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Fuse Finder.

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I have a Martindale Fuse Finder Kit. It comprises a plug in FD 600/T sender unit and a FD-500/R receiver unit. The receiver unit does not appear to work properly. I have stripped it down and tested it. Its L.E.D. oscillates when the receiver unit is placed right next to the transmitter/ sender unit so I think that the receiver is receiving a signal, but it does not make a sound. I have taken out the little 5V sounder but it is dead on temporary batteries out of the unit. I suppose that it is suitable for a D.C. supply. It may need a varying supply at 5V I do not know. Anyway I have ordered a new sounder unit to try to see if I can repair it.


The sounder unit looks like this.

https://www.ebay.co.uk/itm/Miniature-Electronic-Buzzer-Sounder-5v-Subminiature/123750468773?hash=item1cd01a4ca5:g:RmAAAOSwiDFYM1dn


Any suggestions please?


Bye,


Z.
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    mapj1:

    if you put a meter on volts where the sounder used to go, do you see a DC  or an AC signal ?


    Those little sounders either need driving at AC (test that with audio from a headphone jack) or the DC models contain a one transistor oscillator,  but then there are a number of variations on the oscillator  same theme, the loudest  making the piezoelectric disc into a 3 terminal device, so that it i s driven by the collector of the transistor, but there is a pick up  electrode that acts as a crude microphone and drives the transistor base - these are automatically on-tune for the self resonance of the disc.




    Hello Mike,

                           when I used a D.M.M. I got 1.7V set to D.C.and 2.4V set to A.C. So I then used an analogue moving coil meter and confirmed that the output from the circuit board is A.C. as the needle moved violently backwards and forwards about at about +4.5/5.0 Volts.


    Z.

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  • 0

    mapj1:

    if you put a meter on volts where the sounder used to go, do you see a DC  or an AC signal ?


    Those little sounders either need driving at AC (test that with audio from a headphone jack) or the DC models contain a one transistor oscillator,  but then there are a number of variations on the oscillator  same theme, the loudest  making the piezoelectric disc into a 3 terminal device, so that it i s driven by the collector of the transistor, but there is a pick up  electrode that acts as a crude microphone and drives the transistor base - these are automatically on-tune for the self resonance of the disc.




    Hello Mike,

                           when I used a D.M.M. I got 1.7V set to D.C.and 2.4V set to A.C. So I then used an analogue moving coil meter and confirmed that the output from the circuit board is A.C. as the needle moved violently backwards and forwards about at about +4.5/5.0 Volts.


    Z.

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