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#1 2014-06-01 17:07:28

max1zzz
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Registered: 2014-05-18
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Garbled screen on portable

So, a month or so ago i finally got my hands on a portable, at £50 it was a smidge more than i normally spend on old macs (but hey - if i can get this thing working it is deffinatley worth it)

But all i can get is a garbled screen (a mix of vertical and horizontal stripes) and chimes of death (Well i get a normal chime and a second or two later chimes of death)

The portable has been recapped with good quality capacitors and i am running it from a new 6v SLA battery

very occasionally i will get a sad mac with a not entirely clear screen (will always have horizontal stripes on the screen), the top line of the error is always 00000005 the bottom line changes with each boot (first half changes, i have seen 0001, 0008, 0036 and probably a few others, the second half is always 0000)
i'm not quite sure how to interpret this, the portables error codes seem to be really complicated

I can't see any obviously damaged via's but i'm guessing there is a bad one or two somewhere, but where....

Anyone have a idea where i should start probeing this one?

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#2 2014-06-01 18:59:20

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 955
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Re: Garbled screen on portable

good question...

I have been waiting for info from 2 guys...  Hap... for the schematics for the 5120 and 5126... apparently there is an old apple engineer that hap knows that is on his death bed right now...   Hap doesn't really want to ask him considering his condition... but i mean he might be the last hope for schematics for these things.   --- we need the schematics.

and techknight...  Techknight.. he has   2 Mainboards...     a Dead 5120 and 5126,   I sent him with the exact same type issues.
so i when he gets around to throwing these up on his bench and getting to town... Is when he does it...

but until any of that happens... there is nobody else in the entire world that i know if that can help you with this.
so if you figure it out..  --- witch you might... because you are super intelligent.   please share..!! smile


#I Re-Cap √Mac √NeTX √Amiga Boards - A/B - PSU# (MacCaps.com)  Modern SCSI HD's - For Old Macs - Pre Cfg'd - 10k RPM! 73gb!! $50 + free shipping  -- Mac 128K Re-Ram kits (16 Chips) $35 + shipping, Floppy Issues?-> Bourns Filter Solution 128k - SE/30, $16 + shipping

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#3 2014-06-01 19:22:54

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Hrmf..... thats not good then....

Guess i'm just gonna have to just keep fiddling with this board and hope i eventually fix the problem

And with that - dose the portable have dedicated video memmory? i know bad ram in the original macs can cause funky video problems and it *think* that sad mac error is referring to a failed ram test. So takeing a wild guess i wonder if this could be bad ram? i wonder if anyone still makes it (shouldn't be too hard to swap the ram)

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#4 2014-06-01 20:30:25

bbraun
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Registered: 2014-05-29
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Re: Garbled screen on portable

I spent some time looking at the ROM test code again, and Apple's Sad Mac Error Codes, and the 00000005 seems to mean an addressing test, and the second row is a bitmask of the address line(s) that failed the test.
Basically the address line test takes RAM bank A (only one bank on the Portable, I think) and writes a pattern based on the address, to RAM, then reads the pattern back, incrementing through RAM, then once it reaches the top, inverts the pattern and decrements back to 0.
This is part of a series of RAM tests performed at boot.  Some of the other tests write fixed or repeating patterns to RAM to make sure what they write out is read back successfully, but since the pattern can repeat, it doesn't necessarily catch it if they're not reading & writing to the location they think they are, just verifying the contents.  The purpose of this test is not necessarily to test the RAM, but when they write to a given RAM location, it actually is the location they are expecting.
This might indicate bad RAM, but is more likely to indicate bad addressing lines to RAM I think.

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#5 2014-06-01 21:16:03

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

ok so bad via's / traces are the probable cause

I have found one bad via already (proabley not causing this, since it seems to be connected to the keyboard & mouse i/o) but if there is one you can bet there are more
20140601_212214131.png

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#6 2014-06-01 23:10:32

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

Youll find ALOT of bad vias, look around the capacitor farms.

Every board sent to me thus far has bad vias, just havent had time to fix.

Last edited by techknight (2014-06-02 03:27:32)

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#7 2014-06-02 00:29:03

mcdermd
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From: Corvallis, OR
Registered: 2014-05-12
Posts: 940
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Re: Garbled screen on portable

What's your normal method of repairing a via? What qualities make one a better candidate for repair than another?


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#8 2014-06-02 03:21:20

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

I typically run a piece of 30guage wire from point to point. Unless the via is large enough, I can fit the wire through the hole and solder on both sides. But in alot of cases the via isnt large enough.

The tricky part, is if the via connects to a trace on an inner-layer. Those are fun and require some bright lights to figure out if it goes to anything near by, or just a power plane. I dont have an x-ray or anything like that which inner layers would show up on.

You can tell the bad Vias from the good vias, as most of the time during manufacturing the via gets filled with solder mask. The Vias that are affected will have a slightly off-color compared to the rest of the unit. sometimes a little black, or a little more green. Much like his photo, but his is actually an extreme case. Most of the time its much more subtle.

By far the hardest break to locate is the junction between a trace and solder pad. they are almost microscopic, and definitely broke. Then of course there are the discolored traces underneath the solder mask which is tarnished/corroded and sometimes missing copper. Even harder is gold-plated or tin-plated circuit boards over copper, the plating breaks away on the solder pads from the copper itself and goes often unseen. but it can cause thermally intermittent failures, or complete failures with no visible faults. But soon as you hit it with a soldering iron, it "appears" the pad actually lifted off. But after cleaning it up, the copper is still there. Thats because the plating lifted.

