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Try to fix Electric Door bell

Minder

Apr 24, 2015
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It looks a very simple circuit, the best way is to reverse-engineer it by tracing it out and draw up a diagram.
If the AC in goes to the transformer, then there should be a voltage on the secondary.
 

pharaon

Oct 28, 2014
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It looks a very simple circuit, the best way is to reverse-engineer it by tracing it out and draw up a diagram.
If the AC in goes to the transformer, then there should be a voltage on the secondary.
but there's smoke come out of that resistor , how will i be able to check AC if goes to the transformer
and what could cause that resistor to blow up?
 

73's de Edd

Aug 21, 2015
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Sir pharaon . . . . .
I initially need you to AC meter those two RED AC input leads . . . .to know if there is REALLY 230 VAC coming into those two red wires, then I can proceed.
I am wanting to expect that A.C. input voltage . . . . . actually . . . . . . being in the 16 VAC range.

In the interim . . .on that somewhat centrally heated film resistor in the RED line input.
Have the unit totally un powered and dormant and then use metering in ohmmeter mode and connect 2 jumper clip wires, using one to each resistor end.
Then the other clip lead ends go to a shared ohmmeter lead and the other ohmmeter lead goes to a bare metal single edge razor blade or utility knife blade. You hold the ohmmeter lead into pressed constant contact with the metal of that blade
Then you carefully do lateral linear soft scraping on the very center of the resistor to get down thru the coating to . . .HOPEFULLY . . . make contact with the spiral resistance path which routes around the resistor.
We can suspicion that resistor didn't burn open right at center of the resistor. When / if a resistance shows up, double that resistance value and that should give the initial value of the resistor.
NO LUCK ? then work at 1/4 from the end of the resistor, until you have tried both ends.
If so finding resistance, in that case, then quadruple the read resistance value.

Also due to lighting . . . . causing color registration shift . . . . .it appears ? ? ? ? ? ? that one resistor is Blue Red Orange Gold . . . . .62K 5%
The other seems to be Brown Black Red Gold . . . . .1k 5%
And the third is being totally hidden or being in an un viewable end shot.
I see the green .047 caps fine.

73's de Edd . . . . .
EatingPopcorn.jpg


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Last edited:

bertus

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Nov 8, 2019
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Hello,

As @73's de Edd said, there is most likely a transformer for the bell.
I know of transformers that deliver 4, 8 or 12 Volts.
There are also transformers for 8, 12 and 20 Volts.

Bertus
 

73's de Edd

Aug 21, 2015
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ADD ON:
I can't see the precise situation of the door bell wiring, but expect someone to have to hold the door bell button, for you to be able to take your voltage reading.
 

73's de Edd

Aug 21, 2015
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Weird . . . . I must have missed some photos initially
Two odd value 1300 ohms and a 62 k and the 27 ? Ohm monster.
And a 1N4007 at no extra charge.
 

pharaon

Oct 28, 2014
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I initially need you to AC meter those two RED AC input leads . . . .to know if there is REALLY 230 VAC coming into those two red wires, then I can proceed.
yes there is and it cause that resistor to smoke

I am wanting to expect that A.C. input voltage . . . . . actually . . . . . . being in the 16 VAC range.
what do you mean being in 16 VAC range? it's 230 ACV in
 

pharaon

Oct 28, 2014
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Also due to lighting . . . . causing color registration shift . . . . .it appears ? ? ? ? ? ? that one resistor is Blue Red Orange Gold . . . . .62K 5%
The other seems to be Brown Black Red Gold . . . . .1k 5%
what application can i use to make notice on picture and write the right colors?
 

pharaon

Oct 28, 2014
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Also due to lighting . . . . causing color registration shift . . . . .it appears ? ? ? ? ? ? that one resistor is Blue Red Orange Gold . . . . .62K 5%
The other seems to be Brown Black Red Gold . . . . .1k 5%


also something strange when i start to cut through that big resistor it was very difficult anyway i saw like very small metal and it gave me 1.6 Kohms but i know it's wrong
i tried the measure again the whole resistor and it give me 3 kohms i'm sure it's wrong according to two colors red and violet on the resistor
 

Minder

Apr 24, 2015
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Did you try to reverse engineer it as suggested?
Very simple one sided board circuit to trace.
 

Minder

Apr 24, 2015
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What I did was pick up one of the programmable audio boards for a couple of $ 's off ebay, you can program what ever takes your fancy.
ISD1820 IC.
Ebay 191674431418

1666461371867.png
 

Minder

Apr 24, 2015
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Trace the circuit out on paper, it is a very simple one.
 

Minder

Apr 24, 2015
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Doesn't look viable to me unfortunately.!
IOW does not look like a workable circuit.
 

pharaon

Oct 28, 2014
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i draw it whole again in different way
the faulty resistor is R1
 

pharaon

Oct 28, 2014
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that's what i did i shorted that black line or bypass R1 and the diode and connect the circuit with 20V DC , it worked fine and the sound were acceptable although i'm not sure how higher DC voltage can it up to
anyway i'd like to know what was the R1 value that make it work on 220V AC

 
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