50g - strange power on problem

[e_emil]

Just wanted to say hello to everyone, I'm new on this forum.

After some time of using various casio's and TI's, I just came in possession of my first HP calc It's a 50g, used, but visually in great condition.

When it arrived it wouldn't power on at all, despite changing batteries (main and backup; it came with old batteries inside). Trying a hard reset didn't help either - just a blank display with no sign of life... I checked all connections inside the battery compartment with a voltmeter and there was always a good stable voltage as far as the probes could reach. Trying to power it on with a usb charger and no batteries didn't work either.

I finally left it without batteries for some time, and when I re-inserted batteries after maybe half an hour, it resurrected! It's been working great ever since (well I own it for no more than three weeks but it's heavily used, on a third set of batteries already) and I've never had any more problems with it.

Any ideas about what the problem was and why it disappeared?

[rprosperi]

(04-17-2017 06:20 PM)e_emil Wrote:  third set of batteries already) and I've never had any more problems with it.

Any ideas about what the problem was and why it disappeared?

I can't speculate what the exact problem was, but often situations like this can be remedied by removing all batteries and shorting the primary (+) and (-) terminals together with a piece of wire (or anything conductive - I've even used a pair of scissors). Just connect the leads and hold for a few seconds; this seems to dissipate any pending charge in internal caps, and essentially drains away whatever the problem was. This technique is especially handy for Voyagers and Pioneer models, but I've done it with a stubborn 50g as well.

[Geoff Quickfall]

Start up sequence is software which can be corrupted especially by low batteries in conjunction with constant memory sustained by a super cap.

One must drain the super cap as Bob states by shorting the battery terminals or letting charge drain over hours to days dependent on the super caps ability to hold a charge.

Ex.

Had an HP 01 with low batteries and when tested displayed garbage. Replaced all two display batteries and still garbage. No super cap, but I did not change the memory battery button cell. Still displayed garbage and figured the display driver failed. Removed battery thinking trouble shoot another day. Two weeks later installed batteries to trouble shoot and it worked perfectly.

Google HP 41C memory reset, static charge, synthetic programming faults and you will see a plethora of super cap charge retaining corrupt memory.

Geoff

[Dave Frederickson]

(04-17-2017 08:18 PM)Geoff Quickfall Wrote:  Start up sequence is software which can be corrupted especially by low batteries in conjunction with constant memory sustained by a super cap.

Volatile memory is maintained by a coin cell while the main batteries are being changed. Why a super cap? Seems unlikely.

Dave

[Han]

(04-17-2017 10:31 PM)Dave Frederickson Wrote:  

(04-17-2017 08:18 PM)Geoff Quickfall Wrote:  Start up sequence is software which can be corrupted especially by low batteries in conjunction with constant memory sustained by a super cap.

Volatile memory is maintained by a coin cell while the main batteries are being changed. Why a super cap? Seems unlikely.

Dave

What maintains the RAM when you are changing the coin cell?

[Gerson W. Barbosa]

(04-18-2017 12:40 AM)Han Wrote:  

(04-17-2017 10:31 PM)Dave Frederickson Wrote:  Volatile memory is maintained by a coin cell while the main batteries are being changed. Why a super cap? Seems unlikely.

Dave

What maintains the RAM when you are changing the coin cell?

The main batteries, I presume.

---------------------
Memory Backup
battery!!
Please don't
remove the main
batteries while you
replace it
---------------------

I haven't checked how long memory is preserved when all batteries are removed, though.

[Dave Frederickson]

(04-18-2017 01:03 AM)Gerson W. Barbosa Wrote:  

(04-18-2017 12:40 AM)Han Wrote:  What maintains the RAM when you are changing the coin cell?

The main batteries, I presume.

---------------------
Memory Backup
battery!!
Please don't
remove the main
batteries while you
replace it
---------------------

I haven't checked how long memory is preserved when all batteries are removed, though.

That would be my presumption as well.

[Geoff Quickfall]

Sorry, don't have a 50 so it was an assumption, with a retention coin cell then no super cap required; however, corrupt boot sector wil still need to be cleared and residual charge in non super caps residing on the PCA may retain enough current to hold corrupted boot sector.

This regardless of battery removal over an undefined short time period of non specific length :-). There, a vague but purposeful statement.

Just a thought as I have not tested this out but have seen the like in similar battery backup and super cap systems.

Funny history lesson: no backup ram, then separate battery backed up ram, then super caps and now back to battery backup : ignoring flash ram of course.

[Vtile]

In 50g there is one 1000 microFarad elecrolytic condensator parallel to the battery system. Not a supercap though.