> (FWIW, they also sold > me a new pH probe, because the original, after 8 months, would no > longer register under 14.3. Unfortunately, the "new" one won't read > above -3.5, so I'll be doing without the controller for a while.) This definately sounds like a controller problem and not an electrode problem. It sounds like that the reference inside the controller has a problem, and that the amplifier is going into saturation somehow. Marque APD - ANGFA(NSW)