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Punkyclown's picture
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Joined: 2017 Nov 9
Checker board screen

Started up my Mac SE today and loaded the system (through an external drive).
Ran okay until I swapped out the disks, then the screen deteriorated with 
a butch of lines that broke up the screen.  Shut it down and on subsequent restarts
all I get now is a checker board pattern on my screen.  Any ideas?
Thank you,
Brad Hansen

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WhosIt.There's picture
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Joined: 2014 Aug 23

Most likely a RAM issue. Amoung many other links:

Apple Support Communities: Checkerboard Screen on a Classic?

Vintage Computer Federation: Mac Classic Checkerboard

Google Groups: Mac Plus repair and checkerboard screen problem

Google Groups: Mac Classic - "Checkerboard" on powerup

YouTube: How to fix checkerboard on Mac Classic Computer

Punkyclown's picture
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Joined: 2017 Nov 9

Okay, so now I cleaned the sim sockets and the ram with alcohol and
reseated and restarted and the system came up. It loads the system
but if I try and do anything, or after a minute or two the system crashes
and the the screen starts tearing and disintegrates... Any suggestions?
Thank you,
Brad Hansen

SkyCapt's picture
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Joined: 2017 Jan 11

So if cleaning the RAM connectors made a difference, it seems like you had a very bad connection and now have only a slightly less bad connection. Can you inspect inside the sockets looking for bent pins? And now past cleaning, how do folks here feel about an additive to help make better connections? I'd smear "dielectric grease" along the RAM module edge conductors, let it soak in a few hours, then wipe 'most' (not all) of the grease away and try that.

How many slots and modules are you using? Is there motherboard RAM so that you can test the sys with no SIMMs? Or try SIMMs one at a time to isolate a bad slot or bad module?

SkyCapt's picture
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Joined: 2017 Jan 11

Hmm, wikipedia says dielectric grease (if it's silicone based) isn't the best choice for ensuring conductivity with low pressure mating surfaces; the stuff I'm proposing is actually called "polyphenyl ether". Er, no, because adjacent conductors for high speed digital cannot be encouraged to interfere with one another. I'll stick with the dielectric grease, and slot pins aren't low on pressure. Also in my last msg, "a few hours" is overdoing it > a few minutes or upto one hour is ok.

WhosIt.There's picture
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Joined: 2014 Aug 23

Could be a bad RAM module.

Or it could be the sockets themselves are coming loose from the circuit board due to ageing solder and need to be re-soldered ... but that is not something you should attempt yourself, unless you REALLY know what your doing.

Punkyclown's picture
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Joined: 2017 Nov 9

Guys, Thanks for your input, much appreciated. There are 4 simm sockets, no on board ram.
The funny thing was I updated my ram from 1 to 4 mgs, but today when I put the original ram
back in, just to check what would happen, the screen got all wavy and ended up with
up and down black and white bars. When back to 4 mgs I just purchased and got what I
described. loaded system then Crashed and the screen tore up. Must add two at a time, tried that
with no good result. Simms are numbered 1 to 4. Do you know if it matters which simms get loaded?
Thanks

WhosIt.There's picture
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Joined: 2014 Aug 23

Not sure if it matters which sockets you use, but it does of course matter that it's the correct RAM type (size, speed, etc.) for that Mac model. You may also have to do some sort of reset on the motherboard. Someone / somewhere should have the service manual for that particular Mac model.

If you've just purchased it, then it's probably old second-hand RAM from eBay or similar, so of course there's no guarantee that it actually works in the first place.

sfp1954's picture
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Joined: 2013 Dec 29

Almost all Mac Motherboards of this vintage need to be recapped. i.e. all the electrolytic capacitors need to be replaced. Electrolytic capacitors usually have have a useful lifetime of 20 years and then the electrolytic fluid in them dries up (or leaks out) rendering them useless. Sometimes they will absorb enough moisture from the air to run for a few minutes, but then the heat of use will drive off that moisture and they will fail.

24bit's picture
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Joined: 2010 Nov 19

Good point. Similar issues with my Mac II´s let me decide to give them away.
I was no artisan solderer even 25 years younger with good eyes. Smile
But then we did not have the huge knowledge data base we have today, nor the helpful community.

Tantalum capacitors look like good spare parts, if matching ones are available.