Electronics > Repair
Agilent E4421B RF generator restoration project
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nctnico:
My E4421B has thrown me a nasty curve ball today. It starts but when it gets to the splash screen I hear a loud click from one of the RF modules and it seems to reset into the splash screen. This cycle keeps continuing  :-BROKE Just as I wanted to make some measurements on my new HF differential probes.  :rant:  :rant: Just what I need. Maybe it is karma. A few days ago I have bought a different RF generator which hasn't arrived yet. Hopefully that is in a somewhat workable condition.
Samogon:
Looks 5V power rail has an issue, fail at load, making reboot cycle. That is first thing i would check.
Then if 5V ok, remove all boards except digital and check it
nctnico:
The 5V looks ok with a DMM. I also see the diagnostic LEDs keep counting in a binary sequence. With all the RF modules removed the behaviour is the same. Maybe I need to try and reflow the SRAMs. There is a message about the RAM but it isn't clear if something is bad or not. It says:
Start = 0x300000
End =  0x3F9800
Errors =0x0

With the 'local' button pressed during power on, the E4421B won't start the firmware so the self test result stays on screen.
nctnico:
I made some progress. When it is cold and no RF modules are installed it will start succesfully. I tried using freeze spray but so far no joy.
Samogon:
Thermal camera?
Measure cold and warm current consumption on 5V rail
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