Mac SE no bong, no display. not getting anywhere with troubleshooting

[marcocet]

A lot of rust also in the other side of the board, some legs are rusted in the ROMs area.

I will remove everything in a socket for checking purposes.

the rom and IWM chips look fine the sockets are clean. I can try reflowing some of those rusted joints.

 

[marcocet]

.

 

[bibilit]

is the reset switch doing something ? Can be stuck also.

 

[marcocet]

is the reset switch doing something ? Can be stuck also.

Nothing seems to happen when i press it.

The reset button shows 450 ohm not pressed and 0 when press so seems to be working?

The Interrupt shows 3750 ohm when not pressed in though? Is 450 for the reset button too low?

also interupt button may be broken as it doesnt change resistance when pressed

 

[richmacr]

Yea im getting all the necessary voltages on the logic board from J12 and on the floppy connector.

12 volts is around 13.5 now which i didnt think was the case before. Is the 12 volt rail used for chips themselves or just HDD/FDD drive?

13.5V is high - not sure exactly what would cause that (power supply issue?). Usually the problem is the opposite with voltage too low. I think most (maybe all) of the chips would run off 5V.

At this point, it really could be anything wrong with the logic board.

May be worth taking a close look with a magnifying glass on backside to see if there are any broken solder joints, and on the component side to look for broken or corroded traces or components.

After that, I'd go through the diagnostics in a systematic way. For example, follow the algorithms for "dead sets" in the Larry Pina repair books.

Good luck!

 

[marcocet]

13.5V is high - not sure exactly what would cause that (power supply issue?). Usually the problem is the opposite with voltage too low. I think most (maybe all) of the chips would run off 5V.

At this point, it really could be anything wrong with the logic board.

May be worth taking a close look with a magnifying glass on backside to see if there are any broken solder joints, and on the component side to look for broken or corroded traces or components.

After that, I'd go through the diagnostics in a systematic way. For example, follow the algorithms for "dead sets" in the Larry Pina repair books.

Good luck!

Yea im not sure why it is that high. I didnt think it was that high when i measured previously

Yea I will do that and look closer for traces

Oh interesting i didnt realize there were books other than dead mac scrolls. I will take a look at the dead sets section!

Thank you !

 

[richmacr]

Yea im not sure why it is that high. I didnt think it was that high when i measured previously

Yea I will do that and look closer for traces

Oh interesting i didnt realize there were books other than dead mac scrolls. I will take a look at the dead sets section!

Thank you !

Yeah you could also check out: https://vintageapple.org/macbooks/pdf/Macintosh_Repair_&_Upgrade_Secrets_1990.pdf
and https://archive.org/details/macclassicse00larr

 

[marcocet]

Yeah you could also check out: https://vintageapple.org/macbooks/pdf/Macintosh_Repair_&_Upgrade_Secrets_1990.pdf
and https://archive.org/details/macclassicse00larr

Yea sorry I meant I would check that out. I didn't realize the author had more books other than dead mac scrolls.