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Annoying coil whine coming from Powerbook 100

adzq88

Member
Hi again!

My second laptop project was to fix a badly cap leaked Powerbook 100. So far I was able to make it to work with capacitor replacement and the computer became usable again! :) I also did a comprehensive cleaning procedure for this laptop. I'm going to max out the memory with Siliconinsider's beautiful purple RAM module. I was also planning to install an internal version of BlueSCSI (or SCSI2SD?) for hard disk replacement. This laptop came without an original HDD.

One thing that I noticed after of little use is that the Powerbook 100 is emitting an annoying high-pitched sound when it is powered. I was able to locate the area where that annoying sound comes from. It is near to battery area, on the right side of the motherboard. Some SMD coils are laying around on this area of the motherboard. I wonder if I could fix this coil whine issue by replacing these old problematic coils with newer ones to eliminate the coil whine? Does anyone here know what are the correct values for these SMD coils? I suppose these kinds of components are still available from the electronics part store like DigiKey, Mouser, etc. Has anyone done here also an SMD coil replacement in addition to basic SMD recapping?
 

adzq88

Member
I've been thinking about coating it... Should I use hot glue? But I'm wondering if this coating solution is a permanent fix for this coil whine issue or not?
 

ymk

Well-known member
I'd still go with a conformal coating or lacquer over hot glue.

It will penetrate better, trap less heat and won't soften when warm.

I don't see a reason why it wouldn't be permanent.
 

Cedsrepairs

Well-known member
If you have that, I would have a look at the shape of the DC voltages with an oscilloscope, just to be sure the power module is not sending you too much AC together with the DC.
ALternatively, try a different powerbrick (I use cheap amazon multi voltage one, set at 8v on a PB100)
 

adzq88

Member
Good to know! At the moment, I'm using a brand new 7,5 volt DC (2,5 A) power supply instead of the original Apple PB 100's now. The original DC power bricks voltage range fluctuates way too much (measured by a multimeter, the range is between 5-9 volts), thus making it unstable and unreliable for any use with the PB 100. I've got erratic behavior (like random resets, HDD not spinning up) with the Powerbook 100 by using the original DC power supply. So I bought a total new DC power supply.

Unfortunately at the moment, I don't have a way to test the voltage fluctuations with an oscilloscope, even though it would interesting to check it! The same happens with a bit powerful version of the Portable's white power supply. Both DC's seem to be too old now nowadays.

I'm still considering swapping the old SMD coils to new ones. Because I don't have original schematics available at all, I don't know their values. Perhaps someone here on 68klma has access to the schematics of Powerbook 100 (and even for the older Portable one!)?
 

techknight

Well-known member
or you can just get old like I have, and you cant hear it anymore. haha. I cant hear the TV flybacks anymore either. quite nice actually.
 

adzq88

Member
But I hear that high-pitched noise :( I can still hear old CRTs (like TVs) if they are turned on...
 

CC_333

Well-known member
I had been working on a Mac Plus analog board recently, and I could hear a terrible whine coming form it.

Normally operating Pluses (and other CRTs) don't do that, I find, so I guess I will hear it if it's loud enough.

c
 
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