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Servicing Fast Track Torch And Rebuilding Broken Adapter
This torch along with its broken adapter was brought to me with a complaint that the torch is dead and the adapter got thrown down accidentally. (This was the same customer who had brought another torch earlier. In Kerala (India), power failure is frequent and in almost all homes there will be at-least half a dozen of these torches! This is because; the rechargeable torch will go off anytime without any warning, especially when we need it urgently! So it is a common practice to keep a few more in ready to use condition. Moreover, in the night, snakes sneak around the house and we need to have a good powerful light always in hand)
I dismantled the primary parts and observed that the battery was dead and there was fungus formation on the (-) side spring. Cleaned it with IPA and tried charging the battery using my bench top power supply. It did not take the charge. Moreover the ESR reading also showed that it is dead. (Another good use of the ESR meter, as suggested by Jestine Yong!). Checked the LED side using my PS and found it to be working perfectly.Though I tried to fetch a replacement battery both in the local market and online, this was not available! The customer took the battery even to a far away place (around 60 Kms away) where generally almost all electronic parts are generally available. But returned with a 700mAh/2.4V, the diameter of which was far less than the original, and requested me to do something to fit this in the torch. Even the length was slightly less. But that does not matter, as the spring will take care of it. Since the voltage was same, I wrapped a sheet of paper on it just enough to ensure that the positive and negative points come to the exact centre for making contact with the terminals.
After cleaning the terminals once again thoroughly, put the new battery inside and switched on. The torch worked well:
I then turned my attention to the adaptor; found the screws were covered by the label, peeled it off and removed the screws and dismantled it. The ACA had a lot of dust and filth in it and many components and jumper wires were found to be rusted. Cleaned the board thoroughly using IPA ensuring that it does not seep inside the SMPS Transformer. Cleaned all rust formations which are only on the surface. Tested whether it was working using a series bulb. It was working! So, proceeded with further work on the ACA. Replaced the jumper wires. Plucked the remaining square type pins, as these are not used in India. Did dry solder patch up on the board. And once again cleaned it thoroughly.
The PWM on this ACA was an SMD, with its number THX208. Just for the sake of knowing downloaded the data sheet from the following link. http://www.datasheetcafe.com/thx208-datasheet-pdf-pwm-controller-thx/
I had already retouched the joints on this IC. This PWM seems to be very compact and good and specifications were also superb!
Checked and ensured that the ACA was working. Looked through my salvage box and found one two pin plucked out of a moulded AC wire. Just the thing that I wanted! As there was sufficient place on the ACA Board, kept the two pin and marked the places for drilling holes. Drilled two holes in the right places using a drill bit to match the diameter of the stem of the pins. Put another hole in the centre and widened it to insert the middle portion of the pin. Fixed it with Fevibond and superglue, one after the other. Following pictures will be more self explanatory:
The wired the stems of the pins from the component side, using only one fuse wire on one side for an added protection, as there was no fuse in this ACA. Tested the ACA once again using a Series bulb, and checked the output voltage, which was 3.4V; might drop to a little higher than2.4V on load.
Then fit it inside the box, replaced the screws and pasted the label back on top of it, covered the exposed areas with two to three layers of ‘steel grip’ insulation tape. Once again checked it by directly plugging it in. It worked super fine!
Why did I go to this extent of servicing this ACA, without opting for a replacement? This torch belongs to an old man working as a delivery boy in an Ice Cream Dealer. In all probability, this would have been given to him by someone as a gift. The replacement ACAs may not have the quality that I found in this ACA. And, most importantly I always love to do such ‘odd-man-out’ jobs just for the love of it!
Thus the Torch and ACA was saved from the dump. Why do I take so many pains to avoid some device going to the dump? A lot of human labour (efforts and sweat) might have gone into making a thing. Many people would have burnt their night oil, before something reaches in front of us. Let it be a pin, a gem clip or a stitching needle, however trivial it might be, the human efforts behind it should be honoured! Why, you might ask? Are they not being paid for what they are doing? Yes, they are being paid. But just remember that no sincere and strenuous work can ever be rewarded befittingly! People like us who can resurrect a device, should spare no efforts to bring it back to life and prevent it from a dump! At-least, that is the return we can give to those poor souls who all toiled for making a device, and another set moved it around before it reached our hands (any many others in the chain handling each job concatenated in the process!) That is what I strongly believe! Whenever a foreign set comes to my table, I used to remember with gratitude and visualize how this would have been handled by many unknown persons in the factory during its make and me sitting here at a faraway place in the globe is trying to set things right the way it was originally made! In fact, that gives me enough thrill and fuel to handle the task in front of me very enthusiastically! Especially, when the set is being opened for the first time, the thrill is inexplicable!
Another job done to my utmost satisfaction!
This article was prepared for you by Parasuraman Subramanian from India. He is 68 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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You may check on his previous repair article below: