The Zurich 30 Amp Regulated Power Supply was marketed under several other names, including MFJ. I have had mine for some 12 or 15 years now I recon. It is a 'real' PSU with a chunky transformer.

When it started to play up I was on air, I saw 10 Amp or more pulses of current indicated on the Ammeter. I was operating on PSK31 with a friend. When I mentioned it he said 'does that not worry you it could damage your rig'.
No, no worries here, this was the practical demonstration of one more reason for the system of 12 Volt supply I use in the shack. The PSU float charges two 40 Amp Hour Lead Acid Batteries individually via Schottky Diode isolators. A fault like this did not apply 15 to 17 Volts to my expensive radios, it might just do the batteries a little good by giving then a few de-sulphating pulses.

'Surely' he said 'your power supply is protected against Over Voltage'.
Yes it is, and Over Current, but this fault was obviosly not related to over voltage, the voltage involved must be a 'legal' one. Any voltage between 0 and 15 is 'legal' it being a variable voltage supply with a front panel adjustment pot.
This should have been a good clue to the cause of the problem, I didnt find it instantly, adjusting the voltage set pot and wriggling it made no difference to the pulses of extra current so I ruled it out at first. Finally I substituted a large preset pot and the problem was cured. I suspect that the connection of the earthy end of the potentiometer track was intermittent possibly under the riveted tag.
I ordered three 10K Ohm pots from different sources and one turned out to be very similar physically to the original.

The original has an indent at the center 13.8 Volt point, the replacement does not. No problem I don't use that point anyway, remember the Shottky Diodes, their foward volt drop means I set the output above 13.80. The original also has a splined shaft the new one is plain so I provided a different ponter knob.

Whilst inside I soldered the wire wrap connections on the control PCB.

Also the wire wrap connections to the load share resistors, these connections do get warm, I am much happier to see some solder on these after several years of use and possible corrosion of contact.
The Regulator Transistor connections on these boards had also had many hot /cold cycles so the joints were all re soldered.

Finally back in use on the rack, Battery Terminal Voltages set to 13.8 Volts.