dgfeldma@isis.cs.du.edu (Dave) (10/22/90)
I am preparing to open my Mac + to install 4M RAM (courtesy of chip merchant, who delivered correct parts on time...) I understand from reading news that the + uses a linear power supply. Is it possible to replace it with a switcher? If I do that, then is there enough room inside the machine (which I have never opened yet) to install a hard disc drive? There are some very low power drives out there (my conner 3204 for the PC takes about 4 watts for 210MB), so with a switcher I think I wouldn't need a fan (the + doesn't have one now and has a linear supply which puts out lots of heat) even with the extra 3-4 watts of a good HD. I really would like to avoid adding extra things onto, above, under, behind, in front of, or in the general vicinity of the machine. Thanx. h
davisson@milton.u.washington.edu (Gordon Davisson) (10/25/90)
In article <1990Oct21.221035.20584@isis.cs.du.edu> dgfeldma@isis.cs.du.edu (Dave) writes: >I am preparing to open my Mac + to install 4M RAM (courtesy of chip >merchant, who delivered correct parts on time...) I understand from >reading news that the + uses a linear power supply. The Mac Plus uses a switching supply; whoever said it was linear was misinformed. >Is it possible to replace it with a switcher? Well, aside from the fact that it already is a switcher... Electrically, there should be no problem using another supply in its place; just cut the 110V lines going into it and connect the new supply's outputs in parallel with the old one's. Physically, you wouldn't be able to actually *remove* the old supply -- it's on the same board as the video drive circuitry, and you don't want to remove that. So, it's possible, but pointless. >If I do that, then is there enough room inside the machine (which I >have never opened yet) to install a hard disc drive? Yes. At least two companies used to sell drives with mounting brackets for this purpose. They both used old half-height ST-506 interface drives that, in addition to the drive itself, needed external shock- mounting, a supplementary power supply, a fan, and in one case, a SCSI controller. With a modern, internally shock-mounted, imbedded-SCSI drive, there should be no problem. (Well, aside from having to build the mounting hardware yourself.) >There are some very low power drives out there (my conner >3204 for the PC takes about 4 watts for 210MB), so with a switcher I >think I wouldn't need a fan (the + doesn't have one now and has a linear >supply which puts out lots of heat) even with the extra 3-4 watts of a >good HD. With a sufficiently low-power drive, you should be able to run it off the Mac's regular supply (though if you do this, you should avoid adding any additional load, such as an external floppy drive). The safer approach is to add a supplementary power supply to run the hard drive. One caveat: do not connect the outputs of the two supplies together; if you do, you're likely to kill at least one of the supplies. You *will* want to add a fan. >I really would like to avoid adding extra things onto, above, >under, behind, in front of, or in the general vicinity of the machine. >Thanx. I'd really recommend getting an external drive. Internal drives in the Plus can be made to work, but I've never seen one that really worked *well*. -- Gordon Davisson Westwind Computing (206) 632-8141 4518 University Way NE, Suite 313, Seattle WA 98105