Author Topic: SMD component identification (Powerbook 3400c motherboard/PSU input)  (Read 177 times)

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Offline lausvi

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I have an unknown condition Apple Powerbook 3400c laptop from around 1997. It came without PSU and told to be non-working. I bought a 2nd hand PSU. When I plug it in and press the power button, I hear a faint crackle from the speaker, then silence, and after few seconds another crackle. Sounds like it's trying to power up but fails and repeats.

I haven't been able to find schematics for the model. I have been looking at the board and noticed that there is a charred 3-pin component on the board, right next to the PSU connector. It's labeled DZ4 (zener diode?). So pretty much the same as described in here (

Here is how my board looks right now:

I found some nice photos of how the board should look: The 5th photo shows the component nicely. There DZ4 (down-right to the PSU connector, next to a small 000-resistor, which measures fine after cleaning) appears to be marked "6H8" (or is it the other way round, "8H9"?) Or is it B, not 8?

Is there any way to figure out what that component is (in order to get a replacement)?

(Yes, I am mostly going blind here, and just looking at the obviously burnt thing first). Would be a nice machine to get up and running  :)
« Last Edit: January 31, 2020, 05:58:14 pm by lausvi »

Offline Dacke

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Re: SMD component identification (Powerbook 3400c motherboard/PSU input)
« Reply #1 on: February 01, 2020, 04:17:14 pm »
Looks like it may be connected between two pins on the DC jack but difficult to tell,  possibly a protection diode?  I would check to see if it's shorted and if it is,  remove it and see if the machine boots.

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