Keithley 2400 SourceMeter review and teardown

[exe]

Congratulations, looks like you are just one step away from having a working smu!

[kawal]

Found another issue on the 10UA range.  This range I was not able to calibrate due to offset.
I found this out when i could not measure resistance in Auto Mode but could do it in manual mode on 100uA range. Auto defaults to 10uA BTW
The sense resistor for this range is switched on by a series DG444DY switch ( which seems to work) and a Mosfet transistor Q400.  The transistor  seems to be the issue.
The mosfet q400 which is a VN0605T (obsolete )  must be damaged . Its crating a big offset on this range.  A good replacement ( actually has better leakage current by 10X) is 2N7002E-T1-E3
Ordering yet more parts.

Attached some pictures of resistance measurements  on 2400 and 2700 and a microscope (Just got a nice stereo microscope used locally for good price.) picture of the Voltage DAC.

[kawal]

Got some 4094 chips in today and replaced the U253  I guess I was wrong about the output being pulled up. The meter is doing this the same way on the new chip.  Not sure if the ram is corrupted in the meter but the data is definitely being pushed into the register.    Seems wrong to me but oh well. not sure what can be done

[kawal]

Can someone with a 2400 confirm how the relay K206 is supposed to work. Can someone measure their unit at the test point near Q234 (this is the gate of the mosfet).

Measure this voltage in reference to T500 FCOM when output is disabled
Measure this voltage in reference to T500 FCOM when output is enabled

Thank you in advance.
 

[kawal]

Removed Q400 from the 10uA range. The transistor has a short (54 ohms or 20mV  voltage drop with Diode test.) between Gate an Source. This would explain the offset issue on the 10uA range. Still waiting for replacement. 

[kawal]

Ok - I could not wait for a reply and started looking at the much better Keithley 236 manual. There is a similar architecture in that SMU and the relay  should stay on per the manual. Still would love to see if that is the case in the other units that are 2400. I only have the one I am currently repairing so I cant be 100% sure.  Seems to be the same in firmware C11 and C32  that i tested.
So it would be great  if you guys can open up your 2400 and let me know if this behavior is normal.

[TiN]

That Q234 is 4.95V, no matter if output enabled or disabled, in either front or rear. I think that relay provide connection for Guard terminal, and always ON does sound correct in such case.

[kawal]

TiN

Thank you for checking I really appreciate it.  That contact was driving me crazy especially that when the NIDAC was bad the output was -240V before i could enable the output. I thought that relay somehow would be off to protect the user. Thank you for confirming that  this is the intended way the unit should be working . I guess I did not need to replace the shift register that controls the output - oh well.  Per my recollection the relay provides connection from the amplifier out to the Hi out terminal .  From what i see Guard is not switched through this relay.

Also checked out your Video on the 2425 repair https://www.youtube.com/watch?v=e-T1DK5Z2h8. Did not know about the secret menu for self testing.
Thanks again

 

[kawal]

The 2400 Lives. !!!!!!
Ok transistor Q400 replaced and 10uA range working now.  Looks like all ranges are fully functional time to send the unit for calibration. I did a calibration  with precision 1M resistor to check for functionality of 1uA and 10uA range.
 And that horizontal line is not a scratch if anyone asks.

[TiN]

That reminds me I need to calibrate my 2400, after taking it apart to do measurements for you.
My K2400 also non-original, I have modified it with LM399 reference for each oomph.  Not that it matters really, but was fun easy mod.

Calibration Python program and E5810A aid adjustment automation and verification.

Code: [Select]


