REPAIRING  AUTOMATIC VOLTAGE REGULATOR

REPAIRING AUTOMATIC VOLTAGE REGULATOR

HOW TO REPAIR AN AUTOMATIC VOLTAGE REGULATOR {AVR}

the back of the avr

AUTOMATIC VOLTAGE REGULATOR [AVR] 

The automatic voltage regulator [AVR] is a device designed to regulate voltage automatically – that is, to take a fluctuating voltage level and turn it into a constant voltage level.lets take for instance, if the input voltage is 150 volts it will automatically yield an output ranging from 220 to 230.
Automatic voltage regulators not only vary in size and design, but also in names

COMPONENTS OFTEN FOUND IN AVR

1.       Relays
2.       Capasitors
3.       Transistors
4.       Resistors
5.       Variable resistors
6.       Ic
7.       Diodes
8.       Transformer
9.       Output and input volt meter
AN AVR  without  the above components is like a car without an engine or a man without a brain hahaha its quit funny but its true.
As the name of the above components  differs so there functions are.
 You can search to read   about the components found in AC automatic voltage regulator and there functions in this blog .

NECESSARY WORKING TOOLS THAT ARE NEEDED

1.       Set of screw drivers {star/flat}
2.       Soldering iron{40 watts or 60 watt} original
3.       Led [original highly recommended]
4.       Multi digital volt metter[ the best quality one highly recommended for accurate readings]
5.       Variac
6.       12volt DC source
7.       Socker
8.       Small knife
9.       Plire
10.   A small cutter
With the help of this tools and  proper use of it you can be able to repair an AC AVR.
Since all the tools are now ready lets  start working.

Possible faults  that can cause your AC AVR to misfunction

1.       Bad relays: relays are those black components that looks like a cube of suger .  To test the relay”
Use an independent voltage source appropriate for the rating of the relay coil. If the relay coil is diode protected, make sure that the independent voltage source is connected with the proper polarity. Listen for a click when the relay is energized.
avr circuit board
 
2.       Transistor failure:

Testing the transistor first you check if there is any that was bunt  if no

Remove the transistors from the circuit for accurate test results.
Step 1: (Base to Emitter)
Hook the positive lead from the multimeter to the to the BASE (B) of the transistor. Hook the negative meter lead to the EMITTER (E) of the transistor. For an good NPN transistor, the meter should show a voltage drop between 0.45V and 0.9V.
Step 2: (Base to Collector)
Keep  the postitive lead on the BASE (B) and place the negative lead to the COLLECTOR (C).
For an good NPN transistor, the meter should show a voltage drop between 0.45V and 0.9V.
Step 3: (Emitter to Base)
Hook the positive lead from the multimeter to the to the EMITTER (E) of the transistor. Hook the negative meter lead to the BASE (B) of the transistor.
For an good NPN transistor, you should see “OL” (Over Limit).
Step 4: (Collector to Base)
Hook the positive lead from the multimeter to the to the COLLECTOR (C) of the transistor. Hook the negative meter lead to the BASE (B) of the transistor.
For an good NPN transistor, you should see “OL” (Over Limit).
Step 5: (Collector to Emitter)
Hook the positive meter lead to the COLLECTOR (C) and the negative meter lead to the EMITTER (E) – A good NPN  transistor will read “OL”/Over Limit on the meter. Swap the leads (Positive to Emitter and Negative to Collector) – Once again, a good NPN  transistor should read “OL”.
If your bipolar transistor measures contrary to these steps, consider it to be bad.
Then the next step is to change it with the same type of transistor NPN
3.      Capasitor failure: the capacitor that mostly fail is the most bigger { the N receiver}. It normally get blow off or swollen { change it with the same type of capacitor}
4.      Ic failure;
5.      variable resistor failure
6.    diode failure :A multimeter’s Diode Test mode produces a small voltage between test leads. The multimeter then displays the voltage drop when the test leads are connected across a diode when forward-biased. The Diode Test procedure is conducted as follows:
  1. Make certain a) all power to the circuit is OFF and b) no voltage exists at the diode. Voltage may be present in the circuit due to charged capacitors. If so, the capacitors need to be discharged. Set the multimeter to measure ac or dc voltage as required.
  2. Turn the dial (rotary switch) to Diode Test mode . It may share a space on the dial with another function.
  3. Connect the test leads to the diode. Record the measurement displayed.
Reverse the test leads. Record the measurement displayed.
  • A good forward-based diode displays a voltage drop ranging from 0.5 to 0.8 volts for the most commonly used silicon diodes. Some germanium diodes have a voltage drop ranging from 0.2 to 0.3 V.
Resistors failure.
After the proper replacement of the damaged component  plug your AC AVR to your variac socket  to test your AVR but before that reduce the  voltage{variac} to 100 to 120 volts then on the switch of the AVR to see  the performance.
Then gradually race the voltage of the variac you will notice that  as the input put voltage gets high the output voltage will still retain the same unit . if the reverse is the case try to set your variable resistors.

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