Mac Plus Black Screen After Inserting Floppy

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Joined: Jul 29 2012
Posts: 26

When I powered on my Mac Plus, I always got the floppy disk icon with a question mark. Once I popped in a System 6.0.8 floppy disk, the screen went blank and its making a very faint beeping noise. I thought that this was just the boot process but it doesn't stop. I flipped it off and then back on again and I don't get the screen asking for a floppy, just a blank screen with the faint beeping. Since there's no physical button to eject a disk, I'm not sure what to do next. Anyone have any ideas? Thanks for the help!

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Offline
Joined: Jun 18 2010
Posts: 107
Re: Mac Plus Black Screen After Inserting Floppy

Stick a paper clip into the small hole on the right side of the floppy slot to eject it. You may have to push fairly hard.

Sounds like the power supply may be failed.

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Joined: Jul 29 2012
Posts: 26
Re: Mac Plus Black Screen After Inserting Floppy

Got the disk out, thanks! I don't suppose there's an easy way of fixing the power supply?

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Joined: Jul 29 2012
Posts: 26
Re: Mac Plus Black Screen After Inserting Floppy

Strangely, by hitting the side of the case, I got the floppy disk screen again. When I hook up my floppy emu, I can boot the system fine. However, when I put an actual floppy into the drive, I get the black screen again

Update: So now everything works fine; I can even boot from a floppy disk without issue. I didn't do anything, it just started working! So sorry for inconvenienceing everyone, I thought it was genuinely bricked!

gobabushka's picture
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Joined: Apr 26 2004
Posts: 494
Re: Mac Plus Black Screen After Inserting Floppy

Has the system been recapped, or solder joints been looked at?

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Offline
Joined: Jul 29 2012
Posts: 26
Re: Mac Plus Black Screen After Inserting Floppy

I don't think so, the guy that gave it to me hadn't booted it in years

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Joined: Jun 18 2010
Posts: 107
Re: Mac Plus Black Screen After Inserting Floppy

Definitely check the yoke connections at the analog board socket. They're prone to breaking or becoming intermittent.

ericF's picture
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Joined: Sep 22 2013
Posts: 28
Re: Mac Plus Black Screen After Inserting Floppy

I repaired a Mac Plus with similar symptoms this past summer. Sometimes the physical jolt of inserting a disk is enough to mess with a weakened solder joint on the analog board. Slapping the left side should restore, but eventually it will probably just get worse (mine did). This is probably why the floppy emulator doesn't cause the black screen.

Luckily, this is one of the easier repairs---see page 42 Dead Mac Scrolls, and "Classic Mac Repair Notes" by Thomas Lee:

www.ccadams.org/se/classicmac2.pdf

Took a few tries, but renewing the solder on J1 (4 pin connector near the flyback transformer), J4 (connector to motherboard), J2 (connector to yoke) worked. Be sure to note instructions on RE-soldering (not just reflowing the old solder) and keeping the connectors intact while you work on it.

Discharging the CRT is a must, but not as bad as it sounds. Each time I worked on the board, I discharged the CRT using a flathead screw driver under the CRT HV cable cap and jumper to the CRT ground terminal connection. The jumper had a 1/4 watt 1 MOhm resistor in series. No audible snap was heard. I double checked each time by removing the resistor and recontacting the HV connection.

I wouldn't mess with the PSU until I checked out those solder joints. Wanton "recapping" is unnecessary, except when it comes to RIFA line filter caps.