Digital Angle Gauge won't reset after battery change...

[DavoDavo]

Hi guys,
I'm hoping someone will come up with a fix for my Digital Angle Gauge, it's the same as this one (http://www.ebay.com.au/itm/Digital-Bevel-Box-Inclinometer-Angle-Gauge-Meter-Protractor-360-Magnets-Base-/270985840582?pt=LH_DefaultDomain_15&hash=item3f1803c7c6#ht_4553wt_1150).

It came with batteries (3 x CR2032) installed and worked fine until the batteries died, but I didn't notice the dead batteries due to a house move a year ago and only a few weeks ago saw no display when I went looking for it.
Putting three new batteries in just gives me a permanent display of all the characters that the LCD has. I thought maybe that I was glitching it when the batteries were going in so tried many times after suitable in-between long wait times (that usually fixes my digital calipers when I put new batteries in them).

I took the back off and tried using a 9V battery instead of the 3 CR2032's in case it was somehow because of the way I was putting the batteries in but despite trying many, many times I still get the same display and no reset. 

Does anyone have any ideas? I'm loath to throw it away unless I really have to.   

[Davo J]

Hi,
I cant help but,
I know you probably never bought it off him, but drop Meister on ebay a message. They are all pretty similar and just tell him your problem and don't mention what brand yours is.
He has been selling them for a few years now and I have one of his, and if anyone can help you it's him, as he knows what he sells and repairs most things himself as well.
http://stores.ebay.com.au/DROStore
If your not on ebay I have his email address, but it's down the shed so I will have to get it if needed

I had a problem with a Meister DRO recently (5+ years old) and he told me how to fault find and was more than helpful.
I highly recommend him for buying any of his products, full service back up even though most rubbish ebay overseas guys and say there is no back up service, this guy stands by his products 100%.

Dave
PS,
Davo, great name by the way, LOL
Where are you in Aus, I am in Newcastle NSW

[AdeV]

Does anyone have any ideas? I'm loath to throw it away unless I really have to.   

Just a WAG - does it need recalibrating? Wondering if maybe there's a reset switch somewhere, possibly recessed & requiring a bent paperclip to operate, which puts it back to zero?

[DavoDavo]

Dave
PS,
Davo, great name by the way, LOL
Where are you in Aus, I am in Newcastle NSW

Hi Dave (yep, that is a great name!) 
I'm in Ulladulla, NSW South Coast, about 2hrs drive south of Wollongong.

Thanks for the tip, dunno if I'd be brazen enough to ask him for help though, seeing as I didn't buy anything from him...

[DavoDavo]

Does anyone have any ideas? I'm loath to throw it away unless I really have to...

Just a WAG - does it need recalibrating? Wondering if maybe there's a reset switch somewhere, possibly recessed & requiring a bent paperclip to operate, which puts it back to zero?

No, there is nothing like that inside the darned thing, it's all solid state SMD electronics.
I wonder if it might respond to something like this though... 

I'm beginning to think that because two of the old batteries ended up with small negative voltages they cancelled the small positive voltage on the remaining one and actually presented a negative voltage to the electronics, thus buggering it. 

[z3t4]

thus buggering it. 

Indeed.
Have you tried it in the freezer for a couple of hours/overnight?

[David Jupp]

Mine looks identical - nothing in the (limited) instructions cover your problem.  All I can think of is to try turning off & back on (see if that re-sets it).  Alternatively you could try holding calibrate button for several seconds...

[mklotz]

Sometimes on these devices a reset can be accomplished by removing the battery and then shorting the battery terminals inside the device.

Give it a try.  You have nothing to lose.

[DavoDavo]

...All I can think of is to try turning off & back on (see if that re-sets it).  Alternatively you could try holding calibrate button for several seconds...

Done all of that, many, many, many times. Tried pressing all combinations of buttons while powering up but I think it is supposed to go through some internal reset process  before the buttons become active.

Thanks for the reply though.

[DavoDavo]

Sometimes on these devices a reset can be accomplished by removing the battery and then shorting the battery terminals inside the device.

Give it a try.  You have nothing to lose.

I hoped that would be a simple solution, but... too good to be true, unfortunately. It didn't work. 

Thanks for the suggestion.

