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Welcome, Guest. Please login or register. Did you miss your activation email? This topic This board Entire forum Google Bing. Print Search. I turned out that it needs to be calibrated.
Anyway, calibration of the is not so an easy task. Or not for me as I've never done such thing. I can get a calibrated SMU for the role of calibrator, and I can do the whole procedure in an environment that has controlled temp and humidity. The hard part is still to make the corrent connections and to do the step-by-step calibration procedure through the GPIB interface.
Has anybody here have experience with calibrating the 23x series SMUs? Can I do this sucessfully without the recommended shielded test box? I would use my homemade steelbox. The operator's manual and the service manual says everything about calibration. I should do them prior to the calibration. Thanks for your comments. If you have a that is in calibration, you should be good for all of the current sourcing and sinking. What I suggest is that you connect the directly to the 23X using triax cable s.
You may only need to adjust the lowest current ranges. I have found that the lowest ranges drift the most.
Probably there are large value resistors there and they drift the most. Even if the DMM does not have better specs, it may be good enough to see if the 23X is out of tolerance. For voltage measurement by the 23X, you can use the up to V.
If you have a , you have to find an v calibrated source. I have few 's I'm patching up and that's a recurring theme. Quote from: VintageNut on May 06, , am. Quote from: Ice-Tea on May 06, , am. You can get HP triax cable assembly from parametric analyzer, such as this and re-purpose it. No MB limit, firmwares, photos.
Thanks for the tip! It is not the cheapest solution but the easiest. Quote from: balage on May 06, , pm. Great, thanks! However the communication is still cumbersome.
Once I have established it is working correct, but I can put the instrument to remote and address it to a listener very rarely, something is wrong Just for some fun: Also in the meantime it has turned out that the negative side of the HV supply is not working properly, Now it can source up to Volts, but with one of the output filtering capacitor removed.
It seems like it cannot tolerate capacitive load somehow. The schematic shows the replaced components. When it was oscillating, the green parts became very hot soon. Finally I removed that, and the converter working fine Kleinstein Super Contributor Posts: Country:. Removing C44 kind of negates the function of the transistor block. This cap is there to get some filtering in a kind of capacitance multiplier. It may be sufficient to add some series resistant e. This would at least keep most of the filtering effect.
Dear Kleinstein, Thanks for your help. I have put a Ohm resistor to the base of Q5. The problem is the same - it is getting oscillating loudly below V. Operation of that transistor block is also not clear for me. Is this block smoothing the output voltage by changing the voltage across Q6? Is the ripple voltage opening Q5 through C44, and Q5 controls Q6? I am planning to measure the ripple voltage somehow to see if I can remove C44 permanently. PNG R22 and C44 form an RC filter.
Q5 and Q6 from a emitter follower amplify the current and ideally form a filtered supply. This kind of circuit is not really new and sometimes call capacitance multiplier. It may be a little confusing, but an emitter-follower, especially as a Darlington can oscillate if used with a capacitive load and low impedance source.
The usual countermeasures are resistors sometime ferrite at the emitter or base. My favorite position would be a resistor in series to the base pin of Q6.
Maybe the Ohms at C44 were not enough. Given that the current is relatively small the resistor could be relatively large e. It could also help to have a RC series e.
C44 and Q5,Q6 are there for a reason. So I don't think one can just remove them. Thanks for your suggestions. No success. I am ordering from Mouser soon, and I will include transistors a zener diodes for this part of schematic. I was thinking if this oscillation can come from the capacitor-diode network of the converter.
It is not likely I think. I have measured the diodes, they seem okay, and the caps were replaced by the previous owner I guess. So the problem must be somewhere around this darlington circuit. Ordinaryman Regular Contributor Posts: Country:. I have some very nice triaxial cables with Thrompeter connectors Let me know if I can help.
I also have some longer ones.. I think they are about double the length, about 16 feet or so. I have removed the base resistors, so it is now the original circuit. Nothing has changed, the converter oscillates and gets loud below Volts.
That part also gets hot. C44 was broken when I first realized this error. I was wondering if this can mean something to us but I cannot judge if the breaking capacitor caused the problem or the capacitor was killed by the problem.
I always start such repairs with great pleasure, and it is always resulting in failure. Update: I have not mentioned earlier, but when it is oscillating, the shows around 4uA while nothing is on the output. I have mentioned that when C44 is missing, everything is good. Can the output stage cause this problem? Maybe the output is loading the converter heavily. I cannot judge. Update2: There are the same big ceramic caps on the input of the output stage.
I will remove that capacitor to see if it is resulting in a working converter. Maybe it is overloading the converter. Looking for the actual problem at the output stage, is a good idea. The power supply part could have a current dependent behavior, but should only indirectly via the current depend on the set voltage. So much Oscillation may be a reason for C44 to age faster - either directly or just indirect from the surrounding parts getting hotter.
So a look at the output stage is a good idea. For a test also just loading the output could also give a clue, if the onset of oscillation depends on the voltage or current. If current depending more load should shift the critical voltage to a lower values.
Update here. I have focused now on the output stage. As I have mentioned when the output capacitor 10nF was removed in the converter, it was not oscillating.
Keithley 237 Manuals