DECT baby monitor

[slacker878]

I have a baby monitor that is acting up.
the receiving unit appears to be very soft in volume.

I do not know if its a sender unit problem or a receiver unit issue.
I suspect its a sender unit issue - specifically the microphone, so i bought another cheap electret microphone to replace it - volume is much louder but it resulted in constant static as well.
now i am at a loss and do not know what to do else to test/troubleshoot. is it just the wrong microphone i bought?

original microphone has a DC resistance of 1.26kOhm. no symbols or numbering to indicate maker or model.
open voltage on the end of the wires to the microphone is 2.8v
microphone connects to TP99 (+) & TP100 (-) on the bottom of the circuit.

is it a microphone issue or another common component that can be easily replaced?
I do not have a signal generator , just a basic multi-meter. 

thanks.
A

[rpiloverbd]

Hello,

Actually, it's hard to tell if you don't have the circuit diagram. But don't worry. As you have a multimeter, kindly do a continuity test to figure out what components are connected to the microphone. I think that will give you a lot of answers.

[slacker878]

the only few things that are connected are a few resistors and a single cap (I think) - Z203 bottom right.
can identify the rating though, its a 07 :5 written on  it. using my multimeter it reads 51 microF - make sense? i cant get a chart anywhere on the net.
the cap beside it is also labelled the same but not connected to the microphone based on continuity - can't get a reading on the multimeter though. make sense to any one?

[SoundTech-LG]

The original microphone is likely an electret condenser mic, requiring bias voltage, and correct polarity to power it.
Which is why you have DC voltage you measured.
You did not tell us anything about what your replacement microphone is.

[SoundTech-LG]

Yes, replace items even if they are fine. Then, move on to actual troubleshooting.

[slacker878]

The original microphone is likely an electret condenser mic, requiring bias voltage, and correct polarity to power it.
Which is why you have DC voltage you measured.
You did not tell us anything about what your replacement microphone is.

replacement microphone is also an electret mic 9.5mm. I did attach the correct polarity. it worked after replacing it but there was constant static as well.
 this is the supposed specs but I will take it with a pinch of salt:
https://www.jaycar.com.au/medias/sys_master/images/images/9593315688478/AM4011-dataSheetMain.pdf

Yes, replace items even if they are fine. Then, move on to actual troubleshooting.

slacker878 does not have any tools other than a multimeter. How do you propose that they verify the capacitors are still good?

actually my multimeter can test caps.
the electrolytic capacitors are generally ok - most are reading within their specs.  100microF - reading as 226 microF, 300 microF reading as 220microF, 470microF reading as 540microF, 47microF reading as 52microF.