Powerbook 180 ressurection attempts help!

[Genjoke]

Hi folks. I got an "as is" Powerbook 180. It was extreamly cheap for Brazilian standards: R$200 what translates today to US$41.

I tried to power it on with a 7.5V center positive power supply. Nothing. I noticed a little of a burning plastic smell on the power supply connection.

Next step was to open it:

• HD is missing (no problem)
• No apparent battery leakage.

Problems I noticed:

• Components near the power input (voltage regulators?) are getting BURNING hot:

Now i resource to the mac gurus to point me in the direction of trying to repair it!

Do I have to replace only the hot components? What else should I test?

As always thank you very much for any help.

 

[Daniel Hansen]

A couple things I'd check quickly:
1. the fuse F1 down by the battery terminals (though I don't think it would cause components to heat up?)
2. there's a zener diode on the reverse side, right under those IC's - D15 = if it's shorted it gets hot ... seems to happen quite a lot.

I'd also suggest checking for shorts on the +5V and -5V rails --- if U3 and U4 are getting hot, maybe there's something there, as they are the -5V regulators (pin 11 on each, pin 5 is ground).

 

[Genjoke]

A couple things I'd check quickly:
1. the fuse F1 down by the battery terminals (though I don't think it would cause components to heat up?)
2. there's a zener diode on the reverse side, right under those IC's - D15 = if it's shorted it gets hot ... seems to happen quite a lot.

I'd also suggest checking for shorts on the +5V and -5V rails --- if U3 and U4 are getting hot, maybe there's something there, as they are the -5V regulators (pin 11 on each, pin 5 is ground).

Thanx!!

I know near to zero about electronics.

I probed D15, with a multimeter, in continuity mode, and it beeped. F1 also beeped but I suppose thats ok for a fuse.

I understand D15 is shorted, then.

Should I replace only this diode and test the system again?

Would you be kind enough to point me to the right replacement component?

Thanx again!

 

[Daniel Hansen]

Sorry for the late reply, I was away all weekend.

You should be able to test / run the system with the diode removed as it's merely there as a means of protection... you should test the diode out of circuit anyway to be sure you're not getting a false result due to a short to ground elsewhere in the circuit. But if you can boot the machine without the diode, then that pretty much narrows it down.

If the diode is indeed shorted, its exact replacement is difficult to find at that package size... the exact replacement in terms of properties is the DDZ13B (https://www.digikey.ca/en/products/detail/diodes-incorporated/DDZ13B-7/700105) but it's a bit smaller than the original... but folks have managed to make it fit by 'extending' the leads and/or pads in some fashion.

 

[Genjoke]

Once again thank you very much!!!

I removed the diode and confirmed it was indeed shorted.

I kinda reassambled the powerbook to test it, and it chimed!!!

I could not test it further because the screen is cracked. I didnt know if the crack was superficial or if it affected the screen. It does, I got only a partial image of the folder with the blinking question mark.

Next steps: replace the diode (easy) and find a new screen for the PB .

If anyone has this spare part to sell I'd be happy to buy it!