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| HP 3458A - Fails Slave Test - Convergence |
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| Ade911:
--- Quote from: Dr. Frank on July 02, 2023, 10:39:46 pm --- --- Quote from: Ade911 on July 02, 2023, 07:21:15 am ---Hello Frank, Not sure if you can answer ; if i have access to another unit , would board swapping cause issues with the other unit, not ideal but run out of ideas before asking for a quote from the OEM. Im stuck, I don't seem to be able to find out anywhere where it states the system will still sample even if U180 is dead. It will sample if TRAM is activated , no input and DCV dropped to mV but im not sure why this happens but not in volt range. OVLD signal on U228 is working fine. --- End quote --- You have probably damaged A1 with all your component changes and measuring / injecting signals (I'm partly confused about your descriptions so far.). U180 rarely fails completely. That didn't seem to be the problem, initially. Ade > Correct, something failed slowly over a couple of days , firstly try Autocal , I would read 10V then the autocal would fail, leave for 10 min try again ,10v would pass, the 1 volt would pass , then next test may pass or fail and so on. Thats when I made the mistake of changing components on A1 PCB As the comparators A3U110, U11, U112, 140 are fully overloaded, is A1P100 set correctly? Ade > I believe yes, between Pin 2 & 5 Have you touched the LTZ1000 reference board, and are its voltages and potential applied correctly, especially reference zero? Ade > no not touched , voltage out reads 7.2 volts Is the input amplifier with U100 / TP100 now working correctly, as described above? Ade > I believe yes If you apply input signal of 10V in 10V range, w/o AZ,does that appear correctly @ DC_AD on A3 board? Ade > AZ OFF DC_AD signal on A3 = + 10V What are the voltages on A3U110, pin 2 +3? Pin 2 Zero Volts Pin 3 Zero Volts As long as you can't confirm that A1 is working properly, I would not swap any boards any more. In your situation, I would not jeopardize the other working boards by swapping, to write it in a polite manner. Frank --- End quote --- Please see my comments Ade > xxxx Is there a signal that shuts down the A/D if the voltage is to high or should the A3 board sample continuedly , its like something is blocking the A3 board reading voltage. Thanks Frank. |
| Dr. Frank:
--- Quote from: Ade911 on July 03, 2023, 07:21:08 pm --- --- Quote from: Dr. Frank on July 02, 2023, 09:32:25 pm --- --- Quote from: Ade911 on May 05, 2023, 11:47:16 am --- Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again. Ive checked the Convergence circuit with my very limited understanding of the circuit. :palm: FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working. As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in] |O --- End quote --- @ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle. Therefore it's completely normal, that you see varying voltages on that pin. If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle. If you switch off AZ, then the 10V should be visible continuously @ TP11. Please try that out --- End quote --- when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts. --- End quote --- Which NPLC length do you use? For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi. Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly. Under these conditions, that same signal should be visible @ TP100. If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message. Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1. Or try sampling with APER 1. Frank |
| Ade911:
--- Quote from: Dr. Frank on July 03, 2023, 10:37:08 pm --- --- Quote from: Ade911 on July 03, 2023, 07:21:08 pm --- --- Quote from: Dr. Frank on July 02, 2023, 09:32:25 pm --- --- Quote from: Ade911 on May 05, 2023, 11:47:16 am --- Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again. Ive checked the Convergence circuit with my very limited understanding of the circuit. :palm: FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working. As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in] |O --- End quote --- @ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle. Therefore it's completely normal, that you see varying voltages on that pin. If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle. If you switch off AZ, then the 10V should be visible continuously @ TP11. Please try that out --- End quote --- when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts. --- End quote --- Which NPLC length do you use? Ade > Default value at switch ON. For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi. I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be. Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly. Under these conditions, that same signal should be visible @ TP100. Ade> TP100 = +10VDC If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message. Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1. Or try sampling with APER 1. NPLC set to 0.001 still +10VDC on A1 TP10 APER =1 still +10VDC on A1 TP10 Frank --- End quote --- Evening Frank, The error messages I get at present when turning the unit on are 202 Hardware failure - Slave test convergence 110 Calibration Required - SCAL 0 No Error I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not. If I enable TARM [beeps as well] Inject +10VDC to the front of the unit Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC Error message 114 System Error - balanced rundown convergence 0 No Error If I enable TARM [beeps as well] Inject +1mVDC to the front of the unit Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?] The unit only samples when the voltage is too high for the from screen, in auto nothing works. Is there another A->D that says the input is too high or ?? |
| Dr. Frank:
