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toples50

IIfx and some issues

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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!

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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.

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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.

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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.

Edited by IIfx

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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.

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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.

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I have replaced the caps, they are identical. Here is the schematic:

macIIfxsch.GIF

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.

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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.

Edited by IIfx

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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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