Older computer (90's Mac) troubleshooting

[Mattata]

Hey y'all 

My friends told me to come here to ask for assistance with this. I'm not sure if anyone will be able to help, but anything is appreciated

So, I am currently in possession of a Macintosh LC 520: https://en.wikipedia.org/wiki/Macintosh_LC_500_series

It is in pretty good shape, for sitting in an attic for who knows how long. There is yellowing of the plastic, some rusty corners on the inside shell, and the inside was dusty (until I cleaned it off of course). Everything seems intact: no broken pieces, no wires disconnected/ without something to plug into. I've tested to power supply cable and it works like a charm, yet if i plug the computer itself in and turn it on, it gives off that quick electric whir of the CRT turning on, but that goes away a second later, and then no response from it past that. Subsequent attempts do not bring back that whir again unless I leave the computer unplugged for at least 10 mins. 

So, any tips on trying to find out whats going on with this thing? I'd really like to see it work again. Again, anything helps, thanks in advance!

[Master Disaster]

Probably a dead power supply tbh though it's kind of hard to say for sure. With these older systems its very usual for hardware to die, I mean the thing is 20ish years old by now and unless you've got a second donar machine or spares lying around it's not easy for you to work out what died.

[KarathKasun]

Blown/leaking capacitors, probably the bulk caps in the power supply.  Honestly, I would replace every electrolytic/can capacitor in the system at that age.

[Radium_Angel]

21 minutes ago, Mattata said:

Hey y'all 

My friends told me to come here to ask for assistance with this. I'm not sure if anyone will be able to help, but anything is appreciated

So, I am currently in possession of a Macintosh LC 520: https://en.wikipedia.org/wiki/Macintosh_LC_500_series

It is in pretty good shape, for sitting in an attic for who knows how long. There is yellowing of the plastic, some rusty corners on the inside shell, and the inside was dusty (until I cleaned it off of course). Everything seems intact: no broken pieces, no wires disconnected/ without something to plug into. I've tested to power supply cable and it works like a charm, yet if i plug the computer itself in and turn it on, it gives off that quick electric whir of the CRT turning on, but that goes away a second later, and then no response from it past that. Subsequent attempts do not bring back that whir again unless I leave the computer unplugged for at least 10 mins. 

So, any tips on trying to find out whats going on with this thing? I'd really like to see it work again. Again, anything helps, thanks in advance!

As the others have said, most likely a bad/failing PSU with some blown caps to add into the mix. Being in an attic has done it no favours...

[Ace McPlane]

19 hours ago, Mattata said:

Hey y'all 

My friends told me to come here to ask for assistance with this. I'm not sure if anyone will be able to help, but anything is appreciated

So, I am currently in possession of a Macintosh LC 520: https://en.wikipedia.org/wiki/Macintosh_LC_500_series

It is in pretty good shape, for sitting in an attic for who knows how long. There is yellowing of the plastic, some rusty corners on the inside shell, and the inside was dusty (until I cleaned it off of course). Everything seems intact: no broken pieces, no wires disconnected/ without something to plug into. I've tested to power supply cable and it works like a charm, yet if i plug the computer itself in and turn it on, it gives off that quick electric whir of the CRT turning on, but that goes away a second later, and then no response from it past that. Subsequent attempts do not bring back that whir again unless I leave the computer unplugged for at least 10 mins. 

So, any tips on trying to find out whats going on with this thing? I'd really like to see it work again. Again, anything helps, thanks in advance!

Yea, probably a dying power supply, but open it up and have a look.

Maybe something is just loose like a plug or a PCI card or something.

In my experience with old computers, never assume anything without first opening it up and poking around..

Lol, I fixed a powerbook 180c by dropping it once so anything goes.

If it has any blown or swollen capacitors though, either replace them or ditch the computer because that would be a fire hazard to keep running.

[Mattata]

@Master Disaster @KarathKasun @Radium_Angel @stateofpsychosis thank you all for the responses. I took a good look at the capacitors, none look blown, but i will still have to test them once i get my hands on a DMM. Ill post some pictures to give some insight on what exactly im working with here. So, for now, i got 2 questions:

1) theres this dried glue-esque paste on some of the capacitors, is that actually glue, or the capacitors leaking? (Do note that none of them have that blown-top look to them)

2) i have no clue where the PSU is om this thing. Presumably its whatever is under this small metal box next to the power switch, but i want some knowledge before i stick my hands in there

Thanks again for your help

[Mattata]

Also, i apologise for my lack of knowledge on all this, im still in the process of learning from helpful folk like you

[Ace McPlane]

7 minutes ago, Mattata said:

@Master Disaster @KarathKasun @Radium_Angel @stateofpsychosis thank you all for the responses. I took a good look at the capacitors, none look blown, but i will still have to test them once i get my hands on a DMM. Ill post some pictures to give some insight on what exactly im working with here. So, for now, i got 2 questions:

1) theres this dried glue-esque paste on some of the capacitors, is that actually glue, or the capacitors leaking? (Do note that none of them have that blown-top look to them)

2) i have no clue where the PSU is om this thing. Presumably its whatever is under this small metal box next to the power switch, but i want some knowledge before i stick my hands in there

Thanks again for your help

Yes, that small metal box with the power switch is the PSU, but don't open it or touch anything inside of it. The components in those are dangerous even when unplugged. If you do have a bad PSU, the only course of action is replacing it which brings up a whole host of other questions on what you should replace it with. Maybe better answered by someone else who has done it before. With this old of a machine, I'm really digging at dinosaur bones trying to remember anything  

 

The good news is that the glue on your capacitors looks fine to me.

What comes out of capacitors is yellow or orangish so I think you're good.

It looks like hot glue to me to be honest.

I could be wrong though. Wait until more people comment to be sure

[Master Disaster]

34 minutes ago, Mattata said:

@Master Disaster @KarathKasun @Radium_Angel @stateofpsychosis thank you all for the responses. I took a good look at the capacitors, none look blown, but i will still have to test them once i get my hands on a DMM. Ill post some pictures to give some insight on what exactly im working with here. So, for now, i got 2 questions:

1) theres this dried glue-esque paste on some of the capacitors, is that actually glue, or the capacitors leaking? (Do note that none of them have that blown-top look to them)

2) i have no clue where the PSU is om this thing. Presumably its whatever is under this small metal box next to the power switch, but i want some knowledge before i stick my hands in there

Thanks again for your help

This will sound odd but smell the caps, electrolytic fluid smells fishy and is a very noticeable smell.

 

Looking at the PSU I think you'll have a hard time replacing it. Do you have access to a multimeter? How familiar are you with board diagrams?

[KarathKasun]

Caps that old can fail internally without bulging or leaking.

 

Another culprit could be the fly-back transformer used as the HV power source for the CRT.  It should be what that huge red wire connects to on the board.