Kocom kc mc-32 no sound

[dolphod]

Hello everyone,

I have a Video door phone and i have a problem at door camera. I have no sound at camera door.
I can hear sound at monitor but no sound at camera door.
I measure frequency with a multimeter and the frequencys are too high... and the result is no sound from the speaker.

Can you please please give me some advice of which component might be with broken?

Everything is working except the sound that cames from monitor...
Heres some pictures of the door camera board:

 

[panic mode]

this is only part of the system. are you sure problem is here and not with the microphone at monitor?
i can't make out the chips but it looks like this is all analog. you have two options, trace signal from mic or from speaker.

long time ago in a galaxy far far away i was learning to repair radios using signal injector and tracer. those could be handy here too (and are easy to make)

 

[dolphod]

Yes I'am pretty sure that the problem is here, let me tell you some of the history...
Some guy just wet the camera door with water and i just knew one day later because someone rang at the door
I just heard noise at the monitor... (I couldnt prove that was that guy fault... but it was his fault thats for sure...)
Then i just dry the camera and assemble it again without reparing anything and the noise disappeared and can hear
at the monitor but not at the camera door...

At first I just thought that the speaker was dead but i connected another sound source to it and it just work although the sound is a little bit low but i can hear perfectly.

So I took Multimeter and measure the frequency at the red dots of:
https://www.electro-tech-online.com/attachments/microviewfront-jpg.74167/
And checked that frequency of a normal sound source is a lot lower then that.
The values are above 200 or 300... and a normal source not even 30...

Another thing is that theres only 2 wires from the monitor to the camera door... so video/audio/power are caming from those 2 wires...

Another thing is that if I just tap at the monitor with fingers I can hear at the monitor speaker even with no camera connected so I presume that the Monitor Mic is working...


Thank you any kind of help...

 

[alec_t]

theres only 2 wires from the monitor to the camera door... so video/audio/power are caming from those 2 wires...

Are the 'wires' in fact miniature screened cables, or just 2 single insulated conductors?

 

[panic mode]

they have to be wires, you can see underside of the pcb, it is just a 4-pin connectors and 4 wires are connected to it - two of them are speaker...

 

[alec_t]

At the bottom of pic 3 there seems to be some greyish deposits on the pcb. They could be providing a current leakage path. Worth carefully cleaning the board in that region?

 

[dolphod]

Heres a video of camera instalation(2 wire):

In the video the frequency just goes from ~100 to ~130 i dont know why... maybe my multimeter was crazy when it just show 200 and 300...

Worth carefully cleaning the board in that region?

How would you clean it?

I have Isopropyl alcohol

 

[dolphod]

I just went for a video just to show what i meant:

What components could split audio/video and power?

My hint is capacitors and coils... or am I wrong?
and if the only audio is not working could it be the blue coil?

I measure it with connectivity and is OK, but dont know for sure what tests could I do more...

 

[alec_t]

I have Isopropyl alcohol

I'd try that.

What components could split audio/video and power? My hint is capacitors and coils... or am I wrong?

Those are what would be used.

 

[dolphod]

I'am not a expert cleaning so I clean the best I know... can you checkout please images below?
I already test it and didnt workout... Everything stills the same, all working except sound of camera speaker...

I decided to take some measures for you to give some advice:
Marked | Measured
C33 10 uf 16v O.L.
C22 47 uf 16v 50.1 uf
C26 10 uf 16v 10.3 uf
C2 470 uf 10v O.L.
C21 100 uf 25v 101 uf
C12 3.3 uf 50v 3.3 uf
C11 3.3 uf 50v 3.4 uf
C1 470 uf 25v O.L.
C6 10 uf 50v 10.2 uf
C5 47 uf 16v 54.1 uf
C9 100 uf 25v O.L.
C14 10 uf 16v 11.3 uf
C7 2.2 uf 50v 2.5 uf
C25 10 uf 50v 10.4 uf



L1 ???? 0.3
L5 ???? 0
(I measure L5 with no polarity like so:
1 connects with 2 I get 0 (connectivity).
And 3 connects with 5 also get 0.
Another combination does get connectivity)


D4 ???? 0.593
D8 ???? 0.593
D9 ???? 0.587

Heres the images (with more quality) with capacitors and coil indentified:




In this measures I did not desolder components out of PCB i decided to take them out only when they cause some doubt...
(I was kind surprised beacause i did get the values too close of what they mark without take them out of PCB)
And thats my problem because I dont know where is the problem. How can I test if its a moisture problem? Connectivity test is enough?

