Recent content by Mr_formal

Does anyone know where I might be able to source the dfac chip for the classic II, I've checked the audio amplifier IC and using the datasheet to test it it looks fine. I can't find a datasheet for the dfac chip, and I think it's bad. I want to replace it to see if the audio works.

Another note is that 12v and -12v on logic board is different.I turned the Mac on its side to measure, and 12v is 11.47 and -12v is 11.74. the -12v is higher.

Another quick note, the system boots at 4.85v but is unstable, best I've found so far is 4.80v

I finished reflowing the entire board and Mac logic board is no longer sensitive to movement, however I still can't raise the voltage above about 4.85v (read from floppy port) and 11.61v. If I raise voltage to 5v the Mac either freezes on startup, or gives random sad mac error code. The audio...

I just finished running a heat gun across the entire back side. I'm going to reflow the solder on the chips on the front side as well. I noticed a crack near where the ram is while reflowing, I did have some issues with the ram, so I might have fixed it, but I'll reflow all the chips and whatnot...

I can't exactly pinpoint where the cracked joints are, everywhere I tapped made it worse, but I got a bus error when I turned the Mac on its side, could that point toward the right direction? I don't really want to reflow all joints, but I'll start doing that now since there's probably no way to...

Thanks, I'll try and reflow the solder on logic board. Another thing I did was check diodes dp3 and dp4, that I heard go bad. I desoldered them and checked them, and they were fine. Hopefully reflowing the joints will help.

I had another question about classic II. It seems every time I adjust the voltage to a perfect 5v it freaks out. I'm attaching an image. I also noticed that it does this if I don't have the back cover on and I jiggle the logic board. Is the Mac classic II logic board sensitive to movement?

I just realized I said 5.8v and not 4.8, I want to clarify that 5v is 4.8v not 5.8v. I have to keep both rails below their rated voltage.

I just tested a laptop charger and USB port and they read correctly, so I'm getting mixed messages. I don't know if my multimeter is accurate, so I'll try and get one to compare to.

I tested multimeter on a battery and it read 1.6v, tested 12v barrel jack and it reads 14v, yeah thanks for pointing that out. This is a brand new multi meter, so I figured it would be correct, but I guess it reads a little high on the dc side. Testing it on an outlet reads a perfect 120v, so ac...

Thanks, I tested it this morning and the speaker works, this is Mac classic II though, and not SE 30. Just wanted to mention that, but now I can cancel new speaker order since it works. I also want to mention that I have to keep the 5v and 12v rail low or else it won't boot. 5v is at 5.91 right...

I tested out shorting the pins on the audio jack today, but that also didn't work. It actually corrupted the picture shorting those pins. I was wondering if you could test your speaker to see if it is magnetic, mine isn't and I think that might be an issue. Metal doesn't attract to the back of...

I managed to submerge the jack in vinegar, and cleaned up the corrosion. The switch has perfect continuity, but still no audio out of internal and external speakers.

I checked continuity of the switch and it was fine, I'll try to jump it tomorrow, hopefully it's not the sound chip, I wouldn't know how to diagnose it either.