128k logic board problem

[gooddi]

hello!

recently i got a another 128k.

i like best 128k. and this is my 4th 128k.

but it has some problem on the logic board.

there are no bong sound, but something was came up on the screen.

maybe ram problem? anther issue?

thanks for reading.

nomally this pattern was on the screen.



 
 
but sometime this pattern was on the screen too.

 

 
early cpu type.

 
 
oki 3764 ram.

 

[uniserver]

r a m

 

[gooddi]

r a m

thanks for your comment.

i have a question.

there are no bong sound and error code.

in this case the problem will be "ram"?

 

[max1zzz]

Yep, ram makes these macs do all manner of strange things when it fails. (when i had ram problems with my upgrade board on my 512k i got various striped / checkerboard screens and at times no bong / a screwed up sounding bong)

 

[Elfen]

Most of the time it is the RAM, like in 95% of the cases. But sometimes the 74XXX's chips to either side of the RAM can be bad in 4.95% of the time and in .05% a solder joint or trace goes bad. So check the RAM first, then the 74XXX's chps and finally the solder joints with a multimeter.

 

[gooddi]

Most of the time it is the RAM, like in 95% of the cases. But sometimes the 74XXX's chips to either side of the RAM can be bad in 4.95% of the time and in .05% a solder joint or trace goes bad. So check the RAM first, then the 74XXX's chps and finally the solder joints with a multimeter.

i finished replacing the ram. (16ea)

i found that this computer  booting nomally except the screen.

just screen is not nomall.

screen was not changed, still has vertical lines.

i cant hear bong sound because sound was too low (soft?).

i guess this is not about ram problem.

do you have any idea? please tell me more

 

[max1zzz]

it could be the 74ls244's next to the CPU, but that is pretty rare

 

[uniserver]

i'v had issues with those CPU's before,  had to replace 2, its like they become disconnected some how, from the legs.

 

[gooddi]

i'v had issues with those CPU's before,  had to replace 2, its like they become disconnected some how, from the legs.

thanks for your comment.

I had replaced two LS244 and ASG, but anything was changed.

so i decided to replace more thing.

when i replaced a LS166 beside of ram the screen was changed.


 

i will try more about replacing the ic, i will report the result.

thanks.

 

[uniserver]

Humm… was there a general picture of the whole main board?  can you take a high resolution, well lit picture?

 

[gooddi]

Humm… was there a general picture of the whole main board?  can you take a high resolution, well lit picture?

Yep. here it is.

if it is not enought to figure out something, i wll take it again using the camera.

thanks.


 
 
the red sopt is what i replaced from 512k board.
 

 

[unity]

ALL the RAM chips should be replaced.

 

[Elfen]

I believe he stated the RAM was replaced (at $16 each? DAMN!).

Replacing a few IC fixed it so it now boots but Video is still bad.

If the CPU was bad, it would not be booting the machine. Does it have sound ("Bong" on power up)?

If it as a SE or SE\30, then it would be simple. What's the circuit that does the display on the 128K/512K/Plus?

Also, looks like the raster is too high - time to look at the analog board for that. Darken the screen to near black and then turn it up until you see a screen image but the unlit areas are as dark as possible from the control knob on the front and then adjust the analog board from there. Replace caps and de-seolder/re-solder joints as needed.

 

[unity]

If the RAM was replaced, it would not have an apple logo.

 

[gooddi]

If the RAM was replaced, it would not have an apple logo.

i replaced all of it, but i did not use new ram.

that is the reaseon why apple logo still there.

every ram was tested on the another board using the slot.

(i mean 16 number of ram, not 16$ )

Elfen //

thanks for your comment.

i also think about that. "adjusting voltage and brightness."

but when i connect another 128k logic board with machine, everything was fine.

so i guess the problem is not on the analog board.

and there is bong sound but very very soft (low).

i'm tracing the strange signal for using the osiloscope.

but i can't find the culprit at this time.

i will update as soon as possible.

thanks  all.

