68kMLA Classic Interface

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IIfx and some issues

Posted by: toples50 on 2019-02-21 10:35:22 I have managed to power up my IIfx.I have installed a SuperMac graphics card I had and the machine really flies.The only issue I have is that does not shut down from power button.I don’t know why.The first time the button worked but nothing after that.Otherwise the machine is excellent!

Posted by: IIfx on 2019-02-21 10:40:28 There are two surface mount electrolytic caps over near the power button. Check that they didn’t leak and damage the traces to the button or the associated chips. Other than those two caps most IIfx are surface mount tantalum with a few axial electrolytic through hole caps.

Posted by: Johnnya101 on 2019-02-21 10:44:11 Replace those two caps as IIfx said. I replaced my two and got the traces repaired, works great now.

Posted by: toples50 on 2019-02-21 10:45:02 But it power up normally from button.I don’t know.Maybe not compatible with Apple keyboard?When I fired up for first time I didn’t had this problem.After cleaning the motherboard with compressed air and change the graphics card the problem appeared.

Posted by: IIfx on 2019-02-21 10:47:12 Those caps are related to general functions of the soft power circuit. If power from the keyboard button is not possible you must replace those capacitors.  If you upload a photo photo of that corner of the logic board we can say if it has leaked or not. Its the corner by the RAM and power button, where the batteries are. If you can’t do surface mount soldering, I have redone my IIfx with great success. It’s a easy board to work on, well laid out.

Posted by: Johnnya101 on 2019-02-21 10:56:47 Replace those caps. That is the issue. They all get this issue with bad caps.

Posted by: AwkwardPotato on 2019-02-21 10:59:06 Agreed with the others on replacing the caps. I doubt that the keyboard is the issue; there are different components in the soft power circuit for both powering on and powering off.

Posted by: toples50 on 2019-02-21 11:03:31 I will post some pics tomorrow.Thanks guys.

Posted by: toples50 on 2019-02-21 23:39:22 I have change the position of the batteries and now shut down normally for now... Some pics form motherboard.

Posted by: toples50 on 2019-02-22 09:48:00 Again the same symptoms... :-(

Posted by: Johnnya101 on 2019-02-22 10:15:46 There's nothing else to do except change the caps. If you don't, you risk them leaking and corroding traces. Better to send the board out if you are not comfortable and have it cleaned and recapped. There is nothing else you can do besides replace them. Switching around batteries won't do anything. It isn't the keyboard. It's not the mouse. It's not the monitor. It's not the power supply. It is those couple of silver cans. All IIs get the same issue and every time it is those caps. Replace them.

Posted by: trag on 2019-02-22 11:45:01 From the photos, it looks like there are pads on the motherboard next to the SM electrolytic caps where the equivalent SM tantalum caps could go.  I would not want to try it without testing continuity to confirm that both sets of pads are electrically identical, but I bet they are. BTW, you would still need to remove the old caps and clean the board.   The pads just make it a little more convenient to solder in new tantalum caps.

Posted by: Jinnai on 2019-02-22 20:35:06 I have replaced the caps, they are identical. Here is the schematic: Remember that if one set of pads is corroded, then there's likely no connection with the other pads. The unused pads are part of the traces for the used pads.

Posted by: IIfx on 2019-02-23 21:22:23 Your IIfx board seems to have a lot of electrolytic caps. All of the silver can caps need to be replaced. After 25+ years those caps are no longer at the right value even if they haven’t leaked. if you can’t do it yourself and can’t find anyone else to take it on I could consider it. I’ve done the IIfx board in the past. It’s fairly easy to work on compared to other logic boards.

Posted by: Jinnai on 2019-02-23 21:32:43 I'm sure it would be easy and possibly a good idea to use tantalums instead of electrolytics, too... since the pads are there and all...

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