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Michael_b

Mac SE - checkerboard and repeated chimes

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Working on a Mac SE. It seemed to work fine, when I got it about a month ago. Tried it the other night and had some issues - it would chime, and chime, and chime, then display Sad Macs.  I didn't get around to taking it apart till now, found a battery in the early process of leaking. Removed the battery case and cleaned the board off with alcohol. While there are a few sketchy traces, they actually ohm out fine. 

 

Now my issue is:

  • When I turn it on cold, I get a checkerboard.
  • If I leave it on the checkerboard, it suddenly chimes after a minute or two
  • Often, it will chime multiple times, then gets to the flashing ?
    • CRT flickers with each time
  • When I start it "warm", ie just on for a while, I see a checkerboard for an instant and then it seems to POST normally to the flashing ?

 

I'm inclined to think that this issue is related to capacitors in the power supply. This seem like a good interpretation?

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You have to check the voltages at the floppy port (5 and 12V). If they are to low you get a checkerboard or multiple rebooting. The analog board and the psu should be recapped.

There is a potentiometer where you can regulate the voltages, but that can result in more problems.

 

Edited by dochilli

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7 hours ago, dochilli said:

You have to check the voltages at the floppy port (5 and 12V). If they are to low you get a checkerboard or multiple rebooting. The analog board and the psu should be recapped.

There is a potentiometer where you can regulate the voltages, but that can result in more problems.

 

Voltages are 12.7 and 5.08, which seems fairly healthy.

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59 minutes ago, dochilli said:

Could be an instable voltage. Can you use a scope to check the voltages?

Don’t have a scope, but I used an analog multimeter to double check against the DMM and the needle didn’t move

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2 hours ago, Michael_b said:

Don’t have a scope, but I used an analog multimeter to double check against the DMM and the needle didn’t move

Put in a known good power supply from an SE/30, exhibits same issue. Analog board likely culprit?

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6 hours ago, Michael_b said:

Put in a known good power supply from an SE/30, exhibits same issue. Analog board likely culprit?

So, the SE board exhibits checkerboard for ~2 minutes, than beeps and all is well

 

an SE/30 board has no issues in the same configuration, so I’m assuming the issue is found on the logic board

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On 6/30/2019 at 11:19 PM, Michael_b said:

So, the SE board exhibits checkerboard for ~2 minutes, than beeps and all is well

 

an SE/30 board has no issues in the same configuration, so I’m assuming the issue is found on the logic board

Have you ruled out if its a bad ram card because if one chip on one card fails the whole machine wont boot and having issues that are rare to find a solution for online. What you want to do is check each ram card by pulling them out and testing them 1 by 1 in a 512 configuration. If that dont work try testing the cable connecting the AB to the MB it could need to be cleaned. And if all fails it could be ROM's.

 

Edited by Nathanplus

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3 hours ago, Nathanplus said:

Have you ruled out if its a bad ram card because if one chip on one card fails the whole machine wont boot and having issues that are rare to find a solution for online. What you want to do is check each ram card by pulling them out and testing them 1 by 1 in a 512 configuration. If that dont work try testing the cable connecting the AB to the MB it could need to be cleaned. And if all fails it could be ROM's.

 

The machine boots...

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6 minutes ago, Michael_b said:

The machine boots...

Oh crap sorry let me think... It hast to be a resistor or a cap some analog part that takes a while to heat up right along the video out pin. It could be an voltage rectifier. I know a conman issue is the connector to the motherboard and it could need a cleaning use some metal polish I'll look into the situation you are experiencing.

Edited by Nathanplus

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One of the chips on the logic board could just as easily exhibit problems before warming up. The problematic component in question doesn't even necessarily need to be part of the video circuitry; also, as the OP states above, all the voltages, of which none are regulated by the SE logic board, have been tested good. 

 

I'd suggest waiting for the computer to warm up and chime, then take a can of freeze spray or an upside-down canned air and go around freezing individual chips until you cause the computer to lock up again (my money's on the ROMs).

Edited by AwkwardPotato

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19 hours ago, AwkwardPotato said:

One of the chips on the logic board could just as easily exhibit problems before warming up. The problematic component in question doesn't even necessarily need to be part of the video circuitry; also, as the OP states above, all the voltages, of which none are regulated by the SE logic board, have been tested good. 

 

I'd suggest waiting for the computer to warm up and chime, then take a can of freeze spray or an upside-down canned air and go around freezing individual chips until you cause the computer to lock up again (my money's on the ROMs).

Interesting, I’ll give this a go.. sure seems like this problem could be really difficult to track down. Might start out with hair drying the board to see if it starts right up after that.

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On 6/29/2019 at 5:55 PM, Michael_b said:

Working on a Mac SE. It seemed to work fine, when I got it about a month ago. Tried it the other night and had some issues - it would chime, and chime, and chime, then display Sad Macs.  I didn't get around to taking it apart till now, found a battery in the early process of leaking. Removed the battery case and cleaned the board off with alcohol. While there are a few sketchy traces, they actually ohm out fine. 

 

Now my issue is:

  • When I turn it on cold, I get a checkerboard.
  • If I leave it on the checkerboard, it suddenly chimes after a minute or two
  • Often, it will chime multiple times, then gets to the flashing ?
    • CRT flickers with each time
  • When I start it "warm", ie just on for a while, I see a checkerboard for an instant and then it seems to POST normally to the flashing ?

 

I'm inclined to think that this issue is related to capacitors in the power supply. This seem like a good interpretation?

 

The flashing question mark means that there is “no useable Operating System installed”.

NOT your hard drive is bad / your floppy drive is broken. 

As a matter of fact, get a bootable floppy, and try that when it does try to boot. 

The continus restarts *ususlly* means the analog board has an under volt. Needs repair. 

If you have access to another SE / SE/30, throw the digital board in there. It’ll probably be fine.......

Edited by jimjimx

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