INTERMITTENT ON-OFF PROBLEMS SOLVED IN PHILIPS DVD PLAYER MODEL DVD625K/691
This is a DVD player used by my school mate who stays close by and has visited my workshop a couple of times before. Since they do not use this regularly, it becomes defective for one reason or other and sometimes this was left unused for months together. Therefore, before undertaking restoration I took an assurance from them that they would not neglect this after getting it repaired and if at all it becomes defective due to such reasons, I would refuse to undertake the repair. Many of you might already know that I am a hobbyist and enjoy the work and not running this service for monetary benefits alone. Any set that keeps visiting me often is an irritation for me and I really hate it. I always compare it with a daughter who keeps visiting home having cut up with husband, which is a very unpleasant situation. (LOL) I am sure many of you who are doing such restoration work for the sake of enjoyment, learning and entertainment apart from earning, might agree with my views. Ok, having mentioned this prelude let me go to the crux of the work done.
After opening and cleaning the inside thoroughly, which I always enjoyed, I checked up and found that the set was not getting on. It just remained in standby mode and did not respond to controls. As the power supply was in very good condition with all outputs showing correct readings, I had to investigate further on the front panel as well as mother board. So, I dismantled the set. On checking the ESR of caps on the mother board, many were completely out. I also observed dry solders and traces of fungi formations. I thoroughly cleaned the boards first and using a cutter removed the caps from the top instead of de-soldering. I noted down the number of the cap written on the board along with its value and voltage on a piece of paper and rechecked it before collecting the removed caps in a bowl. I used a helping hand recently bought for working on small boards easily. Then removed the cut leads from the board, which was not only easier, but also caused less damage to the board. Now let us have look at few pictures:
I assume some of you might have a doubt as to why I resorted to cutting the caps instead of trying to de-soldering it. From the last picture above, you would notice that the leads are bent and soldered on the bottom of the PCB. So, while removing through de-soldering method, we may have to put pressure on the leads to straighten it out, which then would tear the track or damage it. But in this method that I employed, I used a sharp tweezer and removed the cut leads from the bottom by pulling it out while applying heat of the soldering iron. If the leads of the components are not long enough to enable this cutting, we can use a player and twist the caps clockwise continuously until the leads get plucked from the insides of the caps. This is another method that I use nowadays. Then looking at the list of caps that I removed, I replaced them one by one, checking and counter-checking that I did not make any mistake. Then resorted to re-touching all the solder joints on mother board as well as the front panel, with the aid of microscope. It was very easy to do this work with these aids.
While inspecting the board this way I noticed dry gum on a few components on one side of the board, obliterating the look or marks there. So, I cleaned the area with a knife and found two SMD components along with a few resistors and caps around it. Then looked for its reference in the service manual, that I had downloaded long back when the set came to me earlier. I saw that the components were these:
Having noticed that the number BC847BPN is a darlington pair, I checked it using my analogue multimeter and found it to be faulty. There was slight leakage on the PNP side. Well, here we are! We have found out perhaps the real culprit that caused the intermittent problems. Anyhow, the other work done was not definitely futile as it would give more life to the set. I got a new IC and replaced it. [pins two and three are shorted – please see the diagram above]
Then I cleaned the boards thoroughly using IPL taking caution not to damage the LCD display. Then lubricated all the connectors and the rails on which the eye unit moves. I also applied one drop of oil on the three motors on the point where the shaft comes out. We should not apply too much oil there as it might then spill over to the eye unit or CD and cause innumerable problems. The oil should also not flash when the motor runs. Well, after completing all these rejuvenation treatments and rectification of the fault found accidently, I assembled the boards with the mechanism and applied power, to get a glee! I loaded a CD and it played very well to give me immense satisfaction for the laborious labor put in! (LOL)
After running it for a few minutes and operating the panel buttons, I felt confident to put the boards and tray back to the cabinet.
Then I played several CDs one after another for a few hours, keeping the top cover open. It worked very well.
Mission accomplished with aplomb causing intense satisfaction to get immersed in the collection bag!
In the height of excitements, I am sorry that I forgot to click a snap of the defective components!
This article was prepared for you by Parasuraman Subramanian from India. He is 72 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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