520c hangs at boot

[aphetica]

I last used it about a year ago, a 520c with (I think) 4mb of ram and some flavor of system 6 or system 7. At the time, it booted with no problems.

Today I booted it to make sure it worked before I went to install Sys 7, but I got nothing on the screen, just white. Tried taking the batteries out, putting them in, attempted to boot from a disk tools disk, but still nothing. I have never had to troubleshoot anything with System 7 on it. Where do I start?

 

[tomlee59]

Troubleshooting a system 7 'book is not very different from doing same on a system 6 'book.

In your case, the problem might be as simple as a flat pram battery. Keep the thing plugged in and let it charge overnight. If you're lucky, all will be well in a day or so.

If that doesn't do it, post back, and lots of folks will pipe up with many additional suggestions (power manager reset dance, ritual sacrifice of free-range soy, etc.)

 

[aphetica]

Alright. I'll leave it plugged in and report back tomorrow. Does it also need to be powered on to charge, or simply plugged in?

 

[equill]

Um, yes. If the backup (secondary, rechargeable, but only about 50mAh max., if you are lucky) is depleted, it will not begin to recharge before the system battery in the right-hand bay has reached nearly full voltage (say 9.5V and up), so you have to offer a carrot for the backup to get off its nether regions. After a year of disuse, 48hr and more could be needed to get the backup battery excited by the thought of new life.

de

 

[Franklinstein]

Also make sure to turn down the contrast. On those old things, often the contrast gets set to maximum as a default state when the PRAM battery is dead. So as soon as it comes up to the white screen, try turning down the contrast.

 

[aphetica]

Okay, so it started this morning and I was able to see the screen... for a few seconds. Then it flickered and faded to bright white, not black... so I'm pretty sure it's not the backlight, right? I could barely see the menu or drive icons, and it would pulse back into view for a moment and then disappear back into the white again.

Adjusting the contrast did nothing.

I'm sure it's a hardware problem. Could this be caused by a dead pram battery?

My next guess would be a dying cap, and after that... a loose screen connector.. but if it were a connector I think it would be flickering instead of pulsating.

So... a battery or a cap. (or possibly something else I didn't think of)

What do you guys think?

I'm just not looking forward to taking this thing apart now. Atleast I will be able to swap the screen into my good PB while I'm in there. (I posted a thread awhile back about how my good PB had a row of dead pixels...)

 

[tomlee59]

... a loose screen connector.. but if it were a connector I think it would be flickering instead of pulsating.

Not sure why you'd think that; flaky means flaky. Neither flickering nor pulsating is therefore precluded.

Does the behavior change as you move or flex the lid, for example? If so, that is a strong indication of a connector-related problem. Intermittent cable connections are very common in these older 'books (this affliction was notoriously widespread in the 1xx series, but affects other models to one degree or another as well).

 

[aphetica]

Well I figured something like a loose cable would cause the signal to cut flicker off and on rapidly, where something like a cap could be affected by radio frequencies and cause bizarre pulses and fluctuations...

(I only pretend to have any idea what I'm talking about when it comes to this sort of thing) :beige:

anyway, the problem fixed itself almost randomly when I adjusted the screen position later in the day. I'll post again if the problem returns.

 

[equill]

... I only pretend to have any idea what I'm talking about when it comes to this sort of thing ... anyway, the problem fixed itself almost randomly when I adjusted the screen position later in the day. I'll post again if the problem returns.

If by 'screen position' you mean the angle between the display and the case, you have just identified the cause of the problem. The flexible PCB that forms the 'cable' from MLB to display either has poor connections (at either end) or has cracked, broken, been torn or corroded at some point in its length. Correction of the fault requires disassembly of case and display, taking care, because the 'cable' is coiled around the display clutch/hinge on one side.

de