PB1400 strange booting behavior on battery power

[mwudka]

Hello!

I got a PB1400 at an e-waste dump that was in pretty good condition, though naturally the main and backup batteries were toast. I recelled the main battery, and it now holds a charge nicely. I also replaced the two backup batteries with a pair of Panasonic VL2330. I confirmed with a DMM that the backup battery reads ~3.2V between the white and black wires, and ~6.4V between the red and black wires. After putting everything back together, I reset the power manager and cleared the PRAM as the service manual describes. I also performed battery reconditioning, which took a bit over 2 hours. When I run off the AC adapter, everything works great. If I unplug the AC adapter, then things are still great: I can keep using the computer for a few hours, so the main battery seems good.

But other than that specific sequence, things pretty wonky. Some things I've noticed:
* If I shut down the computer, unplug the AC adapter, and then reconnect the AC adapter it appears my PRAM has been cleared: date/time are reset, and my brightness/contrast settings are reset
* When on battery power, I can't shut down the computer: it shuts down, but then I immediately get the startup chime, some sad speaker crackles, and then repeat
* If I shut down on AC power (which works fine) and then disconnect the AC adapter, pushing the on/off button does nothing

Any ideas on what's going on? My only idea is to re-disassemble everything and do more tests on the replacement battery, maybe trace the power further. I'm reluctant to jump straight for that, though, because it's a hassle and the case plastic does not feel durable. Since the machine is both usable and a delight, I'm not sure the risk is worth it.

 

[finkmac]

probably a dead PRAM battery causing that

 

[LaPorta]

I’d double-check the polarity and connections of your PRAM battery: I’d also test at the points it connects to on the board with it in-circuit to see if it reads the same.

Also, did you re-cap this thing? They are getting old.

 

[Daniël]

probably a dead PRAM battery causing that

I imagine those Panasonic VL2330s OP rebuilt it with probably weren't dead

This isn't a dual PRAM battery one, is it?
A few of the 1400s had two PRAM battery packs for some reason, if there is another one in there that's dead, it might be throwing things out of whack, though I imagine you'd have found it if so.

 

[finkmac]

I imagine those Panasonic VL2330s OP rebuilt it with probably weren't dead

they could be dead now depending on how the battery was assembled..

 

[3lectr1cPPC]

The not being able to cold start off the battery reads as a PRAM battery problem, not sure about the other two. I'd check your work there as others have said and then recap the logic board if all there looks fine.

 

[mwudka]

Rats! I was hoping someone would say something like "Oh, you need to do XYZ after you change the PRAM battery. If I have to go back in anyway, it might be worth moving the battery into the HDD area, maybe with a little holder PCB, so that I don't have to go through this again. Does anyone happen to know the part number for the 3 pin connector?

 

[LaPorta]

As fate would have it, I just rebuilt one of these last night. Make sure that your connections look the same as in my prior 1400 repair:

Post in thread 'PowerBook 1400 Restoration: Redux'
https://68kmla.org/bb/index.php?threads/powerbook-1400-restoration-redux.39657/post-428736

 

[mwudka]

Posting the outcome for posterity: I rebuilt everything again, and confirmed that on the little ribbon connector I see ~6.4V. Alas, same behavior. So either I got very unlucky for the rebuild, or something is wrong further along (maybe the battery charging circuit, or the PRAM battery power supply). I don't think the plastic can survive another disassembly/reassembly, so I'm going to quit while I'm only somewhat behind. Thanks for the help, and thanks to LaPorta for the very helpful thread.