Mac IIcx no boot

[pyl85]

I just acquired a Macintosh IIcx with a lot of computers I purchased on craigslist. Is there some secret to turning this model on? I hooked up a good ADB keyboard and mouse and plugged power in. There's no switch, so I figure it boots with the power key on the keyboard. I press it and nothing happens. Any thoughts? Don't tell me it's a dead PRAM battery

Thanks,

Greg

 

[Franklinstein]

Don't these models have the little power switch on the back of the computer like the rest of the II series? It should be on the left side as you look at the back of the computer, a round pushbuttton with a large line down the middle.

I haven't played with a IIcx/ci for a while, but I'm pretty sure those things aren't battery-dependent. I could be wrong, though, so check the battery before you go tearing into anything. Next would be anything obviously wrong with the machine (liquid intrusions, missing/broken components, excessive dust, etc). Also, make sure the power supply is seated properly - sometimes they come loose or aren't inserted properly.

 

[equill]

As Franklinstein writes, check that the IIcx is complete, with all parts and cables correctly seated. Check that the ROM jumper W1 is present (near grid reference A8 on the MLB), unless you have a separate ROM SIMM card. The autorestart switch behind the Mac should not be engaged. Use a screwdriver and a 90° rotation to let it disengage.

The IIcx, IIci and Quadra 700 share a power supply unit, made either by Astec or Delta. The TRKL (5V) supply, on which soft-power startup depends, goes bad (most often on Astec units), so that the Mac will not respond to the keyboard power switch, or sits, clicks and looks stupid. Trawl these forums for the many references to this failure, workarounds and cures. This PSU has also a less-frequent oddity, from (probably) the same cause, in which either soft-power shutdown or Special/Shut Down stops at the 'It is now safe to switch off your Macintosh', as if the Mac were a passive power-control machine (like a Classic AIO). All you can do then is pull the mains plug from the Mac (and replace it after the Mac has shut down).

 

[MacMan]

I discovered that the principle cause of Mac IIcx failures is leaking capacitors on the motherboard. Open the machine up, unplug and remove the drives & power supply and have a look on the motherboard for electrolyte residue (it will look a bit like spilled cola). This can easy be cleaned off using some Q-tips and cleaning alcohol such as isopropanol.

A new PRAM battery wouldn't hurt either, but it's not essential for booting.

My IIcx had the appearance of being completely dead until I cleaned the motherboard. It now runs perfectly!

 

[pyl85]

Anybody know off-hand of good place to check for +5V trickle power? According to Apple, the IIcx is not PRAM battery-dependent.

 

[pyl85]

Okay, I pulled out the power supply and checked it with my voltmeter. One of the pins is supplying +5V trickle power. With the drives out, I reinserted the power supply and figured I'd give it a try. When I push the power key on the keyboard, the LED on the motherboard blinks and will continue to do so as long as the power key is held down. But it won't come up.

A jumper is present at W1. There is an empty SIMM slot just to the left of the power supply. I don't see any evidence of leaking capacitors, but do these symptoms say otherwise? I wonder if it's grounding out somewhere. Thoughts?

 

[equill]

The SIMM slot is that for the ROM card, when there is one, as opposed to the cache slot next to it for a cache card or a DayStar PowerCache 030 accelerator card (33, 40 or 50MHz). The 33 and 50MHz (2x and 3x multipliers, with the possibility of on-card 68882 FPUs) are the ones to look for for a IIcx.

Did you trawl for past posts in these forums? What you describe about the behaviour with the keyboard power key held down is classic borked PSU stuff.

You can try the 'quick flick' startup. You can remove the power supply and your spanking new 3.67V in circuit battery completely for 5-15min (ie, a hard reset of the MLB and a return-to-taws for the PSU), then replace the PSU and try the power key again, followed by the quick flick if that doesn't work. Finally, you can get another PSU, or try the recommended repair of the (Astec) PSU according to the given link.

de

 

[bigD]

as opposed to the cache slot next to it for a cache card or a DayStar PowerCache 030 accelerator card (33, 40 or 50MHz).

Well, you won't find such a slot on a stock IIcx - the only way to add an accelerator is to pull the socketed CPU (if it wasn't socketed you were pretty much SOL) and mount an adapter to it.

I have a 50MHz accelerator. And I have an adapter. I just don't have a working IIcx!

 

[equill]

And with the adapter card replacing the processor, and projecting to the left of the PSU, what comes into view but (wait for it) the 030 PDS slot, or cache slot. But you are right. It isn't there unless someone puts it there deliberately, although it ends up in nearly enough the same position as the IIci's. I was seeing a IIci in my mind's eye as I wrote about a IIcx.

In my defence: I did at least go and fossick around in a IIcx to find the grid position of the W1 header for the ROM ...

de

 

[pyl85]

I'll give the various power supply tricks a shot. I'm not sure that the power supply is bad because all of the solutions describe a case where the power supply isn't providing trickle power. When I took the power supply out and plugged it in, I measured +5.12V on pin 10.