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Any fixes for an I/O board that is randomly shorting out?


Hot Rolled
Dec 16, 2011
I posted last year about a strange alarm I was getting on a Brother TC-31.

Basically, I am getting a random alarm for an option I don't have. I found where the alarm signal is coming from, and there is nothing plugged into that spot on the I/O board. I measure voltage at the pin, and when it goes above 1.4 V, I get an alarm (It's a 24 V system). It has been hovering around there lately, so it it goes in and out of alarm a lot. I'm guessing that something is shorted internally on the board which is causing a small voltage to be seen at this pin. Do I have any options other than replacing the I/O? I'm guessing not, but I thought I'd ask to see if anyone with more electronic experience than me knows a way my board can be fixed.



Cast Iron
May 29, 2014
ca, US
Look at the chip(s) connected to that pin and get the data sheets on them. Check whether that pin should be grounded if unused. If it is an input pin for the unused option you could try grounding the pin and see if that alarm still happens. Usually an unused input will have a pull-down or pull up resistor or just grounded. Check your parameters to see that the option is turned off. Having it on and the input floating might cause an unwanted alarm.