Having been left overnight, it powered up immediately, so it's looking like the IRF-BC40 MOSFET, QP2 on the schematics, was the reason for the slow start.
In retrospect, as it seems to be the main switching transistor, I probably should have replaced that first, but TBH the electrolytics on these boards are known for leaking, and in fact the first batch I did last year, about 10 in the main PSU section, were all sitting in a puddle of brown goo!
So overall, the PSU has had a pretty comprehensive refurb!!
- All electrolytics (PSU and Video circuits)
- TDA4605 (IP1, switching controller)
- CNY17 (QP1 Optocoupler)
- IRF-BC40 (Main switching MOSFET)
- MBR1045 (5v circuit main diode)
Also, changing the caps in the video circuit showed me that such a simple act can require a degree of re-tuning via the many pots, to get the picture stable on screen, plus how easy it is to upset a CRT by accidentally knocking the tuning magnets around the screen.
So, this machine is going to be temporarily parked whilst I look at Brett's STE, the final problem being that of the non working RAM expansion.
It's been quite the journey!!