Third Visit Of PHILIPS PRESTIGE 556 Radio With Complaint Of Low Gain
This radio seems to be liking my company and keeps visiting me! After I repaired it in August, 2011, it made its first visit in November, 2022, second in February, 2024 and again now in July, 2024. Just see the following links:
https://jestineyong.com/return-of-a-philips-prestige-556-radio-with-hum-sound/
Since I have already covered the basic photos of the set, I am not repeating these here and going straight to the complaint and resolution.
This time it was brought to me with the complaint that the Radio has low gain and he was not able to get his favorite MW stations properly. I checked and found that it was genuine. I checked the Radio side board and found a few fixed capacitors cracked! This is something that I am accustomed to with Radios and I went ahead and straightaway replaced those seven major filter and coupling capacitors. Then re-aligned the Radio using my RF Signal generator setting it to deliver 452KHz modulated signals and fed it to the aerial, keeping the band in MW and needle at the extreme end of 500 Meter band. Then started retouching the four IFTs; beginning from the detector IFT, then two inter-IFTs and finally the oscillator stage IFT and I did this repeatedly until a peak sound without any disturbance was heard. Then disconnected and tuned the radio to pick up a station at the same place. Then adjusted the antenna coil on the ferrite rod to get a full gain and fixed it in place using Carpenter Wax. Then the radio was found working very well. Since I loved working on this type of Radios, as mentioned by me in the past, and also loved the owner like my own elder brother, I did a few more things on the Radio.
I provided a ferrite core coil at the AC input end with a 1.5A fuse inside an automobile fuse holder, and fixed one 0.1uF 250V AC capacitor along with a 3.3nF of same type and did the same thing on the other side also. Then fixed this on top of the mains transformer and also provided 0.01/1000V paper capacitor between the centre tapping and 6V AC tapping for the dial bulbs. I used silicon sealant on the exposed portions. Following pictures might make things clearer:
Then observed the drastic improvement in the performance as it reduced a lot of unwanted pick up which is very usual with Mains Radios.
I am giving below another picture of the Radio Board, in which I replaced the caps and marking the MW antenna coil and IFTs for those who may not know about it.
The performance of the Radio returned back to almost its original condition and I delivered and fixed the Radio in my neighbor’s house. He was extremely happy and though I told him to treat this service as a gift, he refused and insisted on accepting payment again and paid me well too! Mission accomplished with pride on this Prestige Radio and greater satisfaction gained entry into the collection bag.
Those of you who are interested in learning IF tuning may please visit these very useful sites: https://antiqueradios.org/gazette/align.htm and http://vrps.org/documents/Alignment.html [The second one covers almost all stages of valve radios].
Here is the picture of the caps replaced this time.
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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Albert van Bemmelen
November 8, 2024 at 8:43 pm
Although you tried to explain adding a ferrite core with several capacitors to limit any AC noise that still might interfere with any clear reception and took some photos of the result as well, it sadly never is as clear as a drawn circuit of it would have been!
Parasuraman S
November 9, 2024 at 11:25 am
Yes, I understand. Shall give a diagram later if and when it comes back for a service! Thanks for your expert comments, dear Albert!
Mark J
November 9, 2024 at 3:57 am
Parasuraman great job on the repair.
Parasuraman S
November 9, 2024 at 11:25 am
Many thanks, dear Mark!
Waleed Rishmawi
November 9, 2024 at 5:37 pm
another successful surgery done and was sent to the intensive care unit for healing...LOL. very good job my friend. I envy you for having such patients to work on such devices and I appreciate you sharing with us this great work. have a blessed day
Parasuraman S
November 9, 2024 at 9:37 pm
There was an advertisement by Onida for CRT TVs when they marketed in India many years back: Neighbor's envy, owner's pride! I remembered that (LOL) Many thanks for your continued encouraging comments, my dear friend! It values a lot!
Yogesh Panchal
November 16, 2024 at 1:02 am
Good Fix! Sir,
Parasuraman S
November 16, 2024 at 2:34 pm
Thanks!
Ramachandran P V
December 5, 2024 at 5:07 pm
I was a Radio/TV technician from 1976 to 2005. Stopped doing repairs after my regular job requirements wouldn't leave me much time for electronics repairs.
I have a Philips Prestige 556 Radio which was lying unused for a couple of decades. After my retirement I thought of using it. When I switched it on there was a very high motorboating sound which is not controlled by the volume control. I changed all the electrolytic capacitors in power supply section and audio section. Changed the audio driver transistor. When I disconnect the audio section from the detector section the motor boating stops. Despite repairing hundreds of Radios and TVs, this problem has made me very humble. It would be of great help if you could provide me with the circuit diagram of Philips Prestige 556.