Author Topic: HP E4418A  (Read 1015 times)

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Offline wijogrTopic starter

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HP E4418A
« on: July 25, 2017, 02:05:17 pm »
I recently purchased an HP E4418A. It was sent out for calibration and has been used a few times. I went to turn it on yesterday and the power LED went from Red to Green and then back to Red. Hit the button again and then it turned on. I tried it this morning and it will not turn on at all now. I don't see anything in the manuals I have for troubleshooting this. Has anyone seen this or have any suggestions? I have the users manual and a service manual from the Keysight website.
 

Offline alm

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Re: HP E4418A
« Reply #1 on: July 25, 2017, 02:24:14 pm »
If you are lucky, it could be something with the power supply. Start by measuring the voltage rails (DC voltage and ripple). There may be instructions for the manual for this, otherwise you will just have to reverse-engineer it. For example, if you see an 7805, the output should be very likely about 5V DC. If you find that the output is much lower, there is likely something wrong. Many large value electrolytic (aluminum and tantalum) capacitors will often be across a voltage rail, so could be a good place to measure voltage. There will be most likely be some 3.3 or 5 V rails for the digital logic, and some analog rails (possibly symmetric, e.g. +6 V and -6 V). Since it is not powering on at all, if it is a power supply issue, there are probably rails that are way off.

Try to find the most recent power meter that still had schematics published. The HP 437A/438A is much older, but still had full schematics in the user manual. Not sure about more modern models. The principle of operation and possibly even the circuit of the probe interface and reference output may very well be very similar (since they could use the same sensors). The digital circuit is probably all different.


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