MACINTOSH COLOR CLASSIC TURN UP HELP!!!

[ROLLERMANZ]

I have a macintosh color classic, a very nice and clean piece with no rust dust or any molding anywhere in it.. the only issue it has it is it doesnt turn on.. ive stripped it all down and cleaned it all up.. when its fired up without the logic board, it turns on fine, i can hear and see the fan running, i can hear the hard drive spinning well good.. it just all sound good but nothing on the display.. however when i put the logic board in and turn it on, i dont hear any fan or hard drive sound neither anything on the screen. 

I have researched and theres only a very brief help on with this specific macintosh model as its just very rare.. I have read online where the guy advised to clean the logic board connectors to the other parts inside.. did that very well, replaced all capacitors, cleaned the connector inside the machine aswell.  tried with or without PRAM battery, tried it with swapping the ROM SIMMS around, tried with the ram chips around.. still no help.. 

its very strange as it turns on without the logic board and it doesnt with it so it is the logic board for sure, and while the macintosh is running, i tried put the logic board in then and i do see the green light turning on at the front but thats still no help.. 

the motherboard is actually very clean compared all the other macintosh's ive dealth with in the past most probably because its the newer model then them.. see the image attached and any help would be deeply appriciated.. please dont ask stuff like whether ive left the machine on for a whole night as ive already read about that because it really doesnt help .. 

Thanks 

 

[dougg3]

The leaky caps can cause extra nearby damage even if it looks clean. The problem is probably from leakage from the capacitor nearest to the battery. There's a particular via that tends to rot out. Have you checked the advice from this thread? You should check continuity between the two points on the bottom of the board that I jumped together with wire. If there is no continuity, that via probably rotted out. If there is, it might be wise to check all of the other vias in that area of the logic board. You can see the traces underneath U7 and U8 in my picture. Those chips are involved in the startup circuit on the logic board, so broken connections in that part of the board could definitely be causing the problem you're seeing.

 

[ROLLERMANZ]

i am just about to have all the board now and see whether if theres a link broken.. i hope it is and so i can fix it now haha 

 

[MinerAl]

Silly question...  you are using the power button on the keyboard after you flip the switch on the back, right?

 

[beachycove]

Even several years ago, when their capacitors were in a healthier state, disused CCs sometimes needed to be left plugged in overnight (switched on round the back) and then booted. Try that.

 

[ROLLERMANZ]

dougg3 
I to be honest dont know how to spot a rotted trace but i have stilled patched it just like you did in your picture but it didnt work.. would it be okay for you to tell me what other ones need patching please??

 see the image attached please..

MinerAli dont think its jus about the keyboard button as ive already tried that but didnt work..

beachycovei will try that after i fix all these patches on the board as recomended by dougg3.

 

[uniserver]

also literally douse these areas with 91% IPA,  Flood it,  and get that tooth brush and start brushin.   

goo gets pulled into tough spots causing electrical shorts.



then after you do that, remove the pram battery,  plastic battery holding clip, and ram and vram simms.

put it in the oven about the middle, set temperature and bake it @ 190 degrees F for 15-20 minutes

( non preheat ) that is the key.

 

[ROLLERMANZ]

Do i have to remove he capacitors while doing all this and also will anything burn out while i put it in the oven for 20 minutes? Like that yellow motherbooard connector to the machine?

 

[dougg3]

I wouldn't blindly apply the patch I suggested...if you have a multimeter, put it into continuity test mode and see if there is already continuity between those two points.

 

[ROLLERMANZ]

Unfortunately dont have a multimeter .. How can i spot a rotton link anyways?

 

[Macdrone]

Your gonna have to replace those capacitors. When you remove them and clean the board look for bad traces.....then repair and replace capacitors. If not your fighting a losing battle.

 

[ROLLERMANZ]

Can i not just take the capacitors off, clean the board then put them back on?

 

[uniserver]

anything on that board can handel high temps.  except the plastic that holds in the battery, the soldered battery holder is also good for those temps. 

I wouldn't suggest something that would melt your board…  

 

[ROLLERMANZ]

Right okay.. I will get the 99.9% isopropyl alcohol, take the stuff off, clean it up bake it all .. Then cool it down and re solder NEW capacitors and hopefully it should work then.. Shell i leave the logic board soaked in the isopropyl alcohol for a whole night maybe?

 

[uniserver]

really electrolyte likes water the best. if your gonna wash it.

super hot soapy water… in the kitchen sink.  scrubber down.   then a hot water rinse with the spray hose.

compressor dry, then bake.

if you were not going to wash then a good douse with IPA and tooth brush can do the trick.

 

[ROLLERMANZ]

Okay then i'll just use fairy liquid with very hot water and still use brush to clean it and leave it for a night then bake and all

 

[uniserver]

na i wouldn't leave anything in liquid over night.

that is just silly ness…    a good hot wash, rinse and (compressor dry) then bake…   everything with in 30 minutes.

 

[ROLLERMANZ]

Okay

 

[ROLLERMANZ]

Thank you very much