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Macintosh Classic boot – is this normal?


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My Classic has been sitting under my desk for a few months, but the other day I set it up to do some writing on it.

 

When starting up, I noticed that there is a period of several seconds after the 'bong' in which the screen only displays diagonal lines – then there is a quiet click, then the happy Mac and normal boot. I also notice that the top edge of the picture doesn't seem to be perfectly horizontal. I don't know whether it did this before I put the machine into storage – can't remember!

 

A video showing what I mean here: https://www.youtube.com/watch?v=tKjsVB9CFwk&feature=youtu.be

 

Apart from this, there are no faults with the machine and it works perfectly. There are no strange smells or noises. 

 

The logic board was recapped by Uniserver last year, but the analogue board has not been touched. A visual inspection revealed no obvious leaking caps (but I know that doesn't necessarily mean anything).

 

My question is ... is this normal, or is it a possible sign of analogue board trouble? Any views? I'm quite fond of this machine so would like to keep it in perfect order if possible.

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the A/B is going to need a re-cap soon.  pop a floppy disk in the drive , if you start to see any screen jitter as the floppy is accessing, then you know its caps are toast. also the Classic A/B has the odd issue in some situations of burning out the speaker, from leaking cap goo causing shorts.

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Cheers for the replies – it's a relief as it's a lovely little Mac. I often prefer it to my LC475 as the monochrome CRT is so crisp. And System 6 serves me fine for the light word processing I do. Chuck a Floppy Emu in there and sharing files with my modern setup is easy.

 

No screen jitters when accessing the floppy and no speaker trouble so far, but I'm keeping an eye on the analogue board ... it's bound to have problems eventually. At some point I'll see about sending it your way for a recap, when I've figured out how to remove it from the cramped interior of the case!

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Nice machine. The Diagonal Lines is the memory test the Classic is doing. If you look at it closely, you will see the lines shift about a pixel or so. Since it is a "long" period of time, it must be fully loaded with RAM.

 

I have to agree, the analog board needs a recapping and a few other things replaced (Coil, Transformer, etc. What I call the "Usual Suspects"). And what Uniserve says about the speaker, check it out. Should be a simple fix of adding wires where the traces broke.

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The Classic has a ROM Disk you can access with Option-Apple-X-O buttons held down when you turn it on. From here you can put in a floppy disk to format and put in a copy of that system on the disk. while formatting or file copying, if the screen jitters, the analog board needs to be recapped like Uniserver said.

 

Also you should check for cracked solder joints on the wire harness on the boards (logic and analog). Any cracked solder joint you should desolder, clean the area and resolder with fresh solder and flux. Reflowing the old solder will not last long as a repair. It will fix the cracked joint but it will crack again in a couple of months. Fresh solder makes the repair last a lot longer, by years instead on months.

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Done all that – I've run dozens of floppies through it, and no jitters whatsoever at any stage. I haven't done a serious check for dodgy solder joints yet but it's on my maintenance list. At least it looks like there are no immediate obvious problems.

 

I'm mainly relieved that the 'delay' in startup is a normal function – I thought it was maybe a symptom of analogue board problems. It's good to know it's just the normal memory check. And my machine came with 4MB of RAM :)

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Things like this are pretty common, my first post here was about my Plus doing something similar. I had the same concern. :)

 

the A/B is going to need a re-cap soon.  pop a floppy disk in the drive , if you start to see any screen jitter as the floppy is accessing, then you know its caps are toast. also the Classic A/B has the odd issue in some situations of burning out the speaker, from leaking cap goo causing shorts.

 

Does that apply to all models with a floppy drive or just the Classic? And also good to know about the speaker issue, that will definitely be worth remembering.

Edited by Juliet Elysa
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I can't find it but you need Larry Pina's Test Pattern Generator for the B/W Macs. It will display the measurements and alignment of the screen. It's in his Mac Secrets and upgrade book if you can find it.

 

I'm sure the yoke needs a but of an adjustment. A slight twist to it will show greatly on the screen so move it in tiny increments to level it out. The same with adjustment magnets. And be careful. Make the adjustments when you turn off the Mac and turn it back on, and repeat as needed. Do not go poking about back there with the Classic on! If you're lucky it will kill you, as the pain from the electric shock will be greater than death itself!

Edited by Elfen
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Things like this are pretty common, my first post here was about my Plus doing something similar. I had the same concern. :)

 

 

 

Does that apply to all models with a floppy drive or just the Classic? And also good to know about the speaker issue, that will definitely be worth remembering.

Most models, I believe. As for recaps, the SE's board is solid but the analog boards on all need review from time to time.

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The Classic has a ROM Disk you can access with Option-Apple-X-O buttons held down when you turn it on. From here you can put in a floppy disk to format and put in a copy of that system on the disk. while formatting or file copying, if the screen jitters, the analog board needs to be recapped like Uniserver said.

