[artig]

quattttro wrote:

What about Pin16 on the cpu (the 50/60Hz signal)? This signal comes from TR4 on the power supply board # 16. I’m not getting a square wave from the collector of TR4, but I might not be measuring correctly. Is this signal required for CPU startup?

The signal on pin 16 is definitely required for a normal startup. If the signal is missing it goes into standby mode since this is normally an indication that there is a power failure. If there’s no mains power there’s really no point in going into anything but standby mode.

If you switch off the mains power (or disconnect pin 16 signal) while the unit is operating it will attempt a normal shutdown to standby mode, equivalent to pressing the Standby button.