 

[gooddi]

.ㅁ

 

[gooddi]

I believe he stated the RAM was replaced (at $16 each? DAMN!).

Replacing a few IC fixed it so it now boots but Video is still bad.

If the CPU was bad, it would not be booting the machine. Does it have sound ("Bong" on power up)?

If it as a SE or SE\30, then it would be simple. What's the circuit that does the display on the 128K/512K/Plus?

Also, looks like the raster is too high - time to look at the analog board for that. Darken the screen to near black and then turn it up until you see a screen image but the unlit areas are as dark as possible from the control knob on the front and then adjust the analog board from there. Replace caps and de-seolder/re-solder joints as needed.

If the RAM was replaced, it would not have an apple logo.

i replaced all of it, but i did not use new ram.

that is the reaseon why apple logo still there.

every ram was tested on the another board using the slot.

(i mean 16 number of ram, not 16$ )

Elfen //

thanks for your comment.

i also think about that. "adjusting voltage and brightness."

but when i connect another 128k logic board with machine, everything was fine.

so i guess the problem is not on the analog board.

and there is bong sound but very very soft (low).

i'm tracing the strange signal for using the osiloscope.

but i can't find the culprit at this time.

i will update as soon as possible.

thanks  all.

Edited by gooddi, Today, 04:58 AM.

 

[josefl710]

This post reminds me of a 128K upgraded to 512k I got a while ago. After a good cleanup dusting and reflowing cold joints in analog board it got a similar screen. I actually always heard a very loud and clear bong with the screen flashing but vertical lines. Almost as if it was a flashing disk normally seen at boot up but with the vertical bars. I figured it was a memory problem so I replaced all the IC's with 4164 RAM and returned the mac to its original configuration without the 512k upgrade. Did not change a thing, still same screen. I spent all saturday replacing the ram,and I just gave up on it after that. I figured it was some other IC or perhaps a trace on the memory chips that was damaged but I had spent too much time and left it, never got around to tackling it again. Hopefully this thread will provide a more clear fix for my own lol so I can go back end perhaps get it up and running.

Things that were done, 

Tested Analog board with a mac plus logic board and it booted fine so isolated issue to the 128K logic board. 

Took ROM chips from PLUS and inserted them into 128K board but same artifacts on screen, so original ROMS are good.

Removed all memory ICs and replaced ( huge pain! ) but no improvement.

Clear BONG every time for me but vertical bars always present.

Some pics..

 

[gooddi]

This post reminds me of a 128K upgraded to 512k I got a while ago. After a good cleanup dusting and reflowing cold joints in analog board it got a similar screen. I actually always heard a very loud and clear bong with the screen flashing but vertical lines. Almost as if it was a flashing disk normally seen at boot up but with the vertical bars. I figured it was a memory problem so I replaced all the IC's with 4164 RAM and returned the mac to its original configuration without the 512k upgrade. Did not change a thing, still same screen. I spent all saturday replacing the ram,and I just gave up on it after that. I figured it was some other IC or perhaps a trace on the memory chips that was damaged but I had spent too much time and left it, never got around to tackling it again. Hopefully this thread will provide a more clear fix for my own lol so I can go back end perhaps get it up and running.

Things that were done, 

Tested Analog board with a mac plus logic board and it booted fine so isolated issue to the 128K logic board. 

Took ROM chips from PLUS and inserted them into 128K board but same artifacts on screen, so original ROMS are good.

Removed all memory ICs and replaced ( huge pain! ) but no improvement.

Clear BONG every time for me but vertical bars always present.

Some pics..

wow.. same pattern on the screen.

before i replaced the LS166 that pattern was on my screen. 100% same thing.

even if i could not find culprit too, i guess you need to replace the LS166, LS244.

the path is "ram-ls166-ls244-cpu"

so we need to focus this line first.

good luck!!