How to Repair and Restore an Old Philips Major Radio

This is a blog about how I was able to restore an old 1976 model Philips radio Major with IC. (Yes it was a feature hence they mentioned proudly that it's with an IC). My friend had this in his village home (Sirsi, Uttara Kannada) which they got back in 1976. It was working fine till around 2008 and then had stopped suddenly. Since they could not find a proper repairman, it found its place in the attic. While discussing something about the radio and my radio experiments he remembered about this retro radio and asked me whether I can do something about that? I said yes, of course, I can check. So let's see how to restore this amazing old piece of tech which was a major entertainment back then.

Supplies needed for any electronics restoration would be almost similar to this:

1. Screwdriver set, a tester for AC voltage checking
2. Soldering Iron
3. Soldering lead
4. Soldering flux
5. Wire Stripper and wires
6. Multimeter
7. Sandpaper/Flint paper 150 grit size
8. Wood varnish
9. Paint
10. External voltage source
11. Replacement components
12. Paper tapes for identifying and naming wires
13. WD40

This is a crucial step where you need to understand how it is assembled before dismantling it. Once you identify key areas where you need to remove screws disconnect the power cable. Then start removing screws one by one. If they are rusty use some WD40 spray and wait for some time and then try to loosen them. Don't put extra pressure as it may break and since you are dealing with an old and fragile piece of tech it's better we handle it gently. These radios had a simple assembly where the electronics and front panel are combined and there will be a wooden frame around the main chassis and AC mains and other external speaker wires are connected in the back. Make sure you desolder or carefully remove the backside wiring before removing the wooden cabinet. Use a paper tape to write down the connection information like external speaker -ve etc.

Using a flat wall paintbrush clean the dust on the PCB and inside the radio. If you have a low power vacuum cleaner you can use that too. Just make sure you don't disconnect any wire because we are debugging the board without schematics and just by the basic knowledge of electrical engineering. Even if you have to disconnect something write it down on the paper tape and stick it. Wear a mask (needless to say) to protect yourself from the dust. Now it's time to check different sections one by one. Firstly identify the number of PCBs in the radio. Mine has 2 one for the receiver and one for the audio amplifier section. Some may have combined one too.

Identify major components such as transformer, loudspeakers, bulk capacitors, ferrite rod antennas, audio amplifiers etc. So that we can identify the issues in smaller chunks and solve them one by one. It all starts with the main voltage in this radio. Your radio might have a battery source too, in that case, there will be a switch to switch between them.

AC mains check. Warning ! AC voltage is dangerous, please be careful while handling this. Author of this blog is not responsible for any injuries caused by simple mistakes.

Make sure the device is turned off and the plug has been removed from the main socket.

Set the multimeter to continuity mode or buzzer mode and check for the conductivity between the plug and the AC transformer input terminals. If this is fine we can go ahead and start checking for issues in the switch, In many old radios, there were switches in the AC input section itself. Due to rusting and wear and tear these ON-OFF switches would have gone bad. Do these tests without turning on the mains voltage. If everything is fine here you can connect it to the mains plug and then turn on the switch. Using an AC tester screwdriver verify whether there is voltage before the transformer. Once you are sure about this go ahead and trace the output of the transformer.

In my case, it was connected to an incandescent bulb and to a PCB. After close inspection, I saw 4 diodes on the PCB. This made sure that it is a rectifier bridge. Using a multimeter set to DC voltage measurement checked whether the voltage was coming or not. Found out the voltage was 6V and was just fine after the rectifier bridge. In the same way, the bulb had 6.3V inscribed on it which made sure that the transformer is a 6-0-6 centre tapped transformer.

With the help of a multimeter we observed that the voltage required for the board is 6V, we wanted to check whether the device had a power failure due to which it was not responding? After tuning the volume knob to the highest level I could hear a slight hissing noise. So it's time to check both power and audio level. Since I did not have a regulated variable power supply I used a boost converter XL6009 which can give up to 4A of current till 35V. Using a screw driver I had set the voltage to 6.14V and then connected it to the points where the rectified out put voltage appears [Disconnect AC mains before doing this]. Now the hissing and motor boat sound increased slightly.

In my multimeter there is an option to generate the square wave, I changed the frequency to 300Hz and connected it to input of the amplifier. There was a characteristic tone. This tone changed after I increased frequency. By this it was confirmed that the audio amplifier section is having no issues. Even the volume knob was just fine.

Now that we have identified that the problem is there in the superheterodyne receiver section and not the audio amplifier we can focus on the receiver PCB and trace the voltage and antenna signals to verify various stages of the receiver. With the help of a boost power source, I checked the voltage on the receiver board. Which was reading around 5.9V which was just fine so I moved to the next section where there was a transistor looking device with the name BZ148. The strange part is it had only 2 legs instead of 3. By its name and 2 pins, after some googling, I identified that it's nothing but a diode in that package, not a regular diode, our Zener diode. When turned ON this was heating a bit, by the position of the diode it looked like it was a detection diode used in all popular AM radio circuits. Luckily I had a spare IN4148 diode and replaced it.

Still, it was not singing and catching the radio station. So next stop transistor near the wires connected to ferrite core antenna. Ferrite core antenna is an essential part of AM radio circuit as it has the precise number of turns of copper coil wound over it for various bands. There was a transistor for that section that amplifies the signal from the ferrite core antenna. This is then fed to the detector diode. By checking the transistor using the transistor mode on the multimeter it was not responding i.e it was not showing the gain hFE or the β value. This made me clear that I need to replace the transistor.

Back in my college days, I had collected an old electronics circuits magazine which I had as a photocopy from the library. It had many radio projects. I was particularly interested in AM and FM radio projects. In my hometown (Kundapura, Udupi) the FM reception was bad as the stations were around 100KM away. But AM reception was good. So I had planned to make an AM radio and had collected all the required components from all old electronics shops in my hometown. But never got an opportunity to work on it.

But when I saw that the transistor failing was BF195C and the spares I had bought about 11 years back was also BF195C I was very happy. I quickly desoldered the faulty transistor and replaced it with my new BF195C transistor. After turning it on through the boost circuit, and tuning the radio station here in Bengaluru, Akashavani Bengaluru 612KHz. I was greeted with a euphonious old Kannada song.

Now that the radio is back in action. My friend who's the owner of the radio wanted to give it a coat of varnish for the wooden cabinet and black paint for the rusted metal brackets inside. So firstly with the help of sandpaper we scraped off the remaining rust and painted them with black paint. After the paint and varnish are completely dried we re-assembled the radio and now the radio sits in his book rack and sings melodiously. Thanks for your time. :)