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I just recapped my Macintosh IICX because it was having the common issue where the computer won't turn on and the power supply just clicks over and over again. Also, the sound wasn't working. After recapping the computer, the machine turns on just fine, but there is no chime and nothing is displayed on the screen. Do you think that I messed something up while recapping it or is there some other explanation to this problem? By the way, it worked fine before I did the recap on the rare occasion that it would actually power on without clicking repeatedly.

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Well others may have a proper answer, but I will tell you about my IIci. I recapped it, and the nubus slots no longer work. They seem to get power (lights come on on select cards, etc.), but no workie.

 

Of course, you can still see what's going on in a IIci with no nubus slots functioning, but with a IIcx you are sort of cornered.... You could check that there is no gunk bridging the pins around the nubus controller. Maybe something got in there while the board was being cleaned?

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I will try to look into that this weekend. Do you have any idea why the NuBus slots would have stopped working if there is not anything bridging the pins?

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Even when the computer sort of worked before the recap, I did not get a chime. One of the reasons that I recapped it was to try to fix the sound, but I am not sure if it is even working at all now. What are the voltages supposed to be on the power supply connector?

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I have not recapped the PSU, but the fan spins, the power light comes on, and the floppy drive makes a short sound when the computer turns on. Doesn't that mean that the power supply is probably fine when you also consider the fact that I could occasionally get it to turn on before I did the recap?

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I just plugged headphones into the speaker jack and discovered that the computer plays the chimes of death immediately after I press the power button. Does this help to narrow down the problem?

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Reseat memories and rom chips if socketed. 

Check fuses on the motherboard (labeled "F")

Check caps polarity and overall resistance between +5 and ground.

 

Sometimes you can find shorted (or low resistance) aluminum caps (even new) because of unefficient quality control.

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Check for continuity between C2 and R3, and between R3 and the internal speaker jack. Run patch wires between them if there isn't continuity to fix the sound issue. As for the chimes of death, a good starting point would be to make sure your RAM is good, if possible.

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I just checked between C2 and R3 and I realized that there was no connection. I touched up the solder on C2 and now the internal sound works fine. Unfortunately, I don't think that I have any way to test the RAM. Could I just try each stick of memory one stick at a time until I find one that works? Also, what is the purpose of the plastic bar on the RAM sticks that can be seen in the photo at the link below? I would have sent it as an attachment, but it wouldn't let me.

 

https://drive.google.com/open?id=1l4zALUBNmnA2ramvdqvQlL_Vvd4UX-Mi

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30-pin SIMMs need to be installed in identical sets of four, and I'm pretty sure that in the IIcx, that has to be in the correct slots as well. You might want to check that you have them installed correctly before moving to thinking about testing the RAM per se.

Edited by beachycove

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All 8 slots are currently filled and I checked to make sure that each set of four is made up of the same type of stick. Does the Macintosh SE have SIMM slots that I could test the sticks in? I have one of those but I have not opened it up in a while.

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That plastic bar isn't stock. It's hard to tell, but it seems that the tabs for some of the SIMM slots have been snapped off, so I'd guess the bar is there to hold the SIMMs in place (and maybe the RAM not being seated correctly because of this is part of the problem).

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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?

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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.

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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.

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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?

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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.

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