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Partial Failure Of Sony AM/FM IC CXA1238S Found In Module

By on December 30, 2020
SONY radio repair

This board was brought to me by one of my technician friends stating that the FM was not picking up any stations though the AM was working. He tried replacing the crystal, and then replaced all the electrolytic caps, and also retouched the dry solder. He bought a new IC and put it in with the same result.

SONY AM FM REPAIR

He brought only this portion as I declined to add one more set to my already packed service room. On checking by applying power (9V DC) directly to the filter cap, I confirmed that though the hissing noise was there, it was not picking up any stations.

I downloaded the datasheet and took print out of a Radio circuit using the IC CXA1238S and studied the circuit thoroughly for any faulty component. I replaced the crystal once again and also the IC (removing it from a Sony salvaged board that I had) with the same result. Then my suspicion was on the Oscillator Coil. I looked for an Oscillator coil from my old collection and removed one and opened it (let us call this coil as A). Then opened the coil of this board (call this B) and studied the connections. It was similar.

So, fit the coil A in place of coil B in its own case. Fit the oscillator coil and tried. This time it started picking up stations! (I also replaced one electrolytic cap in the AM area also, which my friend had overlooked.) So, refit the board and allowed it to run for a few minutes before keeping it aside for pick up by my friend. I took videos and pictures and sent it to him through Whatsapp. Satisfaction got added to its collection as usual. The reason for not working even after replacing the IC by my friend perhaps indicates duplicate ICs! Here are a few more pictures:

Sony AM FM SCHEMATIC

Sony AM FM SCHEMATIC diagram circuit board

how to fix and repair Sony am/fm radio

This article was prepared for you by Parasuraman Subramanian from India. He is 70 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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https://jestineyong.com/restored-a-liquid-seepage-spoiled-ahuja-power-amp-model-dpa770/

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8 Comments

  1. Albert van Bemmelen

    December 30, 2020 at 6:43 pm

    I guess that Crystals exist in parallel resonating types and in serie resonating versions. Maybe that had something to do with the difference? The meaning of "indicates of duplicate ICs!" however completely escaped my understanding. But I am sure you did another outstanding job here!

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    • Parasuraman S

      December 30, 2020 at 8:59 pm

      By duplicate, I meant 'fake' ICs that are made by cheap methods, that are flooded in the market. While they take the price of a new one, such 'fake ICs' are passed on. Unfortunately, there is no return of such ICs and components like transistors, and we have to bear the cost or pass it on to customer! What else to do? It is a big racket at international level, and most of these are coming from China. Luckily, the import is now stopped due to the pandemic situation! (Is that bad or good (LOL))

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      • Albert van Bemmelen

        December 31, 2020 at 3:35 am

        Understood dear Parasuraman. Maybe in future better just write Fake or Counterfeit parts.
        I have a recent problem in finding a datasheet for the PWM controller in an EVOLine 5V USB charger with smd code '67A'. Assumably sold as Melenix MLX02367A 6 pin SOT32-6 chip. But strangely after asking the Manufacturer they told me that it was a special ASIC and this prohibited them to give any information. Not even what the function of the chip was! And even the Aliexpress seller where I ordered 50 of them couldn't tell me if it was the right replacement chip. The mentioned chip is also used in certain battery charger packs for power drill machines and the likes. And some sellers also sell these as previously used parts which is very strange! Talking about counterfeit parts?! If my 5V adapter works after replacing this tiny mlx02367A chip I know I was right all along!

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        • Albert van Bemmelen

          December 31, 2020 at 1:24 pm

          I meant Melexis instead of Melenix of course!

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  2. Yogesh Panchal

    December 30, 2020 at 11:34 pm

    Good Job! Sir,
    yes duplicate parts! still peoples are available in the market who sale Identical fake Parts by printing part nos On it. you get 4 out of 10 units are fake if you are buying it from unknown resource.

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    • Parasuraman S

      January 1, 2021 at 12:26 am

      Yes, very much indeed! Many thanks!

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  3. Humberto

    January 4, 2021 at 11:30 am

    Other device saved from the dump, and more satisfaction to your collection bag.

    Likes(1)Dislikes(0)
    • Parasuraman S

      January 4, 2021 at 1:18 pm

      Hm! Ha! Ha! Many thanks, dear!

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