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Powerbook 170 not powering up

bibilit

Well-known member
I have been handed a Powerbook 170 to have a look at it.

The Powerbook was not powering up and obviously the PSU connector was shorted (my replacement PSU included a LED, and this was flickering when connected)

Under the Logic Board, a diode was shorted (D16) but it was impossible to find a label on it.

Fortunately, Ferrix97 posted a video with this same problem, giving a valid substitute (1N4007)... the Powerbook booted right away.

probably someone used a power brick with inverted polarity at some point.

 

Tonata

New member
Hi,

I am trying to repair powerbook 145 with 7.5V, 2A input.
What was the specification of the original diode? I have 1n4004 in my possesion.
Do these diodes 1n4000 do a good protection next time someone plugs a bad power supply? I think these diodes have very high voltages in the datasheet or at least the 1N4007. What is the best replacement?

I have the impression that the diode should be BZX85C13 Diode zener 13V 1W. What do you think?
 
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mmu_man

Well-known member
These 1N400x are meant as rectifiers, they can have high reverse voltage (400V for 1N4004, 1000V for 1N4007) and can forward 1A (50A surge), so probably enough to trip PSU's short circuit detection if there's one for reverse polarity, but if not they'd still blow up anyway. It's odd they didn't put a fuse in line.
As for over-voltage they aren't zener so wouldn't help there.

As for the BZX85C13 I'm not sure it'd be enough for reverse polarity though. And even for normal polarity, if it gets 15V I'm not sure it could dissipate well…
 

Tonata

New member
Hi,

Thanks! I am not an electronic guy, just an enthusiast. Can you recommend a proper replacement?
Im my case the power suppy is 7.5V, 2A which I think is different from the powerbook 170.
 
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mmu_man

Well-known member
If only we had schematics for those…
I'm not sure what the original intent is for this diode, I'd have to open one of the powerbooks I have here that needs fixing but I don't have the time right now. If it's just for reverse polarity protection any of those 1N would do I suppose. Not sure about overvoltage, if it's a concern or not. I don't think they'd have used a zener for actual regulation though, so if you trust the power supply you have you can probably go for a regular diode.
 
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