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Could not change voltage on agilent 66332A measurement sour

Question asked by RajuNamburi on May 20, 2010
Latest reply on Mar 10, 2016 by RogerioHein

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Hello Everyone,

I am using agilent 66332A dynamic measurement DC source, i used GPIB to set & read voltage and current from it. i could successfully do it with VOLT <value> & MEASE:CURR?. but today when i switched it on, i found an Err & Prot on the display screen, i am unable to set the voltage manually or using GPIB. can anyone help me find out the problem , what this Err about and how can i clear Prot. I used *CLS, the Err got away but even when i press shift + protect the Prot mode is not going away. i couldnt use my DC source now. Pls help me. Thanks in advance.

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MattC May 21, 2010 6:51 AM
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Hi Raju,

We will be glad to help you. I have a few questions so that we can get a better idea of what is happening:
1. Can you read the error out and tell us what it is?
2. Which protection is tripping?
3. Have you set anything in the startup state (state 0)?
4. Is the output off when the error occurs?
5. Is there a load hooked up on the output?
6. Do you have a program listing that we can take a look at?

Thanks.

Matt
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RajuNamburi May 21, 2010 10:31 PM
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Thanks for your reply Matt, Here are the answers for your questions..
NO LOAD IS CONNECTED WHEN I OBSERVE ALL THE BELOW

1. Errors that were displayed on the agilent when i press Shift + address (error) keys are
      Error 1,2,3,4,5,80,11,0. All these are displayed in order.
2. I really dont know which protection is tripping. "prot" is displayed right from the time the device is switched on. i tried
    pressing shift + protection keys,its of no use. The voltage protection is around 22 volts. Voltages that we work are around
    2.8 to 5 volts as the load that is connected will not take more than 5 volts. its a mobile device.
3. There was nothing as saved setup and nothing is being called as a startup setup. It is starting with default voltage of
    0.001 volts and around 0.00028 amps if i am not wrong with the zero's but i am sure that they are defaults.
4. "Err" is showing right from the start of the device , and no output is given from the device. I measured the voltage and
     current using a multimeter and found that its not giving any output. I tried to set the voltage to 3.2 (did not connect any
     load) but the voltage is remaining at 0.001 the default value after pressing enter key. i could clear the "Err" on the
     display with *CLS command over GPIB PCI interface
5. Finally about the program that i used with this device is, i have two GPIB interfaces connected to the same PC, one with address 05( GPIB PCI ,source meter, the one that is in dicussion now) and other one with address 22 (its a agilent multimeter using GPIB USB) :

source meter is sourcing the device(conside a mobile device) with certain voltage, consider 3.5 volts like a battery. i have another charging equipment(consider USB) which is charging the device meanwhile. the current that flows from the charging device depends on the voltage at which the device is. i change the voltage on the source meter and measure the current (using agilent multimeter) that chargining device is delivering. The source meter is connected via GPIB PCI interface with address 05, the multimeter is conneted via GPIB USB interface with address 22

import visa

voltage = 2.8
source_agilent = visa.instrument("GPIB::05")
multi_agilent = visa.instrument("GPIB::22")

for i in range(0,12):

      command = "VOLT " + str(voltage) ## command here is VOLT <value>
      source_agilent.write(command)
      print "Current value on source meter is:", source_agilent.ask(":MEAS:CURR?")
      print "Current value on multimeter is:", multi_agilent.ask(":MEAS:CURR?")
      voltage = float(voltage) + float(0.1)

With this program and the setup i explained, everything worked for one complete day. i could get all the values and they looked really fine. After that , i mean the next day the source meter stopped supplying voltage and behaving as explained above. the multimeter is functioning fine. when i used one more supply box of keithley over the same GPIB PCI, it also functioned for few days and finally behaved in almost the same way. i dont know what is making these supply boxes go out of order in this manner. Please help me in this regard.

Ground value at the place i am working is at 3.6 - 3.7 volts.

Thanks,
Raju Namburi
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MattC May 24, 2010 8:52 AM
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Hi Raju,

When you say:
"Ground value at the place i am working is at 3.6 - 3.7 volts."
How are you measuring this?

When the supply was working correctly, what did you have connected to the output? Any details that you can provide about the load you were testing would be helpful. Is the load inductive at all? Is there any way that the load fed anything back into the output of your supply? Since two different power sources both had similar issues testing the same load, let's take a look at it.
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RajuNamburi May 24, 2010 11:31 PM
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Hello,

The load is a simple mobile device. the source meter supplies voltage to a 5 volt battery connected to the mobile device. to be exact, the source meter works as a fake battery to the mobile device. nothing more than that. when i say the ground voltage, i meant the potential btw neutral and ground.

