My Stoves 720EF seems to have a timer problem. Of course this means that the main oven won't work. The symptoms are 1) you can't set the timer from reset 2) after setting the timer it will 'drop-out' after running the oven for a random time. I took the timer board out and it looks ok. I could replace it but my question is ; Is the timer board definitely the problem ( or most likely the problem ) ?

Try taking the power wire that goes into the timer and the power wire that comes out of the timer and put them together not hooked to the timer and that should work. If that works you should solder them together and electrical tape them good.
Make sure the power is off when you do this so you don't cook yourself.

I have a similar problem and contacted Stoves. Apparently the timer unit is now obsolete which means replacing the complete oven!

What is the complete model number?

The handbook says:-
To cancel the automatic setting and return the oven to manual operation, press the cook time and ready time buttons simultaneously. These are the second and third buttons from the left. If you have done that and it is not working, try turning the complete oven off for awhile - say 30 mins and turning back on. If this still doesn't work then it may be that the timer/clock has gone faulty.

If the 'A' appears, it means that the automatic setting has been enabled. To stop this and return to manual setting, press the COOK TIME and READY TIME buttons simultaneously.
The COOK TIME button is the second from the left and the READY TIME is the third from the left.
If the 'A' keep s reappearing by itself, then it could mean that the timer is going faulty. ESPARES should be able to supply one.

Both the top and bottom oven will only work if a time (any time) has been set on the clock. Setting the time operates a contact to switch the power through. The only exception is the grill. This will work even if the time has not been set. So if the oven controls/lights and heating work, to me it means that the clock/timer is half working and the only thing that isn't is the display.
I haven't had the clock/timer to bits but a fellow blogger has said that in some timers there is an electrolytic capacitor that controls the display. When this fails as they are renowned for doing, the dispaly mal functions. If there is one then Maplin have some - VHR41W/43W and DT64U depending on value etc. Let us know how you get on.
If you need a new clock/timer they are around £80 from espares.

Try espares. If the part is not listed, there is a contact on the website to obtain a quote for a part. Of course once you have the part number you can try elsewhere.

When you turn the main oven on, does the oven fan switch on?
When you turn the main oven on does the cooling fan come on?
Does the dial illuminate when the oven is turned on?
Does the oven thermostat neon come on the the oven is switched on?
Have you had a power failure recently and have not set the clock?
Are you sure that the clock/timer is NOT set and in manual mode?

When you say the main fan, do you mean the background cooling fan or do you mean the circulating fan in the bottom oven?
Do you have the handbook for this oven as the wiring diagrams are included in it. If you haven't, you can take a copy from my BT Digital Vault - all I need is an email address to register you.
Looking at the diagram, the power for the cooling fan comes via the timer board. If, as you say, the fan doesn't work at all, the timer board could have gone faulty.

This is a solution - of sorts - but probably not the one that you were hoping for.

My Stoves 720EF oven developed the same fault.

I tried pressing the buttons in various combinations and I tried switching the power off and on, restting the timer and the clock, no joy.

I then tried getting hold of a copy of the manual and trying to fix it, no joy. Called up Stoves and booked a visit from a specialist service engineer, costing £75 +VAT for the call out, and was advised that the engineer would attempt to repair it but it might need a replacement circuit board, costing a further £110 plus VAT.

engineer arrived on the appointed day and was straight onto swapping out the circuit board - not much scope for "attempt to repair" - so that was about £190 plus VAT to fix it. job took about 25 mins and didnt seem to need anything beyond what any electrician (or electrically-expert DIYer) could do.

comes with a 12 month warranty - hopefully it will work without any issues !

If you have a regular electrician you might prefer to buy the board and get your electrician to do the job - or do it yourself, assuming that you are suitably skilled and qualified.

hope this helps

cheers

David