Black screen on Macintosh plus

[rabbitholecomputing]

Thks! I have several questions :
- Is a mac plus able to power the ZuluSCSI Mini V1.0 ? I understood it need to be powered via USB with the particulary mac plus ?
- Where on the Internet I can find disk images of systems and softwares to copy on this ZuluSCSI ?
- Is a standard nowadays PC running windows OK to transfert files on the ZuluSCSI SD card?

Unless you've installed the diode that Apple chose to omit from the Mac Plus logic board, it must be powered externally via USB.

 

[marcushe]

Hi Everyone! Thank you in advance. I have a fully recapped analog board for my Plus that went to a black screen after 30 minutes of use.

I followed JDW's guide here: (His process recaps literally everything)

My Plus worked great for about 30 minutes after recapping the analog board. After 30 minutes, the screen went black while it was sitting stationary on the desk & in use. It has never returned on this particular analog board. Another non-recapped analog board I have works fine.

The Mac Plus otherwise boots up just fine (can hear it), but no screen anymore on this recapped analog board.

I have tried:

1) Resoldering all the board power connectors multiple times as pictured (they are definitely soldered)
2) Two other CRT screens
3) Replaced the fuse photoed from another Mac Plus analog board
4) The other two soldered glass fuses look okay not black or shattered inside
5) Another analog board works okay and shows screen correctly.
6) Triple checked all the newly soldered capacitor polarities - look correct
7) Tried other known good board power cables

What would we suggest we try? I have a multimeter but hardly know how to use it. Feels like something blew 30 minutes in after clean full power was running through it again. Could a new capacitor have gone bad? A resistor? A component?

What resistors / components are related to video output?

Any help would be appreciated... don't want to lose another Analog board to the wild especially after a 8-hour recap & $60 of capacitors.

I do have another corroded PCB analog board I can pull components from.

Thanks so much!

- Marcus

 

[MattBranth]

Unless you've installed the diode that Apple chose to omit from the Mac Plus logic board, it must be powered externally via USB.

Hi! No, it's nows perfectly working without USB power but only adding the "missing" diode

 

[bibilit]

The other known issue for a black screen is a failure of the Flyback transformer.

 

[marcushe]

The other known issue for a black screen is a failure of the Flyback transformer.

Thanks - a bad flyback would stink. It's not buzzing or showing any arcing in the dark, epoxy seems good model C. Any way to test it?

 

[bibilit]

No that i know, but i had a FBT on a Plus at some point, exact same issue (the screen remained black after a while) i swapped it with a spare and worked first try.

the first FBT had none of the above symptoms.

 

[marcushe]

Thanks - hmmm - would it be safe to power on the other known good analog board on a table, and hookup only the flyback to the CRT from the known good table analog board to the Mac Plus running off the internal analog board, to test the flyback?

 

[bibilit]

Pretty heavy setup and dangerous… you are dealing with high voltage.
Removing the flyback from the AB is just a couple of minutes work.