Paper Shredder Fault

Thread Starter

spike1947

Joined Feb 4, 2016
293
Hi

Have a Amazon Paper/Credit Card Shredder and it as stopped working, checked feed to the PCB and the fuse on the PCB, to be honest I am not sure were I start with finding the fault, can find a schematic or it , maybe there is one under a different brand name !.
So any idea's as to what and how to check , there is a ir emitter and receiver , but I can't really remember how to check those, been awhile since I was active in the repair of electronics in items .

Spike
 

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Dodgydave

Joined Jun 22, 2012
9,919
Looks like Transformer less supply, unless there is a another PSU attached, these are operated by breaking the IR beam on the paper gap, this triggers the relay to power the motor.
So simple to check with a DVM.
 

AlbertHall

Joined Jun 4, 2014
11,144
With a transformerless power supply one of the commonest failures is the capacitor - in this case that large yellow rectangular block.
Do you have any means of measuring its capacitance?
 

Thread Starter

spike1947

Joined Feb 4, 2016
293
With a transformerless power supply one of the commonest failures is the capacitor - in this case that large yellow rectangular block.
Do you have any means of measuring its capacitance?
Hi
Just a multimeter ! , could just test to see if it holds a charge, that’s about it
 

Thread Starter

spike1947

Joined Feb 4, 2016
293
With a transistor, there is one on the PCB.

Check for DC voltage first across the output of the bridge rectifier and the led TX, also the RX photo diode will go high or low when covered up.
Hi
Thanks for that , just another quickie, will attach pic of the Yellow Capacitor, similar to the one I have on this PCB, but numbered 104 not 105 as in the pic, question what capacitance is it ? .

cheers
Spike
 

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Thread Starter

spike1947

Joined Feb 4, 2016
293
With a transistor, there is one on the PCB.

Check for DC voltage first across the output of the bridge rectifier and the led TX, also the RX photo diode will go high or low when covered up.
Hi Dave

Am I having a bad day today !, where the heck is the " Bridge Rectifier", set up , is it the cluster of diodes underneath the PCB .

Spike
 

Dodgydave

Joined Jun 22, 2012
9,919
Yes looks like there are two sets of Black diodes, it would be better to draw the circuit out so you can see what's going on, start with the Live and Neutral.

It's definitely a transformer-less PSU with the Yellow capacitor probably a 1uF into a bridge rectifier , .
 

AlbertHall

Joined Jun 4, 2014
11,144
There may even be two of those supplies on the board. There are two yellow capacitors with each having a pair of resistors across them which is what you would expect.
 

Thread Starter

spike1947

Joined Feb 4, 2016
293
Yes looks like there are two sets of Black diodes, it would be better to draw the circuit out so you can see what's going on, start with the Live and Neutral.

It's definitely a transformer-less PSU with the Yellow capacitor probably a 1uF into a bridge rectifier , .
Yes good idea, will do
When light between the sender and receiver is blocked, transistor Q1 switches on the relay coil and the relay contacts close to switch the motor on.
Thanks for that, that helps a lot.
Spike
 

Thread Starter

spike1947

Joined Feb 4, 2016
293
Any chance you can put directions on the black diodes.
Hi Dave
Am just about finishing a drawing for it, will post it .
PS: I don't think there is any marking on the small black diodes to show flow direction, will look again to make sure .

Cheers

Spike
 
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