Mac 128k Sad Mac 048000 error

[snuci]

I just got a Mac 128k (serial F41314HM0001) with it's original motherboard. On boot up, I get a Sad Mac with 048000 error.  I tried to piggy back a 4264 chip onto G12 but I get the same results.  Below the 048000 I get moving dots.  I also get two vertical lines of random dots on screen.  There's a quick pic below.

I am thinking of just removing the G12 RAM chi and replacing it but I don't have Apple RAM to replace.  I have 4264-15 and 4264-20.  Does anyone know if it's 200ms or 150ms or slower/faster?

Do yo think replacing the one RAM chip at G12 will work?

Thanks for any clues.

   

 

[Paralel]

You wouldn't want to use Apple Ram that is time period appropriate since its all likely rotten. Just use newer RAM.

 

[Elfen]

150ns is faster than 200ns. Better to have the same speed ram on all the chips is you can get them.

 

[snuci]

You wouldn't want to use Apple Ram that is time period appropriate since its all likely rotten. Just use newer RAM.

I hear you but I have the non-Apple chips that are old on hand already so why not try them?

150ns is faster than 200ns. Better to have the same speed ram on all the chips is you can get them.

Sorry, I was probably not clear. The 4264s on the 128k motherboard are not marked with speeds so I was wondering if I should use a 4264-15 or 4264-20 to try to match the unmarked chips on the board.

Thanks.

 

[Elfen]

Send a picture of the board.

As for the age of the RAM CHIP, it depends on the integrity of the epoxy casing of the chip but sometimes the casing fails, allowing air to go into the matrix and corrode the silicone die of the chip.

You can use a faster chip on the board; as in if the Mac 128K uses 200ns RAM, you can replace it with a 150ns chip. But you can not replace a 200ns RAM chip when the other are 150ns. Macs of that vintage used I believe 200ns RAM.

 

[Elfen]

Also, keep in mind that though the RAM Chip looks like it went bad, it could also be one the 74LSXXX Address or Data Mux Chips that supports it and the ram is fine. So look at those chips closest to the chip and follow traces.

 

[uniserver]

you want to replace all 16 chips... piggybacking doesn't work.

All the ram needs to be replaced. its a big nasty job but any chip with any ram chip with an apple on it is especially bad.

I'v done many re-ram's for people, and so far only had 2 that needed more chip's one had a ceramic purple cpu that was bad, that was an interesting find.

you could replace that one chip, and it may or may not work, for a while, chances are it won't even last a full 2 hour burn in with out another chip going bad.

the method that it uses to tell you that a ram chip is bad is ok. if it doesn't work, then the code will change to a new one.  and if it does last 2hr burn in... then once you shelf it, and go to power it up again in 6 months you will have a new sadmac code as this apple logo'd ram is total shit.

 

[snuci]

Thanks for the advise guys.  I did find a picture of an original Mac 128k board with one chip replaced and it was 150ns.  I think I have only one of these RAM chips so for giggles, I'll swap G12 and see what happens.  If it works, I'll run it for a bit.  If I see a new code, I'll consider replacing all RAM chips.  

I have a solder rework station with a hot air gun so I'll give it a shot myself (it is a hobby after all).  If it's too much of a hassle, Uni, you will see a package soon   I'll start by using a solder sucker to remove as much solder as I can.  Then I'll use the hot air tool from below as I try to remove the chip from above.  Hopefully that will leave me with some nice clean holes for the new chip.  For those that have done this, does this sound reasonable?  I'm just not sure of the temperature of the hot air tool at this point but I can try on an old board first and figure it out.  

I'll post a picture of the board later tonight or on the weekend.  

 

[uniserver]

yep that sounds about right.

Add solder to each joint, the pins are bent so bend each pin from the bottom side straight again, then heat up each and suck out each joint.  Then from top side use hot air to remove the chip as it will still be slightly soldered to the portholes.

be easy, once you heat it up from the top, it will easily come out,  if not them more heat time from the top.  i use 550F on my Torch, but i move pretty fast.

For what ever reasons those portholes are fragile and if you try to pop it out when its not ready, you will pull the porthole right out of the pcb.

 

[360alaska]

On something like this it might be wise to find yourself a pair of flush cutters and clip each pin right where it comes into the chip and desoldering each pin. Doing this will certainly take longer then hot air but it will minimize and heat damage.