Keithley Model 2400 - detected, S/N 0788393, Version: C32   Oct  4 2010 14:20:11/A02  /H/H
Pre-cal K2400 Calibration data
0.2 DCV Range, SENS:DATA? = -1.375303E+00,-1.721084E-05,-1.375407E+00,+0.000000E+00
0.2 DCV Range, SOUR:DATA? = +2.764157E+05,+9.152109E+02,-2.764087E+05,+9.467695E+02
2.0 DCV Range, SENS:DATA? = -1.375422E+00,-1.811981E-05,-1.375288E+00,+0.000000E+00
2.0 DCV Range, SOUR:DATA? = +2.761708E+04,+2.052578E+02,-2.761636E+04,+2.083945E+02
20.0 DCV Range, SENS:DATA? = -1.375513E+01,-1.375198E-03,-1.375385E+01,+0.000000E+00
20.0 DCV Range, SOUR:DATA? = +2.761523E+03,+2.085977E+02,-2.761447E+03,+2.050625E+02
200.0 DCV Range, SENS:DATA? = -1.375421E+02,-1.382446E-02,-1.375290E+02,+0.000000E+00
200.0 DCV Range, SOUR:DATA? = +2.761715E+02,+2.086133E+02,-2.761635E+02,+2.050547E+02
1.0e-06 DCI Range, SENS:DATA? = -6.845910E-07,-9.356427E-11,-6.845222E-07,+0.000000E+00
1.0e-06 DCI Range, SOUR:DATA? = +5.548882E+10,+2.040664E+02,-5.548042E+10,+2.104687E+02
1.0e-05 DCI Range, SENS:DATA? = -6.890184E-06,-5.320544E-10,-6.889600E-06,+0.000000E+00
1.0e-05 DCI Range, SOUR:DATA? = +5.513167E+09,+2.019297E+02,-5.512313E+09,+2.127148E+02
1.0e-04 DCI Range, SENS:DATA? = -6.869998E-05,-4.991307E-09,-6.869353E-05,+0.000000E+00
1.0e-04 DCI Range, SOUR:DATA? = +5.529379E+08,+2.017656E+02,-5.528538E+08,+2.128203E+02
1.0e-03 DCI Range, SENS:DATA? = -6.857473E-04,-4.994217E-08,-6.856770E-04,+0.000000E+00
1.0e-03 DCI Range, SOUR:DATA? = +5.539511E+07,+2.017305E+02,-5.538684E+07,+2.128320E+02
1.0e-02 DCI Range, SENS:DATA? = -6.872036E-03,-5.178154E-07,-6.871379E-03,+0.000000E+00
1.0e-02 DCI Range, SOUR:DATA? = +5.527761E+06,+2.018398E+02,-5.526910E+06,+2.127383E+02
1.0e-01 DCI Range, SENS:DATA? = -6.876468E-02,-5.178154E-06,-6.875831E-02,+0.000000E+00
1.0e-01 DCI Range, SOUR:DATA? = +5.524166E+05,+2.018516E+02,-5.523274E+05,+2.127734E+02
1.0e+00 DCI Range, SENS:DATA? = -6.887156E+00,-5.303621E-04,-6.886814E+00,+0.000000E+00
1.0e+00 DCI Range, SOUR:DATA? = +5.518421E+04,+8.602578E+02,-5.517694E+04,+9.663477E+02
HP 3458A detected
 TEMP? = 37.5 C
DCV Calibration step -0.2 mV , measured : -1.999948835E-01 VDC, deviation -25.583 ppm
DCV Calibration step  0.2 mV , measured : 1.999991793E-01 VDC, deviation -4.104 ppm
DCV Calibration step    -2 V , measured : -1.999991983E+00 VDC, deviation -4.008 ppm
DCV Calibration step     2 V , measured : 1.999986310E+00 VDC, deviation -6.845 ppm
DCV Calibration step   -20 V , measured : -1.999999159E+01 VDC, deviation -0.421 ppm
DCV Calibration step    20 V , measured : 1.999993647E+01 VDC, deviation -3.177 ppm
DCV Calibration step  -200 V , measured : -1.999974777E+02 VDC, deviation -12.612 ppm
DCV Calibration step   200 V , measured : 1.999964677E+02 VDC, deviation -17.662 ppm
DCI Calibration step -1 uA , measured : -9.999818293E-07 ADC, deviation -18.171 ppm
DCI Calibration step  1 uA , measured : 9.999825290E-07 ADC, deviation -17.471 ppm
DCI Calibration step  -10 uA , measured : -9.999831268E-06 ADC, deviation -16.873 ppm
DCI Calibration step  10 uA , measured : 9.999901602E-06 ADC, deviation -9.840 ppm
DCI Calibration step -100 uA , measured : -9.999936766E-05 ADC, deviation -6.323 ppm
DCI Calibration step  100 uA , measured : 9.999918902E-05 ADC, deviation -8.110 ppm
DCI Calibration step -1 mA , measured : -9.999886353E-04 ADC, deviation -11.365 ppm
DCI Calibration step  1 mA , measured : 9.999875093E-04 ADC, deviation -12.491 ppm
DCI Calibration step  -10 mA , measured : -9.999853206E-03 ADC, deviation -14.679 ppm
