Re: Tx Rx fault finding HELP update

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I wrote on the 20may05

I need help with fault finding a car alarm key fob transmitter and its
For some time the operating range has been decreasing and my fix was to
adjust the tuning capacitor in the Tx.
At short range I can see the code being received on a CRO and the voltages
around both ccts seem ok using a DMM.
Question 1. How do I determine which cct is at fault ?

 Since then, with some help, I put more distance between the Tx and Rx and
found one of the amplifier stages of the Rx (a 741 opamp) not pulling its
weight.  Replacement, fixed.

I've learned my tuning of the Tx was only fine tuning, and I needed to
increase the distance between the Tx and Rx until the fault became obvious.

Hope this helps someone in the future and thanks again everyone for your


ps: now WE'RE happy SHE'S got her 'beeper' back.

Re: Tx Rx fault finding HELP update

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Well done. How did I know that there was a SWMBO in there somewhere? By the
desperate tone of the post :)))


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