I have a rather nice bench PSU with an intermittent fault ...Both displays indicate correctly and you can set the current limit.
but 99% of the time there is no output votage ,,,meter indicates zero as expected ...I have checked the back end and the usual 2N3055 and associated drivers are fine.
The drive voltage from the main board is what is missing ...have sweated joints etc etc and at one stage it started working ..put it all back together still fine...swithche on next day ...no volts!!
If anyone has any cct details or experience with this model psu it would be much appreciated ...I think that the RAcal RS Thandar Thurlby are pretty much the same PSU ..just rebadged