Macintosh IICX No Video After Recap

[AlexTheCat123]

It turns out that the problem was indeed with the RAM. All of the SIMMs were good, but one of the sockets that still had the tabs on it needed pressure applied to its SIMM in order to make a good connection. I simply wedged a small piece of plastic between the SIMMs to apply pressure and now it mostly works great.

However, when it is at the blinking floppy disk screen, it constantly flashes the floppy icon with the x over it, even when there is no floppy in the drive. I unplugged the hard drive and floppy drive as well to confirm that they were not causing this. Once I had an OS installed on the computer, I found out that the strange problem continued, in the form of an alert repeatedly popping up telling me that a disk is unreadable and needs to be initialized. The icon that it showed pointed to a disk in an external drive, even though there was not one connected. Each time I hit the "Eject" button on the menu the menu would disappear but it would come back a few seconds later and ask the same thing again. The only way to make it stop was to insert a floppy disk into the internal floppy drive. After I inserted the disk, the message went away and it never reappeared, even if I removed the floppy from the drive. I think that something might be messed up on the logic board near the external floppy port. What do you think is going wrong here?

 

[beachycove]

Have you cleaned and lubed the floppy drive as directed? I'd start there, and assume a signal is coming from the drive that a disk is inserted, because some sensor has been tripped by the sticking mechanics.

 

[AlexTheCat123]

Yes. I have already cleaned the floppy drive and it works fine. The computer still exhibits the symptom even when the drive is unplugged, so the drive itself is not the problem. In addition, the dialog box asking to initialize the disk shows an arrow pointing to an external drive, not the internal drive. It thinks that I am inserting a disk into a drive connected to the external floppy port, even though I don't even have one connected.

 

[AwkwardPotato]

Sometimes SEs and SE/30s (with which the IIcx is closely related) have the issue you describe when the Bourns filters go bad. The IIcx doesn't seem to have the same kind of filter found in the SE/30, although it does have one at RP13 right next to the external floppy port. Maybe that part is causing issues?

 

[AlexTheCat123]

How would I go about testing that part? What does it do exactly?

 

[Bolle]

RP13 is just a resistor network. You can probe it with a multimeter. I think it should be 47 Ohms.

First you check resistance between pins 1 and 16, 2 and 15, 3 and 14 and so on. They should all read around 47 Ohms.

Then you check resistance between each pin and every other pin on the resistor network. There shouldn’t be any connections besides the ones you checked before. Sometimes those packs short out internally.

 

[AlexTheCat123]

Sorry for the late reply, but I checked the resistor network the way that you described and it seems to be fine. I don't know what the problem is at this point. Do you think that I should just give up on it?