Mac IIfx Clock/Time not working

[Johnnya101]

Title.

Time does not advance, and stays still... 

Ive reset PRAM.

Im confident the batteries are in correctly.

Any ideas?

 

[BadGoldEagle]

Rotten traces? That can happen. Especially if you had leaky caps on that logic board...

Get a MMU and check continuity. I bet one trace has gone bad.

 

[ArmorAlley]

Do the batteries have enough of a charge to function properly? I've forgotten exactly how much of a charge it needs to work (3.2V maybe?). Someone here should know the figure. If you have a multimeter, you can check the voltage.

Are other settings forgotten, like AppleTalk settings, mouse-speed settings and the like? Can you boot cold-boot the IIfx from the power button on the keyboard?

 

[Johnnya101]

Brand new batteries.

Has not been recapped either, and its having the power off issues, so I think its safe to assume caps! Thats where the batteries are too, right by them

Luckily theres no visible leaking so it can't be too bad. Ill send it off and get it done soon once I get money.

 

[tjjq44]

Had exactely the same problem since I got my IIfx 5 years ago... The first thing I made when I got it was recapping but the problem was still there!

This WE I went on the problem to see if there was any broken trace with the power circuit and RTC schematics... but everything was fine...

In purple, the traces I tested were all OK!

At last resort I decided to pull a RTC chip from an old mac Classic in order to replace the IIfx's one... and... it works, clock is counting!!! What a surprise since I had never seen a RTC fail before!

I still have the power off issue (I have to unplug the mac for shutdown), maybe I'll have to replace the Nand gates and the related transistors?

 

[Bolle]

maybe I'll have to replace the Nand gates and the related transistors?

Worth a shot. I had a few IIci logicboards where those were dead.

Replacing them fixed any weird startup/shutdown behavior.

 

[tjjq44]

I can easily find the MMBT3906 and MMBT3904 but the PC74HC132T is quite expensive and I need two of them... Do anyone know a equivalent component?

 

[Bolle]

Any 74HC132 will do, they shouldn’t cost more than 50 cents a piece.

You don’t need the exact same part from the same manufacturer that’s on there right now.

Any other type of 74*132 might work, but in circuits like this I would always use the same type (HC in this case)

 

[tjjq44]

Ok thanks, I thought the pinout could be different... I'll try on aliexpress  ;-)

 

[toples50]

I have also shut down issue with my IIfx.I haven't  recap it yet unfortunately.