Analog Instrument repair
Analog Instrument repair
(OP)


I have a faulty analog instrument. The needle does not move. I checked the signal coming to the instrument and signal is Ok
I feed the instrument with a 9V battery and nothing so I open up the instrument
Found out that there is a tiny coil that is damaged (the little black coil in the pictures)
How can I repair this?
What is the function of this coil? Is it part of an internal LR filter?
Any comments will be appreciated





RE: Analog Instrument repair
RE: Analog Instrument repair
The input signal comes from a Tachometer of a DC motor
RE: Analog Instrument repair
RE: Analog Instrument repair
Possibly you could use the calipers in background of your picture measure the wire count the turns on coils and rewind them. Just a thought.
Chuck
RE: Analog Instrument repair
Use a limiting resistor to pass 5 or 10 ma through the meter movement. Change resistors to find out the current required to produce full scale deflection.
If the meter will not respond, buy a 0-50 ma milliammeter to replace it.
Or, if the wound resistor is open, calculate the resistance required to produce full scale deflection with your signal and replace the resistor.
If you don't need high accuracy, you don't need a wire wound resistor.
You may have to replace both the meter and the resistor.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Analog Instrument repair
I am trying to rewound the coil: same wire size, same turns and see what happens
I will come back with results
RE: Analog Instrument repair
The coil was rewound
Thanks to all!