LC Power Supply - Died after recap+load

[Phipli]

I had some 1.44MB floppies that I tried to format but the machine always failed at “re-verifying format”, not sure why.

Might need cleaning. Have you cleaned the heads? Take care - don't lift them too far appart or catch anything on them in a way that causes them to go misaligned. A gentle rub with a cotton bud or kitchen towel with IPA should do it.

Should I really continue bothering with a 30 year old hard disk that’s doomed to fail sooner or later?

We all die some day, but I almost exclusively use spinning SCSI disks. They're not /that/ unreliable.

They can be tricky to format right. You can easily soft brick them by damaging they system folder, or the disk driver, or formatting with the wrong tools... or a power cut or bad luck.

I suspect there are a lot of good drives sat in drawers because they got corrupted.

A pack of bad disks is another option. I bought a pack on eBay and (almost) every one wouldn't format in a known good drive.

 

[luRaichu]

That’s interesting, most everyone out there seems to hate old SCSI drives like the Antichrist. I’ve never heard someone vouch for them until now. As for the floppy drive, I have definitely cleaned the heads to a pristine state (Remember, this drive was caked with dust). However, I think I remember lifting the top arm almost vertical to try to clean it, but it was already good. So hopefully I didn’t screw up anything there. When I push the top arm down to the head on the bottom they seem to match up perfectly so I doubt there’s a misalignment, but I’m not familiar with floppy drives either. (Is it ok for the top head not to touch the magnetic media upon initial read?)
Another issue I’m having is that the floppy drive really likes to inject without a disk sometimes. Then in gets into a loop where it “reads” a nonexistent disk, ejects, and injects nothing again. I’ve found a remedy for when this happens but I haven’t figured out how to cure it, and I haven’t been able to reliably replicate it either. Also, I found someone on Reddit who had the same thing happen to them but I’m unable to relocate that post.
Also, for some reason when I start the machine I occasionally get nothing but *tick tick tick tick tick…* from the PSU. I’m not sure how to fix this, or replicate it! It just sometimes stops working, and occasionally starts up again without my intervention. So far I’ve done things like shorting 12v to ground or touching the PSU’s shell (ground) while standing on my carpet (when I do this, the ground light on my X-outlet surge protector lights up) and they seemed to help. I’m a little confused on why the ground light on my surge protector multi outlet thing doesn’t normally appear when I use grounded equipment.

A pack of bad disks is another option. I bought a pack on eBay and (almost) every one wouldn't format in a known good drive.

You call this an option? Why’d you buy a bunch of bad disks if you can’t even format them? I bought NEW disks and they were the ones I couldn’t format that night. Sorry dude but I just don’t understand.


In the case of the SCSI disk’s failure being down to bad luck, I now have a lucky cat near the machine at all times.

 

[cheesestraws]

There is nothing wrong with old SCSI drives that work. No need to replace them until they stop working.

I’m a little confused on why the ground light on my surge protector multi outlet thing doesn’t normally appear when I use grounded equipment.

You need an electrician. Either the socket-outlet is dud or your house has a whole has bad earthing.

I might gently suggest, in such a scenario, that being the path to earth for 30 year old power supplies might not be the most prudent course of action until you know you've got a working safety earth.

 

[luRaichu]

There is nothing wrong with old SCSI drives that work. No need to replace them until they stop working.

I get you, but let’s say for some reason you decided to type up some super important document on your vintage machine. Then your SCSI drive gives out.
You could call a data recovery company, but it’ll cost you.
So why not replace it with something that’ll (almost) never fail? Sure, SD cards and flash memory for that matter will degrade and corrupt after a certain amount of write/erase cycles, but at the speed a vintage Mac operates at, I doubt it’s a concern even if you made it your daily driver (lol).

You need an electrician. Either the socket-outlet is dud or your house has a whole has bad earthing.

That’s quite a shock to me. I’m actually living in an Airbnb at the moment, and I’ve already been suspecting the presence of some dubious wiring (You get that aura just by walking around the house). However, I’m hesitant to go up to the owner unless I’m sure the whole house has bad grounding. Are there any things besides plugging the surge protector into a different outlet I can test to see how well I’m grounded

 

[cheesestraws]

I get you, but let’s say for some reason you decided to type up some super important document on your vintage machine. Then your SCSI drive gives out.

