My Macintosh 512Ke did exactly the same thing. The Plus uses the same Analog Board, so it's relevant here too.
First of all, I think you'll find that the noise is from the Floppy Drive, as it attempts to start up over and over again. Listen closely to the drive from the opening on the front of the machine.
It sounds like you have a solder joint issue. In the case of my machine, the problem was simply the result of cracked solder joints on the Flyback Transformer. Like yourself, I left the machine turned off for a while. Then I discharged the CRT - the Flyback Transformer is the part of the CRT assembly that still packs a punch even after it's been shut off for a while, so discharging the CRT is strongly advised. Then I reflowed the following 10 solder joints:
You'll recognise them at a glance since they're located near the top of the board and are the only solder joints on the back of the Analog Board to be arranged in this manner.
Once that was done, the machine booted right up and ran stable. I've had to perform the same repair to my other 512Ke and two Macintosh Plus Analog Boards since then.
Your board could still require additional work, and this may not necessarily be the fix, but I would look closely at it since there's a good chance it could be.
Cheers,
~ Mic.
- No Video / Loss of Video on Display
- "Flup", "Whup" or "Blip" noise from inside machine
First of all, I think you'll find that the noise is from the Floppy Drive, as it attempts to start up over and over again. Listen closely to the drive from the opening on the front of the machine.
It sounds like you have a solder joint issue. In the case of my machine, the problem was simply the result of cracked solder joints on the Flyback Transformer. Like yourself, I left the machine turned off for a while. Then I discharged the CRT - the Flyback Transformer is the part of the CRT assembly that still packs a punch even after it's been shut off for a while, so discharging the CRT is strongly advised. Then I reflowed the following 10 solder joints:
You'll recognise them at a glance since they're located near the top of the board and are the only solder joints on the back of the Analog Board to be arranged in this manner.
Once that was done, the machine booted right up and ran stable. I've had to perform the same repair to my other 512Ke and two Macintosh Plus Analog Boards since then.
Your board could still require additional work, and this may not necessarily be the fix, but I would look closely at it since there's a good chance it could be.
Cheers,
~ Mic.