K8015 timer kit

I have 8015 kit almost for 4 years and now timer doesn’t work anymore like it should.
When I push button (external) to start timer, nothing is happening and when I cut off power 12vdc, wait 2 sec., and put power back on timer is activated and running for the programmed time. Ater timing has ended, it stops. Push button doesn’t work . Already changed ext. push button, same fault. Can it be that transistor BC547B (T2) is out of order?

T2 may have a problem but you may want to look at C2 and C3.
Since you have had it for so long they maybe drying out.

Problem solved, It was transistor T2 who caused the problem.
Now,after changing transistor, timer works perfectly now.
Thanks for reply to find problem, so it was not capacitor C2 or C3.

Glad to hear it’s working