| Electronics > Repair |
| Agilent 34401A Bubble on PCB ... can it be saved ? (SOLVED) |
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| The_Spectrum.A_idiot:
--- Quote from: Kleinstein on September 19, 2024, 07:28:42 am ---From the description the errors 612 and 618 are essentially the same, a problem with the 500 nA current source or 10 M divider. A way to check is to measure the 500 nA current externally. If needed with a resistor and voltmeter. Another point to check could be the resistor readings for the 10 M range (e.g. check 1 M and 4.7 M). --- End quote --- A 10K 1/4w 5% resistor measures 09.912 kohm on auto-ranging |
| Kleinstein:
410 / 420 nA should still be just inside the acceptable range for the current source. It is still be a bit odd that the current is that far off nominal. This could be leakage (e.g. not yet cleaned flux), or maybe extra bias from the OP-amp. If the issue is leakage it may get worse with higher voltage / higher resistance. A test would be to check the linearity with a series connection of 1-2 M resistors in the 10 M range. Another possible point of failure may be the relay connecting the 10 M divider. Is the 100 V range working reliable ? For a test, e.g. check something like a 9 V battery in the 10 V (high Z) and 100 V range and switch between the 2 ranges a few times. |
| The_Spectrum.A_idiot:
--- Quote from: Kleinstein on September 19, 2024, 05:32:04 pm ---410 / 420 nA should still be just inside the acceptable range for the current source. It is still be a bit odd that the current is that far off nominal. This could be leakage (e.g. not yet cleaned flux), or maybe extra bias from the OP-amp. If the issue is leakage it may get worse with higher voltage / higher resistance. A test would be to check the linearity with a series connection of 1-2 M resistors in the 10 M range. Another possible point of failure may be the relay connecting the 10 M divider. Is the 100 V range working reliable ? For a test, e.g. check something like a 9 V battery in the 10 V (high Z) and 100 V range and switch between the 2 ranges a few times. --- End quote --- Used a 9V PSU Tried every range on VDC and values don't change. re measured μΑ on ranges after cleaning the flux and doing the range change. Results : 000. ohm range -999.1 μA 0.1k range - 999.3μA 00.1k range -99.46μA 000.1k range -9.84μA 0.1M range -4.83μΑ 00,1M range - 0.36μΑ ** 000,1Μ range -0,36μΑ ** --- Quote from: Kleinstein on September 19, 2024, 05:32:04 pm ---A test would be to check the linearity with a series connection of 1-2 M resistors in the 10 M range. --- End quote --- How can I do thins without a reference resistor ? |
| Kleinstein:
With little difference at 9 V this suggests a woking relay. Getting less current after cleaning suggests that the cleaning may have made things worse, e.g. leaving moisture or more conductive film at the critical areas. Another possibility could be semiconductor leakage (e.g. at Q211) and a higher temperature for the 2nd test. One could look at how the current changes with temperature: leakage in semiconductor usually goes up with temperature quite fast. Surface leakage from dirt on the PCB tends to get down with temperature or at least not up very much. For a linearity test it does not need very accurate resistors. The deviation from the current is rather large, reaching some 10-20%. So the resistors only need to be reasonabel stable to maybe 5% between the tests. So more normal (e.g. 5 or 10% tolerance, though maybe not use cabon film) resistors should do and the exact value does not matter. It is just to reach a sum in the 8-11 M ohm range. The basic version would be comparing 2 x 4.7 M in series to the sum of the individual measurements in the 10 M range. |
| The_Spectrum.A_idiot:
--- Quote from: Kleinstein on September 19, 2024, 06:42:23 pm ---With little difference at 9 V this suggests a woking relay. Getting less current after cleaning suggests that the cleaning may have made things worse, e.g. leaving moisture or more conductive film at the critical areas. Another possibility could be semiconductor leakage (e.g. at Q211) and a higher temperature for the 2nd test. One could look at how the current changes with temperature: leakage in semiconductor usually goes up with temperature quite fast. Surface leakage from dirt on the PCB tends to get down with temperature or at least not up very much. For a linearity test it does not need very accurate resistors. The deviation from the current is rather large, reaching some 10-20%. So the resistors only need to be reasonabel stable to maybe 5% between the tests. So more normal (e.g. 5 or 10% tolerance, though maybe not use cabon film) resistors should do and the exact value does not matter. It is just to reach a sum in the 8-11 M ohm range. The basic version would be comparing 2 x 4.7 M in series to the sum of the individual measurements in the 10 M range. --- End quote --- ok finally got around to get it sorted, So with a 10K resistor at 10K range manual I get -9.941,10 kohms with 1x 4.42K @ 1% I get 4.429,57 kohms with 2x 4.42K @ 1% I get 8.848,81 kohms at 000.1K range I get with 3x 4.42K @ 1% I get 013.053,2 kohms Thanks |
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