--- Quote from: Ade911 on July 04, 2023, 07:01:09 pm --- --- Quote from: Dr. Frank on July 03, 2023, 10:37:08 pm --- --- Quote from: Ade911 on July 03, 2023, 07:21:08 pm --- --- Quote from: Dr. Frank on July 02, 2023, 09:32:25 pm --- --- Quote from: Ade911 on May 05, 2023, 11:47:16 am --- Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again. Ive checked the Convergence circuit with my very limited understanding of the circuit. :palm: FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working. As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in] |O --- End quote --- @ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle. Therefore it's completely normal, that you see varying voltages on that pin. If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle. If you switch off AZ, then the 10V should be visible continuously @ TP11. Please try that out --- End quote --- when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts. --- End quote --- Which NPLC length do you use? Ade > Default value at switch ON. For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi. I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be. Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly. Under these conditions, that same signal should be visible @ TP100. Ade> TP100 = +10VDC If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message. Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1. Or try sampling with APER 1. NPLC set to 0.001 still +10VDC on A1 TP10 APER =1 still +10VDC on A1 TP10 Frank --- End quote --- Evening Frank, The error messages I get at present when turning the unit on are 202 Hardware failure - Slave test convergence 110 Calibration Required - SCAL 0 No Error I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not. If I enable TARM [beeps as well] Inject +10VDC to the front of the unit Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC Error message 114 System Error - balanced rundown convergence 0 No Error If I enable TARM [beeps as well] Inject +1mVDC to the front of the unit Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?] The unit only samples when the voltage is too high for the from screen, in auto nothing works. Is there another A->D that says the input is too high or ?? --- End quote --- No. There is an analog overload detection / clamp circuit on sheet 4 / 5 for protection of the fast input DCV path, A1R17/18. This is centered around A1U10, Q26/Q27 as low leakage diodes. This circuit has to switch off the input relays very fast to unload the DCV input. Have you already tried to use a very short NPLC number, like NPLC 0.01, 0.001, or so? There was a difference between the slow and fast sampling. All these rundown convergence error point towards A3, most probably the EL2018, maybe U180. But anyhow, as the input amplifier and the MUX might not work at all/incorrectly, maybe the control shift register chain is defect. Please check those on input / output DATA, like A1U105, sheet 3/5, and U6, U17, U9, U201, 203, U1, U4.. sorry, you have to search for the whole chain by yourself.. I don't know where this begins, and how it ends. I would trace from behind, maybe there is already a break in between.. Frank |
| Ade911:
--- Quote from: Dr. Frank on July 05, 2023, 08:49:18 pm --- --- Quote from: Ade911 on July 04, 2023, 07:01:09 pm --- --- Quote from: Dr. Frank on July 03, 2023, 10:37:08 pm --- --- Quote from: Ade911 on July 03, 2023, 07:21:08 pm --- --- Quote from: Dr. Frank on July 02, 2023, 09:32:25 pm --- --- Quote from: Ade911 on May 05, 2023, 11:47:16 am --- Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again. Ive checked the Convergence circuit with my very limited understanding of the circuit. :palm: FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working. As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in] |O --- End quote --- @ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle. Therefore it's completely normal, that you see varying voltages on that pin. If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle. If you switch off AZ, then the 10V should be visible continuously @ TP11. Please try that out --- End quote --- when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts. --- End quote --- Which NPLC length do you use? Ade > Default value at switch ON. For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi. I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be. Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly. Under these conditions, that same signal should be visible @ TP100. Ade> TP100 = +10VDC If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message. Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1. Or try sampling with APER 1. NPLC set to 0.001 still +10VDC on A1 TP10 APER =1 still +10VDC on A1 TP10 Frank --- End quote --- Evening Frank, The error messages I get at present when turning the unit on are 202 Hardware failure - Slave test convergence 110 Calibration Required - SCAL 0 No Error I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not. If I enable TARM [beeps as well] Inject +10VDC to the front of the unit Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC Error message 114 System Error - balanced rundown convergence 0 No Error If I enable TARM [beeps as well] Inject +1mVDC to the front of the unit Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?] The unit only samples when the voltage is too high for the from screen, in auto nothing works. Is there another A->D that says the input is too high or ?? --- End quote --- No. There is an analog overload detection / clamp circuit on sheet 4 / 5 for protection of the fast input DCV path, A1R17/18. This is centered around A1U10, Q26/Q27 as low leakage diodes. This circuit has to switch off the input relays very fast to unload the DCV input. Have you already tried to use a very short NPLC number, like NPLC 0.01, 0.001, or so? There was a difference between the slow and fast sampling. All these rundown convergence error point towards A3, most probably the EL2018, maybe U180. But anyhow, as the input amplifier and the MUX might not work at all/incorrectly, maybe the control shift register chain is defect. Please check those on input / output DATA, like A1U105, sheet 3/5, and U6, U17, U9, U201, 203, U1, U4.. sorry, you have to search for the whole chain by yourself.. I don't know where this begins, and how it ends. I would trace from behind, maybe there is already a break in between.. Frank --- End quote --- Hello Frank, No input, activating the Reset on the front panel All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve. Maybe its not a problem, A1 U10C, Im checking data coming from A1 U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V. Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned. Many thanks |
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