I had a proper 12v power supply next to a 24v one that was used for a different device. They have the same connector size and were indistinguishable. I accidentally plugged in the 24v supply and the board made a horrible whining sound. I foolishly decided to power on the machine, being unaware that I had the wrong connector. After realizing my mistake, I immediately swapped it out for the usual 12v supply and I now get blinking LEDs indicating the board is in error state when I power it on. None of the chips ran hot or smelled burnt, but now I have a $300 paperweight on my desk
. Is there any saving this board?
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Don't Panic. Please wash hands.
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I've never tried this level of human error, but you may be lucky and most of the board itself has survived.
There is a protection diode (against reverse polarity and over voltage) that has surely burned, it's D8 near the switch. Further, the input voltage goes "almost unfiltered" into the VIC and SID chips that are most likely dead now.
If LEDs blink, then all 5V parts of the board are still OK. Depending on how badly the VIC chip is damaged, it has passed a high voltage to the address lines of the system, so the Xilinx chip may be damaged. You may be able to verify this with the remote control menu. In any case, with blinking LEDs, you still have a remote control menu which you should try next. If will let you do small tests in the factory menu - please post the results here.
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I have not been able to get any response from the terminal when I tried opening the remote control menu.
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Interestingly, the 5v line going to the cassette port which powers my SD2IEC starts blinking before all the others.
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After some more power cycles and attempts to bring up a welcome screen on the remote control terminal (all of the chips have been removed before testing the first time), the board seems to have died completely. None of the LEDs on the case, the board itself, or the SD2IEC blink anymore. I feel like it's safe to assume the board is completely dead and I will have to find a replacement.
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It may be that the protection diode D8 is now completely melted and shorts out the input voltage. If you believe that the board is a paperweight already, you might as well remove that diode and make sure to only plug in a proper PSU - the board will come up, but have no protection against faulty input voltages.
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Then I will try just that. I'll also make sure that 24v PSU is nowhere near that board so I have no chance of mixing them up, if it does manage to work properly.
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I was able to remove diode D8, and the board was able to complete all the self-tests. All of my chips somehow survived except for the two CIAs which were already having problems before the accident. Until I can replace the diode and the CIAs, I will keep this board stored somewhere safe. Thanks for the help!
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Be sure to replace the diode with the same type, which is 1SMB5927BT3G (the T3G suffix may be omitted, but it's probably easier to find with the complete type number).
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Just want to give one last update on this topic. I was able to replace the diode and all failing components, and the board is still working like a charm!
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The last reply was more than 365 days ago, this thread is most likely obsolete. It is recommended to create a new thread instead.
