Macintosh Plus with Weird CRT startup

[Jeffrey_Ooi]

Hi all,

2 wierd things:

1. My Mac Plus on startup is initially showing the correct 2 icons but seems to be missing the greyscale background - i.e. the question mark followed by happy mac when a proper disk is inserted.
2. After the happy mac symbol appears, nothing happens after that - it remains … er … Happy!

I have attached screenshots of the two symbols and also a third of a normal mac’s screen in comparison - any ideas?
at boot

People probably remember my original post about reflowing the power supply board.

Macintosh Plus - CRT goes to black 10 minutes after cold boot ... help!

This Mac Plus boots off cold and after about ten minutes the screen goes dead, it used to be fine if I gave it a tap on the side of the housing but today it just refused to come back on unless I let it cool back down, then the cycle repeats. Removing the cover and bending the board back and tapping it in a few spots gets it back for a moment but then goes back to black. any ideas would be appreciated! You can see the fault here: https://youtu.be/vgmE9kPc8xQ

[Jeffrey_Ooi]

after disk insert

[Jeffrey_Ooi]

Normal boot screen from my other mac plus below

[cosmichobo]

No help again, sorry, but by god those are smart looking Plusses!

[Jeffrey_Ooi]

All right, as embarrassing as it sounds I found the issue … I was cleaning the memory chips and putting them back in when I found out that a resistor on the logic board been knocked out. A little bit [sic] of solder later and its fixed. Screen is grey again and everything boots properly.

Thank you all

[Anthony_Karabian]

Hey @Jeffrey_Ooi , which resistor are you referring to?

I just stumbled on the same problem. I have completely reflowed the motherboard but still have this problem. On start-up I get the exact same black background with floppy disk, no cursor at all.