I have found the what has caused these to fail in very large numbers is that the electrolytic Capacitor(s) have gone bad. The unit loses its 'memory' because of this.

I do not know which one however since I have no schematic. If you touch all of them with a hot iron they may 'rejuvenate' but the effect may also be temporary.

Talk to me if you want to explore further......This piece of engineering info will help you greatly.

If you can get me a schematic I will locate the problem to a single component. Talk to me. There are a million of these out there all failed with the same problem. Email me with your phone number and I will call you.

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Dionysius