My SX-424 - From Rock To Ramadhan

Recently I had a bit of free time at home with family. Since I was in a mood of resurrecting old stuffs so I laid down my old Pioneer SX-424 receiver on my workbench. It still look good for a vintage. I had not been listening to it for decades. One of the channel was off. The station indicator was broken due to prolonged heat. Below is how the original indicator looks like from a photo I got from the net. It was a long amber coloured plastic with hidden small bulb on top reflecting the light at the bottom tip.


There was no trace of it. Probably it just vaporized. No need to be CSI about it. Lets move on to the millennium. Most of the indicators nowadays are LEDs and some are super bright. I found some of those in my tool box. LEDs work on DC (Direct Current) that has polarity while the original bulb voltage supply of 7 volts is AC (Alternating Current) that has no polarity. All of the bulbs including the bulbs for blue silkscreen panel are AC based. Amazingly those bulbs are still alive after 4 decades. A simple solution of connecting a bridge rectifier to the AC supply did the job coupled with a resistor to the LED. Actually it just need a half bridge but I only have a full bridge in my toolbox. Looking from the top here is the rectifier soldered at the top of the VU meter pins.

Update (19/1/2010): I have found the SX-424 schematics from the net. The voltage supply for the bulbs are DC and not AC. Since I have the full schematics now I can totally overhauled it. More news update in the future.

Here is the assembly with the LED connected to a small strip of Veroboard and wired through a trimmed mixer fader knob. The white wire is the original wire which is attached (not electrically) to a metal slider at the top of the silkscreen panel.

Here is the final assembly properly placed with the Veroboard been pushed inside the plastic fader which is glued to the metal slider. The LED pins are purposely bend in that way so that it stays close to the silkscreen panel and not protrude out.

Below is the shot of the LED been lighted behind the tinted plastic panel. The pins were painted black giving the illusion that it is floating. The super bright LED has a glassy look compared to the normal LED which looks flat. The illumination looks quite close to the original amber plastic but without the long strip.

So what the big fuss about this receiver unit you may ask. It was the most priced item when I was a teenager. Paired with the turntable and the speakers I could stay in my room for hours and perhaps days and annoyed my neighbours. I could feel the earth moved and even my walls. That was how loud it was and it is only 12 watts RMS per channel.

This is how the tuner unit looks like. All analog and mechanical. Those metal plates are the variable capacitors that tune the frequency of the reciever. It had hosted many legendary music and voices. The legendary voices of Brian Matthew, John Peel and even American Forces Radio in Vietnam had gone through it. Those were the real rock days.

The resurrection of the receiver is not for rock. Rock is dead long time ago. It is for the Ramadhan month. I really missed the radio especially listening to the Adzan during Iftar. It was a tradition many years ago before TV and video took over our lives and we are glued to the tube.