DCI Calibration step  10 mA , measured : 9.999953624E-03 ADC, deviation -4.638 ppm
DCI Calibration step -100 mA , measured : -9.999813773E-02 ADC, deviation -18.623 ppm
DCI Calibration step  100 mA , measured : 9.999842788E-02 ADC, deviation -15.721 ppm
DCI Calibration step  -1 A , measured : -9.999645533E-01 ADC, deviation -35.447 ppm
DCI Calibration step  1 A , measured : 9.999774736E-01 ADC, deviation -22.526 ppm
DCI Verification step Zero  A , measured : -1.788568192E-11 ADC
DCI Verification step   -1 nA , measured : -9.993935778E-10 ADC, deviation -606.422 ppm
DCI Verification step    1 nA , measured : 9.888950700E-10 ADC, deviation -11104.929 ppm
DCI Verification step  -10 nA , measured : -1.000216363E-08 ADC, deviation 216.363 ppm
DCI Verification step   10 nA , measured : 9.988446699E-09 ADC, deviation -1155.330 ppm
DCI Verification step -100 nA , measured : -1.000165300E-07 ADC, deviation 165.300 ppm
DCI Verification step  100 nA , measured : 1.000043848E-07 ADC, deviation 43.848 ppm
DCI Verification step   -1 uA , measured : -9.999055619E-07 ADC, deviation -94.438 ppm
DCI Verification step    1 uA , measured : 9.998880573E-07 ADC, deviation -111.943 ppm
DCI Verification step  -10 uA , measured : -9.999861188E-06 ADC, deviation -13.881 ppm
DCI Verification step   10 uA , measured : 9.999910553E-06 ADC, deviation -8.945 ppm
DCI Verification step -100 uA , measured : -9.999887831E-05 ADC, deviation -11.217 ppm
DCI Verification step  100 uA , measured : 9.999839386E-05 ADC, deviation -16.061 ppm
DCI Verification step   -1 mA , measured : -9.999803701E-04 ADC, deviation -19.630 ppm
DCI Verification step    1 mA , measured : 9.999745446E-04 ADC, deviation -25.455 ppm
DCI Verification step   -4 mA , measured : -4.000350359E-03 ADC, deviation 87.590 ppm
DCI Verification step    4 mA , measured : 4.000267999E-03 ADC, deviation 67.000 ppm
DCI Verification step  -10 mA , measured : -9.999839193E-03 ADC, deviation -16.081 ppm
DCI Verification step   10 mA , measured : 9.999906841E-03 ADC, deviation -9.316 ppm
DCI Verification step  -20 mA , measured : -2.000352007E-02 ADC, deviation 176.003 ppm
DCI Verification step   20 mA , measured : 2.000418054E-02 ADC, deviation 209.027 ppm
DCI Verification step -100 mA , measured : -1.000000364E-01 ADC, deviation 0.364 ppm
DCI Verification step  100 mA , measured : 9.999876289E-02 ADC, deviation -12.371 ppm
DCI Verification step -500 mA , measured : -5.001218448E-01 ADC, deviation 243.690 ppm
DCI Verification step  500 mA , measured : 5.001075087E-01 ADC, deviation 215.017 ppm
DCI Verification step   -1  A , measured : 1.000053606E+00 ADC, deviation 53.606 ppm
DCI Verification step    1  A , measured : -1.000009712E+00 ADC, deviation 9.712 ppm
DCI Verification step Zero  A , measured : 1.384233768E-08 ADC
DCV Verification step 00 (0.000000000E+00), measured : -8.871845474E-06 VDC
DCV Verification step 01 (-2.000000000E-03), measured : -2.010135899E-03 VDC, deviation 5067.950 ppm
DCV Verification step 02 (2.000000000E-03), measured : 1.990735405E-03 VDC, deviation -4632.297 ppm
DCV Verification step 03 (-2.000000000E-02), measured : -2.001099592E-02 VDC, deviation 549.796 ppm
DCV Verification step 04 (2.000000000E-02), measured : 1.999615615E-02 VDC, deviation -192.193 ppm
DCV Verification step 05 (-2.000000000E-01), measured : -2.000073866E-01 VDC, deviation 36.933 ppm
DCV Verification step 06 (2.000000000E-01), measured : 1.999953503E-01 VDC, deviation -23.248 ppm