[DavoDavo]

thus buggering it. 

Indeed.
Have you tried it in the freezer for a couple of hours/overnight?

I'll give that a try, nothing else has worked so far.
Thanks for the suggestion.

[spuddevans]

Just another thought, the battery contacts may also need a really good cleaning. I've had a similar thing happen to my cheap digi-vern and I had to scrape the battery contacts with a file and then give them as good a clean as I could with electrical contact cleaner and an eraser. That worked for me, might be worth trying


Tim

[DavoDavo]

Just another thought, the battery contacts may also need a really good cleaning. I've had a similar thing happen to my cheap digi-vern and I had to scrape the battery contacts with a file and then give them as good a clean as I could with electrical contact cleaner and an eraser. That worked for me, might be worth trying

Tim

Thanks, but I pulled the back off the thing ages ago and attached the battery direct to the bare wires, didn't help at all. 

[kwackers]

I think it looks like you've exhausted all reasonable possibilities...
So at this point I'd strip it. Have a good look over it with a strong magnifying glass, in particular look for tin 'whiskers' shorting stuff out. Perhaps even give it a stiff brush with a non-conductive brush in case there's some I missed.
(Obviously if you've got the 'knowledge' there's other stuff you could do - checking crystals etc)

If that doesn't work, I'd check out whatever the sensor is and consider using it in something else. 

[DavoDavo]

I think it looks like you've exhausted all reasonable possibilities...
So at this point I'd strip it. Have a good look over it with a strong magnifying glass, in particular look for tin 'whiskers' shorting stuff out. Perhaps even give it a stiff brush with a non-conductive brush in case there's some I missed.
(Obviously if you've got the 'knowledge' there's other stuff you could do - checking crystals etc)

If that doesn't work, I'd check out whatever the sensor is and consider using it in something else. 

Yep, tried everything.
There was a bit of flux around the press-button solder contacts on the back of the PCB and I cleaned that off - didn't make any difference of course...
Problem is it looks like I can't get the PCB assembly out of the case without destroying something. It seems to be held in with four screws, which I removed, but although the PCB moves a little where the buttons are it won't come any further. There are four more, much smaller, screws on the board but I'm not game to take those out just yet as I think they might be holding the LCD display (or maybe other components) to the board.
I suspect that the display is stuck to the front of the case with some sort of strong adhesive.

As suggested, I'll try the freezer trick first, but I'm not holding my breath.

One thing that intrigues me is that, at the top left hand corner of the board, there are 2 small black insulated wires soldered to the board. The wire's ends are not attached to anything and where they are soldered to the board is covered with a blob of silicon (or hot glue?). I can't see if the wires are twisted together, and one is slightly longer than the other. I suspect it might be some sort of factory tweaking/calibrating adjustment?
I'll see if I can take a photo of it.

[Bluechip]

A 'twisted wire capacitor' was a fairly common sight in days of yore for trimming XTAL Oscillators etc.

Usually solid wire, stranded stuff unwound and defeated the object of the exercise. Which may explain the adhesive.

Usually get around 1-10pf with the trick.

BC

[DavoDavo]

A 'twisted wire capacitor' was a fairly common sight in days of yore for trimming XTAL Oscillators etc.

Usually solid wire, stranded stuff unwound and defeated the object of the exercise. Which may explain the adhesive.

Usually get around 1-10pf with the trick.

BC

Yes, that's right, however the wires are quite a way from the crystal so... I dunno.
Have a look at the pic, the crystal is the metallic cylinder just below the large orange component on the right.
The wires are close to what I think is the accelerometer. 

[kwackers]

I think the wires where probably attached to something else for calibration/testing. They look like they've simply been snipped off to me.

Might be worth swapping the crystal?
U4 might be worth checking out too - could be a voltage reg or possibly just a transistor of some description, but looks big enough that it may be used to power up and down the circuit?

[AdeV]

I don't think it's any reverse voltage that's killed it, that voltage regulator (small black chip next to the power wires) should have protected it. It might be worth briefly shorting the two pads at the top RH corner (with no battery connected), that should discharge the black capacitor, give it 5 mins for any other capacitors to discharge, short it again (for luck), then re-apply power & see if it's fixed.

