@tronic Just so you know, the forum guidelines are that pictures should be placed in-line, so I have done this for you in this instance.
Check the fuse in the plug and mains lead continuity, and the PSU fuse. The white ceramic item is a fusible resistor, checking continuity across that will tell you if it's bad, and also check the switch is still working properly.
Be VERY careful checking voltages on the input side and be aware the heatsinks can also be live. If you can, test it with load resistors rather than plugging into the ST. Are there any voltages at the output?
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Check to see if all capacitors are placed correctly (+ and -).
Also that you haven't exchanged any capacitors, so they're in the wrong place.
Finally, being a vintage computer there might be potential contact issues (cold solder joints, partly broken PCB traces etc. Check all circuit traces to see, possibly with a magnifier.
STe | MonSTer with dual IDE-CF memory card adapter | NEC Multisync 1990SXi | ST_ESSC | RSVE | Link '97 | Sony HD floppy drive/AJAX controller | Exxos HD floppy module | Battery-backed Ricoh realtime clock module | Discovery cartridge | C-Lab Unitor-2 | C-Lab Export | C-Lab Combiner | C-Lab Steady Eye | C-Lab Human Touch | Unicorn USB
I have compared an original SR98 image and the caps are correctly oriented in terms of polarity, but it is worthwhile checking the values are correct.
As @Pacman mentioned, check the PCB for signs of damage and solder bridges.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
If this was one of my kits, have you swapped the diode pack on the right hand heatsink ? A few people have changed the one on the left with it, which is wrong. Though I would have thought it would have gone BANG if that was the case.
