Macintosh Plus 4Mb Weak Sound on Startup and Slugish Beahaviour

[Paulo Gago Camara]

Hi!

I've recapped the analog board of my Mac Plus, refluxed all the connectors, that were indeed cracked, and the Mac worked fine for some time.

I don't know if its a coincidence or not, but when I bought an external BlueSCSI and did the diode mod on the logic board to power the BlueSCSI directly from 5v on the logic board, the Mac started to slowly get slow and wine down and the speaker started to get really low until it locked and i turned it off because it started to make a moaning like sound.

Now, when I turn it on, it gives the startup chime but very very low. Some seconds after, it starts to make a moaning like sound again and I always turn it off so that nothing bad happens.

I've already replaced 7905 -5V voltage regulator on the logic board, but the symptoms remain the same.

I've measured the voltages at the floppy port and they all appear to be fine +5V -12V and 12V.

Now I'm thinking on replacing the optocoupler before I go into changing the logic board capacitors, or do the documented upgrades to the switching power supply.

The Mac has 4MB RAM and the CRT works perfectly when I turn it on.

Does anyone has more ideas on what can be the problem?

Thanks!

 

[Nixontheknight]

Hi!

I've recapped the analog board of my Mac Plus, refluxed all the connectors, that were indeed cracked, and the Mac worked fine for some time.

I don't know if its a coincidence or not, but when I bought an external BlueSCSI and did the diode mod on the logic board to power the BlueSCSI directly from 5v on the logic board, the Mac started to slowly get slow and wine down and the speaker started to get really low until it locked and i turned it off because it started to make a moaning like sound.

Now, when I turn it on, it gives the startup chime but very very low. Some seconds after, it starts to make a moaning like sound again and I always turn it off so that nothing bad happens.

I've already replaced 7905 -5V voltage regulator on the logic board, but the symptoms remain the same.

I've measured the voltages at the floppy port and they all appear to be fine +5V -12V and 12V.

Now I'm thinking on replacing the optocoupler before I go into changing the logic board capacitors, or do the documented upgrades to the switching power supply.

The Mac has 4MB RAM and the CRT works perfectly when I turn it on.

Does anyone has more ideas on what can be the problem?

Thanks!

I say check the voltages when it's doing that moaning like sound