PB Duo issue

[techknight]

Just ran into a PB Duo, with an issue I hadn't seen before.

It powers on and chimes, but it shows the grey screen. Never makes it to a mouse cursor, or icons or anything. So i stripped it down to the bare board, removed modem, HDD, and memory expansions, also removed keyboard and mouse. Same thing.

Anyone seen this before? I figure its a hardware failure in the logic board but narrowing it down would be nice. lol.

The one thing I did notice, is the HDD never spins up. So its clearly not getting the ON signal from the SCSI IC.

 

[Trash80toHP_Mini]

Which Duo? Got a Dock or MiniDock to test it with a MultiSync CRT?

I've seen that kind of thing now and again with a couple of 2300c boards, sometimes they don't work, most times they do. Any cap leakage in the tank farm?

 

[techknight]

Nope, everything looks good.

the 5V logic voltage going to the SCSI IC, etc is rock solid. HOWEVER. the 5V is missing from the HDD connector, and i noticed the bus phases toggling up and down repeatedly over and over again like its attempting to find an HDD. But of course its not connected, so it cant. And even if it was, the 5V is missing.

there is a MOSFET that connects that 5V to the main 5V, and its not being told to turn on. And this is handled in the GLU. So who knows.

I dont have a dock handy, and that isnt the issue. the screen comes up to a gray dithered screen. (like all macs do when you first turn them on). But it never shows the black mouse curser. it doesnt make it that far. But it shows the gray screen just before the mouse.

 

[Trash80toHP_Mini]

If you ran it inside a dock to bypass the video system it might work, might not, just a thought.

The HDD not spinning up sounds very ungood, but it should still get to the cursor and :?: without it.

Which Duo?

 

[techknight]

270c

 

[techknight]

I bet the SCSI IC is failing initialization. Only thing that makes sense...

Kinda like the SE/30.

 

[uniserver]

sounds about right,, heat gun it off and see if it progresses.

 

[techknight]

I gotta look in my pile-o powerbooks and parts to see if i have another LB. But in the meantime I could rip off the SCSI IC.

Bad thing is, its one of those integrated SCSI/Serial SCC chips. So i wont have serial or SCSI. However, its worth a shot regardless.

 

[techknight]

Removing the SCSI IC didnt make a lick of difference. Only thing at this point is GLU.

So, only thing I can do is take the 2300c motherboard from my true PB2300 as its missing alot of peices, and a ripped trackpad cable. its missing the side rubbers, all the sccrews, and some other little odds and ends. Maybe even the rear LCD lid as well.

I might take that LB and toss it in here, then sell this one off or something. I already have a Duo 270c upgraded 2300 and i dont need another one. lol.

 

[uniserver]

sorry buddy

 

[techknight]

What are you sorry for? This is the fun part about messing with this crap

If we cant hack mod or swap, whats the point? Just my thought. LOL