Macintosh LC 475

[pfuentes69]

I got too those VRAM from @Siliconinsider and are wonderful.
Just be careful of getting the ones with higher speed as the normal ones of 100ns won’t work well with an OC system.
p

 

[ironborn65]

2 new new VRAM SIMMS 512KB 80ns on their way ...

 

[Sinjinhawke]

On my LC475 the floppy stopped working. Just dead, no response when inserting a floppy. I removed the floppy and put it in my beige G3 and it works fine so assumption is its the LC475 board. I recapped the board and now the floppy is getting power (progress) but it now either instantly ejects the floppy, makes noises but never mounts floppy or with some floppies freezes the machine. I also tried putting a floppy emu in the LC475, it powers on but never mounts.

It was my first time doing surface mount caps but no pads were damaged. Cap leaking was minor and I did clean up with IPA before putting down new caps. I used tantalum for all but I do have some replacement electrolytic.

I did recap the power supply when it failed a couple years ago and it has been working fine. Full 68040. 36mb RAM. Maxed video ram. New battery. SCSI2SD drive internally and when needed an external BlueSCSI.

Where should I look on the board for what could be the problem with floppy? Which capacitors? Any support chips? I guess in theory I don't need a working floppy (because of BlueSCSI) but it irks me.

I have not taken apart the floppy (ever) to clean and lubricate it; so even though it works on the beige G3 maybe that could be the problem? wouldn't explain why floppy emu does not work.

 

[ironborn65]

Hi mate
welcome.

Did you ever serviced the floppy drive? Dismount, clean, lube and reassemble? You might want to check the infamous small gear, even if in this case it seems not to be the culprint. I would start from here: a thorough cleaning and lubrication. You can find many videos in Youtube, check from the usual known guys like Bruce, Adrian... Do not remove the track 0 sensor, be very gentle when cleaning the head. Check the pressure of the head, but lift it very little, just as much as necessary.

If you have another floppy swap it to double check the issue is the MB or the disk drive.

I would then focus on the SWIM, identify the IC and check all the pins with a lens looking for gunk or oxidation.
I did a quick check, by exclusion the SWIM is the one identified below. Others can help here.

 

[Sinjinhawke]

Hi mate
welcome.

Did you ever serviced the floppy drive? Dismount, clean, lube and reassemble? You might want to check the infamous small gear, even if in this case it seems not to be the culprint. I would start from here: a thorough cleaning and lubrication. You can find many videos in Youtube, check from the usual known guys like Bruce, Adrian... Do not remove the track 0 sensor, be very gentle when cleaning the head. Check the pressure of the head, but lift it very little, just as much as necessary.

If you have another floppy swap it to double check the issue is the MB or the disk drive.

I would then focus on the SWIM, identify the IC and check all the pins with a lens looking for gunk or oxidation.
I did a quick check, by exclusion the SWIM is the one identified below. Others can help here.
View attachment 51322

I think I will start with servicing the floppy, thank you. It has never been done. I am the original owner of the machine.
The floppy from my beige G3 does not work in the LC475. It's totally dead when in my LC475 but both floppies work fine in the beige.

I should also make sure the connector has no breaks though the Floppy Emu uses it's own connector and it powered on but didn't mount.

The legs around the SWIM chip look clean (shiny silver) but the IC to the left (U22) looks like some capacitor juice may have paid it a visit. I'll clean that up some more.