POWERBOOK 540C WITHOUT POWER

[gordonIIfx]

I have a powerbook 540c which was sleeping for several years with the power hooked up. I just found that it has dead batteries(about 3v) and the power supply has red and blue leads with 16.4v and orange and black leads with 2.1v. The specs call for two 16.6v sources of power. I think there is a power supply problem which caused the problem, but it seems that either the batteries should be dead or the computer unable to run without batteries. Is it possible that the computer is ok once proper power is supplied? I opened the power supply box and it is complicated, so I don't know where to start to trouble shoot it. Before trying to fix it or replace it I would like to find a way to get power to the unit to verify it is still good. Where do I go now. 8-o

 

[tomlee59]

Well, it sounds like you've verified that there is indeed a problem with the power brick, so it seems reasonable to think that all will be well once you fix it.

As to where to start, the most common failure in these things is a blown filter capacitor. These often fail in a visibly obvious way. You may notice that many (perhaps all) of the electrolytics have dimples or crease lines in the top. These are intended to be points of weakness so that if the capacitor shorts out and overheats, it won't explode. Instead, pressure is relieved controllably by breaking those creases. In the process, the top will bulge. A healthy cap will have a ruler-flat top. So the first step is to inspect the caps carefully. I'm willing to bet that you will find a bad cap.

 

[gordonIIfx]

Thanks for the note of optimism. The capacitors look normal, but one of the vertical coils near the output gets warm while the other stays cold. Would that be expected if one of the caps were bad? The 2 large ones look like they would be the filter caps. Is that right?

 

[aphetica]

Sleeping? For years?

Do you mean you had it plugged in, in sleep mode, for years?

I'm confused. This seems odd to me.

 

[gordonIIfx]

Yep, it was in sleep mode with the blinking green light plugged into power to keep the batteries charged. It was used occasionally during that time.

 

[MacMan]

Try resetting the power manager, see these instructions for how to do this.

 

[gordonIIfx]

I got it back to life! Changed capacitors in pwer brick and they all tested good, but both power sources came back on for some reason, maybe bad solder joint fixed. I manually charged both batteries by hooking them to the good pwer supply until they got warm and showed about 11v. After the pwer supply was working the original good side was still 16.4v and the resurrected side was 15.8v. I then plugged the power supply to the powerbook and after about 15 min it booted up and acted like nothing had happened, except the clock was behind about 4 years. I had forgotten how cute and nice the 540c is. I really appreciate all of the help from MLA.javascript:emoticon('[ ]')

 

[tomlee59]

Congratulations on resurrecting it! Another classic mac saved from the bin...

 

[funkytoad]

Congratulations on resurrecting it! Another classic mac saved from the bin...

Man, it sure feels good to see the forum living up to its original ideals.