New Never Used HP41CV ?

[jftman]

I inquired about the battery bay and contact condition, clean or corroded?
I got these pics in reply.

I am guessing here, that this is a storage plate? So, batteries can be kept in one place inside the calculator when not in use?

Am I wrong to think this unit is still unused?
How often do these plates surface?
Does the visible battery PCB behind the plate look like a good set of terminals?
See pics

[Raymond Del Tondo]

I think there is even a separate article about the HP Battery Shield.
It serves some purposes:
- Holding batteries in place when not in the calc.
Often the retainer clips in the battery holder don't hold the batteries back from falling out,
so the Shield will help there.

- From HP: Protect the sensible contact foil from battery leakage.
One of the contacts of your Shield has signs of battery acid, so yes, this workd to some extent.
But at a later point, when leakage got more intensive, the contact foil will be reached by the acid.

- Providing better contact between the battery terminals and the contact foil in the calc.
Unfortunately it's done by damaging the contact foil.
The back side of the metal buttons of the Battery Shield has sharp edges,
which will press into the contact foil, with high potential for cutting into the foil.

Normally, without the Battery Shield, when inserting or removing the battery holder from the calc,
the movement describes a curve around the angle point, so the battery contacts "roll" over the tip of the contact foil, usually not deforming the foil.

The HP Battery Shield was provided with new HP-41 units for a relatively short period.
After all, the Shield has more disadvantages than advantages.

[jftman]

Ok.
The shield is designed not to function with the operation of the calculator but only to hold batteries and must be removed as printed on it.

If it would have been a refined and more stout connection, it seems almost there! For operation, and safety for the PCB.
Is there signs of missing foil in the pic where it is possible to see it?

I hope when I take out the shield it isn’t a sad surprise!

[rprosperi]

(12-27-2023 11:46 PM)jftman Wrote:  Ok.
The shield is designed not to function with the operation of the calculator but only to hold batteries and must be removed as printed on it.

Not correct. The shield is supposed to be removed only if you are using rechargeable batteries (in the HP 82120A). This is what the message embossed on the upper face says.

The purpose of the shield was to prevent N-cell battery leakage from damaging the contacts and interior components, and is intended to be installed inside the machine, and you insert the battery pack into it; it's a precise fit and thought may look like it won't fit, it does just fine. If it was not intended to be used in the machine, it would not have the 4 metal tabs on the upper end to contact the 4 copper contacts on the I/O flex.

[Allen]

(12-27-2023 07:03 PM)jftman Wrote:  Am I wrong to think this unit is still unused?

I suggest this is definitely used, but not much. The scoring lines around the edges of the foot wear away quickly with normal use.

[jftman]

Yeah looks clean throughout. In transit from overseas, Morocco.
Eager to get a look at the terminals for being clean, I hope!

I keep buying the 41C with intent of making it a donor to one tgat has a dead flex circuit over the terminals, but end up finding the donor calculator in better condition overAll.
Not complaining!

As an aside here.
Why after removing the batteries on a 41Cv does the stack register maintain data?
How is continuous memory, in that respect possible, without a battery for any time period?
That therefore says the chips are turned on, and retain their state?
Is this volatile or nonvolatle memory?
Then do these chips have a cycle life? Like a USB drive would, after millions of switching?

[Allen]

(12-29-2023 05:53 PM)jftman Wrote:  1) Why after removing the batteries on a 41Cv does the stack register maintain data?
1A) How is continuous memory, in that respect possible, without a battery for any time period?
2) That therefore says the chips are turned on, and retain their state?
3) Is this volatile or nonvolatle memory?
4) Then do these chips have a cycle life? Like a USB drive would, after millions of switching?

1) Good capacitors and VERY low standby current
1A) Good capacitors and VERY low standby current
2) They are not technically "ON" it's probably in low power mode. I don't have the exact measurements, but on the order of a few micro-amps for this kind of chip is not uncommon.
3) definitely volatile, if you tried to wake the calculator while the batteries were out, it would very likely erase any temporary memory
4) The plastic case, battery terminals, internal posts, motherboard connector and LCD will probably all fail long before any cycling issue with the memory chips. I'm sure they do go bad from time to time, but less common than the other issues we see across the HP41 NUT series.

[Garth Wilson]

On something I was working on in the late 1980's at work, I had an 8Kx8 SRAM (62C64 IIRC) with a 10uF capacitor from its VDD to ground, and removed power at the end of the day, and saw, at the start of the next work day, that the data had been retained, about 16 hours, on just that 10uF capacitor.  I did not experiment to see how much longer it might go.

SRAM does not have a cycle life like the flash memory of a USB drive does.  SRAM (or any RAM, for that matter) can handle an infinite number of writes, with no wear-out.