512k Mac’s-a-Million Upgrade

[DesignComplex]

Hey all,

I bought a pallet of old macs from a warehouse sale, and one of the machines was an old 512k with some weird upgrades.

It looks like someone added more RAM and a SCSI port (which was threaded through the external floppy port hole). I can’t tell if this is one upgrade or two.

I’d like to get this little machine working again, but it looks like whoever upgraded this machine made some strange changes to the motherboard, so I’m not sure if they can be undone.

Is anyone familiar with these upgrades?

The RAM upgrade is called Mac’s-a-Million by Sophisticated Circuits.

The SCSI upgrade board seems to be from Relax.

Both are circa 1986, and I haven’t been able to find any info about either company. Is anyone familiar with these, or the companies that made them? I’m not sure if I want to keep the upgrades, so I may just want to disassemble them completely, but I’d like to get more info before I make any decisions.

When it powers up, there are no chimes, but I there is something on screen which suggests that there is a problem with either the RAM or ROMs. Any pointers would be greatly appreciated.

Photos are attached!

Thanks!

 

[olePigeon]

They could have been bundled together.  The SCSI upgrade looks similar to the later upgrades that came out once the Plus hit the market.  A lot of companies made them.  It essentially turned the 512k into a 512KE by adding Macintosh Plus ROMs and a SCSI controller which (as you noted) snaked out the back.  The ribbon cable out the side could possibly be connected to the RAM card to give it Direct Memory Access for faster SCSI transfers.

Since it had the Plus ROMs, the RAM upgrade could have been anywhere between 512K to 3.5MB (giving you a total of between 1MB and 4MB.)

They're certainly nice upgrades.

You might be able to get it working by pulling all the RAM chips and spraying in some Deoxit.

If you decide to get rid of it, let me know, I'd be interested in playing with it.

 

[Dog Cow]

The RAM upgrade is called Mac’s-a-Million by Sophisticated Circuits.

The SCSI upgrade board seems to be from Relax.

Both are circa 1986, and I haven’t been able to find any info about either company. Is anyone familiar with these, or the companies that made them? I’m not sure if I want to keep the upgrades, so I may just want to disassemble them completely, but I’d like to get more info before I make any decisions.

That is a 2 MB RAM upgrade. That board has 48x256kbit DRAMs on it, 1.5MB there, meaning your 512K will have a total of 2 MB of RAM. Coupled with the SCSI daughter board and the 800K drive which I see is installed, you now effectively have a Macintosh Plus, and you can run System 7 if you want.

I would keep this upgrade, by the way. It's far much more trouble to downgrade this machine that you now have back to a stock 512K.... Unless you already have these parts on hand: You'd need to get the old 64K ROMs, plus the 400K drive and its mounting bracket. Easier to get a stock 512K.

When it powers up, there are no chimes, but I there is something on screen which suggests that there is a problem with either the RAM or ROMs. Any pointers would be greatly appreciated.

Almost certainly a loose connection between one of the daughter cards and the main logic board. Probably the RAM board, and I assume you've already tried reseating the small SCSI board.

 

[DesignComplex]

I reseated the ROMs, but noticed that the chip labeled RP7 on the upgrade board had its pins out of the socket. Looks like a previous owner tried to troubleshoot it by ripping out the MB and unseated them. I reseated it, but no love. 

I reseated the RAM as well, but still no love from the MB.

I removed and reseated the SCSI upgrade, and then the memory upgrade itself and found what may be the problem.

That same chip that was unseated is connected to a swiss-machined socket on the MB via y’all Swiss risers and the pin had broken off inside the socket. Any ideas on how to get it out besides desoldering the socket?

Also, what’s up with this weird non Motorola branded 68000? It doesn’t look like it is a replacement, as the soldering doesn’t look like the rest of the upgrades do.

 

[DesignComplex]

I got it to power up! Don’t know if it’ll actually work 100% because that pin connection is not soldered, I just added some pressure to the connection by replacing the risers with ones that were about 1mm shorter and crossing my fingers.

