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Weird problem with my Mac Plus

MOS8_030

Well-known member
So I replaced most of the caps on a Plus analog board today. I say most because I screwed up and didn't order all the caps I needed.
But it was enough for the moment. I also re-geared the floppy drive while I was there.

So I put the system back together and booted it from a floppy.
It came up fine, the screen is still little dimmer than I'd like, but everything looked ok, set the clock, checked to see if saw 4mb of ram, etc. then shut it down.

Then the weirdness started...
I shut it down for only a minute then turned it on again to boot from the same floppy and it started to boot, gave a smiley mac for a second, then spit out the disk.

The condensed version: It booted up fine one time and there after it refuses to boot up, spitting out multiple bootable floppies from three different drives.
Won't boot from SCSI either.
I even swapped out the Plus mobo and memory with another board and it did the same thing! (wtf?)
Is it possible the remaining old caps on the analog board could cause this behavior? (The ones hi-lighted in red.) Doesn't seem likely.

Anyway, I ran out of time so I'll look at it harder tomorrow.

recapped_analog_board_1.jpg

 

bibilit

Well-known member
I will have a look aat the floppy drive, if a dirty disk has been used, the following won't be usable.

The head should be cleaned first.

 

MOS8_030

Well-known member
I will have a look aat the floppy drive, if a dirty disk has been used, the following won't be usable.

The head should be cleaned first.
Same behavior with three different floppy drives. The internal and two different externals.

I made up some fresh boot disks to try today. I'm also going to try a different analog board.

 

MOS8_030

Well-known member
Yeah ok, so it liked the new system disks I made.

Still very odd that three other good system floppies would suddenly just stop working.

It also crashed after sitting booted up for a few minutes so I probably ought to go ahead and replace those other caps before I mess with it too much more.

Anyway,

 

MOS8_030

Well-known member
Those dirty, dirty, disks! :O

Nah, it's not the disks or the drives. This system has other issues but thanks for the input.

 
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MOS8_030

Well-known member
So today I got the thing with the floppies sorted out. It's no longer an issue.

The real problem was funky ram.

 
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