 

[Elfen]

Most pins I find in a job like this are bent inward from the factory to make it "Claw Hold" the hole it is in to hold the chip in place while being soldered. When I get as much of the solder out of the hole, I take a jeweler's screwdriver and from the bottom push the pin out sideways to straighten the claw. This helps as in if the pin moved freely, then the solder has been removed totally from that hole. If there is resistance or the pin is still frozen, then there is still solder in the hole.

But Alaska's way is faster and neater.

 

[uniserver]

Dammage from hot air?   No man were talking about temperature controlled re-work stations here, with air directing tips, not heat gun's

yeah if you are using a heat gun like alaska, there aint nothing i can say to help ya on that one.

 

[snuci]

Well, I fixed my motherboard with the replacement of G12 using the technique I mentioned.  No problem!

Fire it up all is well. Put in a floppy disk and.. my floppy drive didn't work. I put the disk in (System 1.0) and try to boot but I'd get nothing.  I turned it off, turned it on with the diskette in the drive and see a Happy Mac but no drive access. I opened it up and found an 800k disk drive in it.  Hmm, maybe someone upgraded the ROMs?    I checked the ROMs and they are 400k ROMs. 

Next thing to try it to put in a 400k disk drive.  Will have to try that tomorrow.  Here are some pics:

 

[Elfen]

The date code on of the ROMs says "8410" and the copyright is of 1983, this should make it as an original ROM Mac 128.

The 800K disk should be able to read the the System 1.0 400K Disk. It just might need a lube job. Have an external 400K drive to try the disk on? It will boot on the external drive if you have one.

Great job you did there!

 

[uniserver]

awesome leave it on for 2 hours, then power it up and back on again... if that works then you should be ok for at least a little while buddy.!

 

[360alaska]

Dammage from hot air?   No man were talking about temperature controlled re-work stations here, with air directing tips, not heat gun's

yeah if you are using a heat gun like alaska, there aint nothing i can say to help ya on that one.

I have a hot air station, but I only use it for SMD.

I have been soldering for many years and my opinion remains that if your removing through hole components that you intended to replace you should clip the leads and desolder each pin one by one. Why? because if you leave the chip connected it will act as a heatsink which will mean you'll have to raise your tip temperature and risk heat damaging the board... Why not use a hot air tool? Well, because you risk heat shocking and warping part of the board, that's why your technically supposed to preheat the entire board in an oven before you do your work. Furthermore, I don't think they were ever intended for use with through-hole components, that's why it's called a SMD rework station.

At the end of the day, that's just my opinion

 

[uniserver]

yeah basically you have already sucked out the solder from the porthole… you are just heating up the Ram I/C just enough so legs are not surface stuck to the port holes as as they do.

Working on vintage stuff is like a black art that i am mega experienced at.

A few seconds of 550f directed at mainly the I/C that gets tossed in the garbage is not a problem.

also me personally, have a 300 dollar hakko FR-300 that with a 1mm extended nose tip that i use from the bottom, to straighten the legs and to desolder the porthole. My re-rams always turn out nice… Really nice.   Now i get boards in,  Where someone has already started the project first hand...

Yeah i have seen some stuff… W O W…   Yup but their secret is safe with me… i just fix it right and send it back.

 

[360alaska]

yeah basically you have already sucked out the solder from the porthole… you are just heating up the Ram I/C just enough so legs are not surface stuck to the port holes as as they do.

Working on vintage stuff is like a black art that i am mega experienced at.

A few seconds of 550f directed at mainly the I/C that gets tossed in the garbage is not a problem.

also me personally, have a 300 dollar hakko FR-300 that with a 1mm extended nose tip that i use from the bottom, to straighten the legs and to desolder the porthole. My re-rams always turn out nice… Really nice.   Now i get boards in,  Where someone has already started the project first hand...

Yeah i have seen some stuff… W O W…   Yup but their secret is safe with me… i just fix it right and send it back.

It always sucks working after someone else, where I work sometimes we get well logging equipment from other locations in the company and it looks like somebody soldered with their FEET!

 

[Paralel]

And this is why, after my injury, I don't solder any longer, I'd hate to have to bring it to someone after I made a mess, the shame alone would be too great. Seppuku would be necessary.