Wednesday, July 31, 2019

EPSON SMD-400 Repair - Amiga 500 Floppy Drive

The old Amiga 500 I got had a non working floppy drive. The span up, abnormally fast, and then stopped. When there was no disk in the drive, the magnetic head twitched back and forth, which I think is normal behaviour.

First thing to try is changing electrolytic capacitors. To get to the caps, the drive's disk tray needs to be dismantled. It took me a while to figure it out, but its done like this:

Mounting bracket and casing of drive has been removed (easy). If you need to use force, you are doing it wrong.

Step 1.
Remove lock-screw and spring, marked in the first image.
Push the disk ejection button to release the upper disk holder mechanism. Push it forwards-downwards to release it.

Step 2.
Remove springs marked in second image.
Push disk eject mechanism forward to release it.

Step 3.
Replace the five caps, marked C08, C09, C10, C11 and C05. I used EMLF160ADA100MD73G as replacement caps.

After this the drive works as expected again.

Caps removed

New caps in place

Saturday, July 20, 2019

Amiga 500 power supply repair

I bought a cheap Amiga 500 as non functioning. I knew that the power supply was non-functioning, so I started there.

Amiga 500 PSU
The inside looked OK, but there where several signs of somebody tampering with it.
The bottom part of the PCB had some funny looking solderings with a lot of gunky-looking flux residue.

Bottom side of PSU PCB. Some gunky looking flux residue can be seen to the bottom right, top right and top left.
The board is marked 871, 6L78, A 500.
When I removed the strange looking solder I discovered that one of the pads to the transformer didn't have a connection at all! Maybe it was loose and I sucked it into the solder sucker.

Anyway, I soldered some wire to the transformer and touched up the bad looking solder joints, and the PSU worked nicely after that.

Repaired transformer connection behind the fuse

Transformer pads with solder removed. Pad with no connection to it to the right of the large mounting hole in the middle.

I made a note of the electrolytic capacitors on the board, so that I can order new ones and recap it.

No capsC(uF)U(V)diam (mm)

When I have recapped the PSU, I will properly clean off all the old flux.