Fixing my digital scales..

[hotponyshoes]

Well,
I'm hoping to fix them if somebody can tell me what to do!!

Salter Weigh-tronics
Usually only get used every other month or so, worked fine for years.
Last used them about 6 months ago, did not initially turn on but after being left with the power on for half an hour popped into life.
Now not turning on at all.
Left power on all night but nothing.

So far, I've tested the external psu.
It's supposed to be 15v but is reading 25.5v.
Scales don't work with a different 15v psu connected either though.

Can't see any obvious damage to the pcb.

There is a 3.6v battery (lithium - do not recharge) soldered to the pcb, that's reading 0.3v so presume knackered. I'd guess it's just for memory functions though?

Any ideas?
Or tips on what bits to poke first?

 

[angellonewolf]

as a ruff guess the capactors seam a good bet

 

[hotponyshoes]

as a ruff guess the capactors seam a good bet

Can I test those in situ?

 

[angellonewolf]

Can I test those in situ?

imnot a tech on this stuff only know the basics but capactors need to be removed to test

the is a fourm member in glos area i cant remember his name beer does not help

 

[angellonewolf]

@ajlelectronics ?​

​

and 1 in frome somerset again the name will come to me​

 

[ajlelectronics]

Change the battery first.

 

[hotponyshoes]

Anywhere local/highstreet I might find a battery or is that an online job?

 

[Neilj]

Probably an online job unless you have a local electronics store. Got a part number off it?

 

[hotponyshoes]

Probably an online job unless you have a local electronics store. Got a part number off it?

I'll cut it out and see if there is a number on it somewhere.
It's just got a wire on each end that is soldered to the pcb, I wouldn't think an exact replacement would be required would it?
Just a 3.6v.
It might even be safer (for the pcb with my soldering) if I cut the wires at the battery end and solder some extensions on . Plenty of room to mount the battery somewhere else.

 

[angellonewolf]

its only 2 connections take a pic before you start or as i can do forget what wire goes when when removed a pic is a saver

 

[Barking Mat]

We've got similar post office scales at work.

Try disconnecting the ribbon cable to the display, and reconnecting it, not saying it'll work for you, but saved ours.

 

[Neilj]

Yes, you could cut at the battery end of the leads and solder a new one on there if you prefer rather than tackle the PCB. Anything lithium and 3.6v will work but ideally you'd want a similar capacity to what you have now or it might not last very long if too small. It'll have a part number / capacity on it somewhere, post it up when you can.

 

[500e]

Most likely a CR2032

 

[hotponyshoes]

Most likely a CR2032
View attachment 391174

It's quite a bit bigger,
The purple thing
I'll get it out in a bit...

 

[joebog1]

If the PSU is outputting 25 volts its NOT good. I would have a good look around the power supply on board.
THats the section on the bottom right of your first pic. I suspect the battery is for holding boot data in memory.
By that I mean, if you have set it up to read lbs and ozs it will boot into that. If you have set it metric it will boot that.
It is a lithium non rechargable.
Whatever, with 25 volts I suspect the on board PSU. Check those electrolytic capacitors. Four of them bottom right hand on the board.
That PCB I suspect will be alergic to AC leaky soldering irons. Its not CMOS that I can see, but they are still extremely sensitive.
If you dont have test equipment, or experience working on stuff like that, take it to a reputable repair company.

THats friendy advice, I am not saying dont work on it, just be VERY careful.

Joe

 

[Alan Reynolds]

As someone else said, change the battery first. It’ll be a Tadrian 3.6v. Cut the wires instead of trying to desolder the wires as you can damage the through plating if you’re not used to working on PCB’s. Just note the polarity. You’ll find them on Ebay and if you can’t find a wired Tadrian, go for any wired 3.6v of the same shape.
I recently got asked to look at a couple of running machines that wouldn’t light up. I diagnosed it as batteries but they decided they could do it themselves to save money. They ruined both boards as they didn’t realise they were multilayer boards.

 

[500e]

That is a biggy
Maybe

Battery Lithium 3,6V 1,4Ah 2/3AA 1 pin + , 2 pins - (SL761/P) - Vlad

www.vlad.fr

 

[hotponyshoes]

As someone else said, change the battery first. It’ll be a Tadrian 3.6v. Cut the wires instead of trying to desolder the wires as you can damage the through plating if you’re not used to working on PCB’s. Just note the polarity. You’ll find them on Ebay and if you can’t find a wired Tadrian, go for any wired 3.6v of the same shape.
I recently got asked to look at a couple of running machines that wouldn’t light up. I diagnosed it as batteries but they decided they could do it themselves to save money. They ruined both boards as they didn’t realise they were multilayer boards.

I've snipped it out, and yes, it is a tadrian.
It was glued down with a silicone type adhesive. If there is a part number it must be under the glue so probably easier to match it by size than pick that off!
There is a good 10mm of wire left so I can solder to that easily enough without risking the pcb.
I'll get a replacement ordered up...

 

[hotponyshoes]

If the PSU is outputting 25 volts its NOT good. I would have a good look around the power supply on board.
THats the section on the bottom right of your first pic. I suspect the battery is for holding boot data in memory.
By that I mean, if you have set it up to read lbs and ozs it will boot into that. If you have set it metric it will boot that.
It is a lithium non rechargable.
Whatever, with 25 volts I suspect the on board PSU. Check those electrolytic capacitors. Four of them bottom right hand on the board.
That PCB I suspect will be alergic to AC leaky soldering irons. Its not CMOS that I can see, but they are still extremely sensitive.
If you dont have test equipment, or experience working on stuff like that, take it to a reputable repair company.

THats friendy advice, I am not saying dont work on it, just be VERY careful.

Joe

The power supply I have measured is an external thing. It's the original one. (or Salter branded at least)
Instructions say it's supposed to be 14v.
On the psu the sticker says 15v
Measures at 25.5v.
I suppose it might drop down to 15v when loaded?
I wondered if the scales might have some sort of over-voltage protection so tried another 15v supply but still nothing.

The 4 capacitors look ok physically, no swelling or leaking. I'll try the battery first (then maybe see if I can find someone to fix it) before trying to remove them!

To save risking ac damage from a soldering iron can I just heat up a bigger iron then unplug it before fixing the new battery in with the residual heat?
Or should I just crimp it back on?

 

[joebog1]

The power supply I have measured is an external thing. It's the original one. (or Salter branded at least)
Instructions say it's supposed to be 14v.
On the psu the sticker says 15v
Measures at 25.5v.
I suppose it might drop down to 15v when loaded?
I wondered if the scales might have some sort of over-voltage protection so tried another 15v supply but still nothing.

The 4 capacitors look ok physically, no swelling or leaking. I'll try the battery first (then maybe see if I can find someone to fix it) before trying to remove them!

To save risking ac damage from a soldering iron can I just heat up a bigger iron then unplug it before fixing the new battery in with the residual heat?
Or should I just crimp it back on?

I like your humour :-).

10 points

Joe