1980s Pioneer SPR-30 Solar-Powered AM Radio Repair

A couple of weeks ago, I spent the bank holiday at two car boots sales – one at Stokesley Showground and one at Thirsk – and ended up buying quite a few nice pieces of kit.

Amongst my purchases was a quirky AM radio, a Pioneer SPR-30 – I struggled to find anything about this radio online, so it seems quite rare, and it uses a 3V solar panel for power instead of batteries. It seems to be from the 1980s.

The radio was unfortunately in a state of disrepair – the solar panel was smashed, and the two 10F 2.3V supercapacitors inside it (used to store power from the PV) were physically leaking corrosive electrolyte; one had failed short-circuit.

The SPR-30 is easy enough to dismantle – the case is held closed using four cross-head screws, the mainboard is held in place by one cross-head screw, and the front cover is held in place using double-sided tape.

The supercapacitors aren’t a major problem, as these are readily available. The solar panel, however, seems proprietary to this radio – a 3V 58mm x 39mm x 1mm low-profile glass panel (part numbers JGN1001-A SAS03005) from SHOWA ARCO Solar K.K. of Japan.

I was actually able to contact the derivative company, Solar Frontier K.K., to see if they happened to have any new-old-stock parts lying around. Unfortunately (but not at all surprisingly), they were unable to help.

I made several experiments with various solar panels of various sizes, including larger glass panels that I tried to shave down to fit the case, and larger flexible panels that I tried to bend into shape to fit the case. None of these were particularly suitable.

I then found a 3V 100mA 60 x 48 x 3mm glass solar cell, which was slightly wider and quite a bit thicker than the original solar panel, however it seemed to be the best option. I decided to try to modify the original case slightly to allow the new panel to fit – this was easy enough width-wise, and height wasn’t really a problem, but the thickness was quite challenging. I had to shave down the base of the case centre evenly by several millimetres to allow the new panel to sit properly with the front cover installed; I also had to drill two holes in the case centre to allow the cable entry for the new solar cell.

The original supercapacitors were easy enough to remove using my desoldering station – I cleaned the board thoroughly using isopropyl alcohol to remove all of the leaked electrolyte, and cleaned the switches, sockets, and potentiometers using contact cleaner.

I then installed two replacement supercapacitors – high-quality 10F 2.7V parts. These are physically smaller than the originals, which is no surprise given advancements in the design and manufacture of aluminium electrolytic capacitors since the 1980s.

The mainboard can then be reinstalled into the case, and the new solar panel connected (PV positive to “B+”, PV negative to “G”).

With the radio reassembled, I left it in our conservatory for the day (with the power switch in the off position) in the sunlight to try and charge the supercapacitors. After that, I tried it out, and sure enough it was now working! A very positive result.