Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Mac II No Video Output

bunnspecial

bunnspecial

macrumors G3
Original poster
May 3, 2014
8,359
6,498
Kentucky
I have a Mac II that I've been dabbling with for a few weeks.

Initially, it was completely dead. I soldered in a pair of replacement PRAM batteries(my logic board has the soldered batteries, and I was able to find the correct 1/2AAs with leads on Ebay) and got the computer to chime.

My problem is that now I don't see to get much past there. I have a known good 13" Trinitron Multi-Scan that I've used with multiple computers(and plugged into my LC last night just to double check while I was tinkering with this). I've also tried a variety of video cards. All have been Mac II or Apple High Resolution video cards, but all tested good in the IIci that sits next to the II. I've also shuffled them around and tried half of the slots(admittedly not all of them) to see if I just had a bad/oxidized slot.

I seem to get no disk activity, although admittedly the HDD is nearly new(it's a 2.5" 80 pin that works fine in other computers) and not that loud. I also get no signs of life from the floppy drive-when I boot with a disk in the drive, it doesn't spin or do anything else-I have to manually eject it.

Any thoughts on where I could/should check next? I should also add that there are no signs of damage from leaking capacitors.
 
Have you verified the power supply voltages yet? Pin 1 should be +12v, pins 2-6 should be +5v, 7-12 are ground, 13 is not used, 14 is -12v and pin 15 is to power on.
 
DZ/015 said:
Have you verified the power supply voltages yet? Pin 1 should be +12v, pins 2-6 should be +5v, 7-12 are ground, 13 is not used, 14 is -12v and pin 15 is to power on.
Click to expand...

Sorry for the delayed follow-up on this, but I just checked the PSU and all the voltages are as you specified.

As for re-capping the video card-bear in mind that I've tried a half dozen different cards, all of which are good in other systems.

I did just try washing the board a few minutes ago. I don't see any obviously leaking caps, but figured it wouldn't hurt. I'll let the board dry for a few days and try again...
 
If the motherboard has not been recapped it must be as the 47uf 16volt caps are bad. There is no doubt. No troubleshooting really can reliuably take place until then.
 
I once had 5 MacII machines come in, in various states of "not working" - they all need the SMD caps replacing and some even needed tracks repaired with prototyping wire. This was about 10 years ago. I wouldn't believe that any MacII would not have leaking SMD caps, but I'd love to be proven wrong. o_O

Check tracks for black spots - this will be where corrosion has begun to eat/etch away the tracks. You'll need to trace the tracks to see if there is continuity. It's tiring work, and you may not find all of them the first time around. IC pins should be silver and not black, which would also indicate corrosion has set in. :(
 
Thanks guys-time to go cap shopping

(I hate working on PCBs, but it's a necessary evil when you like to play with old Macs)

FWIW, there are a couple of wires soldered on the underside of the board.
 
Thats normal, especially if they were trying to repair the soft power on failure from bad traces. But again with bad caps no real troubleshooting will help. I have a IIx that I need to repair a trace somewhere. I can "jump" the battery to turn it on and it chimes and boots and will power off )as on and off are 2 different systems. But I have recapped it and that was a start. Now I just need to equate the schematic with the actual board.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back