| Electronics > Repair |
| [SOLVED] HP 34401a - Error 612, 613, 615, 617, 618, 619, 621 |
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| Dr. Frank:
--- Quote from: abnormalalien on July 11, 2018, 09:15:09 pm ---Took some time to get the AD706s from Newark but I finally replaced both U201 and U400 and now the multimeter passes all self-tests. I also tested various functionality: DCV, ACV, and 2WR are all great. Tested 4WR with a handful of resistors and found that the values seem reasonable. The only oddity is that when nothing is connected to the inputs and 4WR is selected, it does not read Overload. I believe it should read OL when there's no inputs right? Is that a sign of another problem? Haven't tested ACV yet (too many researchers not enough machines) or ACI (how does one even go about sourcing ACI?). Thanks again for all your help! --- End quote --- Ok, so my error prediction was correct. The behavior of the open 4W mode is fully normal! In this configuration, the Input jacks (the right ones) work as a constant current source and the Sense jacks (the left ones) operate as a voltmeter input with high impedance. There is no internal connection between the current source jacks and the sensing jacks, therefore, there is no overflow indication and display simply indicates the floating voltage on the sensing jacks, as if you would put the 34401A into DCV volt mode, with High Impedance mode and jacks open. So if the sensing jacks accumulate enough charge by its leakage current, the voltage might drift up or down, and finally might lead to an overflow. Frank |
| abnormalalien:
Awesome, thank you guys so much! I talked to my advisor about calibrating and he didn't seem that concerned. He had me test it against our Keithley sourcemeter and it is accurate over a large range of voltages (our primary measurement). So thanks again for helping me prove two people - department electrical engineer and thesis advisor - wrong when they said they didn't think I could get this thing up and running again! |
| Zucca:
Don't tell them we helped you :scared: |
| bitseeker:
--- Quote from: abnormalalien on July 13, 2018, 04:16:46 pm ---So thanks again for helping me prove two people - department electrical engineer and thesis advisor - wrong when they said they didn't think I could get this thing up and running again! --- End quote --- Hehe, that's excellent. :-+ Beware you don't get drafted into fixing everything that goes wrong from now on. |
| bobof:
Hahahahaha... if you don't laugh you cry. This time the joke is on me! Saw an auction come up for a load of test gear with a local auction house. 3x 34401A units (1 HP, 2 Agilent) in what looked like nice condition. Got them for what I thought was sensible money for 3 good instruments... Of course, no opportunity to test them. All 3 have significant issues; 2 have the various combinations of codes which have often been fixed by U201 replacement. I figure I'm likely to need one at least by odds so why not order one. Might as well open them up firstly to see what is going on inside... First one I open... The other two at least don't have any physical damage and measure small DC volts OK, though resistance isn't right on either. Projects for another day I guess... ho hum! On a 3 out for 3 basis I certainly can suggest where to think twice about buying test gear from from in future... |
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