Alot of times you can catch lifted plating if you flex the board and everything works perfect when flexed. But there arnt any visible cold solder joints, or cracks. You are a victim of broken plating if this is the case. Same thing can happen to Vias as well, but its VERY rare. This happens alot in xbox/PS3s.

Its not very common for older PCBs for the latter to occur. Its much more common these days because the quality of PCB production is in the toilet. But eh... I digress.

Last edited by techknight (2014-06-02 03:46:12)

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#9 2014-07-20 11:41:49

max1zzz
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Registered: 2014-05-18
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Re: Garbled screen on portable

Ok finally got around to haveing a go at this

Started by fixing the broken via i found, this seems to have helped - i no longer get random sad mac codes, when i get the sad mac it is always them same (still referring to a failed ram test though)

Now the more i look at this the more splotches i find in traces, but i'm haveing one big problem - that "hybrid" board. There is a load of dogey looking traces heading under it but i just don't know where they go (And i'm not confident in lifting that board without damaging it)

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#10 2014-07-20 23:20:53

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

What is your code? I can tell you were the problem is by the code.

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#11 2014-07-20 23:55:30

max1zzz
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Registered: 2014-05-18
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Re: Garbled screen on portable

first line is 00000005, second was i think 00090000

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#12 2014-07-21 03:10:49

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

Yea, you have a broken address line somewhere. Most likely the break is near the connections by the Left side Keyboard connector. Those caps eat alot of traces/Vias.

it would be more helpful if we had both FULL upper/lower sad mac codes.

Last edited by techknight (2014-07-21 03:11:17)

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#13 2014-07-21 10:53:20

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Ok, so it seems the dogy looking traces i found are in the right area

Guess i will have to pull the hybrid board to find where they are going (looking at it again it dosen't look too bad)

And what exactly do you mean by the full codes? that is all the portable gave me (00000005 top line and 00090000 bottom line)

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#14 2014-07-21 23:53:28

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

Ah nevermind, I misread your word "line" as "code" lol. Sorry... mind tends to wonder....

Anyway, yea that 05 code comes up as RAM addressing failure.

the RAM Address lines connect to the two 74AS244 ICs just above the processor, you can check it from there. Also the data lines connect through the two 74AS245 ICs just to the right of the RAM bank.

Last edited by techknight (2014-07-22 00:00:35)

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#15 2014-07-31 14:19:51

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Ok wonder if anyone can help me out here, Anyone know where this line should be connecting to?
photo%2868%29.JPG

I would assume it should connect to a pin on the hybrid board (which i did try to remove, but i was haveing trouble getting all the solder out the holes, si i decided it was better to stop and not cause any more damage to the board)

(btw, the two other dogey looking lines in that group of 3 have been checked and are fine)

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#16 2014-08-01 00:12:20

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

is that top trace dead? if so, just expose some good copper and run wires.

As far as in particular, where it goes? I dont know yet as I dont have the tools to remove the hybrid, such as a hakko 808.

Last edited by techknight (2014-08-01 00:12:36)

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#17 2014-08-01 00:21:41

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

I think so but who knows where it is going

Might just try that, the trace looks ok where it goes under the hybrid board so hopefully it isn't actually damaged under there

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#18 2014-08-01 01:22:48

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

Well, I would scratch away some of the solder mask on both ends of the trace that you can visibly see, if it reads open, its bad just jump a wire between the two spots you scratched off. If good, leave it alone.

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#19 2014-08-01 12:27:21

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Ok, that trace tested ok, however seems i managed to miss a mas of damaged looking via's under the RAM
Like this:
20140801_132223632.png
(that and a couple of others under that chip are the worse of the lot, going to pull that chip and hopefully find some open via's....)

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#20 2014-08-01 14:18:40

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Seems not, all the via's are good

Also i wounder if you can give me a little guidance here, you mentioned the address lines can be checked from the two 74AS244's above the CPU (And i assume i should be checking to the address pins on the RAM chips right?) how are the address pins ordered on the 74AS244's? Just i'm not sure which pins on the 74AS244's correspond to which address pins on the ram?

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#21 2014-08-01 16:50:24

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

You ned to check RAM-to-RAM interconnects between all chips for continuity. They are in pin to pin order. There should only be one or two pins not connected between banks as this is for decode logic.

Any RAM ic that appears to have black or otherwise corroded pins, pull the chip and check the pads. They break at the trace to pad necks.

This goes for any chip.

Last edited by techknight (2014-08-01 16:53:31)

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#22 2014-08-01 17:49:04

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Fun fun fun... Now i wish i had a backlit portable smile

Just about half way through, so far no faults (except it seems my re soldering was a tad dogy on one ram chip.....)

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#23 2014-08-01 20:32:16

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

Ok, all the ram interconnects are fine, so the fault must be elsewhere

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#24 2014-08-02 00:15:26

techknight
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Registered: 2014-05-22
Posts: 449

Re: Garbled screen on portable

is the sad mac codes random? or are they pretty consistent?

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#25 2014-08-02 01:08:47

max1zzz
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Registered: 2014-05-18
Posts: 207
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Re: Garbled screen on portable

They are pretty constant the top lime is always 00000005 the bottom line is currently 00001000 (I think, I will cheack this tommrow) the bottom line seems to change from time to time (but not like it is random, if you sit and reset it 20 times in a row you will get the exact same code each time, but leave it alone for a week and it might change)

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