Please help, don't mess around with J16 on a iisi

jajan547

jajan547

Active Tinkerer
Mar 25, 2022
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Hello everyone I was hoping someone here could help me figure this out. So if you look at J16 on a iisi it is unused I figured that maybe I could use it as a more reliable means for other speakers because it shared continuity with the same pins as the speaker/led contacts underneath the board. well I thought I had hooked everything up correctly and well I got a click noise from the speaker and the LED works but I got either no image or a blue screen, also I had no distinct sad Mac or normal Mac booting noises. However, the iisi turns on and the fans spin, and the floppy drive works, and even the SCSI HDD spins up and runs. But then again no picture, no sound nothing. I have tried everything and yes the capacitors are okay. I even tried diagnosing issues with my TechStep. I didn't look at the schematics before I did this but I have included the schematics for the iisi below and the configuration I used to test J16. Any help is greatly appreciated!
 

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mmu_man

mmu_man

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Jan 30, 2022
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Are you sure you wired in the correct order? The pins are out-of-order on the schematics, although they also are for J20, so either it's ok or it's all reversed.
Does it work without it connected? Did you try just plugging the LED or just the speaker wires separately?
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
Are you sure you wired in the correct order? The pins are out-of-order on the schematics, although they also are for J20, so either it's ok or it's all reversed.
Does it work without it connected? Did you try just plugging the LED or just the speaker wires separately?
Click to expand...
I did it the same 1-5 pin array as under the board. I did not try it all reversed but can confirm LED lit up and speaker clicked both when they were the only components connected. And no I still had the same issues. Even disconnected or set back up how it is supposed to be I run into the same problems.
 
mmu_man

mmu_man

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Jan 30, 2022
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Ah ok so it's the logic board that is failing, not this gear. Or did it work before you tried it?
 
mmu_man

mmu_man

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Jan 30, 2022
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jajan547 said:
Logic board was working perfectly before I tried this disastrous project lol, any ideas of what’s fried?
Click to expand...
Not really, even plugging it wrong shouldn't do much damage, I mean even it it shorted the HDD LED output to ground it wouldn't fry the transistor there…
You could still check the transistors around (9, 10, 11) for working junctions…
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
Not really, even plugging it wrong shouldn't do much damage, I mean even it it shorted the HDD LED output to ground it wouldn't fry the transistor there…
You could still check the transistors around (9, 10, 11) for working junctions…
Click to expand...
I’ll do it when I get home but what a strange issue, I’m confused as to why it’s acting the way it is.
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
Not really, even plugging it wrong shouldn't do much damage, I mean even it it shorted the HDD LED output to ground it wouldn't fry the transistor there…
You could still check the transistors around (9, 10, 11) for working junctions…
Click to expand...
Here is what happens. So I did what you said PRAM did nothing I did get sound once with the speaker connected to J16 and it was sad Mac noises other than that all the same, also voltages are perfect. I noticed when I try to use my floppy emu (just seeing if it would boot) that it wouldn't boot, it has the lock icon so I'm assuming a SCSI/FLoppy control issue. I have two spare parts boards if anyone would be willing to repair this board for me (obviously I'll pay you).
 
Last edited:
jajan547

jajan547

Active Tinkerer
Mar 25, 2022
732
295
63
North Carolina, USA
jajan547 said:
Here is what happens. So I did what you said PRAM did nothing I did get sound once with the speaker connected to J16 and it was sad Mac noises other than that all the same, also voltages are perfect. I noticed when I try to use my floppy emu (just seeing if it would boot) that it wouldn't boot, it has the lock icon so I'm assuming a SCSI/FLoppy control issue. I have two spare parts boards if anyone would be willing to repair this board for me (obviously I'll pay you).
Click to expand...
Did I maybe fry the ROMs somehow?
 
MacKilRoy

MacKilRoy

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Dec 10, 2021
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jajan547 said:
Okay posted here is the video.
Click to expand...
So it looks like it briefly initializes video, then goes black screen. Is it the grey 1 bit pattern seen on a brief stripe or just a solid color?

Seems like something is shorted or got shorted out from your experiment.
 
MacKilRoy

MacKilRoy

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Dec 10, 2021
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jajan547 said:
And that’s the problem what could be shorted?
Click to expand...

I've never messed with J16, so I couldn't tell you what the outcome of shorting something out connecting to it.

I think you're going to not get much help on this, as you're probably one of the first people to try something new in that way, and you got unpredictable results. An oscilloscope would probably help you, if you knew how it was supposed to behave. I can't really give you solid advice because unless I repeat your 'test' with my working IIsi and make it no longer work, it's going to be hard to duplicate your problem, I'm afraid.
 
jajan547

jajan547

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Mar 25, 2022
732
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North Carolina, USA
MacKilRoy said:
I've never messed with J16, so I couldn't tell you what the outcome of shorting something out connecting to it.

I think you're going to not get much help on this, as you're probably one of the first people to try something new in that way, and you got unpredictable results. An oscilloscope would probably help you, if you knew how it was supposed to behave. I can't really give you solid advice because unless I repeat your 'test' with my working IIsi and make it no longer work, it's going to be hard to duplicate your problem, I'm afraid.
Click to expand...
I have a scope still learning how to use it but, I wish I knew what made this go haywire.
 
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