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Pitou

Mac IIfx turns on but no chime

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Hello,

 

I have a Mac IIfx that I just recapped. I now turns on, but I get no chime/sound at all.

 

I tested the ROM SIMM and RAM simms in another Mac and it's fine.

 

Any ideas/pointers?

 

Thank you.

 

Pitou!

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Yes the speaker was connected. I am lucky enough to have another logic board. I replaced many logic chips and still no luck. I'm thinking the main 68030 CPU might be blown. It happened before on another Mac II. I played around with the scope, but it's a bit hard without the schematics.

 

I'll hunt for a new CPU.

 

Do you know if I should at least get the startup chime *without* the 68882 co-processor?

 

Also, to get it, I must have at least for banks of RAM filled. Is that right?

 

Thank you.

 

Pitou!

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I replaced the CPU but still the same. I'm about to try a new 68882 FPU.

 

My guess is that the fx needs both the CPU and FPU in order to boot what's in the ROM SIMM.

 

Will let you know.

 

Pitou!

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Ah, in my case it turned out to be the ROM. I tried a ROM-inator II from BMWOW and it's working now.

So now the question is: Is it possible to repair the bad ROM? How do I go about troubleshooting it? I don't see any replacement Mac IIfx ROMs available anywhere but I'm interested in restoring OEM parts as much as possible..

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if the ROM is bad, then it COULD be suffering from bit-rot if it started life as a PROM so it works exactly like EPROM but with no window. So you burn it and its done. 

 

if its mask-ROM its likely something different like failing buffer circuits etc internal to the IC. 

Edited by techknight

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I took a closer look at the Apple ROM SIMM and noticed the contacts were looking pretty dull. I wiped them down real good with some IPA and now it's working fine!

P.S. - A/UX doesn't boot with ROM-inator II

Edited by zuctronic

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I'm now getting the startup chime.

 

However after a couple of seconds, I get another sound/chime.

 

I tried the RAM simms in another MAC and they are good.

 

Can you tell me what it could be related to?

 

Thank you.

 

Pitou!

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