Problem with Mac Classic II

[flalvare]

Hi:

I would like to purchase a Macintosh Classic II. The computer has a known problem, displaying the following pattern in the screen:



The computer was working good a few years ago, but was stored for several years and moved during the owners home change. Following the information on this and other sites, it seems like the check board problem, but as i have never seen one of these patterns other that the jpgs posted in the help pages, I posted the image to have feedback from people with more experience in this regard.

Thanks in advance and best regards

 

[techknight]

caps

 

[J English Smith]

Recently had to replace my PRAM battery in my Classic II, that solved my startup issue. Can't remember if the screen looked exactly like this or not. I got some variability, I remember. It is probably the caps, but do replace the battery first and see if that changes anything. A $3-4 attempt, try it.

 

[flalvare]

Very well, i went over the cliff and bought the system (tough at a lower price )

I opened the system, and looked pretty close to the motherboard caps, and to my sight, there is no apparent leakage. I have some photos right here:

Other thing that i checked was the memory, and IMO it looks pretty cheap, with no text in the chips:

I was thinking in washing the mobo, to see what happens; for me, there is no apparent problem with the caps, but anyway I'm no expert, so I would like a little advice. Probably I'll wash the mono and see what happens.

Any ideas?

Thanks and regards

The strange thing is that sometimes, the mac starts with a very low bright screen (same pattern, but just noticeable):

 

[mcdermd]

C7 looks pretty nasty. I think that greenish yuck is corroded leakage. In recapping a few boards now, I note that a lot of times the really bad stuff is directly under the black plastic base making it difficult to see before actually removing the capacitor.

 

[flalvare]

Thanks for your reply.

I have seen information that washing the mobo is a possible solution for this kind of problems, what do you think about it?

In your opinion, as I don't have the skill in electronics, is the recapping unavoidable?

Thanks and regards.

 

[zuiko21]

Washing the mobo is likely to help -- it removes the nearly invisible crud from the capacitors which in turn is what makes for most of the malfunction. But sooner or later it will need recapping.

Just don't forget to take out the battery and the SIMMs... and let it dry for a week to be safe!

 

[protocol7]

Washing worked for me, but ultimately you'll need to replace those caps at some stage. It should get your Classic II up and running until then.

 

[flalvare]

Hello:

After the tips from the ppl at these forums, I washed the motherboard and the computers works! I been able to boot and enter the Os without problems, everything is working even the programs (I believe the computer was last used around 1999).

Anyway, I have two further problems:

1.- High pitch noise: as I understand is a symptom for bad caps. I have worked around this problem installing a plug in the audio out of the mac. It eventually stops after 5 minutes of continuos use of the Mac. Any advice for a long term solution (other than recapping)?

2.- The system is not recognizing the installed memory (2x1mb simms). These simms have been tested in a SE/30. Any tips as to installing the memory or other hidden issue that could be causing problems with the RAM?

Many thanks to every1

 

[phreakout]

Replacing the capacitors on the top side of the logic board can help, but I think the symptom you've described and checkerboard pattern best indicate issues with the RAM. One thing you can try is to remove the sticks of RAM from their slots and thoroughly clean the contacts. You can use Isopropyl or denatured alcohol as a solvent on both the cards and slot contacts. Also, try a pencil eraser as well on the contacts. For more stubborn caked on filth, use a small wire brush specially built for circuit boards. Radio Shack sells a cleaning tool kit with the brush; catalog number 64-087, sells for $12.99. Not sure if there is a ROM SIMM slot on the Classic II. Can that be verified? If so, clean that as well.

73s de Phreakout. :rambo: