Electronic scales slowly breaking

[julianf]

Ive got a set of these -

On startup, they lock up with error 2 - whatever that is (the manufacturer claims to have no record at all, but was happy to tell me about their current range pricing...)

Curiously, and i have no idea how i even worked this out -

If you boot them up on their side, they boot fine. And work fine when the right way up, apart from the max capacity then is about 350g (which may be relevant, i dont know)

Ive seen Err-5 on boot before also but that seemed to flash up and then vanish, but thats not shown up for since the Err-2 started happening.


Anyone got any ideas?

I probably dont mind even paying to fix them, as a new set is silly money, and, whilst for paint, 1 decimal place is fine, for the ink i use, 2 places is nice (i often have to weigh up half gram quantities of catalyst)

Thank you.

 

[Kram]

If they are not calibrated your probably better off with a £6.99 pair of digital kitchen scales, and mini drug dealer/jewelers scales for the small quantities. 2dp for anything over 10 grams is a bit silly, but I think my small ones do 200g.
As for repair, likely moisture inside. Open up and dry the pcb.

 

[julianf]

If they are not calibrated your probably better off with a £6.99 pair of digital kitchen scales, and mini drug dealer/jewelers scales for the small quantities. 2dp for anything over 10 grams is a bit silly, but I think my small ones do 200g.
As for repair, likely moisture inside. Open up and dry the pcb.

Ive got some kitchen ones too, but their auto off time is so frustrating, however, I dont disagree with anything you are saying, except...

Its not a moisture issue (i dont think anyway) as they live indoors, not in the workshop.

 

[OJCar]

This is purely a guess.

Might the mechanism that operates the load cell be rubbing or catching when you boot it up the right way up?
And not rubbing/catching when booted up on its side.

Does it boot up OK if held upside down?

 

[voipio]

Are they being powered on with nothing on the pan? Some of the internal gaps between moving parts can be quite small in these types of scales. It's worth checking if powder or grit may have got into the mechanism, forcing the pan support downwards, causing it to error because the initial "load" is too high. Do you know if the measuring cell is of the strain gauge type or a force compensation mechanism? There's often a small clunk on power up with the latter type, and the pan moves slightly.

 

[Kram]

Its not a moisture issue (i dont think anyway) as they live indoors, not in the workshop.

Open it up and find out, its not much good as is. My second guess would be a bad connection/solder joint.. be careful of the lcd zebra strip if it has one - I can never get those to work properly if they ever come apart.

 

[julianf]

Thanks to all - ill open it up and take some photos. I opened it when this first started happening, and was non the wiser, but ill upload some photos here, and hopefully someone will be sharper than me!

 

[julianf]

This is purely a guess.

Might the mechanism that operates the load cell be rubbing or catching when you boot it up the right way up?
And not rubbing/catching when booted up on its side.

Does it boot up OK if held upside down?

ERR-5 when upside down - the one ive not seen for a while (ERR2 is the usual one)

 

[julianf]

 

[tommullin]

that bare wire thats being used as a ground isnt flapping into another solder pad is it? try wrapping some tape around it?

 

[julianf]

that bare wire thats being used as a ground isnt flapping into another solder pad is it? try wrapping some tape around it?

View attachment 343137

I spotted exactly that also, and, no, its not to blame (i made sure it was out of the way, and same result)

 

[voipio]

Check that the load cell arm, to which the pan is attached, has free movement, including the limit screw next to the capacitor. Have the scales been dropped, or had a heavy weight land on the pan? At one end of the battery compartment, next to the p-clip, there appears to be a loose strand of wire. Check all of the multiway connectors are properly seated. Also, U1, close to the bank of orange capacitors, presumably the strain gauge amplifier/conditioner, appears to have some corrosion around pins 3-6.

 

[Screwdriver]

Wonder if the load cell has drooped over time and constant loading. Have you tried supporting the scale bed while switching on?

If the problem is with gravity, lifting it up might reduce the "pre-load" which is tipping the scales over their operating range.

 

[julianf]

This is, what i assume, people are referring to as the load cell?

The top is covered in some sort of epoxy - i assume theres some sort of, umm, bend sensor under it?

Anyway, this photo is without the pan carrier attatched. Boots up fine like that.

If i add the carrier, it wont boot again.

I assume its right on the edge, and thats why putting it on its side lets it boot also.

Does that make sense?

 

[voipio]

Yes, that's the load cell, with a strain gauge bonded to the metalwork, and potted with epoxy.

Your thinking makes sense to me.

These things are precision made. Any drift in the strain gauge elements, due to oxidation/chemical reaction, could easily take the straing gauge "bridge" out of balance, and present the electronics with an apparent "excess load" at start up. There may be some sort of bridge balance adjustment and calibration, but it may need a factory procedure, which may involve button combinations, or more likely a debug lead and appropriate software. Ravencourt is probably only a rebadge. The Furi brand seems very similar in appearance.

 

[mike os]

If it works bare the the problem is in the case/ mechanics

 

[Agroshield]

...Ravencourt is probably only a rebadge. The Furi brand seems very similar in appearance.

Agree. Look also at Vetek (https://www.vetek.com/precision-scale-600g001g-fr-h-bs600h-en/article). Vetek say that if you drop them an email, they will send you a manual for 'older versions'. Just tell them you have an FR-H and ask them for a list of error codes. Accidently neglect to mention that it is not a Vetek FR-H.

 

[angellonewolf]

is there any part numbers off the board now you got it open

ive used these to good effect to find the makers on pc motherboard etc

 

[galooph]

I fixed a similar one years ago by removing and replacing the 40 pin IC from its socket. Might be worth a try if there's nothing else obviously wrong.

 

[Screwdriver]

This is, what i assume, people are referring to as the load cell?

The top is covered in some sort of epoxy - i assume theres some sort of, umm, bend sensor under it?

Anyway, this photo is without the pan carrier attatched. Boots up fine like that.

If i add the carrier, it wont boot again.

I assume its right on the edge, and thats why putting it on its side lets it boot also.

Does that make sense?

View attachment 343147

Yep. I'm guessing some mechanical element of the construction has distorted over time which is giving a false flag on no load. If removing the scale base or holding it up (against it's own weight) stops the error occurring then it's a mechanical issue with the load cell.

Don't know much about these things but there may be a calibration adjustment, a mechanical cure, swap repair for the load cell or, lets be honest, you might just have to put it down...