color classic will not boot

[mraroid]

Hi folks...
 
I have enclosed some photos.
 
A few days ago, Elfen asked me to take the case off the CC, and see if the CRT would light up in the dark. I did not get to that suggestion until this morning.  I should have done it sooner.
 
With the CC assembled, the hard drive installed, and the case removed, I turned on the back power switch, then the soft power switch on the keypad.  I hard the familiar sound of the CC coming alive, but no light what so ever on the CRT or neck.  I repeated this again and had the same issue.
 
I know of the power connector on this board.  I would like to pull the power connector and look for 5V and 12V on the pins on the board.  Can I do this with the CC powered up with out damaging anything?
 
On this board I found a two prong connector with nothing connected to it (see a photo of my finger pointing to it).  It is BD-11.  I found a second two prong connector under the CRT (see a photo of my finger pointing to it).  It is also not connected to anything. I could not read the stenciled lettering for this connector.
 
I found a fuse near the power supply.  I suspect that since I have good 5V and 12V on the power connector to the hard drive, then the power supply is putting out voltage (?).
 
This board has been re caped and cleaned by Uniserver with in the last 6 months.
 
I tried a coin test and tapped on the CRT.  I am not exactly sure what I should hear.  But to my untrained ear, the tube sounds good.  An inspection of the tube found no cracks.  It looks to be sound....
 
A few months ago, when the CC was apart, I cleaned the connector on this board as well as the connector it slides into.  I could probably take the entire thing apart over the weekend and put it back together if need be. 
 
But I think that if I see no light in the neck of the CRT in the dark, when I turn on the CC, maybe I am not getting voltage to the tube???
 
Thoughts?
 
Thanks again for all the tips.
 
jack

 

[mraroid]

If you try everything, and you absolutely have no success, its probably a busted trace inside the board, which you can't see. We have seen that around here every once in a rare while. You can try gently "flexing" the board in one dimension or the other and then see if you can get it to boot right away.

I only suggest this as a last resort, since flexing an older PCB can, in and of itself, be risky.

I have been reading this thread, but my memory is not 100%, have you tried replacing the ROMs with known working ROMs? ROM rot is possible, its rare, but it does happen.

Hi Paralal... I see the logic behind this.  I will try a board flex before giving up.  No, the ROMs have not been replaced.  I removed them, sprayed contact cleaner into the connector, sprayed some compressed air and plugged them back in.  No joy.  Yep, I think a new set of ROMs is probably the next step if I can't fix it.  I may have found a power issue with the logic board.  ....  Thanks for the tips!

jack

 

[mraroid]

I would double check the connections for sure on the analog board as that single ground wire is very pesky.  Like I said the carriage tabs where the motherboard slides in are notorious for bending into the spot across.

By carriage tabs, you are refering to the metal stand-offs on the bottom of the analog board?  If so, as I understand it, the metal tabs are suppose to connect with the metal skirt around the CC and extend ground? 

I sure with I had a schematic.....

jack

 

[mraroid]

I need to re take the photos below.  Here are some shots of my analog board.  Uniserver re caped and cleaned this board several months ago...

jack

 

[bibilit]

You mean Logic Board ...

The only strange thing about it is that you can have the "Bong" sound, green light and fan

 

[Elfen]

I may have missed it, but dumb question: have you tried turning it on without any RAM SIMMs? The board already has a minimum of RAM on it.

By carriage tabs, you are refering to the metal stand-offs on the bottom of the analog board?  If so, as I understand it, the metal tabs are suppose to connect with the metal skirt around the CC and extend ground? 

Yes.

You mean Logic Board ...

The only strange thing about it is that you can have the "Bong" sound, green light and fan

My LC 475  does the exact same thing. And from that thread, there are a couple of forum members in the same situation. So it appears that this symptom is something new or never came up before until recently. Figuring it out and fixing it would make a lot of people, including I, happy.

 

[mraroid]

I may have missed it, but dumb question: have you tried turning it on without any RAM SIMMs? The board already has a minimum of RAM on it.

No.  I should have tried that.  I will pull the RAM and try it tonight when I am home. 

Can I safely pull the power cable off the board feeding the CRT, power up the CC, and measure voltages on the board?  I was going to do that this morning, but thought I should ask first....

