PowerBook 540c Daughtercard misbehaves

[AEChadwick]

I got a good deal on a PowerBook 540c "for parts", i meant to strip out a couple pieces, but the screen is immaculate and the case is good (hinges still strong!) so, of course, i set about trying to fix it. (i have a box of 500-series pieces, I figured i must have whatever the machine needed...)

Pressing the power button would "start" the 540c—you could heard the hard drive spin up—but no chime, and the screen stayed dark.

to establish baseline, I removed the 16MB RAM card that came with the 540c... and the machine booted with the 33/66 processor using just the onboard 4MB RAM. It got to the desktop and ran fine.

I tried a couple known 16MB cards, and the 540c reverted to starting-but-not-booting: no chime, no screen.

I swapped out the 33/66 daughtercard with a 25/50 from a 520c, and the machine booted fine. So apparently the problem is the 33/66 daughtercard? the heart of the 540c. I cannot see any visible damage of any kind, no bent pin or scratch or crack. I’m stumped.

In the meantime, it runs fine as a 520c (with an active matrix screen—does that make it a 520ce…?).

 

[AEChadwick]

one more thing... whatever controls the trackpad seems to be possessed. See attached; the cursor does not actually track the movement it jumps and skips crazily. a mouse works fine though the rear serial port.

Here’s the kicker: i replaced the entire upper case with a spare (from a 520c)--ie., replaced the entire trackpad assembly--and the behavior stayed exactly the same. So, it’s not the trackpad itself...? it’s somewhere on the motherboard? hooooooo boy.

*FWIW my fingers are clean and dry and work fine on every other trackpad in the house

 

[3lectr1cPPC]

In the meantime, it runs fine as a 520c (with an active matrix screen—does that make it a 520ce…?).

If you want to give it an unofficial name I’d call it a 520ct. Apple never used the T suffix, but Toshiba and others did to denote an active matrix screen. Really wish apple called the 520c the 520cs though. Would have made a LOT more sense with what other manufacturers did for passive color, and they used cs for the 5300 and 1400… Anyways, 520ct makes more sense to me than 520ce, as the 5300ce had a jump in screen resolution not type, and also was faster.

Can’t offer much help with either of your issues though, sorry…

 

[AEChadwick]

If you want to give it an unofficial name....

Can’t offer much help with either of your issues though, sorry…

no worries, thanks for chiming in—i’m glad my naming suggestion provoked some funny inspiration.

*full disclosure, i noted “my fingers are clean and dry” because of your own trackpad situation

 

[3lectr1cPPC]

Right… yeah yours does look a bit different from my issue. I’d check the condition of the trackpad connector on the logic board, if it’s got bad solder and such. Perhaps some line is dodgy or broken.

 

[Fizzbinn]

I swapped out the 33/66 daughtercard with a 25/50 from a 520c, and the machine booted fine. So apparently the problem is the 33/66 daughtercard? the heart of the 540c. I cannot see any visible damage of any kind, no bent pin or scratch or crack. I’m stumped.

I had this behavior on a 540c but in my case it cropped up after I was testing a couple other RAM modules. I had somehow bent a couple pins on the CPU daughter card RAM module connector. One was only off a bit the other was mashed over at a ~45 degree angle. I very gently and slowly bent the pin back and all was good. I'm now extra careful when working on stuff with these types of connectors.

Looking at your first picture, pin 70 looks suspect... pretty sure it was 68 and 70 on my CPU daughter card I had to fix.


L

 

[imactheknife]

I had this behavior on a 540c but in my case it cropped up after I was testing a couple other RAM modules. I had somehow bent a couple pins on the CPU daughter card RAM module connector. One was only off a bit the other was mashed over at a ~45 degree angle. I very gently and slowly bent the pin back and all was good. I'm now extra careful when working on stuff with these types of connectors.

Looking at your first picture, pin 70 looks suspect... pretty sure it was 68 and 70 on my CPU daughter card I had to fix.

View attachment 56885
L

Yup, had bent pin in ram slot of 520 / 540. So check for bend of misaligned pins

 

[AEChadwick]

Looking at your first picture, pin 70 looks suspect... pretty sure it was 68 and 70 on my CPU daughter card I had to fix.

you magnificent creature, this is why i posted pictures and why i appreciate this forum. I got an alert while drinking wine, i seriously said "OMG BABY I GOTTA GO DO A THING—” grabbed the tweezers and magnifying glass and it worked, you were 100% correct.

PowerBook 540c restored / no special rename needed.

tl;dr check the pins, kids

 

[Fizzbinn]

you magnificent creature, this is why i posted pictures and why i appreciate this forum. I got an alert while drinking wine, i seriously said "OMG BABY I GOTTA GO DO A THING—” grabbed the tweezers and magnifying glass and it worked, you were 100% correct.

PowerBook 540c restored / no special rename needed.

tl;dr check the pins, kids

LOL

Very glad that was it and an easy fix for you. Everybody helping each other out when they can is what makes the community great! IMHO It feels just as good if not better to be able help someone as it does to find a solution to a problem you are having.

 

[3lectr1cPPC]

Amazing!!! Will note this fix down for the future if I see someone with issues again.

Have you gotten the trackpad fixed though?

 

[AEChadwick]

Have you gotten the trackpad fixed though?

will tear machine apart (again) tomorrow and search (again) for any damage on the Motherboard; will update with results. (see prior, already happy hour here)

 

[3lectr1cPPC]

Hahaha, have fun! Always feels nice to fix a problem like that

 

[AEChadwick]

Trackpad connector at J16 is immaculate. No insight there.

 

[3lectr1cPPC]

Ah it’s one of those style. No idea then other than checking for broken connections around that area.

 

[AEChadwick]

Troubleshooting Trackpad from the PowerBook 500 Series Service Manual.

by benefit of spare parts, i have done every step except #7. Trackpad completely unchanged, still twitchy.

(I don’t have another motherboard... so the nuclear option is off the table; sigh.)

 

[AEChadwick]

i have a busted motherboard from a 520 (it burned itself a hole in one of the ICs near the battery, took out a couple capacitors on the way).

i was able to use the bad mobo to confirm continuity on trackpad pins.

after [way too much] tracing lines, i found a bad pad:
trackpad PIN 4 is supposed to connect over to that via near D15, passing through the test point under R97.
on the 540c motherboard, the test point that had corroded, leaving the route broken.

I used a tiny bit wrapping wire to finish the connection... (much smaller and finer soldering than i ever do)

...and now the trackpad works perfectly.

TL;DR sneaky bit of corrosion, fixed with a bodge

 

[3lectr1cPPC]

Nice! I figured it had to be something like that - excellent troubleshooting throughout!

 

[MacUp72]

a testing point, thats good to know..you have a nice glass, I only have my iphone for magnifying that much.
you can use a bit of pcb varnish over the wire to secure it from shorting.
I had a hard time soldering a tiny silver wire into a via hole because of a ripped pad..

 

[AEChadwick]

you can use a bit of pcb varnish over the wire to secure it from shorting.

it's wrap wire! it's actually covered with enamel; i scraped off barely half-a-millimeter at each end. wrap wire is my preferred bodging wire because it's inherently secure from shorting.