Mac IIfx immediate death chime no video

[pezter22]

I have two Mac IIfx boards I am working on. Both give me an immediate death chime at boot.

Here's the history of these boards. I pulled them out of storage in 2014 and found the batteries had leaked. Not knowing how to repair the damage then, I removed the batteries and placed them back on my shelf. Fast-forward to today and I now repair MacBooks, iPhones & iPads, etc...

I cleaned the area around the battery vomit and fixed all the broken traces involved with the startup/shutdown circuits. They work now.

But my issue is the immediate death chime.

One one board I did replace two RAM sockets and repaired some broken traces. The other board did not have that issue.

Before anyone says it's RAM, I have tried on both boards three sets of RAM. I have tried them in Bank A and Bank B. One set is from a newly printed PCB. The reason I say it can't be RAM (I could be wrong) is because I purchased a ROMinator that bypasses the RAM check on startup. I have three other ROM chips as well.

I have tried using both my power supplies and still have the same issue.

What is confounding is both boards have the same issue, yet still can't boot. I have checked continuity on nearly all the sections of the boards.

I need a second eye on this. Can anyone offer any suggestions on why both boards are suffering the same issue? Thank-you.

Photos are of the board, a close up of where most of the battery damage occurred (I have temporary batteries connected) and a FLIR image (there is some life).

 

[volvo242gt]

Any chance that the traces going to and from the ROM SIMM slots have been damaged? Last time I had a Mac (a IIcx) that did what you describe, the ROM chips were fried. Swapped in a IIfx ROM SIMM, and said machine booted up. Ran happily with the SIMM installed.

 

[joshc]

Its reading from ROM OK I think because it is death chiming. It wouldn't get that far with a dodgy/no ROM connection, it would just sit there doing nothing (my IIfx does this sometimes because its ROM socket is a bit dodgy).

These RAM sockets can be bad too - and that's where I'd point first, is each SIMM sitting very tightly in each socket? Had this problem with a IIx, where it would death chime if the RAM was loose and as soon as I applied hot glue to each RAM SIMM with them seated tightly (bodge fix I know) it worked fine.

 

[cheesestraws]

The good(ish) news is that for a death chime to happen, quite a lot of the computer has to be working, because the CPU is running code from the ROM successfully.

The reason I say it can't be RAM (I could be wrong) is because I purchased a ROMinator that bypasses the RAM check on startup

This, rephrased is, "RAM can't be broken if the computer doesn't look to see if it's broken", which seems optimistic. If a bit of ram that will subsequently be used later in boot is broken, it doesn't hugely matter if it's caught during the RAM test or when something tries to use it shortly afterwards.

 

[pezter22]

I just think it's weird that both boards are doing the same thing, but with the same three sets of RAM, four ROM chips (one ROMinator) and two power supplies. I've placed them in Bank A and Bank B. With no ROM there is nothing. With a Mac IIx Rom also no boot.

I do have some freshly printed 64pin RAM PCB's and memory IC's to solder on. I guess I can try some newish RAM.

 

[joshc]

I really would investigate further into the RAM sockets themselves - it's common for these to be weak and not provide a good connection, so it wouldn't surprise me if both boards are suffering from the same problem. Try the RAM with rubber bands or card inserted in-between each SIMM to give them as tight a fit as possible.

 

[pezter22]

Thanks, On one board I did change out the top two RAM sockets because there was battery residue under J37 the top socket in Bank A. On the back of the board I checked continuity across the socket and down to the sockets connected within the bank.

I do have a few questions.

If anyone can check voltages on a few spots that would be great. On both boards I am not getting any voltages at R2, R3 and R64. At Q1 I get voltage in, but nothing coming out. I've replaced it a few times, same result. These are connected to the Sony Sound chip which is part of the POST sequence. I do have continuity but no voltage readings when the board is on. Just wondering what a working board voltages would be for these parts?

