68kMLA Classic Interface

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Macintosh classic - orizzontal stripes
Posted by: tony1999it on 2016-03-29 11:27:52 Hi, I bought a Macintosh Classic but when I opened it I discovered that the battery leaked .... there was some traces corroded ... I cleaned the board and rebuilt the traces with copper wires. There was also leakage from the electrolitic capacitors so I removed them ... cleaned and replaced with new electrolitic smd capacitors. But the Mac still doesn't want to boot. I have orizzontal stripes .... I attached some pictures of the screen and the board. Hope someone can help me fixing this baby ... Thank's in advance for your help. p.s. on the screen picture there are oblique stripes. They are not generated by my Mac but by my camera. Please don't care.
Posted by: Paralel on 2016-03-29 12:20:44 I suggest a re-do of pic 2 to start with, you're way out of focus, way too hard to see anything. As far as Pic 1, go over everything in that area with a fine tooth comb, it looks like a disaster area. Chance are your problems are somewhere in that area.
Posted by: tony1999it on 2016-03-29 13:16:25 Hi, I attached better photos of the pic2. Yes I'll go to re-check the disaster area :simasimac: [ 🙁 ] Do you confirm that the board should boot also without the battery ?
Posted by: bibilit on 2016-03-29 23:13:16 Yes, will work without battery. Good luck, i have one also, but is worse than yours.
Posted by: techknight on 2016-03-30 17:05:42 Its pretty much JUNK. Sure, you can fix the traces. BUT... what you CANT see is the inner-layer trace runs, those are likely broken at the Vias. Also, in the 2nd pic, I noticed quite a number of annular rings that have been eaten away/broken that you have not repaired yet. You have a loooong way to go. You will need a schematic to chase this one and attempt a repair.
Posted by: tony1999it on 2016-03-31 00:27:08 Hi, Generally speaking I agree with you but in this case we are talking about a four layer pcb. The signal tracks are on the top and on bottom of the pcb. The two inner layers are the power supply (5V and ground). There are some vias corroded that goes to the bottom layer. I rebuilt them connecting the top tracks with the bottom ones. If you put the pcb on a strong light it's possible to see which vias are connected with the inner layer and which not. Yes if I could have the schematic for sure would help a lot. But I wasn't able to find on the net... Someone could send me it?
Posted by: techknight on 2016-03-31 17:36:54 If you put the pcb on a strong light it's possible to see which vias are connected with the inner layer and which not. Not always. the traces are very very hairline thin run in between layers. Light tends to reflect and refract, sometimes making these traces appear "invisible" or not present. You cant always assume that the middle 2 layers are copper planes only, and nothing else as I know for a FACT that isnt true. There ARE traces run in between layers. Trust me on this. Anyways, good luck.
Posted by: Paralel on 2016-04-01 00:10:37 The fact that one can flex boards and make them work temporarily proves technight's assertion regarding small interlayer traces. If they didn't exist, then flexing the board would make no difference.
Posted by: tony1999it on 2016-04-01 10:00:46 Thanks for your info. I'll keep in mind to repair this board. But really no one have the schematics of the macintosh classic ??? :simasimac:
Posted by: uniserver on 2016-04-01 11:09:00 maccaps.com has them
Posted by: tony1999it on 2016-04-02 11:36:01 Yeah ! But for 16$ ... [🙁!] !]'> No one have the schematics of the Macintosh Classic for free ? I can't believe that for a so famous computer the schematics are not available on the net ... :simasimac:
Posted by: techknight on 2016-04-02 13:03:39 They are not free because the amount of time and money involved to obtain them isnt free....
Posted by: tony1999it on 2016-04-02 13:29:43 I would understood if Apple should ask for a fee in order to access information covered by copyright ... but not a third part asking a fee for access information of what doesn't own the rights. Anyway ... that's just my opinion B)
Posted by: uniserver on 2016-04-02 22:36:51 the classic is not an apple schematic.
Posted by: techknight on 2016-04-03 10:38:20 I would understood if Apple should ask for a fee in order to access information covered by copyright ... but not a third part asking a fee for access information of what doesn't own the rights. If it were an Apple Official schematic your statement would be true. However... I can only assume you've never heard of BOMARC. Hes retired now, but he would do the pain staking labor of reverse-engineering the technology to come up with a schematic. So your saying he doesn't own the right to his drawing and reverse-engineering and shouldn't charge for that? Sure there are some gray areas with apples design and the whole reverse engineering principal. However the guy DID do it. and has labor time into doing it, so hes going to charge for it!
Posted by: tony1999it on 2016-04-04 05:03:12 There aren't official schematics from Apple for the Macintosh Classic ... [:O] ]'> I didn't know. That's why there is nothing on the net ! Ok ... I'll try a way to fix my board ...
Posted by: techknight on 2016-04-04 15:09:11 There probably were, but they never made it past engineering or service centers. Apple certified hardware developers could get them from Apple, I know because I got a copy of the Macintosh Portable schematics from a person who owned Dynamic Engineering which made RAM cards for them, among other things.
Posted by: rsolberg on 2016-04-04 16:49:46 I wonder if the Classic's very limited internal expandability meant that Apple did not make schematics available to hardware developers or other parties-- perhaps this is why the Apple schematics don't seem to exist in the wild?
Posted by: tony1999it on 2016-04-05 00:49:59 That' s really strange .... I suppose that in the past at least the Authorized Service Centers should have had the service manual of the Macintosh Classic ... ... a mistery ... [?]
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