Do you want me to make another test and can you give some more advice?

 

[tunedwolf]

If water made it into the speaker on the camera, there's a fair chance that the cone has distorted and possibly jammed the voice coil. Have you tried substituting the speaker on the camera? The four wire connection would suggest composite video plus audio and power with a common ground. You are however, going to have real difficulty fault finding an audio signal with a multimeter, there's probably more mileage in it for you if you just use a small speaker or headphones. Identify the audio wires at the monitor and place a small speaker or headphones on it at that end and see if you are at least sending audio to the camera, then work from there

 

[dolphod]

Thank you for your answer.

Have you tried substituting the speaker on the camera?

Yes, there is another one on the monitor and I switch them... both the speaker is working but when connected to camera door none of them works.
Already test the Mic the same way... Both Mic are working...

The four wire connection would suggest composite video plus audio and power with a common ground.

Theres only 2 wire, i dont know what you mean... Please checkout the 2 wire video instalation...
If you see 4 wire at some picture I posted let me tell you that this system allows to connect a electric door gate (like the door automatically opens when press a button)
Please check KCV-352:
https://www.enaco.pt/downloads/flyers/domotica/monitores/flyer_kcv_w352~354_c301_eng.pdf

going to have real difficulty fault finding an audio signal with a multimeter

Did you see when i tap the Mic at the monitor the frequency changes?? Also monitor was working before camera "gets wet" so...
I think the problem is when the audio is splitted, the frequency is a little bit high so the speaker doesnt move (that means no sound)
as you can see in the video... if the frequency was right and it wasnt "audio" it would produce noise...
I dont know but i think the question is what component is splitting the wrong way the audio or adding some wrong values before the speaker out...

And about the values are they right??

 

[alec_t]

In the bottom right corner of the last pic it looks like a large part of the pcb copper trace is damaged/corroded/missing.

 

[dolphod]

It was corroded, so took a sandpaper and clean it, but it didnt make any diference...
It has connectivity between those points...


What about these, anyone has something to say?

I decided to take some measures for you to give some advice:
Marked | Measured
C33 10 uf 16v O.L.
C22 47 uf 16v 50.1 uf
C26 10 uf 16v 10.3 uf
C2 470 uf 10v O.L.
C21 100 uf 25v 101 uf
C12 3.3 uf 50v 3.3 uf
C11 3.3 uf 50v 3.4 uf
C1 470 uf 25v O.L.
C6 10 uf 50v 10.2 uf
C5 47 uf 16v 54.1 uf
C9 100 uf 25v O.L.
C14 10 uf 16v 11.3 uf
C7 2.2 uf 50v 2.5 uf
C25 10 uf 50v 10.4 uf
View attachment 74228


L1 ???? 0.3
L5 ???? 0
(I measure L5 with no polarity like so:
1 connects with 2 I get 0 (connectivity).
And 3 connects with 5 also get 0.
Another combination does get connectivity)
View attachment 74227

D4 ???? 0.593
D8 ???? 0.593
D9 ???? 0.587

Heres the images (with more quality) with capacitors and coil indentified:
View attachment 74225
View attachment 74226


In this measures I did not desolder components out of PCB i decided to take them out only when they cause some doubt...
(I was kind surprised beacause i did get the values too close of what they mark without take them out of PCB)
And thats my problem because I dont know where is the problem. How can I test if its a moisture problem? Connectivity test is enough?

Do you want me to make another test and can you give some more advice?

 

[alec_t]

It has connectivity between those points...

Does that mean zero Ohms?

What about these, anyone has something to say?

Without the schematic the values don't really help.

 

[dolphod]

Yes, of course it was zero, i mean, internal R of my multimeter is 0.1 Ohms so it in every point i said it has connectivity i get 0.1 Ohms.
But guess what: I found the problem. There was a broken trail. How dont know how i couldnt see it before...




Thank you everyone.

 

[dolphod]

By the way i would you protect that part of PCB with open copper? Nail varnish would do it?
I want to protect it from rust and moisture...

 

[alec_t]

Good find. Looks as though the circuit board under the track has a split too, so worth supporting with a blob of epoxy or similar if you haven't already done so.

Yes, of course it was zero

Not all meters are the same. Some may indicate 'continuity' even with a few Ohms present.

The green layer over the pcb tracks is a protective coat, but if in repairing the track you've exposed copper then yes, nail varnish (or polyurethane varnish etc) would provide protection.