My friend Chris M0KTT has a TS940 transceiver. It is a 1980's vintage unit which is showing signs of age related distress (who isn't...). Chris brought the FT940 to visit when it appeared to be completely locked up: the displays were lit but no frequency was displayed and there was no response to almost any pushbutton. I'd anticipated the problem might be a loose or failed connector, but that didn't seem to explain that nothing functioned.

In the mid 1980's such a radio would have a microprocessor and battery-backed-up RAM. If the numbers in it were rubbish, what would it do? An internet search revealed that the radio had 2 backup batteries: one is on the timer board (visible behind the front panel) but the one we wanted was buried on "Digital unit A". To get to that remove the top lid; then remove the metal right angled panel that holds the speaker (4 screws). Then remove the lid on the unit under that (8 screws I think) and et voila, there's a processor board. It has a Z80 processor (the same as the ZX spectrum used to have all those years ago). And a soldered in lithium battery, which was very dead.

We were able to get a new coin cell holder from Maplin, and soldered that with two flying leads in place of the old one. The required polarity is clearly marked on the PCB. A CR2032 battery (quite possibly the most expensive one on the planet - also from Maplin) was inserted. I encapsulated the holder in heat shrink sleeving then "hot glue"d it to the top of one of the ICs in that module. Then put everything back together.

The radio has a "factory reset" procedure. With the power switched off, press and hold the "A=B" button; then while it's pressed in, turn the power on. All settings were erased, and the radio functions as normal.

There is an unusual feature in this radio - a timer that can turn it on and off automatically at different times. If the "timer" button is presed 9next to the power switch) then the radio will appear totally dead unless it is within a time range at which the timer wants to turn it on. Tht can be very confusing!

There is a service manual available on the internet, which was very helpful. One thing to note is that many of the pages were intended to be a lot bigger than A4. Some schematics for example should be around 60 inches wide: print on A4 and they aren't legible. But if you soom in on the screen they are quite readable and you can do a "screen print" of part of the page.