Battery Only/ Powered On

R2
Pin 1 - 0v / 0v
Pin 2 - 0v / 0v

R3
Pin 1 - 0v / 0v
Pin 2 - 0v / 0v

Q1 MMBT3904 - 1A transistor
Pin 1 - 0v / 5.2v
Pin 2 - 0v / 0v
Pin 3 - 0v / 0v

R64
Pin 1 - 0v / 0v
Pin 2 - 0v / 0v

L1
Pin 1 - 0v / 0v
Pin 2 - 0v / 0v

L2
Pin 1 - 0v / 0v
Pin 2 - 0v / 0v

Thank-you in advance.

 

[Jockelill]

Did you ever get your boards working? I have a iifx that also had battery leak that is doing the exact same thing. I do however only get death chime with a rominator. It could be the ram, but I’ve tried two different sets in a lot of combinations but without success.

 

[pezter22]

I was finally able to buy a replacement motherboard and now have a working Mac IIFX. I am guessing there is some battery damage to an inner layer of the board that is the issue. I have shelved my two FX boards for the time being. I will probably attempt a repair again some time in the future. I just can't seem to find the issue.

 

[joshc]

Where did you find a spare working board? I’m looking for a IIfx board at the moment.

 

[Jockelill]

I got my board working! What I did was to check and slightly bend all the pins in the ram sockets. If one of them is too far back it will not get contact with the simm and cause this exact problem. Maybe not same issue on your board, but worth checking. I also had a set of bad ram, but I assume you tested yours in another board.

 

[pezter22]

I got my board working! What I did was to check and slightly bend all the pins in the ram sockets. If one of them is too far back it will not get contact with the simm and cause this exact problem. Maybe not same issue on your board, but worth checking. I also had a set of bad ram, but I assume you tested yours in another board.

Thanks. I was about to replace all the RAM sockets. I did replace the top two. I found a lot of battery vomit underneath them. I had not considered the pins. Great advice.

 

[pezter22]

Where did you find a spare working board? I’m looking for a IIfx board at the moment.

Years of scanning eBay daily. Someone finally listed one and I won it beating out a lot of bidders. I set my top bid at $350. Thankfully it did not reach that and sold for $244. It's tough to find one.

 

[joshc]

Years of scanning eBay daily. Someone finally listed one and I won it beating out a lot of bidders. I set my top bid at $350. Thankfully it did not reach that and sold for $244. It's tough to find one.

Wow, that's a lot, but good to know. Thanks

 

[CC_333]

$244? Wow, I think I paid like $200 for a complete IIfx back in 201...3? Granted, it didn't have a video card, but it did come with 32 MB of expensive and hard to find RAM — more than enough for most things — and a neat looking CPU upgrade thingy, so it was a fantastic deal, even back then.

c

 

[volvo242gt]

My last fx was purchased for $50 from the Seattle RE-PC store in 2014... Mainly bought it for the case that didn't have engraving in the lower front corner. If I remember correctly, the Sony power supply was dead. Board did power up with the Astec I was using in the Stealth fx, though.

 

[Jockelill]

I bought a Macintosh II upgraded to iifx (official upgrade with new sticker on the bottom, but old PSU) that unfortunately turned out to be partially battery bombed (one battery had gone). Luckily after cleaning, only the startup circuit was gone, so it would start using 5V on the PSU. After replacing two diodes, four resistors and a few caps I’ve been able to also resurrect the startup circuit. Only issue now is that it hangs a few extra seconds when turning off, which is likely due to some corrosion around the power button. All in all so far I’ve paid 100$ for it. Usually prices here (Sweden) tend to be comparably low, but you need to have a lot of patience to find stuff due to lower supply.

 

[pezter22]

After a few years of working on my two Mac IIfx boards, I have put the repairs on pause. I actually was able to purchase a clean board on eBay last year and have that working. This month I was finally able to purchase another replacement Mac IIfx board. So now I have them both running again after nearly 10 years. I wish I knew enough and had the foresight to remove those damn Maxell batteries.

Both Mac IIfx's have clean and lubricated floppy drives and BlueSCSI running System 7.1.