I've got really bad news for you about the reliability of some SD cards.

If you aren't keeping backups, you're going to suffer from data loss, regardless.

A whole boot image of each machine I have can either be reconstructed in ten minutes or is backed up on the fileserver.

 

[Phipli]

Also, for some reason when I start the machine I occasionally get nothing but *tick tick tick tick tick…* from the PSU. I’m not sure how to fix this, or replicate it! It just sometimes stops working, and occasionally starts up again without my intervention.

This means you have an intermittent short in the system somewhere. This isn't good. Check your cabling, check for lose items on the board, check for lose items or items touching inside the PSU.

One of my laptops arrived with a screw just floating around inside on the logic board. Sigh.

So far I’ve done things like shorting 12v to ground

Argh! Why! That's not a great thing to do?!

You call this an option? Why’d you buy a bunch of bad disks if you can’t even format them? I bought NEW disks and they were the ones I couldn’t format that night. Sorry dude but I just don’t understand.

An option as in, out of the selection of things that might be wrong. Option 1 : someone set fire to the computer, Option 2 : It got thrown in a river, Option 3 : Aliens stole it

I didn't intentionally buy bad disks and I'm not suggesting you do, I'm suggesting that you might have.

I get you, but let’s say for some reason you decided to type up some super important document on your vintage machine. Then your SCSI drive gives out.
You could call a data recovery company, but it’ll cost you.

1) Don't do super important work on 30 year old computers
2) This is what backups are for - if you are doing super important work, you should be saving to two locations, even on a modern computer. I've lost more disks in modern computers than vintage ones.

You need an electrician. Either the socket-outlet is dud or your house has a whole has bad earthing.

I might gently suggest, in such a scenario, that being the path to earth for 30 year old power supplies might not be the most prudent course of action until you know you've got a working safety earth.

@luRaichu : What cheesestraws said

 

[luRaichu]

Argh! Why! That's not a great thing to do?!

I’m really sorry about that!! I’m not an electrician at all. The first time I shorted 12v to ground was an accident, and after I did the PSU started working again, so I thought I was doing something right. I’ve shorted things that make me wonder why the computer still works and I’m saving you the cringey details.
I’ll go look over the PCBs soon.

Also, I measured the 12v line from the PSU. it’s actually giving 13.39v. Should I be worried?
On top of that, occasionally I get a sad mac when booting. It’s always 0000000F, 00000001. I really think this is something related to the floppy drive.

 

[Phipli]

On top of that, occasionally I get a sad mac when booting. It’s always 0000000F, 00000001. I really think this is something related to the floppy drive.

0000000F,00000001 means that the ROM checksum failed.

 

[Phipli]

Also, I measured the 12v line from the PSU. it’s actually giving 13.39v. Should I be worried?

Whats the 12v loaded with? Is there a hard disk plugged in?

If it hasn't got a hard disk connected, I'm not really surprised. It is likely to float high with minimal loading.

If a spinning hard disk is plugged in, that is a bit higher than I'd expect.

 

[cheesestraws]

It’s always 0000000F, 00000001. I really think this is something related to the floppy drive.

Why do you think this? Have you looked up what this error means? 0x0F 0x01 is not a floppy-related error code

You are making wild guesses and suppositions and in the case of the PSU taking your life in your hands in doing so.

Please slow down, diagnose one thing at once, and do it safely.

 

[Phipli]

If shorting it made the PSU behave, there is a possibility that you have recapped with the wrong type of capacitors and the voltage is struggling to stabilise.

How did you pick your capacitors?

 

[Phipli]

Also,

Do you have a capacitance tester? After leaving the power supply unplugged for a day, dismantle it carefully - don't touch the high power end until you have touched something metal between the two pins on the big capacitor for safety. Nothing should happen after a day of waiting, but its always a good last "lets not put 200V through my heart check".

Desolder the big capacitor and check its capacitance - is it within about 25% of its original value?

 

[luRaichu]

I need some quick help with something- I made a boot disk for the LC using a USB floppy drive and dd. I pop it into the LC and it just spits it back out as bad. The top head isn't touching the magnetic media as it should.

 

[joshc]

The manual-inject drives are not really very repairable, they are quite different to the earlier auto-inject ones. If you have no way of knowing if that drive works, I'd assume it doesn't. Which floppy image did you use and which system software version is on that image?

