Revisit Of PHILIPS 2-In-1 MODEL 15DR437-00
I request you all to read the report submitted about this set attended by me in November, 2023, to know the background, before reading this article.
https://jestineyong.com/no-radio-pick-up-solved-in-philips-2-in-1-model-15dr437-00/
This was brought to me again in August, 2024 stating that it was dead. I saw a lot and lot of dust collected on the set, which was indicative of what could be the cause. I applied power to the set in front of the customer and operated the function and band switches in quick succession to clear of any fine dust formation inside, upon which the set got on and stations picked up.
But again it went dead and it did not work though I repeated my attempts. I told the customer to go and wait for my call to come for pickup. I took it up for service when I had finished the pending works in my workshop. I opened the set and subjected it to a thorough cleaning once again. Then removed the boards to trace the faults.
Since any amount of cleaning and lubricating the switches did not wake up the set, I checked the voltage that goes to the Radio Board. It was very low and it was around 2V. As TEA5591A was used, the voltage should be a minimum of 1.8V as per its datasheet; but I remember it was 5V when I checked it during my last service.
So I checked the transistor, BC548B which was controlling the voltage for giving out 5V and found it to be weak; the hFe was as low as 16 instead of a normal 110 -800. Here are the readings of the weak transistor and a new one.
The normal voltage of 5 was restored as soon as I replaced the transistor. But even then the Radio did not work.
A signal injected to pin 11 was found sound and strong enough!
I suspected the band-switch and internal dry-solder on the pins of both the switch and IC. So, removed both and cleaned up the area:
I did patch up of torn tracks on the band switch and resoldered the switch as well as the IC, upon which I found the Radio working so very well, that it was perhaps better than before! I tried all bands and stations and the pickup was damn good! I allowed the Radio to work for hours and tried it for two days on various times before giving delivery to the customer.
I demonstrated its performance and functions in front of the customer, when he responded to my call for pickup of the set and collected a nominal charge to cover the cost. Mission accomplished with a different experience on the same set, adding new knowledge. Needless to add that satisfaction happily jumped to the bag!
I advised the customer to clean the set as often as possible and keep it covered with a dust cover to protect it, which was readily accepted.
This article was prepared for you by Parasuraman Subramanian from India. He is 74 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 article on Odd Jobs Done In This NATIONAL RX-C46F Two-In-One
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Albert van Bemmelen
December 14, 2024 at 4:02 pm
Good job! Hopefully that BC548B transistor that provides 5V to the radio with a maximum of 800mA won't cause new problems in the near future again.
Waleed Rishmawi
December 14, 2024 at 5:08 pm
great job my friend. better than factory repair..thanks for sharing and have a blessed day