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PowerBook Duo 250 recapped but...


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I’ve recapped it, washed the board and it chimes, screen lights up and stayed as it. 
 

There isn’t activity of booting, no sound from the SCSI drive and even I unplugged it there’s no disk icon. It doesn’t do anything after chimes. 
 

Any trace or parts I should be looking at?

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Dreaded Duo blank screen of death :'( No idea if it's a universal fix, but my 280c presented the same symptoms after a recap when I first got it. Here's a thread detailing what fixed mine:

 

 

 

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22 hours ago, sutekh said:

Dreaded Duo blank screen of death :'( No idea if it's a universal fix, but my 280c presented the same symptoms after a recap when I first got it. Here's a thread detailing what fixed mine:

 

 

 

Ok thanks much, I’ll take a look at it 

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On 3/21/2021 at 11:59 AM, sutekh said:

Dreaded Duo blank screen of death :'( No idea if it's a universal fix, but my 280c presented the same symptoms after a recap when I first got it. Here's a thread detailing what fixed mine:

 

 

 

Checked and my DZ6 isn’t shorted. Guess I’m out of luck. 
 

still thank you for sharing your repair.

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I have a couple of these Duo boards too.

 

  • Is it D76 in particular that goes bad or could it be any of these kind of components on the board?
  • Can I test these components on the board with a multimeter or do they need to be taken off first for a proper test?
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6 hours ago, David Goodson said:

I have a couple of these Duo boards too.

 

  • Is it D76 in particular that goes bad or could it be any of these kind of components on the board?

 

I can only speak to my specific application, when my Duo 280c manifested the same symptoms (chime, backlit gray screen, no other activity), I discovered that DZ6 was open and replacing it immediate brought my 280c back to life. If nothing else, it's worth a quick check to rule it out. Pin1 is the anode and pin3 is the cathode. 

 

6 hours ago, David Goodson said:
  • Can I test these components on the board with a multimeter or do they need to be taken off first for a proper test?

 

I wouldn't trust a reading in situ indicating a diode was shorted (could be finding continuity elsewhere on the board), but you should be able to at least rule out that it isn't open as was the situation in my case.

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On 3/20/2021 at 11:59 PM, sutekh said:

Dreaded Duo blank screen of death :'( No idea if it's a universal fix, but my 280c presented the same symptoms after a recap when I first got it. Here's a thread detailing what fixed mine:

 

 

 

 

Oh wow! I didnt even see this. I have 2 or 3 Duo boards that i threw in my junk pile for this reason. they dont spin up the HDD either. 

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Wow. I fixed mine. Same diode. Unbelievable. My diode testing found several that were open but I snagged a diode off of a ruined logic board & replaced my DZ6. I ordered a few from Mouser in case more of them die on me. I also used my ruined logic board to practice removing and installing a diode since I've only done caps so far. Thanks so much for the tips. A duo 280 returns to life with a recap & a diode swap.

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14 minutes ago, David Goodson said:

Wow. I fixed mine. Same diode. Unbelievable. My diode testing found several that were open but I snagged a diode off of a ruined logic board & replaced my DZ6. I ordered a few from Mouser in case more of them die on me. I also used my ruined logic board to practice removing and installing a diode since I've only done caps so far. Thanks so much for the tips. A duo 280 returns to life with a recap & a diode swap.

Nice and wow you are lucky! 

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Posted (edited)
2 hours ago, techknight said:

this would be a first for me. Ive never in my life see a diode go open unless you can see it physically. They typically short. 

 

I agree. Now that you mention it, I recall that my original DZ6 had a hairline fracture I only noticed after discovering it was open. It would be interesting to know what you find with those "2 or 3 Duo boards that i threw in my junk pile for this reason". Given my experience and now David's (even if only fleeting), the Duo blank screen failure mode does appear to have at least some connection to DZ6 (and perhaps other adjacent Zeners?)

Edited by sutekh
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On 5/10/2021 at 7:15 PM, sutekh said:

 

I agree. Now that you mention it, I recall that my original DZ6 had a hairline fracture I only noticed after discovering it was open. It would be interesting to know what you find with those "2 or 3 Duo boards that i threw in my junk pile for this reason". Given my experience and now David's (even if only fleeting), the Duo blank screen failure mode does appear to have at least some connection to DZ6 (and perhaps other adjacent Zeners?)

 

It might be. its been over 10 years, but i remember the machine powering on, but staying at the gray screen, and no HDD would spin up either. I cannot remember if i had a cursor or not, but it just stayed there forever. 

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