Macintosh II Series 1/2 AA Battery B2: Alternative Solutions

[sadmanonatrain]

Hello all, 

I recently received a Macintosh IIx that had its soldered PRAM batteries removed.

I believe battery B2 provides the voltage for the power supply to start up once the power button is pressed.

Since I didn't have any 1/2 AA batteries/holders I soldered a 9v battery to B2. The Mac did not come on when the power button was pressed.

After this I removed the 9v battery and replaced it with a AA battery holder, supplying 3v altogether. The Mac did not start in this configuration.

What am I missing? Do batteries need to be present in B1 and B2 for the Mac to start?

 I'm sure a similar technique was shown inside a Macintosh II on an episode of Jason's Macintosh Museum.

 

[max1zzz]

i think both are needed for it to start with the power button (when i was playing with that mac IIx i did try wedging a couple of 3.6v batteries in their before and i'm sure it started fine then)

 

[sadmanonatrain]

I've ordered another AA holder so I'll report back when it arrives.

 

[max1zzz]

Good luck

Having a quick look at the II/IIx startup circuit: http://home.earthlink.net/~gamba2/images/macIIsch.GIF it dose indeed appear that both batteries are required

 

[sadmanonatrain]

Cheers! 

Thanks for the confirmation!

 

[unity]

 

[sadmanonatrain]

I've just added an AA battery holder to B1 and B2 for 6v in total. It still does not let the Mac start up.

Does this mean that the trickle voltage is not enough to start the Mac?

 

[max1zzz]

Have you tried both the power button on the keyboard and the one on the back? My other IIx had a broken trace leading from the power button on the back, it's possible this one could aswell

 

[sadmanonatrain]

I've just powered on the IIx via the keyboard and it works!

Which trace did you have to fix Max? Did it happen to be the trace that leads to the the ADB port? This one looks a bit rotten.

The other three power button traces tested good for continuity. 

 

[max1zzz]

It was leading in that direction, but i'm not sure if it was actually connected to a adb port or not

But if there is a rotten looking trace test it anyway

It is one of the traces in the red oval

 

[sadmanonatrain]

Today I have been messing around with the IIx and this is what I have found out:

It will not turn on when the power button is pressed but once the IIx is on pressing the power button will turn it off.

The IIx can be turned on via its keyboard.



Out of the four traces highlighted one does not test for continuity. Even when I bridged the two points with wire the IIx power switch still did not power it on.

Could the switch be dead?

 

[techknight]

I am actually working on my first IIx today. its a wreck like yours, bad continuity on one of the switch traces, and there was some rot at the 74HC132s, breaking connections there as well. 

Once i fix all that mess, it might actually work haha. 

 

[sadmanonatrain]

I've fixed the offending trace and the IIx switches on like it should!

Could a Moderator please remove the diagram in my last post? It is incorrect because the red trace actually connects to pin 4 of the black component; it does not connect to the ADB post as the diagram suggests.

Thanks 

 

[techknight]

I had the same trace open as well, along with an open trace at the 74HC132s near the nubus slots, responsible for power switching. 

Fixed it.

 

[sadmanonatrain]

A working solution!



A new trace diagram:

View attachment 4686

 

[max1zzz]

Ditto - that was the trace open on my proto IIx

I really need to get that some batteries for it and see if it's power on circuitry actually works

Anyway, I'm glad to see you have it fully working

 

[CC_333]

Huh, this reminds me that I have two Mac IIx board that need recapping.

Anyone care to take a look at them as part of this apparent research project?

c