Having something for external SCSI you can boot from is very useful when dealing with these machines. That could be an external CD-ROM drive, an external SCSI2SD or an external spinning SCSI disk.

As for the PSU stuff, I would advise against PSU repair if you don't have much experience or don't have some idea of the risks involved - some of your previous posts suggest you don't, and it's really best for your own health and safety to avoid that type of work in that case. There are safer ways of doing this - like enlisting the help of someone who is experienced, or purchasing a spare machine with a known working power supply.

But the best advice I can give is, take your time. There's no need to rush, planning ahead and researching lots can help a great deal with this hobby.

 

[luRaichu]

The manual-inject drives are not really very repairable, they are quite different to the earlier auto-inject ones. If you have no way of knowing if that drive works, I'd assume it doesn't. Which floppy image did you use and which system software version is on that image?

I believe the LC came with an auto-inject drive, like the ones shipped with the original Macintosh. I used System 6.0.5L for compatibility and got it from WinWorld: https://winworldpc.com/product/mac-os-0-6/system-6x
I also tried Disk Tools from System 7.1.1, which I also got from WinWorld.
And yes, I did strip the headers and such with

bs=84 skip=1

(I'm using Mac OS 10.13 to make boot floppies and I do have good experience with the command line).
I think the problem is a spring that had been stretched and is no longer pushing the head against the disk. If not, I'll buy either a Zip CD-ROM drive or have a BlueSCSI built by JLCPCB. I could also try connecting the mechanical SCSI hard disk to a modern computer, but the SCSI to USB cables on the market seem to have a different shape than anything used in a desktop Mac.

Can the LC boot from a Zip CD drive without any drivers?

 

[Phipli]

Can the LC boot from a Zip CD drive without any drivers?

Unlikely - its best to use an Apple branded drive to be certain.

I've never seen a Zip branded SCSI CD drive. I have a USB ZIP branded CD drive though.

As an aside, you can boot from zip disks if they are prepared correctly. Personally I'm not a fan of Zip drives because they are dataloss manifest.

 

[joshc]

I believe the LC came with an auto-inject drive

Sorry, yes, you're dealing with an original LC not a 475! Not sure why that was in my head...

 

[Phipli]

Sorry, yes, you're dealing with an original LC not a 475! Not sure why that was in my head...

Because 475s are awesome?

 

[joshc]

Because 475s are awesome?

Yeah, the LC doesn't really exist in my brain anymore for this reason.

 

[luRaichu]

Okay so I'm pretty sure the floppy drive is toast. I just could never get the machine to boot off a floppy. I tried pushing the top head down onto the magnetic disk with my finger but it still didn't boot. So I guess I gotta buy an external BlueSCSI! I found that it'd probably be cheapest to get the BlueSCSI PCB with SMD parts presoldered, buy the Pi and such separately, and solder the DB25 connector and Pi headers myself.

If shorting it made the PSU behave, there is a possibility that you have recapped with the wrong type of capacitors and the voltage is struggling to stabilise.

How did you pick your capacitors?

I used same value capacitors from DigiKey.

Do you have a capacitance tester? After leaving the power supply unplugged for a day, dismantle it carefully - don't touch the high power end until you have touched something metal between the two pins on the big capacitor for safety. Nothing should happen after a day of waiting, but its always a good last "lets not put 200V through my heart check".

Desolder the big capacitor and check its capacitance - is it within about 25% of its original value?

I don't have a capacitance tester unfortunately, and I don't really want to attempt anything that invasive (desoldering) on the high voltage side anyways.

The PSU has been a little touch and go- but I've made some observations.
The Ground light on my surge protector seems to be an indicator of the PSU's health(?). If plugging in the system gives a bright Ground light, then evil things will happen inside the PSU. Usually it'll boot, get to the floppy disk icon, then hang or give a sad mac (almost always the same code I've mentioned before) and death chimes. Then restarting from the sad mac will typically result in nothing but ticking. The voltages can be <1v and/or fluctuating ~½v. From there it takes some voodoo to get the PSU restarted. Discharging the fat capacitor seems to work? I'm not gonna say I'm sure.
If the PSU is healthy the ground light will be very dim. I've found leaving the system running for hours helps reliability & normalizes the 12v rail (startup -> ~13.30v. hours later -> ~12.02v). which leads me to believe that maybe the large cap could be faulty. Let me know what you think.