Strange Mac Classic problem

[Peter.Howard]

Ok so I have a standard Classic 4mb/40mb hard drive running system 7

used it a few weeks ago fine, however now when I plug it in, with the stard ADB keyboard and mouse, it will just sit on "Welcome to Macintosh" and refuse to boot any further, if I unplug the keyboard and mouse, it continues to boot up, obviously plugging the keyboard and mouse back it will not function.

It just sits there stuck and will not boot any further

I stick a mac plus startup disk in, system 6 or some such, it started from that okay with the keyboard and mouse connected, but mouse and keyboard refuse to work, mouse is just stuck in the top corner of the screen.

I have swapped around the cord for the keyboard, none of the pins are broken or missing or bent.

tried just the mouse by itself, no joy ether.

help!!!!!

:'( :'( :'(

 

[H3NRY]

Will it start up with just the keyboard? That will tell whether the mouse is bad or the ADB port on the Mac is bad. Do you have another mouse & keyboard? If it's the Mac, there is a fuse on the motherboard for ADB power, and that may have blown. If it's mouse or keyboard, the most common failure is a short circuit or broken conductor in the cable. It's a process of elimination, Dr. Watson...

 

[Peter.Howard]

wish I did have another keyboard and mouse

well just tried it again and it would startup with the keyboard and mouse connected

but obviously not do anything

but I had done it like 10 times before and it wouldn't

keyboard and mouse were both working about 3 weeks ago okay on this computer

Ill check the fuse, I assume its a visual inspection one, you can see when it has blown?

thanks.

 

[Dennis Nedry]

The fuse is not normal looking, and it probably doesn't look any different when it's blown. Here's a common one used in old Macs:

MUCH smaller in real life.

I don't believe you've told us if it works with ONLY the keyboard, with the mouse disconnected though. I have an ADB mouse II that shuts the whole Mac off when you plug it in.

 

[Peter.Howard]

Well I'm pretty sure the keyboard refuses to work, like when it boots to the Finder "macintosh hd" on the desktop is selected, and pressing return etc does nothing, tab, etc..

is that fuse soldered down?

never seen a fuse like that before

I will have to dig it out again over the weekend and have another look.

 

[JDW]

I never had a problem "booting" my SE/30 with a IIgs ADB keyboard attached, but sometimes the keyboard would work and other times not. I know you're not supposed to unplug and replug an ADB keyboard while the Mac is powered up, but when I would do that, the keyboard would start working again. I ultimately, took the time to open the keyboard and examine the circuit board. Sure enough the electrolytic capacitors had leaked. I replaced them with tantalum versions and tested. The problem was gone, and so far it has not come back. This may not be the source of your problem, but it would not hurt to replace any fluid-filled capacitors with tantalum equivalents.

 

[Dennis Nedry]

What's interesting is that neither the keyboard nor the mouse work individually. Either both simultaneously became faulty or something is wrong inside the Mac.

These fuses are soldered onto the logic board. You will need a continuity tester/ohm meter/multimeter to test them. The freezing and unfreezing worries me a little, it seems that the Mac is trying to communicate to your ADB device(s) and is sitting waiting for a response. I'd definitely check the fuses, but beyond that it might be something fried on the logic board, possibly from static discharge somewhere along the line. It could even be a capacitor or battery that leaked onto something critical for ADB. It wouldn't be a bad idea to give the logic board a good washing.

 

[trag]

If the keyboard worked by itself, I would guess the mouse because the mouse cord where it meets the mouse body is subject to a lot of bending. This is a likely place to get internal broken wires and shorts in the ADB circuit.

 

[Dennis Nedry]

If you do ever run into such a mouse, where the cord entering the mouse is obviously a problem, you can chop the cord off right there, drill it out, and feed the cord through the hole with a little silicone glue. Then on the inside of the mouse, you can reconnect the wires where they go.

I even had good luck with some mouse cords where the plug was chopped off. The recyclers were so quick about their business that they chopped the end off instead of disconnecting from the keyboard. I carefully sliced the ADB connector along the seam on one side and split it open. Once opened, the insides pop right out, and with just a slight pry on the metal sheath, the pin assembly also pops out. I soldered the wires back on to the backs of the pins, reassembled with super glue, and tightly wound tape around it for a good while. I did this successfully to several mice, including some of the original ADB mice. I did the first one with silicone glue and you can tell, but the rest are very good, I scraped away the glue that squeezed out and they look brand-new.

The first one with silicone ended up with something touching ground inside the connector so that's the one that makes the Mac shut off! It took me a few tries but I did eventually fix it. A smarter guy might have run a quick continuity test before risking one of his Macs' ADB. Gotta learn somehow I guess.