Funny Tuner IC Complaint Found In SONY Car CD Player
This Car CD /Tuner/USB Player was brought to me by a new customer with a complaint that all functions work except Radio. The complaint was confirmed on my checkup. So, I opened up the set and dismantled the boards. Located the IC handling the tuner section, which was on a separate board vertically fit.
As you can see from the picture, this set used TDA7706S, an SMD Tuner IC. (For the those who might be conscious of language: I use ‘an’ in place of ‘a’ whenever pronunciation of the following word starts with a vowel. According to Wren and Martin, quoted by my School Teachers, one should use ‘AN’ under these conditions: – “A, E, I, O, U with W and Y, when they do not begin a syllable.” ‘An’ rhymes well with SMD instead of an ‘A!’ )
Having dismantled the PCBs from the case, it is very difficult to power up for checking, without attaching the Front Control Panel. So, I attached it manually, using Rubber Bands, as you can see from the following pictures:
Checked and found that the DC voltages were present on the tuner IC. Those who are interested to see the datasheet can do so from the link TDA7706 Datasheet(PDF) – STMicroelectronics (alldatasheet.com) The crystal was checked and found to be ok both by voltages as well as wave form in the oscilloscope. The possible cause could only be the Tuner IC, which was not available in the market. The online search showed a prohibitively high price for the IC. When I shared my experience with my Techie Friends, one who had handled this particular model said that he found this IC working after heating, but might go back to ‘slumber’ when not in use for a long time.
He asked me to try heating up the IC. I used my SMD rework station and heated up the IC to a safe level. Then when I applied power, the Tuner section was working in AM/FM mode very well! What kind of a defect is this in an IC!!! After I shared the result, many others also shared their similar experiences stating that this was the same problem in this model of Sony! Perhaps a manufacturing defect or something else unknown to us. Anyhow, I switched it off and switched it on after an hour and found the Tuner was working. It was working in the next day also. So, fixed the set back and delivered it to the customer, charging only very nominally to cover the cost of service. I told the customer that if he leaves the Car Stereo Off for a long time, he would face the same problem again. Could I have kept a heat zinc on top of the IC, extended from the Audio Power Amp IC? Well, I should try it next time! (LOL)) Anyhow, this looked like a very funny solution to fix a defect!
Nevertheless, the satisfaction did not find any excuse not to jump into its collection bag! (Sorry, I forgot to click the set when it was working in Tuner mode! My apologies!) Following pictures are that of CD/USB Modes. The front panel changes the display colour in sequence, something that could be distracting and irritant to the driver of the Car. I do not know why Sony made a Car CD Player in this way, though I agree that there could be an option to switch off!
This article was prepared for you by Parasuraman Subramanian from India. He is 71 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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