 

Also you should check for cracked solder joints on the wire harness on the boards (logic and analog). Any cracked solder joint you should desolder, clean the area and resolder with fresh solder and flux. Reflowing the old solder will not last long as a repair. It will fix the cracked joint but it will crack again in a couple of months. Fresh solder makes the repair last a lot longer, by years instead on months.

I looked and looked and could never figure out how to format a floppy.  I am running 7.5.5.  When I put the Color Classic back together, I will give it a try.  Thank so much Elfen!!  IOU a beer next time I see you - no, wait - I have been looking so hard, I will make that dinner.  Next time you are in Portland Oregon.......  :)

 

jack

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  • 5 months later...

I have a Mac Classic that boots (with a startup chime) to those diagonal lines. But it never completes this step. It does not show a happy mac or question mark disk icon. Is it stuck doing the memory test?

 

I washed and re-capped the board. Before recapping the behavior was the same, but with no startup chime.

 

I wonder if my on-board RAM is bad?

 

Has anyone seen a case like this?

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I've had a memory daughtercard go bad on one of my Classics... thought the logic board was toast initially but swapped in another daughtercard with the same SIMMs (i cant remember how i diagnosed it but i think it was by accident) and it worled again. tried the removed card in the other classic (before the A/B went) and it didnt play ball either, with or without SIMM's installed.

 

But yes, that dark grey raster prior to bootup is normal... But it shouldnt stay there.

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I have a Mac Classic that boots (with a startup chime) to those diagonal lines. But it never completes this step. It does not show a happy mac or question mark disk icon. Is it stuck doing the memory test?

 

The Classic range has issues with both logic board capacitors and Analog board ones, if the logic has been done, keep an eye on the capacitors on the AB (mostly 1000 µf and 2000 µf) 

 

You should have steady voltages.

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The Classic range has issues with both logic board capacitors and Analog board ones, if the logic has been done, keep an eye on the capacitors on the AB (mostly 1000 µf and 2000 µf) 

 

You should have steady voltages.

Thanks for the tip! I'll check the voltages from the analog board. That gives me an avenue to investigate. It was quite the anticlimax to boot to the same screen after recapping the logic board and hearing the startup chime for the first time :)

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  • 3 weeks later...

OK, I'm back from my "little medical vacation..."

 

You need to look at the screen with a magnifying glass and see if it is a tiny checker board pattern that shifts and then freezes or is is it grey lines Raster. Both are different problems.

 

In either case - the logic board should be recapped.

 

In the first case (if you see a shifting checkerboard that freezes) That means problem with the ROM more than the RAM. If there was an error with the RAM, it would give you a Sad Mac Error. But in freezing, that means that it is not going to the proper ROM address. Could be corrosion on the pins (if they are on sockets), or cracked/broken solder joints or traces. If the ROMs is in a socket, you can pry the chip up slightly and push it back down to break the corrode crap and test it to see if it turns on properly. If it does, then this is a temporary fix - congrats! Your next step is to carefully remove the ROM and carefully buff out the pins with some metal polish, steel wool or pencil eraser and blow out the socket with some compressed air. And put the ROM back into place.

 

If it is the second case, where it is just a grey raster, then there is a lot more to do. First check the analog board and recap it, as this is where most of the time this situation happens. Then check to see if your voltages are spot on, make adjustments as needed. Once the analog board is fixed/recapped, then its the logic board's turn. Washing and recapping the board usually fixes most problems. If not you will need to track down broken traces.

Edited by Elfen
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I found a 2nd (mostly) working Classic on eBay, and have been able to narrow things down by swapping components.

 

What I have learned:

- The analog board and screen are working perfectly. I tested the voltages from the analog board and they were right on. I can get to a sad mac if I press the programmers interrupt button. And if I swap the logic board with the newer board from eBay, It boots to the desktop.

 

- The ROM is fine. I swapped ROM between the working and broken logic boards. The working board continued working, the broken board continued broke.

 

- The RAM expansion card is working perfectly. As is the disk and floppy drive.

 

In poking around I did find one trace where there is a very clear and obvious run from a chip pin to a via, but no continuity measured between the two. The connection looks perfect to the eye, but not to the ohm meter. In light of this, I think my next step will be to reflow the board in an oven. I've never done this before, but it sounds fun :)

Edited by chadseld
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I replaced the capacitors, but that did not fix the issue. I also ran a small rewire at the pin where I noticed the discontinuity (after verifying that this same connection has continuity on the working logic board). I suspect that there are more broken connections that I have not found. Without a schematic I don't think I will locate any more since I get cross-eyed trying to follow the maze of traces.

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  • 4 months later...

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