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Classic - memory board damaged?


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Hello!

 

I have a Macintosh Classic here with a memory problem.

About 2 years ago the Classic worked without a problem with 4MB RAM. About 1 year ago it started that after a few minutes the Classic crashes. About 6 weeks ago I tried to start the Classic again and it crashed immediately.

 

Because that I found this forum I recaped the Classic and it booted again but after a few minutes it crashes again. A reboot leads to a crash. I switched off the classic and after a few hours it started again with a crash after a few minutes.

 

So I started searching: if I switch off the extra 2MB of RAM the Classic runs without a crash. I changed the RAM-modules - same problem.

 

Well after some time I found out that when I put some pressure at the top of the memory board in the direction of the analog board the Classic works!

So I tried a few thing: clean the connector, etc. but nothing solved the problem.

If I put some paper between the memory board and the metal frame to put some pressure to the memory board the Classic works without a problem.

 

What do you think? Is it a problem of the connector? Is it a problem with the memory board?

The error happens when I remove the pressure. It is gone when I set the jumper on the board to "Memory not installed" (only the soldered 1MB is used) or I set the Jumper to "Memory installed" AND put some pressure on the board to use the additional 2MB DIMMS.

 

Bye,

eweri

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Take it for what it's worth, I'm no electronics guy, but I do understand electron plumbing a bit.

 

I'd be looking for a cold or failed solder joint on the memory slot a/o MoBo slot connectors.

 

Most likely I'd just reflow all the joints on the side of the memory card that needs pressure applied to it.

test

Re-flow the other side if the fault persists.

test

Re-flow the joints on the side of the MoBo Connector if it's still borked

test

Ditto the other side.

test

Scratch my head and wonder where I can find another Memory Card to test.

Do the last thing first, maybe you'll find one to borrow, they're in a bit of demand, or were . . . :-/

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. . . could not find a suspicious solder joint.

That would be why I'd just go ahead and re-flow 25% of the joints at a whack in the order I listed . . .

. . . that way I'd be all warmed up and ready to tackle the MoBo for the final 50% of the crap most likely to need pressure applied to it to function properly. [;)]]'>

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Take it for what it's worth, I'm no electronics guy, but I do understand electron plumbing a bit.

 

I'd be looking for a cold or failed solder joint on the memory slot a/o MoBo slot connectors.

 

Most likely I'd just reflow all the joints on the side of the memory card that needs pressure applied to it.

test

Re-flow the other side if the fault persists.

test

Re-flow the joints on the side of the MoBo Connector if it's still borked

test

Ditto the other side.

test

Scratch my head and wonder where I can find another Memory Card to test.

Do the last thing first, maybe you'll find one to borrow, they're in a bit of demand, or were . . . :-/

 

Also, Dont turn it upside down! the electrons will fall out.

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i would check the caps, look for leaks,

then remove the caps, wash the board good.

install some new ones. dry it off with the air compressor.

 

then check the RAM expansion header,

maybe some one went APE on it and broke one of the header pins free from its soldered joint.

 

Hello uniserver!

 

As I wrote it - I've already done the recap and cleaning of the board. Before the recap the Classic crashed immediately - after the recap it runs with 2MB RAM stable. It only crashes with 4MB RAM after some time.

 

Bye,

eweri

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I missed that tidbit about the 2/4 twist. That might narrow your bug-hunt and reflow/patch wire project down to something on the order of the CAS/RAS lines of that particular memory bankage. It might only be the SIMM slot(s) that are the problem, I wish I had my Classic/Memory boards handy, they've been MIA for a while.

 

Where is the necessary wedging pressure applied to the MemCard?

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AHA! [:D]]'> I was just looking everywhere for the still cased 12" RGB (found that one under a pile of clothes recently slated for Goodwill/Keeper testing) and looked into a dimly remembered "Memory Box" (been organizing SIMM/DIMM/Chip boxes while searching for particular DIMMs for the Win98 PC junkyard assembly project) and found the ClassicCrap inside!

 

Just go ahead and re-flow the first of or both SIMM Sockets to see if your vicious little intermittent bug-bite inflicter gets immolated. [}:)]]'>

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My has this error too. xx(

 

So I am not alone ;)

 

Well, I think it is a problem of the connector. I tried to clean the pins, I took my multimeter and tried to find bad connections between the main board and the memory board but nothing. I knocked on every solder point, as long as I put some pressure at the top edge towards the analog board 4MB works.

 

I think the connector lost its strength and now makes bad connections.

 

Bye, a little helpless,

eweri

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AHA! [:D]]'> I was just looking everywhere for the still cased 12" RGB (found that one under a pile of clothes recently slated for Goodwill/Keeper testing) and looked into a dimly remembered "Memory Box" (been organizing SIMM/DIMM/Chip boxes while searching for particular DIMMs for the Win98 PC junkyard assembly project) and found the ClassicCrap inside!

 

Just go ahead and re-flow the first of or both SIMM Sockets to see if your vicious little intermittent bug-bite inflicter gets immolated. [}:)]]'>

 

Hm, I looked at the simm slots but I can not see any problem - I cleaned the ximm slots connectors and the SIMM modules. I try to re-flow the first simm socket - I am going to report later.

 

Bye,

eweri

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Where is the necessary wedging pressure applied to the MemCard?

 

Well, If i put some pressure at the top edge of the memory board toward the analog board - it works (do not know for how long). I took some paper and pressed it between the board and the metal frame - this way I put some pressure at the lower third of the board towards the analog board - this worked for 1 hour and than the Classic crashed again. So everything looks like a bad solder point. But I still think the connector causes the problem.

 

Bye,

eweri

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:)

 

think if've got it

 

I just reflow the connector pins without success, but than I reflow two smd-resistors between the simm-slot and the mounted memory and voila - the Classics boots up.

I can now shake the memory board but the Classic does not crash.

 

At the moment it is running for about half an hour - still no problem

 

:)

 

Bye,

eweri

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