DCV Verification step 07 (-1.000000000E+00), measured : -1.000055863E+00 VDC, deviation 55.863 ppm
DCV Verification step 08 (1.000000000E+00), measured : 1.000063591E+00 VDC, deviation 63.591 ppm
DCV Verification step 09 (-2.000000000E+00), measured : -2.000200776E+00 VDC, deviation 100.388 ppm
DCV Verification step 10 (2.000000000E+00), measured : 2.000241744E+00 VDC, deviation 120.872 ppm
DCV Verification step 11 (-1.000000000E+01), measured : -1.000062483E+01 VDC, deviation 62.483 ppm
DCV Verification step 12 (1.000000000E+01), measured : 1.000049089E+01 VDC, deviation 49.089 ppm
DCV Verification step 13 (-1.500000000E+01), measured : -1.500109513E+01 VDC, deviation 73.009 ppm
DCV Verification step 14 (1.500000000E+01), measured : 1.500119825E+01 VDC, deviation 79.883 ppm
DCV Verification step 15 (-2.000000000E+01), measured : -2.000004998E+01 VDC, deviation 2.499 ppm
DCV Verification step 16 (2.000000000E+01), measured : 2.000003855E+01 VDC, deviation 1.928 ppm
DCV Verification step 17 (-1.000000000E+02), measured : -1.000070850E+02 VDC, deviation 70.850 ppm
DCV Verification step 18 (1.000000000E+02), measured : 1.000052509E+02 VDC, deviation 52.509 ppm
DCV Verification step 19 (-2.000000000E+02), measured : -1.999974277E+02 VDC, deviation -12.861 ppm
DCV Verification step 20 (2.000000000E+02), measured : 1.999966999E+02 VDC, deviation -16.500 ppm
DCV Verification step 21 (0.000000000E+00), measured : -2.192978188E-04 VDC
Post-cal K2400 Calibration data
0.2 DCV Range, SENS:DATA? = -1.375304E+00,-1.619756E-05,-1.375398E+00,+0.000000E+00
0.2 DCV Range, SOUR:DATA? = +2.764154E+05,+9.151484E+02,-2.764104E+05,+9.473320E+02
2.0 DCV Range, SENS:DATA? = -1.375421E+00,-1.704693E-05,-1.375296E+00,+0.000000E+00
2.0 DCV Range, SOUR:DATA? = +2.761707E+04,+2.052461E+02,-2.761638E+04,+2.084570E+02
20.0 DCV Range, SENS:DATA? = -1.375512E+01,-1.420975E-03,-1.375377E+01,+0.000000E+00
20.0 DCV Range, SOUR:DATA? = +2.761523E+03,+2.086992E+02,-2.761452E+03,+2.049922E+02
200.0 DCV Range, SENS:DATA? = -1.375419E+02,-1.417542E-02,-1.375297E+02,+0.000000E+00
200.0 DCV Range, SOUR:DATA? = +2.761712E+02,+2.087305E+02,-2.761636E+02,+2.049766E+02
1.0e-06 DCI Range, SENS:DATA? = -6.845868E-07,-9.220003E-11,-6.845208E-07,+0.000000E+00
1.0e-06 DCI Range, SOUR:DATA? = +5.548899E+10,+2.039805E+02,-5.548046E+10,+2.105508E+02
1.0e-05 DCI Range, SENS:DATA? = -6.890186E-06,-5.265974E-10,-6.889579E-06,+0.000000E+00
1.0e-05 DCI Range, SOUR:DATA? = +5.513168E+09,+2.018594E+02,-5.512315E+09,+2.127813E+02
1.0e-04 DCI Range, SENS:DATA? = -6.870023E-05,-4.889444E-09,-6.869372E-05,+0.000000E+00
1.0e-04 DCI Range, SOUR:DATA? = +5.529382E+08,+2.016289E+02,-5.528539E+08,+2.129570E+02
1.0e-03 DCI Range, SENS:DATA? = -6.857464E-04,-4.877802E-08,-6.856792E-04,+0.000000E+00
1.0e-03 DCI Range, SOUR:DATA? = +5.539507E+07,+2.016250E+02,-5.538670E+07,+2.129336E+02
1.0e-02 DCI Range, SENS:DATA? = -6.872036E-03,-5.168840E-07,-6.871358E-03,+0.000000E+00
1.0e-02 DCI Range, SOUR:DATA? = +5.527748E+06,+2.017773E+02,-5.526900E+06,+2.128164E+02
1.0e-01 DCI Range, SENS:DATA? = -6.876391E-02,-5.215406E-06,-6.875829E-02,+0.000000E+00
1.0e-01 DCI Range, SOUR:DATA? = +5.524202E+05,+2.018477E+02,-5.523324E+05,+2.127852E+02
1.0e+00 DCI Range, SENS:DATA? = -6.887750E+00,-5.336404E-04,-6.886620E+00,+0.000000E+00
1.0e+00 DCI Range, SOUR:DATA? = +5.518539E+04,+8.598516E+02,-5.517846E+04,+9.664961E+02
Calibration complete!

