Worth a try, Maplins etc should have one cheap.
BSA Super10 addict, other BSA's inc GoldstarSE, Original (Diana) Mod75's, Diana Mod5, HW80's, SAM 11K... All sorted!
Just a thought, Phil.
As yours is a fold up chrony, have you checked for a break in the wires to the rear sensor ?
If it is your actual sensor buggered I have a scrap Prochrono here we can rob next weekend if we need.
To buy a Combro!
I have also heard that the unit responds more consistently if the gun is shot from about 3 feet from the first sensor and held at a slight downward angle. Whenever I try this method outside the unit works consistently and at other times , well lets say I have shot it twice but the damn thing is still working. Lighting level is its worst enemy indicating that perhaps the sensors are not all that sensitive.
A.G
Best location for my F1 I have found is,
Muzzle at least 3 feet from F1 and shoot more than 6 inch above sensors.
Master Debater
"Every normal man must be tempted at times, to spit on his hands, raise the black flag & start slitting throats"
Doesn't help with the internal light set ups but ...
This time of year many start to have problems with the Chrony.
The slits above the sensors are quite narrow. This time of year the sun is at a lower angle to us in the UK. So the sensors struggle to get a reading outdoors.
Put a kitchen table chair on the lawn. Put a plank of wood against the chair so that the face of the plank is facing towards the sun. Put the Chrony on the plank ( put a screw in the plank and use the hole in the Chrony on the screw if you wish ). Shoot downwards and into the lawn ( replace lawn with box full of paper etc if required ).
Basically you are angling the sensors in line with the sun, so the Chrony is at an angle ( towards the sun ) and not parallel to the ground.
Dah Dah.
Or in Phil's case ... stop trying to re-use old batteries and go and get a brand new one.