Since my Apple //c is an original, it has an old ROM. Needless to say, I can’t just plug in a UniDisk drive and expect to read 3.5” floppies. I need a //c Plus or a ROM upgrade to do that. Luckily, I found a guy on eBay selling new ROMs for $12 bucks.
Let’s get to it.
Remove the top cover.
Remove the keyboard by disconnecting the ribbon cable.
Locate the W1 and W2 jumpers. You’ll need to take a razor blade or knife and cut the W1 jumper. You’ll also have to fire up your soldering iron and drop a blob of solder on W2.
Using a chip puller, pull out the old ROM.
And pop in the new one, making sure pin 1 is on the left.
Now for W1. Break the connection in the middle with a knife or razor blade.
And W2, drop a blob of solder on it to connect both sides.
Before I button everything back up, I’ll make sure it works first. If all is good, the new ROM should give me a new diagnostic mode.
Power the machine on and you’ll notice that it now displays 3.5” Disk at the top.
Holding the open-apple and closed-apple keys while powering the machine on will initiate a diagnostic. The diagnostic will run for a minute. If all is good, it’ll wrap up with a “System OK” message.
With the ROM upgraded, this bad boy is good for reading 3.5” floppies. I just need to get my hands on a UniDisk. I’ve missed the past 2 or 3 auctions. The last one went for about $160 bucks! People are crazy. I expected to score one for $20 bucks or so, but it seems these drives are pretty rare. I guess I’m spoiled after scoring those two Macintosh 3.5” drives for $1.50.