HP-1: HP1 - Real Time Clock battery

[phask]

I just opened my HP-1 and the supposed Super Cap at location marked BT-1 charges in all operating modes of the HP-1.
So... as long as the AC power adapter is plugged in, the BT-1 device sees charge voltage in mine even if I never select Yes for the charge icon on the touch screen. Or if I select No at the charge prompt regardless if the HP-1 is on or off, BT-1 gets charge voltage at all times the external wall wart is plugged into the radio.

It's odd that it's marked as "BT" when all the caps are properly marked with the letter C prefixing their number.
Either there was a design change and a battery was replaced with a small super cap or it really is a small rechargeable Lithium cell like the early model 536HPs had in them which always failed and caused the RTC recall. Those 536HP Lithium cells were replaced with a super cap but it's significantly larger than the thing marked BT-1 in the HP-1. In fact, the BT-1 item is the same size as the 536HP's rechargeable Lithium cell was before they replaced the entire front board with a super cap and proper LED's for the dimming problem.
I measured mine and it only showed just over 1 volt before I plugged it in for the charge test. When plugged in, it was slowly approaching 3.15 VDC but I didn't wait to see where it would stop charging.
Even with just 1 VDC on BT-1, my RTC was still holding time in my HP-1. I sometimes leave it unplugged for weeks on end and have never had to set the clock. I do check the clock now and then just to see how much it drifts but that's it.
I'm not going to unsolder BT-1 from the board and look for any part numbers but I may be doing that soon being as it only had 1 VDC showing on my DVM.
I had just had my HP-1 plugged in to power for about a week within the past two days or so. I think that's a sign my BT-1 may be failing regardless it it's a super cap or a tiny rechargeable lithium cell.

I also wonder what the two large Elna brand super caps are for that are mounted right next to each other laying flat on the PCB.
I lifted one and they are rated at 2.5 VDC 1 Farad (not microFarad!) so they are also a super caps. They are Elna Dynacap DZN series wired in series so each sees about 1.65 VDC across it and of course 3.3 VDC across the pair.
Possibly something to hold a setting through a AA cell battery change perhaps. These large super caps measure 0.320 inches in diameter and 0.915 inches in length. They are mounted to the PCB via thru holes on one end and then they folded them down to lay flat on the PCB and affixed them with some type of glue to hold them in place. They are located very close to BT-1.

I know Elna makes caps but I do wonder now if BT-1 is a tiny rechargeable Lithium cell like the early design 536HP's used or if it really is a small super cap.
I swear I can remember Paul (UPMan) saying the HP-1 did use a lithium cell for its RTC backup. I also seem to recall some HP-1 owners having similar RTC battery failures in their HP-1s but there was never much said about that.
My HP-1 is an early model bought not long after they became available and it's never been back for any service so it should be the original design.

I don't remember the exact quote, nor whether it was here on RR or elsewhere. Paul (Upman) stated that the RTC circuitry was the same on the HP1 as the 536 and he anticipated the same failures. FWIW - I have 2 HP1 and 1 HP2 that all exhibit the issue.

 

[fxdscon]

I don't remember the exact quote, nor whether it was here on RR or elsewhere. Paul (Upman) stated that the RTC circuitry was the same on the HP1 as the 536 and he anticipated the same failures. FWIW - I have 2 HP1 and 1 HP2 that all exhibit the issue.

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This was one of the first posts on RR from UPMan regarding the RTC failures, indicating that the Home Patrol 1&2 shared the same RTC design as the BCD536HP and the BCD436HP:

After investigating internally, we were at first unable to explain why this was happening. All units we checked worked as designed (and this is a common design as the HomePatrol-1 and HomePatrol-2,

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This was a follow up post from UPMan on RR ….. but here the Home Patrol 1 was not said to share the same design that may fail, only the Home Patrol 2 was included:

We will issue an update for the BCD536HP, BCD436HP, and HomePatrol-2 (which, while not currently exhibiting the problem shares enough of the design features that we suspect they might start to arise on some units) that will do the following:

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The BCD536HP and the BCD436HP received a temporary firmware update that allowed you to bypass the "set clock time" boot-up screen and continue without being forced to re-set the time... while a repair campaign for a permanent repair for those 2 scanners was being set up. A similar firmware update for the HP-1&2 was not released, nor was a repair campaign set up for the HP-2.

Several years after those posts, there were a few scattered reports of the Home Patrol RTC failures starting to show up. At that point in time, I recall UPMan stating that after that time span had elapsed, those few HP RTC failures would most likely be attributed to normal component aging.

 

[JoeBearcat]

The BCD536HP and the BCD436HP received a temporary firmware update that allowed you to bypass the "set clock time" boot-up screen and continue without being forced to re-set the time...

That same behavior is being considered for all applicable models. ('set time' times out)

 

[Tinkertek]

Is the battery in the HP-2, also a super capacitor? It looks identical to what’s described above. I had that RTC time problem as well. I ended up replacing that component with a rechargeable battery, couldn’t find the right size anywhere,. It was a bit physically too large for the mounting, but I made it work, and it’s been working fine for years now. I wonder if that exact same super capacitor works in the HP-2 and maybe I just got lucky.

 

[KC2EIP]

That same behavior is being considered for all applicable models. ('set time' times out)

Bypassing the "set time" message would be very helpful for my HP-1.

 

[centauri61032]

Well, just to give everyone an update on this...

I ordered the caps from this eBay link... 3pcs ELNA DSK-3R3H204T614-H2L 3.3V0.2F backup power supply SMD Farad capacitor | eBay

They are shipped from China. And the auction said I would get them sometime in late Aug to mid-Oct. However, for some unknown reason, I actually received them in only 9 calendar days! Even Mouser and the other US distributors were saying a 30-60day lead time. So needless to say, I was very pleasantly surprised.

Installation was easier than I expected. If you have average or better soldering skills and a decent soldering iron, you shouldn't have much trouble. I had already removed the cap itself, thinking it was just a button battery. But that worked out well, because it made it much easier to de-solder each of the metal terminals separately. Once they were removed, I added just a bit of solder to each of the pads on the circuit board. Then I put the new cap in place on top of these pads, and held it down firmly in place using a small wooden stick that I had handy.

Once in place, it was fairly easy to just reheat one pad at a time, and re-flow the solder to the new cap contacts. I didn't end up having to add any more solder. (There was very little solder holding down the original cap, too.)

The scanner is now plugged in and charging. I did turn it on, and set the clock. Then I turned it back off, but left the power connected. I'll leave it like this for a day or two, and then turn it back on and see what happens. Hopefully, the time should still be correct.

So if you are considering making this repair yourself, just be aware that the eBay supplier above was super fast. And making the actual repair is pretty straight forward with average soldering skill and equipment. The hardest parts were holding the new cap in place until I got the first pad soldered, AND reconnecting the darn display ribbon cable during reassembly.

I'll post again in a few days with the final results. And thanks to all that replied! The information was most helpful.