Wall clock chime circuit westminster

Thread Starter

grandmaster

Joined Oct 12, 2019
6
Hello everyone

I was hoping for some help if possible.
I have a clock from a late relative that was given to my uncle, it had corroded battery terminals so he cleaned them however snapped some wires in the process. He brought it to me to see if I could do anything.

The clock has two wires for a trigger (I have probed these with a multimeter)
Two wires that go to a speaker.
Two wires from the battery.
Two wires from a switch (I assume this is to change the tone or silence it?)

There is (I assume) a PIC under some epoxy.
A 4.7 uf Capacitor
A 5080 Transistor
A Resistor (not sure of the value)

I have mapped the board out and also taken some pictures which are attached.

I was hoping someone with more knowledge than me would be able to help me map out which wires go where so I can restore the chime for my uncle.
From the research I have done I think that the cap and the transistor make an amplifier? to drive the speaker.

Thank you in advance

Grandmaster
 

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Thread Starter

grandmaster

Joined Oct 12, 2019
6
Thank you for the reply, The unit is attached by the trigger wires to a quartz movement which seems when probed with a multimeter to close the circuit when the hour is struck. would that negate the need for a crystal?

I replaced the capacitor with a new one with all the same values just to ensure that was not the issue and I was going to source a transistor from eBay to replace that as well.
I have no idea what is underneath the epoxy and I presume there is no way to find out without trying to remove it.

Thanks

GM
 

Ramussons

Joined May 3, 2013
813
Thank you for the reply, The unit is attached by the trigger wires to a quartz movement which seems when probed with a multimeter to close the circuit when the hour is struck. would that negate the need for a crystal?

I replaced the capacitor with a new one with all the same values just to ensure that was not the issue and I was going to source a transistor from eBay to replace that as well.
I have no idea what is underneath the epoxy and I presume there is no way to find out without trying to remove it.

Thanks

GM
I was referring to the 70's era UM34xx series IC's, where 3484 ( if I recollect right) had the Westminster clock complete chime. I remember making it authentic afap by using a clock pulse counter that terminated the chime depending on whether it was 15/30/45 min past the hour, and the full chime every 60 min followed by the hour rings.
This COB may be a scaled down version of UM3484.
 

Thread Starter

grandmaster

Joined Oct 12, 2019
6
Hello,
Sorry I have had to work away with not much internet access (or time!).
The unit is now chiming, I just need to work on the triggers I had some help to get it working :)

For anyone else that needs this info:

Speaker (-) to collector
The emitter should go to ground, battery (-).
Speaker (+) to battery (+).

As I said I just need to work on the triggers and that will have to be this weekend when I have time.

I want to thank you all for replying!
 
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