Metcal MFR-1100 / MFR-PS1100 - erroneous "tip open circuit" trips

[philpem]

Hi,

I've got a Metcal MFR-1100 power supply with an extremely annoying problem. It randomly trips out with a red error light (tip is open circuit).

Cleaning the tip on the brass sponge or catching it on the inside of the stand is just about guaranteed to trip it, but it happens during normal soldering too.

I've replaced the tip and handpiece (suspecting a bad cable or tip connector), but I'm still having the same issue. I'm starting to suspect something's aged in the base station and the tip-open detection circuit has become very twitchy.

Has anyone repaired an MFR power supply with this fault?

Cheers,
Phil.