One other thing a ham friend just pointed out to me.
on some of the old ones under the tin plate box where
the eprom is held there are two memory chips and the pins and pcb had corroded with a green copper rust.
He found that on lots of them all had the same problem
so might be worth a look there as well.
hope this helps...
cheers Mark

Callsign G0NMY

Thanks Mark, I,ll give your comments a try an dput on here what happens

To force a full reset, either disconnect the backup battery jumper (chevron pcb pad with a solder blob over it visible through the cutout in the metalwork behind the fromt panel, wait 30 secs and reconnect. Or remove RAM chip from logic/AF board wait 30 seconds and replace - set should beep when next powered up and will have reset to 70.0000MHz.

Check that the EPROM chip is properly seated with all pins correctly inserted into the socket.

N.B. As long as I still have the bits available I can offer a spares/repair/upgrade service for 4m Ascoms if you are having problems

Callsign G8LYB

Thanks for the info Stephen. May take you up on that offer. Seems to be ok now but will check what you have suggested.