mastech triple power supply spiking

[garydirkse]

My new Mastech linear triple power supply produced intermittent spikes to 56 Volts! I found cold solder joints by pulling on diode leads years ago. The problem persisted and destroyed a few items so, I put it on the shelf for years.  Once powered down and back on it behaved until it was ignored then lost control of he slave regulator. Comparing Voltages from the master regulator to the slave regulator, two pins on N1 differed by about 400mV.  V6 a 6.2V zener had shorted somewhat. A new zener cured it.  If you replace a zener, use long leads to space the diode a half inch above the board. I had built a monitor to alert me when the beast was losing control and tried freeze spray etc.. Finally, aldue

[Jwillis]

Another problem that can cause weird voltages and funny current limiting is wore out pots. Problem is finding 6K pots from general vendors.