Broken Performa 475

[jajan547]

Start with the two RAM chips closest to C127 and C128 and see if when you boot after the death chimes go away.

 

[JP_2208]

To be honest I'm considering admitting defeat. I've taken of half of the chips and still nothing happens. In addition I've had the bad luck that I managed to rip of one of the solder pads per chip and I'm most likely not able to repair that or even put the chips back on if the pads were all okay.

Ttl;dr I think I have overestimated myself and the machine is thoroughly broken

 

[MrFahrenheit]

To be honest I'm considering admitting defeat. I've taken of half of the chips and still nothing happens. In addition I've had the bad luck that I managed to rip of one of the solder pads per chip and I'm most likely not able to repair that or even put the chips back on if the pads were all okay.

Ttl;dr I think I have overestimated myself and the machine is thoroughly broken

If you remove all of the RAM chips, you can just install a SIMM and it should work. I have a 475 board that was needing a recap, and after recap it did the same thing as yours. However, it works fine with a RAM SIMM installed.

 

[joshc]

It is probably repairable still, don't throw the board away - it might be useful to someone else.

Next time, practice hot air/soldering on stuff you don't care about.

Also, you don't need to remove RAM chips to clean under them, a good scrub at the legs with soapy hot water followed by a rinse with isopropyl alcohol would probably be enough most of the time.

 

[JP_2208]

So Update: I managed to remove the remaining 4 chips without ripping pads of but it still does nothing. No video, basically imediate chime. On one side I'm a little concerned that the heat gun may have damaged something but if I'm honest with myself that doesn't seem likely. Any other ideas?

 

[jajan547]

So Update: I managed to remove the remaining 4 chips without ripping pads of but it still does nothing. No video, basically imediate chime. On one side I'm a little concerned that the heat gun may have damaged something but if I'm honest with myself that doesn't seem likely. Any other ideas?

Check three vias near the power connector had similar issues three were bad.

 

[MrFahrenheit]

So Update: I managed to remove the remaining 4 chips without ripping pads of but it still does nothing. No video, basically imediate chime. On one side I'm a little concerned that the heat gun may have damaged something but if I'm honest with myself that doesn't seem likely. Any other ideas?

Just checking, you removed RAM chips, and installed a RAM SIMM, 4MB or >, and you have a good PRAM battery on the board? Have you tried turning on while holding COMMAND OPTION P R and waiting for at least 3 boot chimes?

Your 475 board should have a PRAM reset button, if the above doesn't work, try pressing the button when the machine is powered off, wait 30 seconds, then power on.

 

[uliwitness]

Yeah on topic of that. I've heard that sometimes even if you have a battery the PRAM needs to be reset. How do I do that? I only know its got something to do with the keyboard.

Hold Command+Option+P+R during startup. I think you'll get a second reboot chime and then you can let go. But it's been abou 20 years, so I might be mis-remembering that bit.

 

[JP_2208]

Just checking, you removed RAM chips, and installed a RAM SIMM, 4MB or >, and you have a good PRAM battery on the board? Have you tried turning on while holding COMMAND OPTION P R and waiting for at least 3 boot chimes?

Your 475 board should have a PRAM reset button, if the above doesn't work, try pressing the button when the machine is powered off, wait 30 seconds, then power on.

Yes all 8 RAM chips are removed, I do have a new battery (bought when I recaped the PSU) and I tried the key-hold-down multiple times to no result. There are a few unknow variables though:
1. I have no clue what the capacity of my RAM SIMM is (just that it has 8 chips and the pads for one more)
2. I'm not even sure wether the keyboard I have actually works and because I'm suspicious of that I'm now borrowing one that I know does

And also I just noticed that when trying the keys before I might have been holding ctrl+command+p+r instead of command+option.
Do they need to be already pushed down when I flick the power switch?
I also might ad that this is my first ever atempt at working on a retro computer of any kind

 

[MrFahrenheit]

Yes all 8 RAM chips are removed, I do have a new battery (bought when I recaped the PSU) and I tried the key-hold-down multiple times to no result. There are a few unknow variables though:
1. I have no clue what the capacity of my RAM SIMM is (just that it has 8 chips and the pads for one more)
2. I'm not even sure wether the keyboard I have actually works and because I'm suspicious of that I'm now borrowing one that I know does

And also I just noticed that when trying the keys before I might have been holding ctrl+command+p+r instead of command+option.
Do they need to be already pushed down when I flick the power switch?
I also might ad that this is my first ever atempt at working on a retro computer of any kind

You need to hold the command option p r keys BEFORE switching on the Mac. Then keep holding them for 3 reboot cycle chimes before releasing

 

[JP_2208]

OK noted. Another question about the SIMM, is there any way to tell the capacity just by looking at it, maybe the numbers on the sticker?

 

[MrFahrenheit]

OK noted. Another question about the SIMM, is there any way to tell the capacity just by looking at it, maybe the numbers on the sticker?

Often, yes. Please take a clear photo of the entire SIMM, and upload here if you want to try that. Numbers on the chips themselves are the key.

 

[JP_2208]

Here you go

 

[MrFahrenheit]

Pretty sure that’s a 4MB module

 

[JP_2208]

Thanks, good to know