Excelvan watch winder not working?

[Rob30]

Hi Hi all, first of all, this is my first post, if in te wrong place, I'm sorry.



I have a excelvan watch winder which does not work. I will show pictures of the circuit board, i have changed the capacitor but to no avail.



I have tested the board with a multimeter and tere appears to be 12 vols on te board but i cannot get the motor to kick in.



Would anyone know where i am meant to test to try to find the fault please?



I am not an electronics expert by any means, just like tinkering. But if someone could explain in really simple terms what can go wrong with this setup and what i could possibly do to fix.



I have tried the motor, that works, i have changed the big cap but still no joy?

--- Updated Feb 20, 2021 ---

Also could someone please explain to me how this circuit works from power input to the motor powering up, in other words, what is the sequence of events that ultimately powers the motor?

Thanks again to anyone who may be able to answer this thread.

 

[d123]

Hi,

I don't know about this kind of circuit. Naming the ICs, transistors and diodes on the board from their markings/smd codes may give a clue. Maybe it's an h-bridge or a pwm, etc. kind of circuit. Have you read this, not great but has some hints of typical issues:

REPAIRING A WATCH WINDER

From the article, the motor may have worn out, but I really have no idea or expertise in this area.

 

[Rob30]

Hi, thank you for your reply.

I have checked the motor and this apoears to be working ok when connected to a power source, and thank you for the info but they are just on the track of motor or belt drive problem?
Regards rob.

 

[d123]

Hi,

I couldn't say, sorry, I don't understand what you mean about '(...) but they are just on the track of motor or belt drive problem?'. If the red PCB is the one you have, you could check that Q1 through Q4 (2 x NPN 8050 and 2 x 8550 pnp BJTs) do something 'normal'. maybe one of them has gone short, who knows. What is the 14-pin IC? What's it meant to do? I can't see the IC name/marking, so can't begin to guess. Must be a motor driver IC, maybe, if it's not an MCU...

 

[Rob30]

Hi, thanks again for your input.

I am not sure what value i would be looking for if i checked with a multimeter and how would i check if they were bad?

The ic is, i believe, to tell the motor to torn for several minutes and then turn the opposite way, and a few other rotations dependant on the switch on the front of the machine.

Thanks again.

Regards rob.

 

[d123]

Hi,

Can you see the name/code/number on the top of the 14-pin IC and write it here, please? It might be an MCU, it might be a motor driver IC. If the latter, it might have IR2110, L293, etc. or something entirely different written on the top. If you read the datasheet of that IC - the general description(s), waveform/ timing diagrams, typical application schematics, and especially the 'electrical specifications' section (not the 'absolute maximum ratings' section) - you will be able to assess what voltages to expect on each pin to see if it is working properly.

Regarding the BJTs, it might be a fair assumption to expect (assuming it's an h-bridge) that: when you set it to turn one way, one PNP base voltage should go from e.g. Vsupply to Vsupply - 0.7V and one NPN base should go from 0V to +0.7V; the other pair should do the inverse. The PNP, if at the top of the h-bridge (it should be) should drop its Vce from Vsupply to e.g. ... more or less, less than a volt when its base is at Vsupply - 0.7V. If you can follow the pcb traces, you might be able to figure which half is clockwise and which half is anti-clockwise before powering it up. Below is a picture of a typical h-bridge circuit - your board may have the bases of the BJTs connected differently, people do it all manner of ways, but the general premise should suffice to troubleshoot a bit. When Q1 is on, Q4 should also be on and Q3 + Q2 should be off. If Q1 and Q2 or Q3 and Q4 are on at the same time - to paraphrase Peter D. Hiscocks of Syscomp: 'That is a Bad Thing.'

No idea here, don't want to waste your time on wild goose chases, checking those components is just a suggestion.

 

[Rob30]

Hi, sorry for the late reply, no the ic has no id numbers on it?

Would you know where i could get a similar board for it within the uk.

I'm at odds with this now.

Or can i somehow wire it so it goes from power to switch then to motor and place on a timer socket in the mains?

Regards agaon rob.

 

[d123]

Hi,

I don't know where you can buy those, you'd have to look.

Without knowing the board well, wouldn't like to say. You can try if you know what voltages should be where.