exxos's Atari, Amiga & retro forum

I have replaced the capacitors, resistors and rectifiers but the Atari ST does not power up at all.

Would someone mind looking at the pictures attached to see if I've made any visual mistakes, please?


The power supply was working before I swapped these components out.

Thanks guys! :idea:

@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?

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.

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.

Take a photo of the underside....

Also double check +/- for the rectifier....

And check the fuse! :)

My favorite in these power supplies is the diodes that like to be resistors

Tom

I have split this topic as it is a hardware issues topic not a tweaks and fixes topic!

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.

Ok maybe my eye sight but the diode on the dc side looks like the leg is cut

Tom

R101 would be my first check. Check it hasn't gone OC.