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Mac IIfx turns on but no chime

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#1 Pitou

  • 6502

Posted 07 February 2017 - 04:30 PM



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.



#2 mac-man6

  • 6502

Posted 09 February 2017 - 02:17 AM

Are you sure the speaker was reconnected after recapping?

iMac 17" intel 1.83ghz, Quadra 840av, PB150, iMac G3 266hmz ATX hack, SC20 HD.

#3 Pitou

  • 6502

Posted 13 February 2017 - 02:06 PM

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.



#4 CelGen

  • 68000
  • LocationKamloops, Canada

Posted 18 February 2017 - 05:06 PM

Minimum of one bank of ram filled but no idea bout the missing processor.

Verify you don't have leak damage somewhere.

#5 zuctronic

  • 6502
  • LocationChicago

Posted 22 February 2017 - 09:57 PM

Any update on this? I have the same issue with a Mac IIfx.

#6 Pitou

  • 6502

Posted 24 February 2017 - 07:11 PM

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.



#7 zuctronic

  • 6502
  • LocationChicago

Posted 25 February 2017 - 11:39 PM

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..

#8 techknight

  • 68LC040

Posted 27 February 2017 - 01:16 AM

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, 27 February 2017 - 01:20 AM.

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#9 zuctronic

  • 6502
  • LocationChicago

Posted 27 February 2017 - 01:28 PM

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, 27 February 2017 - 01:29 PM.

#10 Pitou

  • 6502

Posted 09 March 2017 - 05:50 PM

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.



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