Thanks,
Raju Namburi
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MattC May 25, 2010 1:11 PM
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Hi Raju,

From everything you have said so far, it sounds like something has happened to the Interface Board (though the broken Keithley unit is still striking me as odd). It looks like you have to send the power supply in for service. Please contact Agilent to set up the service. I am not sure where you are located but this page: http://service.tm.agilent.com/infoline/servicelocations.aspx should provide you with all of the contact information that you need.

Please let me know if you have any questions or concerns.
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RajuNamburi May 25, 2010 7:23 PM
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Hello,

           Thanks for your support Matt, it might be the interface board that is malfunctioning, I know that some hardware was not functioning right but i just want to know what made that or what might make that interface board behave like that. what can cause such behaviour? i am trying to know the reason just because i just want to eliminate those things which might cause the same problem once it comes back from repair. What can cause problems to interface board ?

         1. GPIB commands ?
         2. High ground value?
         3. Anything related to the load ( i think its very small in my case)
         4. Ways of using it ?

             Can you help me in finding the reason why the interface board is gone ?

Regards,
Raju Namburi
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MattC May 27, 2010 2:07 PM
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HI Raju,

None of the things that you have mentioned seem like they would hurt the interface assembly. I spoke with one of our designers and he agrees. Unfortunately it could just be that a component failed or a wire or something like that came loose. Just to go through your list of concerns:

1. GPIB commands should not effect your supply unless you sent something to re-initialize your unit (we publish this program in our service manual and you would know if you sent them).
2. The ground value is not really high enough to be a concern here. This seems like it would affect the input stage more than the interface if it was an issue.
3. If your load is not kicking voltage back into the unit , I do not think it would break the interface. One test that we can have you do to chack the interface is to send a *IDN? command and let me know what the response is.
4. The only thing that could have caused this error is something erasing the Non volatile RAM on your unit. The errors that you mentioned in your previous post all point to an issue with the NVRAM on the interface.

Please let me know your thoughts.

Matt
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RogerioHein Mar 2, 2016 12:44 PM
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Matt,

I bought two used Agilent 66332A power supplies, manufactured in year 2000, that presented the same issues, the same error messages in the same order (1,2,3,4,5,80,11,0) as our colleague. The first one fail after about 40 minutes after turn on with no load. The second one was connected to my multimeter and worked fine until the error messages. Then one supressor capacitor (220 nF, 275VAC, X2 film capacitor Kemet PME271M) exploded, probably damaging the neighbours (two 2,2nF Y2 film capacitor. The ground at mains was about 0.8V. Can this NVRAM issue be justified by a noisy AC input, caused by deffective supressor capacitors? Thanks in advance.
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- MattC @ RogerioHein on Mar 3, 2016 11:46 AM
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  Hi Rogerio,
  
  I do not think that those capacitors would be an issue for the NVRAM.
  
  It seems like it is something with the interface PCA to me.
  
  Sorry that I do not have better news.
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  - RogerioHein @ MattC on Mar 3, 2016 1:48 PM
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    Thanks, Matt. So, are they definitively dead? I could register a new value for fan speed in the unit before the capacitor failure and it was stored even after a turn-off/turn-on cycle. Even in this case, is the Ad2 board dead? Can it be repaired?
    Thanks again!
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    - MattC @ RogerioHein on Mar 7, 2016 12:13 PM
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      Hi Rogerio,
      
      Without having the unit to test, it is difficult to answer definitively. There is a service manual for these at Service Manual. This should give you some clues as to what to look at (the troubleshooting flowcharts are very useful).
      
      The one thing to note is that these units have gone to unit exchange instead of repair in terms of support strategy so a lot of the parts might not be available from Keysight.
      
      Let me know if the service manual helps.
      
      Matt
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      - RogerioHein @ MattC on Mar 9, 2016 5:34 PM
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        Thank you again, MattC. Could it fail due to a bad capacitor in A1 board? I am suspecting of C305 and C306, since I could not measure any reference voltages at table 3-3 from service manual, except for the +5V Interface, OK at 4.973V. Looking the boards with a thermal camera, the A2 board seems energized, but A1 seems to be only energized in the circuit for +5V interface bias supply. For the rest of A1 board, I can only observe a hot R300. Does it make any sense for you?
        Correcting my last message, I could not store any new fan speed data on memory. After a turn-out, it returns to anterior value.
        Thank you for your help, and sorry about my queries.
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        MattC @ RogerioHein on Mar 10, 2016 12:15 PM
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        I have never repaired one of these myself so I cannot offer too many tips! It definitely does look like there is an issue with the bias voltages though.
        
        Sorry that I can't help more.
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        RogerioHein @ MattC on Mar 10, 2016 3:51 PM
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        Please forgive me, and many thanks for your help and patience! This discussion was really helpful!
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Could not change voltage on agilent 66332A measurement sour

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