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Help identifying Component

Rleo6965

Jan 22, 2012
585
Joined
Jan 22, 2012
Messages
585
14V would be closed to 15V. It's possible that pin7 voltage has exceeded 15V upon power on and FAN7554 have function momentarily and shutdown due to defective components on its load. You can confirm this by placing dc voltmeter on output connector and monitor it upon power on.
You can also monitor output of FAN7554 for inverter output of around 20khs to confirm inverter IC was functional. Place your multimeter probe ( with Frequency counter capability ) to FAN7554 pin6. Power on power supply and monitor a short 20khs signal. This therefore confirms that inverter circuit was functional and you have defective components on output and feedback circuit. You test each component for short, changed value, bulging capacitor need to be replaced.

good luck

Note:
Some power supply will shut down its output if it doesn’t have required load. Unless you knew that your power supply have normal output even without load.:)
 
Last edited:

Bruno

Jun 25, 2011
25
Joined
Jun 25, 2011
Messages
25
The charger will only operate when it is connected to a suitable battery.
When I first connect to the charger output I get the battery voltage and a 60mA battery discharge, when I turn the mains supply on the battery discharge drops to 30mA and the voltage at the battery terminals increases by 0.5v.
My multimeter only goes up to 20Khz and when I check across pins 6 & 5 it alternates between an over-range indication and about 3Khz and it keeps doing this every few seconds.
The transformer that the MOSFET connects to reads 0.2Ω on it's primary and secondary windings, I am getting strange readings from a lot of components on the output side of the circuit but when I remove them from the circuit board they seem OK and I can't find any visual signs of problems.
 

Rleo6965

Jan 22, 2012
585
Joined
Jan 22, 2012
Messages
585
Resistance of transformer was normal for pwm power supply.

Try to connect resistive load to the power supply and also check if resistor and capacitor have not changed value on pin4 of FAN7554.
 

Bruno

Jun 25, 2011
25
Joined
Jun 25, 2011
Messages
25
Tried putting a 12v bulb across the output but the charger does not do anything. Instructions say if the charger does not detect at least 5v on the battery connections there will not be any display.
Link for the charger Instructions if they would be any help but it is a 6Mb file
http://www.ringautomotive.co.uk/images/pdfs/SC8-16 instr 26-08.pdf
R & C on pin 4 seem OK, I get a reading of 1v there when the charger is connected to a battery and about 0.3v when it isn't.
I have been trying to identify and check some of the other components and there is an IC marked C16F 73-1/SP4A on a plug in-board that has the display and controls on, I understand this is a programmable microcontroller, could it have been corrupted or something.
 
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