Defective SMPS Ttransformer (Chopper) Found In IBELL DVD Player Model IBL3288
This DVD player is the second defective set being brought by a Carpenter turned customer, mentioned by me in another article. The complaint was that it was left unused for a long time and when they tried to play a CD, they heard a loud noise and it became dead. As usual, I opened the set and cleaned it thoroughly. This time I was careful to look for any exploded parts of any ic and found one top portion of the PWM IC,which was Viper22A. After cleaning, I used another power supply, and switched the connectors to suit the board. When I applied power, the DVD was working very well, assuring me to go ahead with the repair of its SMPS. The fuse of 1.6A was blown.
After removing the burst PWM, I checked the SMPS Transformer with my ring tester and got full glow, indicating that there was nothing wrong in the primary or secondary. As the PWM was burst, I replaced the electrolytic capacitors in the primary and went ahead in replacing the rest of the caps too on the board. I also noticed a shorted optocoupler 817. So, replaced the 817 as well as the TL431. Fit an IC socket for the PWM and replaced the fuse too. Also did a thorough resoldering of the board.
Then when I applied the power, there was no output. Thinking that the audio IC, TEA2025B housed in the SMPS board could be the cause, I disconnected power supply to its pin 16. But same was the result. When I checked the oscillation in the oscilloscope, it showed pulsating in a very low level. In order to check the cause, I used an SMPS module and got the same result. Naturally, the SMPS Transformer (chopper) was defective.
So, I removed it and noticed that the pins were rusted. There was rust all around in the set. The heat zinc of the audio IC also was rusted. Even the speaker connectors were rusted. Called the customer to know whether they were using the audio portion. As they answered in the affirmative, I had no other go except to retry after cleaning and resoldering the SMPS pins. But result was same. As a replacement transformer or a similar board housing the audio IC was not available, I had to fix another SMPS board that I used for testing. So, I removed all the components from the primary of this board and used the other SMPS Board that I have after retouching all the soldering points. I retained the components of the secondary side right from the other end of rectifier diodes and wired two +12V, one -12V, one +5V and two grounds to appropriate places. I used a 7809 regulator fixing it on the heat zinc of the audio IC and gave one +12V to it. It had a 3.3 Ohm Fusable resistor at that point. Then, before fixing the boards, and rearranging the connector pins like before, I tried running the DVD player and found it to be working very well with tray open/close and also played well in USB.
I had already cleaned the speaker connectors using CRC 2-26. I used emery paper and scraped the rust off the heat zinc when I removed it to know the audio IC number. I had to provide two legs as its legs were rusted and broken. So, fixed the two boards side by side and played. All functions were working very well. After trying a CD that was there inside fully and also from USB, fit the covers and moved it to the delivery area. Here are the pictures as usual, without forgetting to add satisfaction to the collection bag:
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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You may check on his previous repair article below:
https://jestineyong.com/rusted-and-almost-ruined-star-induction-cooker-revived-successfully/
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Albert van Bemmelen
May 17, 2021 at 6:47 pm
Good job no doubt but a rather confusing to read article. Since you first wrote checking the SMPS Transformer with your ring tester and got full glow, indicating that there was nothing wrong in the primary or secondary. But further on you wrote that naturally the SMPS Transformer (chopper) was defect? And if it was because of rust or not was not clear either?
So I stopped reading there, but I am sure that knowing the experienced level of your repairs, the used replacement SMPS board prefectly fixed this DVD player.
Parasuraman S
May 17, 2021 at 10:39 pm
What I meant was the the defective SMPS transformer passed all normal tests including the Ring Test. But failed to function normally. So, it had developed some inside problem; probably a partial short or something. Hope I am clear now. Many thanks for your scrutiny and comments!
Albert van Bemmelen
May 18, 2021 at 12:33 pm
Okay!, good to know that the Blue Ring Tester can produce false test results too! So we need another kind of test that captures that event, which probably is the transformer functioning test with added load?
K.R.Nagarajan.
May 18, 2021 at 1:14 pm
Well done Mr Parasuraman.
Albert van Bemmelen
May 18, 2021 at 2:37 pm
Maybe the Ring test should be used by shorting the transformer secundary and primary sides one at a time while measuring the opposite side? And in case the transformer still 'transforms' the expected inductance transformation it should show a shorted low resistance when the opposite side is shorted and a high resistance when the opposite side is left open?
Parasuraman S
May 18, 2021 at 9:46 pm
Well, this is a very good suggestion, something that I never thought of! Many thanks! Shall do that as and when need arises!