Dead SE/30 question
- Thread starter MikeatOSX
- Start date
It's back to the living... kind of at least.
Recapped it - still no video. No HSync and VSync output.
Popped off UE8 and ran it through the tester - dead.
Installed a new LS166 and still no video.
Popped off UF8 and UG8 and they were both dead as well. I started to loose trust in my IC tester as I had never seen three of those failing at once.
I removed two 74F393 from one of my boards to see if my tester even worked correctly and both tested just fine. While I was at it I installed both of my F393s on MikeatOSX's board and finally got a sign of live out of it.
Video is working fine now. It is booting off an SCSI HDD just fine, ADB is good, Floppy drive works.
The only thing missing now is sound. I am rarely getting real sound from the speaker (or even headphones - doesn't make a difference)
It's all just crackling, noise and pops. As soon as I select a different alert sound in the sound CP the machine locks up hard. Pretty sure the ASC is toast.
Recapped it - still no video. No HSync and VSync output.
Popped off UE8 and ran it through the tester - dead.
Installed a new LS166 and still no video.
Popped off UF8 and UG8 and they were both dead as well. I started to loose trust in my IC tester as I had never seen three of those failing at once.
I removed two 74F393 from one of my boards to see if my tester even worked correctly and both tested just fine. While I was at it I installed both of my F393s on MikeatOSX's board and finally got a sign of live out of it.
Video is working fine now. It is booting off an SCSI HDD just fine, ADB is good, Floppy drive works.
The only thing missing now is sound. I am rarely getting real sound from the speaker (or even headphones - doesn't make a difference)
It's all just crackling, noise and pops. As soon as I select a different alert sound in the sound CP the machine locks up hard. Pretty sure the ASC is toast.
Or a data/address line to the ASC is open. Ive seen that more times than I can count. There is also a couple connections that go back to the GLU IC that will open as well.
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Ruled out the soundchip itself by swapping in another one from a known working IIci. Did solder the supposedly bad soundchip onto the IIci board to doublecheck.
IIci still has sound, SE/30 still crackles and pops most of the time.
What I discovered and what really makes me wonder what's wrong here is that sound works just normal like every 20 resets. If you have sound working and reset or reboot the machine it is gone again.
Gotta love intermittent issues... connections to and from the ASC check out fine so far.
So what other players are in the game? GLU has to issue chip select to the ASC. ASC issues interrupts to VIA1. We have the two Sony DACs and the amplifier at UA9.
What is the crystal connected to the ASC used for?
IIci still has sound, SE/30 still crackles and pops most of the time.
What I discovered and what really makes me wonder what's wrong here is that sound works just normal like every 20 resets. If you have sound working and reset or reboot the machine it is gone again.
Gotta love intermittent issues... connections to and from the ASC check out fine so far.
So what other players are in the game? GLU has to issue chip select to the ASC. ASC issues interrupts to VIA1. We have the two Sony DACs and the amplifier at UA9.
What is the crystal connected to the ASC used for?
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Got it.
I measured the crystal right at the beginning of the whole troubleshooting and it did put out the correct frequency.
With everything else basically ruled out (all traces checked out fine and most of the involved ICs swapped with known good ones) I started heating and cooling down parts on the board to see if something changes...
and so it did. When heating up the crystal right next to the ASC the sound came on. When letting it sit to cool down sound disappeared again.
It must have been putting out a weak signal - heating up makes the crystal swing more which strengthens the output signal.
Replaced the crystal resulted in perfectly working sound output.
Another case closed
I measured the crystal right at the beginning of the whole troubleshooting and it did put out the correct frequency.
With everything else basically ruled out (all traces checked out fine and most of the involved ICs swapped with known good ones) I started heating and cooling down parts on the board to see if something changes...
and so it did. When heating up the crystal right next to the ASC the sound came on. When letting it sit to cool down sound disappeared again.
It must have been putting out a weak signal - heating up makes the crystal swing more which strengthens the output signal.
Replaced the crystal resulted in perfectly working sound output.
Another case closed
Excellent detective work Bolle! You're a miracle worker!
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