Electronics > Repair
Agilent 34401A Serial port pints 3 (TX) 5(GND) stuck at 9V on sys (SOLVED)
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The_Spectrum.A_idiot:
Dear All ,

After finally fixing my instrument I have a new issue.

THe serial port regardless of its selected on the I/O between RS232 or GPIB the device directly applies 9V on the TX pin.

Is this normal ? or I am looking at another issue ?

Thanks

Addendum :
Using wrong method to talk to the instrument 

macboy:
RS232 idles at the high voltage level, so this is normal.
squadchannel:
RS-232 protocol, it would be normal operation. There is no problem.

RS-232 detects "0" at positive 3-25V and "1" at nagative 3-25V, not TTL.
The_Spectrum.A_idiot:
okay , but when I connect a USB to serial device seems to not be happy with said levels.

Do I need so have something else in-between the instrument and the USB to serial device ?

Is the first time I am encountering such issue.
jchw4:

--- Quote from: The_Spectrum.A_idiot on October 03, 2024, 11:29:48 am ---okay , but when I connect a USB to serial device seems to not be happy with said levels.

Do I need so have something else in-between the instrument and the USB to serial device ?

Is the first time I am encountering such issue.

--- End quote ---

https://www.keysight.com/us/en/lib/resources/training-materials/communicating-with-instruments-using-rs232.html

TLDR: you need correct cable.
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