lc475 video problem

[mstanutz]

So I'm working on my lc475.. the hd died then I would get no video on boot up. I get full chime and floppy disk action but no video.

Recapped the board AND power supply. Swapped the Vram. Now I end up with this. It will boot with the floppy (HDT Toolkit) but the video is distorted.  Any ideas??

 

[Solvalou]

Ok stupid suggestions and probably obvious but here goes.

Have you checked for polarity and made sure the cap ratings match what you replaced and that they're definitely making good contact?

Did you replace them with a different kinds of caps? I know solid state types are preferred and people often boast about replacing electrolytic for ceramics but they can cause issues.

I also assume the board was cleaned before and after the work was done?

Assuming all this is in order, one more stupid question; have you tried it on a different monitor? It looks like you're using an original Mac monitor but if not, check the VGA adapter too just to rule that out.

 

[mstanutz]

Hey tokyoracer!  No such thing as stupid suggestions

The board recap was done with similar caps.. although I can't rule out a bad new cap.  I might re-do all just to rule it out.

The power supply was recapped with similar caps .. voltages look great. 

Yup, gave the board an iso bath.. light toothbrush cleaning also.

Yup, that is the original monitor (good eye!) but it's the same on a different lcd 15 inch.  

I've tried all the possible settings on the VGA adapter also.. but I don't have another that I can swap with.  Will try that option also.

One thing I am noticing though.. the Vram slot closest to the power supply is not locking the stick properly.  I think it's sitting ok, but it's weird that it won't lock like the other slot. If I touch the stick when it's on I can change the screen distortion to all black and white boxes. I'll post a pic later.

 

[Solvalou]

Sounds to me like you're on to something. I should have suggested using IPA on the slot or SIMM too! Oh well.

I wonder if that the slot may have took a  knock or damaged some other way while there was a SIMM installed (dropped possibly?). Are the solder pads all making connection?

If you need a new slot, you may have to pilfer one from a broken LC (or similar), I can't imagine these being easy to come by being as they're not the usual 30 or 72 pin types.