Now to see if I can get the HD20 that came with it to spin up...

 

[Trash80toHP_Mini]

That busted Machine Pin Riser socket leg looks easily enough fixed. A standard soldertail machine pin socket looks like it might slip right over the leg. You might need to drill out the socked a tad and maybe cut the broked leg a bit, but it might just solder right on from the looks of it.

I'll dig some up and give you the measurements. It's easy enough to stick a few ion an envelope just to see what happens. []

 

[DesignComplex]

I think this little baby may need more love than that. After using it a little bit, one of the caps on the analog board exploded after a couple of minutes, filling my workbench with smoke. Luckily the case was open or there might have been some auxiliary damage.

The machine still seems to work, and at first I couldn’t even see which capacitor was damaged. But, as I was expecting to re-cap anyway, I guess I’ll just be doing that sooner than I thought.

 

[DesignComplex]

BTW, guys thanks for the tips. I’m just getting my little collection started and I’m sure I’ll be asking more questions.

 

[Dog Cow]

That same chip that was unseated is connected to a swiss-machined socket on the MB via y’all Swiss risers and the pin had broken off inside the socket. Any ideas on how to get it out besides desoldering the socket?

Maybe tease it out with a sewing pin?

BTW, guys thanks for the tips.

OK, here's your next tip. That's a safety film capacitor that exploded. Replace it with a Safety Capacitor 275V 0.1uF 20%, such as this PME271M610MR30.  It's not necessary for operation, as you discovered, but it's a safety measure for the power supply.

I advise against replacing any other capacitors, unless you see that the screen image is wobbly or wavy, such as when accessing the floppy disk drive.

 

[Trash80toHP_Mini]

That same chip that was unseated is connected to a swiss-machined socket on the MB via y’all Swiss risers and the pin had broken off inside the socket. Any ideas on how to get it out besides desoldering the socket?

Like I said, albeit not very clearly. Solder another "standard" machine pin header socket strip connector's female end directly over to the broken leg, pin side up per:

     _||_

    | __ |

      | |

      | |

      | |

      | |

      | |

      | |

    _|_|__

 __| __ |___________

___________________  PCB

 

[DesignComplex]

Like I said, albeit not very clearly. Solder another "standard" machine pin header socket strip connector's female end directly over to the broken leg, pin side up per:

     _||_

    | __ |

      | |

      | |

      | |

      | |

      | |

      | |

    _|_|__

 __| __ |___________

___________________  PCB

That’s exactly what I’m about to do. I’ll let you know how it goes.

 

[DesignComplex]

OK, here's your next tip. That's a safety film capacitor that exploded. Replace it with a Safety Capacitor 275V 0.1uF 20%, such as this PME271M610MR30.  It's not necessary for operation, as you discovered, but it's a safety measure for the power supply.

I advise against replacing any other capacitors, unless you see that the screen image is wobbly or wavy, such as when accessing the floppy disk drive.

Gotcha. None of the other capacitors look bad at all. No leakage or bulging, so I’ll take your advice there.

Any idea why the safety cap blew? The machine was connected to a surge protecting power strip, and the fuse (though it looks foggy in the picture) didn’t blow. Could something else have jacked up the voltage on that circuit?

 

[Dog Cow]

Any idea why the safety cap blew?

It was old? Its time was up? Blame it on the Russians? I've had this safety capacitor blow up in a few other power supplies from the same era too. I think the oldest supply was from about 1979 in an Apple II. What a nasty smell it made! Another power supply had two of these and they both cracked, popped and failed.

 

[Gorgonops]

Blame it on the Russians?

Nah, the American astronauts drilled a hole in it.

 

[trag]

Safety devices wear out after a while.   I had a 60 amp breaker in my home box start tripping.   After much hair pulling and testing, determined that even with zero load it was tripping.   It was fine after I replaced it.   Not the same as a safety capacitor, but the same kind of thing.  

 

[olePigeon]

Very cool that you got it working.  Nice machine.  Now it can play Dark Castle.