Rebooting LCIII

[Fred1212]

I have a recapped LCIII that has been working well. It has just started to reboot itself just after it has booted into the desktop and a couple of times has locked and rebooted during startup. I've done all the usual swaps of known good memory drive and power supply from another working LCIII. Anyone know why a reboot is happening. Have had the death chimes once as well. Thanks in advance

 

[Fred1212]

I've given the board a really good clean and visual inspection and cannot see anything untoward. Latest test it chimes lights up monitor and mouse pointer then reboots before splash screen

 

[joshc]

Can you post some high res pics of your logicboard?

 

[Fred1212]

Yes I'll take a couple

 

[Fred1212]

Pics

 

[max1zzz]

Looks like you have a jumper from the positive side of C13 to pin 3 of LP2 which isn't correct, the positive pin of C13 should connect to one side of R37 and one side of R54 (both are on the other side of the board)

This shows where it should be connected to (Blue parts are pads / traces on the top of the board, green are on the bottom)


I have no idea if that would make it reboot though but it's worth fixing

(That picture is of my reverse engineered layout for the LCIII which is available here: https://github.com/max234252/Macintosh_LCIII-Reloaded and might be useful for tracing stuff out, the board is done is sprint layout and there are also scans of a stripped board on the github page)

 

[max1zzz]

Ah, C8 is also the wrong way round, that is on VCC for the EGRET chip so if that's shorting (as tants then to do when subjected to reverse voltage) it will definitely make the system crash / reboot

 

[Fred1212]

Fantastic observation max I did not see C8 I'll change it out. Thanks very much

 

[Fred1212]

That fixed it C8 was the problem but I am going to also sort out C13c as well Many thanks max

 

[Fred1212]

Hi again if you are about max I am trying to fix pin 2 connection on LP2(ZL2) and there is no trace left on board and the hole into the board has no sign of any copper or solder. Do you know where it should connect to? thanks

 

[Phipli]

Hi again if you are about max I am trying to fix pin 2 connection on LP2(ZL2) and there is no trace left on board and the hole into the board has no sign of any copper or solder. Do you know where it should connect to? thanks

I've highlighted the bit max1zzz was talking about in pink. Ignore the green, it is on the other side of the board.

 

[Fred1212]

Sorted thanks all