How to debug this sound COB circuit

Thread Starter

alaasalama

Joined Apr 1, 2021
5
Hi guys!
So, my kid has this "Animals Sounds Book" which is broken and doesn't produce any sound now, although the batteries are good.

I've attached two images showing the COB circuit, but I'm beginner and I don't know how to trigger these metal strips to test the output?

Also, any general idea about how to debug this board would be appreciated, wiring diagrams or what to search for?
 

Attachments

Yaakov

Joined Jan 27, 2019
3,492
First, that connector is a possible source of the problem. I would try to put pressure on it while operating the book to see if that helps.

Second, how many sounds does the book make?
 

Thread Starter

alaasalama

Joined Apr 1, 2021
5
First, that connector is a possible source of the problem. I would try to put pressure on it while operating the book to see if that helps.

Second, how many sounds does the book make?
Thanks for the connector hint! I'll give it a try.
There are six different sounds in this book.
 

Thread Starter

alaasalama

Joined Apr 1, 2021
5
Just an update here: (perhaps you have any idea?)

Also, I've attached some extra images and I feel I need to mention the book was working fine, then some buttons were working and others not, then the voice was cracking, not clear, then no sound at all.
 

Attachments

LesJones

Joined Jan 8, 2017
3,494
I am guessing that connections A0 to A3 and B0 and B1 connect to a number of buttons arranged electrically as a 2 x 4 matrix. Could you post a picture showing all the buttons and LEDs (If any.) so we have some idea how the module is controlled. We can then try to get you to continuity between the A axis and B axis connections to see if all the buttons are working.

Les.
 

Thread Starter

alaasalama

Joined Apr 1, 2021
5
There are no LEDs in this book, and that's a better video showing the whole book and how it works:

Thank you for all the information you are writing here, I appreciate that!
 

LesJones

Joined Jan 8, 2017
3,494
What is the total number of buttons to press that give a different sounds ? (I suspect there will be 8 as a 4 x2 matrix gives this many points. I suspect that one axis is pulsed sequentially and the other axis goes to input pins on the microcontroller. If you have an oscilloscope you could check for pulses on the A or B pins on the board. (With the oscilloscope ground connected to the battery negative.) Another possible fault is the speaker going open circuit. Measure the resistance between the speaker connections. I would expect it to be less than 50 ohms.

Les.
 
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Thread Starter

alaasalama

Joined Apr 1, 2021
5
I don't have an oscilloscope. The speaker is good, it measured 20 Ohms, and I tried it on a different toy, and it worked.
The book has 6 different sounds.
If I just can get a 100% correct way to trigger these buttons and it didn't produce any sound, then I believe it will be something wrong within the IC itself, and that would be impossible to fix right?
 

LesJones

Joined Jan 8, 2017
3,494
Can you do continuity checks between the following 8 pairs of contacts on the flat cable that mate with these connection on the PCB. You will probably need someone to keep a button pressed while you test for continuity.
B0 - A0
B0 - A1
B0 - A2
B0 - A3
B1 - A0
B1 - A1
B1 - A2
B1 - A3
As there are only 6 buttons there will be two of the above pairs that never show continuity. To the right of the above table identify which button creates continuity between the two points. Even if you identify buttons that are not working or breaks in the cable I don't know how you would be able to repair them. You would probably have to replace the buttons with tactile buttons that would be much larger than existing ones. The existing buttons are probably just two layers of the mylar cable that make contact when pressed together. A likely point of failure is the cable where it flexes as a page is turned.

Les.
 
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