Sharp HC-4500 won't power on

I recently bought a Sharp HC-4500. The seller had re-celled the NiMh battery pack (VERY BADLY) but assured me that it would power on when plugged in. The Battery reads at 0.05v, wont charge and the HPC won't power on.

Should it turn on without a battery?
If not does anyone have a wiring diagram so I can rebuild the pack properly?

Ideas and thoughts please, I would love to get this working

Thanks
Huw

Does the LED work when plugged in?
Did you test it also with 2xAA batteries? Or is this device only for NIMH-Pack?

The LED lights, flashing to start then stable orange. The battery pack has 4 connections but the device only has 3 pins making me think one is broken...
I think it needs the battery pack rather than just a pair or AAs sadly

In other news it did turn on briefly earlier but on shut down wouldn't boot again making me think there is a lose power connection inside or perhaps a bad capacitor.

I will update the tread once I've had a look inside :-)

Edited by fantablium 2023-02-28 4:30 PM

If the LED works it could be that the device is booting normally.
Then it could be a problem with the display. Many Sharps does have this issue.
Could be the connection to the display.

The HC-4500 won't turn on without the battery, so if it's providing insufficient voltage as it seems yours is, that would seem to be the problem.

Thanks for the info Citigo, got my fingers crossed its a simple fix!

CE Geek there are 4 terminals on the battery, you couldn't tell me what the charged and discharged voltage are could you? It would give me a clue on whats needed for a battery pack rebuild

I see that this device is color. Theoretically would the monochrome HC-4100 have the possibility of the same problem ?

@torch I think so.

@TO
Would be helpful if you upload some photos.
Want to see the batt. pack and the device. Can you open the batt. pack to see the cells?
Does the whole package show 0.05 Volt?
What charger do you use?

Thank you all for the help so far

I have attached some photos
The foil packed "repair"
The battery pack terminals - its the same at both ends
The unit terminals, 2 at one end but only 1 at the other making me think one has snapped off...

So having opened the battery pack I an unsurprised that it wont charge


I have managed to get the unit to power on using just the A/C adaptor, went through set up and everything was working (other than a slight flicker on the screen) but once I turned it off it wouldn't power on again.

I think this might either be a lose solder on the power jack or possibly a bad capacitor.


What I would like to know is:-
1). Should there be two terminals at both ends on the unit side?
2). What voltages should I have across the upper and lower terminals of the battery pack when charged and discharged so I might hazard a guess at the circuit that's been mangled (I can see a single surface mount resistor on one end but the rest is melted together)
3). Has anyone taken a battery pack apart and taken any photos? (So I can repair the battery pack)
4). Is there a way to bypass the charge circuit all together and run it off a pair of AAs?

I would love to get this machine up an running again thank you in advance
Huw












Attachments
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Battery pack terminal.jpeg (92KB - 1 downloads)
Battery case.jpeg (188KB - 1 downloads)
1 terminal.jpeg (90KB - 1 downloads)
2 terminals.jpeg (117KB - 0 downloads)

Short answers...Im on the road:

One cell should have 1.2 Volt
If one cell is under 1 Volt, it is bad and you better charge the cells seperately with a pro charger.
The contacts in the device are looking bad. So first of all, check your NIMH cells.
If the device runs with a ext power adapter thats great but also there could be co tact problems in the device. Mayve you have to open it

Video below shows the 4500 main unit has a total of 3 brass terminals. With the unit keyboard facing down:

- 2 terminals on right side of battery compartment (near unit id tag)
- 1 terminal on left side

Video also shows polarity and that HC-BN01 battery pack has a total of 4 brass terminals

The factory batteries are not quite AA sized; the huge Japanese electronics stores stocked a lot of these oddball battery sizes but I'm not sure how easy they are to obtain in "regular" cities.

The small metal "resistor" thing inside the battery compartment looks like a thermal fuse. I think they are spot welded at the factory as heat from a soldiering iron causes damage (one can try to heat sink).

Please be careful when working with batteries. Get some nice safety glasses at a minimum. I wouldn't recommend soldiering. These draw a lot of current!

https://www.youtube.com/watch?v=yKXaG9NsOS0

You can clean the terminals with Isopropyl alcohol and a cotton swab (use highest purity you can find).

If you are feeling adventurous, you might remove the back cover of the main unit to see if any (how much) green corrosion has migrated inside.

If there is any corrosion inside the unit, the earlier it is cleaned the better. Over time, this can eat away boards, traces, soldier joints, components. Sometimes cleaning is easy. But it could wreck more damaged traces or compromised soldier etc. so there is some risk, but if these fail from cleaning they were probably not going to last long anyways. Damaged soldier joints can be "retouched" (lead-based soldier with some flux will be easiest.

Wear gloves when touching any of these "messes" as they can be terrible for your skin. I wear safety glasses too. Consider static (ESD) protection.

Finally, avoid touching any data contacts or pins. They are very delicate. Also, the oils on our hands reduce reliability (my colleague did a large study on this but the details are confidential).

Post some photos and questions if you want some guidance from the forum. I am a hobbyist so professionals will have a better view.

Thank you for the help @Citgo, I already tried fresh NiMh cells but couldn't get it to recognise the battery. I think you are right and I'm going to have to open it up... wish me luck!

@AximUser thank you for the video link, I couldn't find any showing the battery pack! I assume a 'thermal fuse' with break contact when heated which would explain why the pack won't work following the dodgy soldering! Yes I think you are right and I will have to open up the unit, thank you for the advice re: oils and data pins, I did not know that. I hope to get time next week to open it up and will let you know how it goes!

@fantablium - I watched a lot of your videos on "Handheld Computing". Including the new Palm LED light video posted yesterday. I vaguely recall that feature but maybe just the icon.

Good luck and keep us posted.