[kawal]

Great job TiN. I should send my unit to you. Do you offer calibration services ?

[Minikisscool]

Hi all, I read all.
I have a 2410 who is not working.
When power off, display shows OVP.

After diagnostics, the MAX EPM7160 on analog board is defect.
He is heating hot. (picture of a thermal camera)


The 5Volt  and power supply is good. I check on capacitor C616
L603 is good. Heating a little due to current consummation of EPM160

Anyone tried to read the binary of this CPLD ? or has binary file 2400-801A01 ?
I looked datasheet of components.
There is 4 pins TDO, TCK,  TDI and TDMS to program component.

Anyone to help me.

Thanks

[Kleinstein]

CPLDs / PFPGAs do sometimes run quite hot. Also a shortet output or open inputs can drive the power consumption up. So a warm chip does not nedessary mean the chip is bad.
The JTAG interface may be a way to check if there is still a response, though even a broken chip may still respond to JTAG.

[inaxeon]

CPLDs / PFPGAs do sometimes run quite hot. Also a shortet output or open inputs can drive the power consumption up. So a warm chip does not nedessary mean the chip is bad.
The JTAG interface may be a way to check if there is still a response, though even a broken chip may still respond to JTAG.

I would second that. I built something with one of those on a long time ago. It runs stupid hot. In the range suggested by that camera.

[Le_Bassiste]

temp of CPLD is defo too high. also, tantalum capacitor at lower left corner of CPLD in your picture seems to be having a hard time.
you may want to check frequency of clock lines that go into CPLD. CPLD is mostly controlling analog switches, so watch out for those as well.

[pppp12]

Dear users of 2400

Today our old 2400 kind of broke. It cannot source (stable) currents below 100uA anymore.
If one connects 8.1k resistor, sets the current source at 100uA then measured voltage is 0.81V - Great!
But if 50uA is set then the measured voltage is anything between -0.8V and -0.3V. Please note the "-".
1. Does one of you have idea/experience how to fix it?
2. Does anyone has a schematic of 2400?

Thanks in advance!

[maddoc]

May be I am necroposting, but always there is a chance.
I have an old Keithley 2400 from the first batches, which came with the very first firmware. It is working fine, except the range 1 mA and 10 mA, it shows current overflow, OVP. Probably, output transistor is toast. Any ideas/suggestions?

[Kleinstein]

Blown output transistors would likely effect all ranges.

A problem only in a few current ranges is more an issue with the shunt resitors or maybe the switching of the shunts.

[EEVblog]

2. Does anyone has a schematic of 2400?

Output stage schematic:
https://xdevs.com/fix/kei2400/

EDIT: Ah, the service manual only has the output schematic:
https://download.tek.com/manual/2400-902-01G-Feb2006Service.pdf