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Saturday, May 21, 2022

Repairing the Sony ICF SW1 Receiver -- Used for Numbers Station Reception? Why no replacement for C-625?

Ten years ago, my friend John gave me this tiny Sony receiver.  It wasn't working.   I tried to fix it but quickly discovered that the tiny size of the device made repair difficult.  All you needed to do was to swap out some leaking electrolytics, but they are surface mount electrolytics -- replacing them is not for the faint of heart.  Kits are available, but again, this is not easy. 

In 2020 I got one of the kits, but didn't try to use it until yesterday.   It only supplied six of the electrolytics.  In the video above, they discuss replacing seven electrolytics, including the one that seems to be placed in the round black holder. C-625.  Why didn't my kit include a replacement for that one?  Could it be that this capacitor was not one of the leaky SMD caps?  

Replacing these caps really wasn't easy. At one point I inadvertently removed not just the bad cap, but also a nearby surface mount resistor.  Luckily the schematic showed it to be 0 ohms.  That was easily replaced.  I lifted one of the pads on one of the other caps -- I just slid it back into place and hoped for the best. 

BTW, I just today discovered that this little receiver may have been used late in the Cold War by those who needed to receive messages from the infamous Numbers Stations: 



  1. Wow, just the care of the solder pads was educational...Ed KC8SBV

  2. C-625 is listed in the service manual as a double layer 0.047uF capacitor (supercapacitor). Supercaps due to their construction (and inherent low capacitance value) tend to have a very long working life at low voltages. I suspect this is why a replacement was not supplied with the kit.

  3. Well, a 0.047 UF cap is a coupling cap. Not a super cap. 0.47 FARAD or even 4.7 FARAD would be considered a super cap.

  4. It is a .047 FARAD cap. For memory. Big. That info is on the parts list. I also spotted one on e-bay: https://picclick.fr/NEW-SONY-ICF-SW1-Panasonic-Memory-Backup-CapacitorSupercapacitor-192482042711.html


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