Chances are it won't, there may be some reset pads somewhere, but TBH it's looking like it's toast. The sensor will amost certainly be an itty bitty chip underneath that blob of black plastic, you won't be able to salvage it without destroying it, and even if you did save the chip, it'll be max 3mm square and impossible to solder by hand... (don't ask me how I know this)...

[DavoDavo]

I think the wires where probably attached to something else for calibration/testing. They look like they've simply been snipped off to me.

Might be worth swapping the crystal?
U4 might be worth checking out too - could be a voltage reg or possibly just a transistor of some description, but looks big enough that it may be used to power up and down the circuit?

Very unlikely to be the crystal I'd think? Anyway, chances of getting another are pretty remote unless it's a standard watch/clock crystal.
Yes, I wondered about U4 and thought it looked like a voltage reg. My good multimeter is still packed away somewhere and I've got no idea where or I'd poke around with a couple of probes.

[DavoDavo]

I don't think it's any reverse voltage that's killed it, that voltage regulator (small black chip next to the power wires) should have protected it. It might be worth briefly shorting the two pads at the top RH corner (with no battery connected), that should discharge the black capacitor, give it 5 mins for any other capacitors to discharge, short it again (for luck), then re-apply power & see if it's fixed.

Chances are it won't, there may be some reset pads somewhere, but TBH it's looking like it's toast. The sensor will amost certainly be an itty bitty chip underneath that blob of black plastic, you won't be able to salvage it without destroying it, and even if you did save the chip, it'll be max 3mm square and impossible to solder by hand... (don't ask me how I know this)...

Yes, you're probably right about the reverse voltage.
I have already shorted the + and - wires together but no luck.
I need to find my good multimeter and have a poke around before I go any further, the positive (red) wire is connected to one of those pads and it looks like the other pad is connected to the black cap so that might be a possibility, maybe shorting the wires together was not enough to completely discharge everything.

The black blob will be the brains of the thing (CPU), if I knew what type or chip number it is I might be able to look up the specs for it and see which pin-out is the reset line.

I think I'll get my magnifying glass and have a good look at all the components.

Ah... I just turned the picture upside down and, guess what? Screen printed just below the CPU is "RESET" so I wonder which track it refers to?
Looks like there's a choice of two tracks that relate to it, one goes to R8 which then goes to (2 legs of?) Q5 (2TY chip) and then to U3, the other goes to a solder pad. But it's anyone's guess what tracks are on the other side of the board or sandwiched in it.

[AdeV]

My guess it's the one that goes to the solder pad. Simple way to check it - short the solder pad to GND with the device powered up. You won't do it any harm, the worst case scenario is that nothing happens. If it needs a high to re-set, then short it to V+, but on the circuit side of the voltage regulator NOT the battery, I'm guessing it's a 2.8v circuit, but it might be less...

[kwackers]

The sensor will amost certainly be an itty bitty chip underneath that blob of black plastic, you won't be able to salvage it without destroying it, and even if you did save the chip, it'll be max 3mm square and impossible to solder by hand... (don't ask me how I know this)...

The sensor is the silver topped 6 pin device. A Memsic D2125E accelerometer.
Plenty of info on the web for reusing it. 

[DavoDavo]

My guess it's the one that goes to the solder pad. Simple way to check it - short the solder pad to GND with the device powered up. You won't do it any harm, the worst case scenario is that nothing happens. If it needs a high to re-set, then short it to V+, but on the circuit side of the voltage regulator NOT the battery, I'm guessing it's a 2.8v circuit, but it might be less...

Hmmm... In the (very) old days, power up CPU resets were done with a cap/resistor combo that held the reset line high or low, as the case may be, until the voltage stabilised.
I'm leaning towards U3, it's a small EEPROM and maybe the R8/Q5 combo does the reset thing on that? As far as I can make out, Q5 is a transistor of some sort, maybe that's gone belly up.

More online research needed, I got sidetracked finding out about the accelerometer and how it works - amazing technology! See the link...

 
http://www.memsic.com/technology/sensor-components.html

[Noitoen]

It seems that you are not the only one with the problem. If you Google around a bit you will see the same problem with other devices even of known brands. Couldn't find a solution though.