Half Dead Mac Performa 200 (Classic II)

[vadersv8]

Hello everyone
So I have this Macintosh Performa 200 I bought few days ago.
When I got home I tried it out and it had some vertical bars and the PSU has issues.
So I recapped the PSU and changed the opto coupler and it's sorted the PSU.
But the motherboard is full of problems!.
I recaped the whole board and repaired traces that might be wonky and even tried desoldering and resoldering the CPU,MMU,RAM and Ergat chip with the hot air station
Also tried soldering new RAM chips and no change
I've looked for bad traces and can't find anything that looks suspicious .
When I boot it it bongs then it throws the error sound and I get nothing else besides the bar screen shown in the photo!.

Can someone help me out getting this beast up and running or can someone sell me a Classic II board that I can use in this Mac?
It's in really really good condition and it would be a shame to go to the dump or to be kept in my garage unused.

Thanks in advance!

 

[joshc]

At this point, I think without a scope and digging through the schematics, you won't find what is causing this. Death chimes are usually caused by problems relating to RAM. Unfortunately this is a bit beyond my knowledge level really, but hopefully someone can offer some more clues as to what is wrong with your board. What you've tried so far makes sense to me.

A lot of Classic II board problems relate to the Egret, sometimes swapping for a known working Egret is necessary but I don't think your problem is Egret related, you said it is getting a happy chime, Egret usually prevents the start process altogether if there's a short or fault there.

Bomarc schematics for the Classic II attached.

 

[vadersv8]

Hello
I have a scope and I have measured all for 4 ram chips and even replaced the ram chips and all where recieving data

Also have resoldered the CPU and the ASIC Chip but no change
Also I lost sound for some reason I don't know why
But when sound was working I used to get the bong and after than it had the crash sound
I replaced all capacitors and checked the traces on almost all of the board and I can't see what could be causing this at all!.

 

[karrots]

I had sound issues like yours. Minus the error bong. It was ultimately one of the caps near the sound chip and removal + clean and resolder of that chip which fixed things.

 

[vadersv8]

I had sound issues like yours. Minus the error bong. It was ultimately one of the caps near the sound chip and removal + clean and resolder of that chip which fixed things.

I've cleaned everything and recapped and nothing changes the problem

 

[max1zzz]

That pattern looks like the junk data in ram before it has been initialized, so I would probably focus your search there
(I'm assuming the Classic II doesn't have and dedicated video RAM? It doesn't have VRAM IC's in the board as far as I can see but I guess it could be intergrated into one of the customs)

 

[vadersv8]

That pattern looks like the junk data in ram before it has been initialized, so I would probably focus your search there
(I'm assuming the Classic II doesn't have and dedicated video RAM? It doesn't have VRAM IC's in the board as far as I can see but I guess it could be intergrated into one of the customs)

It has 2 chips under the board, idk if those are VRAM or not

 

[joshc]

No, the Classic II does not have any dedicated VRAM. It's shared with the onboard RAM.

This is likely a problem with the RAM address lines - have you checked continuity on all those, as per the schematics I linked?

 

[vadersv8]

No, the Classic II does not have any dedicated VRAM. It's shared with the onboard RAM.

This is likely a problem with the RAM address lines - have you checked continuity on all those, as per the schematics I linked?

Yes I have checked all the addresses and all come up good
It's a very weird issue

 

[joshc]

I have had similar problems before on Classic II boards, I sometimes have to remove and resolder all the ICs around the CPU that are near the capacitors in that area. Remove and resolder U12, U15, U10, U11.

You said you replaced with new DRAM chips, what did you replace with?

 

[vadersv8]

i replaced the RAM with Motorola MCM54400AN70
I´m going to look ath those chips you mentioned