Hi, I have recently acquired one of these and managed to successfully repair the AM/PM trigger.....
There are a few areas where the problem can arise, but
1. There is a trigger wheel which is attached to the clock mechanism shaft under the clock face, this spins as its connected to the hour hand shaft. This trigger can become detached from the shaft, if this trigger wheel doesn't spin then no signal is sent to activate the signal to switch the AM/PM motor. You can test this signal is working though with a volt meter, (if i remember there are 3 wires connected to the pins via a plug, red, blue and yellow, Yellow/Red triggers the pre motor activation (at around 11.20), and the Blue/Red activates the motor for AM/PM at 12.00, or the other way around i cant remember which now). Attach your voltmeter to the centre pin and outer pin 1 on which are attached to rear of clock face, and spin clock, do the same with the centre pin and outer pin 2, spin the dial, in both instances you should hear a beep from the volt meter to confirm there is a connection as you spin, if so you have a working connection at the clock face, so your problem is not here.
If you get no signal then unfortunately you need to remove the card clock dial to access the trigger, pull off the clock hands, and apply a little heat to activate the double sided tape apply only a little heat though or the clock face will warp, it should now come off. Hopefully once removed you will see what the problem may be (dirty connections, missing tangs etc). Its not possible to remove the clock mechanism from what i found without taking off the clock face as you need access to the nut which is under the trigger wheel, (so in the factory the clock mechanism was assembled, trigger wheel added, clock face stuck on then clock hands added). I pulled mine thinking it was just tight and broke the mechanism, so had to buy a new one. (SKP Quartz mechanism with approx 15mm shaft length, ensure it has the correct dia shafts for hours (dia 5.6mm), minute (dia 3.5mm) and second arm or your original clock hands hands wont fit!). The trigger wheel does not come with a new mechanism, if trigger wheel is broken then you may need to repair or source another.
2. Check the wires from the 3 pin plug to where they are soldiered onto the circuit board, do each wire in turn, this will just ensure you have no broken wires from pin plug to circuit board, once again you should hear a beep for each wire if everything is ok.
3. If all ok so far it could be likely a circuit board problem, trace where these 3 wires terminate on the board with the clear plastic casing, this is the case that will need opening. (Use the video someone has posted above to dismantle the plastic motor casing), once open be careful as the wheels are spring loaded so can pop off (just take a picture before you fully remove case so you have a reference as to how it goes back together!). Pull off the centre cog (i think its white one with an arm on it) be careful to lift the circuit board also as its tucked under the board, this cog will have a trigger wheel attached with 3 tangs underneath. (make sure you have 3 tangs and they are all make contact with the board, ie not bent somehow.). These tangs activate different circuits and motor depending upon its rotation. Locate each of the 3 wires from the plug (yellow, blue and red) to where they are soldiered on the circuit board and to where the track terminates near the trigger wheel (its like a circular track on the board), try to find its last point on the circuit. Then for each wire (yellow, blue and red) in turn test with volt meter various points to the furthest point on the track, if you get to the end and the volt meter still beeps there is no problem with that track, do the same for all 3 wires, if the beep stops at any point on the track, then thats where the problem area is to investigate. Its also worth checking the motor actually works by applying some power through it from a battery, as this could also be a reason.
For reference : As the trigger wheel rotates it drags over the tracks, (causes a groove and can cross other tracks casing disconnection), concentrate on where the grooves crosses the track, its likely this is where the connection problem will be.
In my case one of the tracks had worn through, so I repaired this and it then it worked fine for AM/PM activation, you can repair with a circuit board pen or a little soldier, (as long as its not a blob or you'll damage the trigger wheel!). You just need to make this connection live again, just test after rectification to make sure its now working.
Hopefully once you have located the problem it should be easy to fix.
I hope this is of some help to the above problems......!.
Cheers Jon
