Return Of A PHILIPS PRESTIGE 556 Radio With Hum Sound
Those of you, who have not read my previous article on this radio, can perhaps see the following link as I am not repeating many images that are covered in it:
This radio was brought back by my neighbor stating that it had hum sound. On inspection, I found the complaint to be true. As this type of complaint is due to problems in power supply, I combed the area and found nothing wrong.
Nevertheless, I replaced the fixed caps in the board, as these can create problems. But there was very little improvement. It worked for some time and then this hum sound returned. I noticed that the output transistors were getting hot. I had replaced one transistor last time. I had used BC558 in the preamp section. I replaced it with BC556, which is better rated. I also replaced the BC149A with a BC546.
The volume control was noisy. I opened it and cleaned it and tried to restore the on/off switch, which anyhow was defective. But I could not succeed in repairing the switch and decided to dismantle that section.
Then fixed it back and tried the Radio. It was working very well. The probable cause for noise was from volume control and the driver transistors. I let the radio work for many hours before giving delivery.
I went to his house, fixed the Radio in its place and operated it to show that it was working very well. He was happy, which made me happy too with utmost satisfaction getting collected to the bag.
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.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous article on Malfunction Of Both Relays Solved In V-GUARD Voltage Stabilizer V-G5
(34)Dislikes
(0)
6 Comments
Leave a Reply
Albert van Bemmelen
June 15, 2024 at 8:29 pm
I understand that you were able to fix and clean the original Philips potentiometer and its switch and didn't need to replace it to solve the hum sound problem. So long the metal closing clips do not break this was lucky still possible.
Parasuraman S
June 15, 2024 at 9:17 pm
No, the switch was not working properly. I had bypassed it last time. I continued with the same as I could not suceed in repairing the switch portion. So, I removed that section of the potentiometer. Many thanks for your keen study of articles and making expert comments!
Imoudu.O
June 17, 2024 at 4:51 am
Experience plays its role whenever you handle such devices.Thanks
Parasuraman S
June 17, 2024 at 3:42 pm
Many thanks, dear!
Waleed Rishmawi
June 17, 2024 at 2:02 pm
I glad it worked out just fine. I would rather replace the faulty pots than cleaning them but if they are not avaiable that is a different story. thanks for sharing and have a blessed day
Parasuraman S
June 17, 2024 at 7:26 pm
Many thanks, dear friend! These pots of the same size that fits properly on the cabinet, are no longer available.