Thoughts?

jack

 

[Elfen]

The Logic board only uses 5V, 12V and -5V (which is rare and only for Serial Communications and /or Floppy Drive I believe), and your 5V and 12V check out OK. No other place is -5V used on the Mac. The Mac can turn on without it.

EDIT: Under the PDS Slot on the edge connector is 5 large pins. Those are the power connectors to the board, and there is where you should measure for the voltages. The problem is getting there.

 

[Paralel]

Despite not seeing anything on the CRT tube, even a loss of seal smaller than you can easily see, the tube will eventually die.

 

[mraroid]

My CC is working..... sort of....
 
I pulled the memory and tried to boot.  Same issue.  I hear the fan run, one chime, a solid green light, but nothing on the screen. I replaced the memory and tried to boot again. Same issue.

I left the power switch on, and walked away from the CC for maybe 4 or 5 hours.  Then I tried to boot it from the keyboard.  And just like magic, it booted to my OS.  The color on the screen was perfect.  No screen issues or any other issues.  I played around for a while.  Maybe 20 minutes.  Then I decide to see what would happen if I rebooted.  So I tried that.  I had one chime, then nothing on the screen.  It was just like before.
 
So I left the power switch on, and walked away from it.  After about 4 or 5 hours, I tired to boot from the keyboard.  The CC booted perfect..
 
That was maybe 15 minutes ago.  I think I will leave the CC on all night and see what happens.  At least I know the CRT is OK.  I have taken the CC apart and put it back together several times in the last week or two.  I was ready to give up.  Do I have a open trace on the logic board?  Some loose connection some place?  I am pulling my hair out.  Maybe with all the building, re building, I almost fixed it.
 
I am running 7.6.1.   I won't be happy until I can turn it off, and turn it back on again. 
 
Could I be dealing with a ROM issue? 
 
Thanks everyone for all the help!  I am so happy to see the screen light up again.  Now if I can just get the CC do that all the time I turn it on.....
 
jack

 

[mraroid]

A photo of my screen....

jack

 

[Elfen]

CONGRATS! IT'S A CCII!!!

Be still my heart! I am so glad its not the CRT!

 

[CC_333]

The analog board probably needs to be recapped. Mine did this (though not quite as severely) until it was recapped, and now it's perfect.

If you can't do it yourself, I suggest sending it to Uniserver. He does a good job, his prices are reasonable, and he has a fast turnaround time.

c

 

[Macdrone]

he said uni recapped the analog, but after the motherboard picture I am not sure he knows that was not it.

It probably needs analog help.

 

[uniserver]

I think its something to do with the EGRET,  the 32KHZ crystal signal... and the corresponding VIAs....   that area is ground zero for issues with the color classic.   maybe the air were he is at has more salt content... causing more of an exaggerated result then were the computer was previously. 

i have had things as weird as barometric pressure affect things..... works at one elevation...   at sea level ... doesn't work.

 

[uniserver]

maybe wash that whole area really really good.....     with a tooth brush and some 91% alcohol....  try to get under the EGRET chip.

 

[Macdrone]

did you do his analog board also?

 

[Paralel]

Such a strange problem, almost anything that could be causing it, a simple soft reboot shouldn't have been enough to cause it to spaz out again. Uni is probably right.

 

[mraroid]

Folks...
 
After leaving the CC on all night, I shut it down and tried to start it again.  It seems to be working OK now.  I have probably shut it down and booted again 6/8 times now.  I am actually afraid to move the CC for fear something is loose inside that I have missed.
 
In the states, the CC was at sea level. Far inland - no salt water near me. Now I am at 7,000 ft.  Quite inland. 
 
I should probably turn the power switch off and leave it off for a while.  Then see if I can turn the power switch on and then boot from the keyboard. 
 
I believe uniserver washed the board when he re caped it.  Should I wash it again? 
 
If I still have issues should my next step be replacing the EGRET crystal? I don't know what the VIAs are.  Is that a chip or capacitors?
 
Thanks every one for the help and suggestions.  I will play with it for the next 24/48 hours and see if it will fail again.  I will report back.
 
jack

 

[mraroid]

did you do his analog board also?

Yes.  Uniserver re caped both boards in this CC.

jack