Macintosh LC SCSI whining?

[Sherry Haibara]

Hello guys!
I've been given a not-recapped Macintosh LC that's behaving strangely. 

It powers up and chimes very happily (though the volume is low, so it's in need for a recap soon), it boots without an issue from an external SCSI drive, it recognizes internally connected SCSI drives (though, if they are bigger than 4 GB, it complains that a 68040 is needed to handle them)... but all along, it makes a very strange whining noise.

It's a high pitched noise, like a whistle of some sort, that gradually goes down in tone until it eventually stops - it's very annoying, and most of all it changes tone when the internal SCSI drive is being accessed. I almost fear turning it on, I don't want to damage anything on the logic board!

What could it be? Is it something caps-related too? I've never experienced such a behavior on any of my other 68k Macs!

 

[Elfen]

Try booting from a floppy and then time from boot time to when the whining stop if it starts. It could be a drive bearing going or the lubricant beginning to flow when the bearing gets hot enough.

 

[Sherry Haibara]

Hi Elfen!
Thanks for your suggestion, but I don't think it's a hard drive issue - I tried booting the system with no hard drive connected to the internal SCSI bus, but the whining still occurs. It sounds like an electrical noise of some sort, so I don't think it's the fan, either, but I'll investigate more thoroughly!

 

[unity]

The whine is coming from the onboard speaker not the scsi drive.   Its because the caps are bad and the goo had leaked all over.

Its a pretty common problem across all the LC machines.  I II III.  here is some info to help you re-cap that.

http://maccaps.com/MacCaps/Capacitor_Reference/Entries/1990/10/15_LC_I%2C_II%2C_III_Power_Supplies_2.html

if you plug in some headphones you should still hear the same wine. or if you pull out the Fan/speaker assembly with the computer on. you will notice the noise will go away as well.  but all in all it needs capacitors pretty bad.

 

[olePigeon]

Yep. My LC did the exact same thing.  Went away after recapping.

 

[Sherry Haibara]

Guess it's time for a recap then I had a feeling it was due to caps failing, these machines are pretty much unreliable when it comes to caps due to their age. I feel a little uncomfortable to replace SMD capacitors, so I'll probably leave the work to someone more experienced in electronics than me!

 

[Elfen]

Ferrix97 has made an excellent video series on recapping an LC. Is on his Macintosh LC Restoration Video Series. Post # 11 has him to a recap with regular caps on the board. You do not need to use SMD/SMT Caps to recap a board, but most do because they look good.

Here's Ferrix97's vid post:

https://68kmla.org/forums/index.php?/topic/23469-macintosh-lc-restoration-video-series/?p=243442

Rocking those caps back and forth really works on not stripping your traces!

 

[max1zzz]

i'll second that, i started out using through hole caps, it's much easier than using the SMD parts

 

[MacJunky]

Rocking those caps back and forth

I used to cut smt capacitors with side cutters until I tried twisting. Now I am happy enough grabbing the top with some pliers and twisting while maintaining down-force, keeping the cap centred in it's plastic bottom. It seems to be faster than these videos of people pulling&wiggling, as well as faster than cutting too.I know a lot of people hate uniserver for suggesting this method but it really does work.

 

[olePigeon]

I use 2 soldering irons to do it.  2 cheap $15 irons from Radio Shack and use them like tweezers.  Melt the solder on both sides of the contacts while pushing gently.  The cap will eventually slide off on its own.  You can add a little bit of solder to the pads first to speed things up.

For soldering caps, I use tantalum caps + solder paste.  A dab of solder paste on each pad, put the cap in the goop, then just heat the goop.  It melts and makes a perfect solder joint.  I suck at soldering, and I found it easy to do.

 

[uniserver]

I think as others have said before if you can get the old caps off with out lifting the pads, Whatever way allows you do achieve this is a good way.

If you start ripping pads off then it just will take more time to fix.

 

[Sherry Haibara]

It's fixed!
I shall really thank Ferrix97 here for the wonderful job he has done recapping my LC! 
As it turned out, he lives pretty close to my place - so after almost three weeks spent arranging a meeting, finally I gave him the baby last Saturday to have it fixed. Guess what? On Monday evening it was done!
I also got the occasion to give him my two damaged Macintosh Pluses for troubleshooting, he's a really nice guy and works very professionally for his young age!
I know most people on this forum are US based, but for those who should happen to live in Italy or nearby countries and need a recap, I can strongly recommend him!

 

[olePigeon]

Cool.