function but for any active function,like RTC, batteries are still mostly used.

Come to think of it, a Denon tuner that I bought in 1988 has a super capacitor for memory.

They were showing up as surplus 20 years ago.

RL

Well I can't understand in that case why there are so few of them listed on Ebay currently. I may have to imrovise here and go back to my initial idea of using a lithium button cell in series with a diode to prevent it being charged.

Anyone see any issues with that approach?

Hmmm. I think clearly the older one gets, the harder it is keeping up to date with new innovations if you're not fully immersed in the field as a career (I'm not!)

Yes. Purchasing anything of that nature from eBay is an issue. Given that a counterfeit - not unknown from that source - could destroy your unit.

Peter Wieck Melrose Park, PA

Here is one that is genuine and exactly like the ones I used to use as a replacement.

Thanks, but you guys have avoided answering the question about replacing the supercap with a cell of whatever capacity in series with a low reverse-leakage diode. Anyone know what the likely voltage that cell would need to be?

NB: when I say "whatever capacity" I refer to A, AA, AAA, C, D etc. cells.

There is a somewhat detailed answer to that question. a) Do you know what voltage is needed to keep the memory function in operat ion? b) Given that a battery is the mother of all capacitors, just a bit slower as a chemical engine, you should be able to do a proof-of-concept. c) And once you have determined the operating voltage (somewhere between 1.

2 and 3.5 VDC at a guess), you will have several choices, including your d iode option. BUT:

Caveat: Batteries do not like seeing a dead/partial short. So when diode yo u install is not in use and the circuit is OFF, the battery is in parallel with whatever device is in place, whether a super-cap or a button cell, or something else. If that is shorted, so is the battery. OOPS! It really does behoove you to find the OEM source and repair/replace it as designed. You do not want to wake up one morning and find that your installed battery has spilled its guts all over everything.

Remember the Revox B760 tuner? It had two AA cells under the fold-down door on top of the faceplate. Trust the Swiss to take the very simple brute-for ce approach.

Peter Wieck Melrose Park, PA