Restoring Mr Light Mr 680V6 Emergency Light
This emergency light was brought to me with the complaint that it is dead. After confirming the complaint, I opened the light and dismantled it.
On checking the voltage of the 6V, 7AH battery, it showed 6.16V and ESR check was also ok (Mr.Jesting Yong had, in his tips for use of ESR Meter, mentioned that good battery should show very low ESR reading and defective or drained battery will be very high). After disconnecting the battery, I checked the LED part by supplying 6V from desktop power supply.
All the LEDs were bright. But it was not working from the battery. Removed the board and did a visual inspection for any swollen caps or burst components. Noticed two jumper wires were rusted. Checked ESR of all capacitors. They were all ok. When I tried to clean the rusted jumper wires, it shattered into pieces and spilled out! See picture below of the pieces that I could retrieve!
Rewired the jumpers with very good wire that I had salvaged from Old Valve Radios, which had not only good sleeve but also had cotton wrapping inside. See first picture below. (The jumper wires were on the places where one line is shown and another resistor is shown on the board). The other picture show bottom side of the board.
Then connected the battery and checked whether the LEDs were lighting up. It did not. Since I know that the FET on the secondary would not have got switched on, without a primary activation from the SMPS power supply, I connected it to mains momentarily and switched off the mains. The power LED lit up indicating that all was well, when the mains power was in. Then I tried moving the switch to two positions, one medium bright and another full bright. After I tried the switch a few times, there was intermittent lighting up, which showed that the switch was defective. So, I replaced the switch. When I checked now, once again connecting to mains, the LEDs lit up on both selections. The red charging LED also was bright enough and when I checked the output voltages it was around 7.36V, which should be ok for a 6V battery. So, fit the light back and switched on. See the pictures below:
Since this is the first time I came across this kind of a problem in an Emergency Light, I thought of sharing it with you all. In most of the cases that I have handled so far it was either battery or tube light or some LEDs.
This article was prepared for you by Parasuraman Subramanian from India. He is 66 years old and has more than 30 years’ experience in handling antiques equipment Valve Radio, Amps, Reel Tape Recorders and currently studying latest techs classes conduct by Kerala State Electronics Technicians’ Association. He was a BBA graduate, retired as MD of a USA company.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below: