[mole42uk]

More work on the 4074 power supplies today. What Karl thought was a bad electrolytic was a bad electrolytic although the top remains flat, removing it revealed the cause of the high current demand on the 260V supply - tracking on the PCB between the two terminals of the capacitor, pictured below.

I have scraped the carbon away and reduced some of the copper ground track, hoping that this will stop the problem. I'm waiting for new electrolytics to arrive before proceeding.

The other supply is slowly coming back to life. One of the BUZ31 MosFETs was dead and changing that got the main regulator working after a fashion with 30V on the supply rails. I put the pre-regulator back on and introduced 100V AC into the board, only to release smoke from a fast schottky diode in the secondary side. I have some fast diodes which I may try now.