Solve : Agilent DSOX 2002A "Voltatge overload on Gen out BNC". Thanks you ! - Page 1
Forum section: electronics / testgear

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 07:00:22 am
content: Hi,I bought a used DSOX2002A last week. I updated it to firmware 2.35 and I started the 30 days of evaluation.The scope functions are OK but I can't use the waveform generator function.When I switch on the scope I have the message "Too high a voltage is being applied to the waveform generator BNC".When I use the button waveform I have the message "Voltage overload on Gen out BNC. The GEN out have been disable".There is nothing connecting to the scope...Can someone help me to resolve the situation ? Is it a serious problem ? Thanks a lot.

author: tautech
author_rank: Super Contributor
timestamp: August 25, 2016, 07:14:02 am
content: Have a hunt through the UI, there should be a Self Cal feature for the AWG. Try that.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 07:21:03 am
content: Hi,I have done the "Autotest" on the scope and the result is OK. In the wavegen menu I have reset the parameters.You advise me to do the calibration procedure on the scope ? Thanks

author: TheSteve
author_rank: Unknown
timestamp: August 25, 2016, 07:21:24 am
content: I don't think there is any self cal option for the waveform feature. I am thinking someone applied too much voltage to it at some point and it is damaged internally.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 07:28:59 am
content: Hi TheSteve,Thanks for your answer. I hope your are not right or that the problem will be easily solve...As someone encounter the same problem ?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 08:32:21 am
content: Yep, that is a very bad news for me.I am waiting for more responses and I will decide if I send it back or if I try to open it and investigate.

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2016, 08:51:05 am
content: How about checking if it has warranty and -if it has warranty- send it back to Keysight?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 08:58:04 am
content: I check the warranty and it was from 05/04/2011 to 04/04/2014. So I can't go that way.

author: Faith
author_rank: Unknown
timestamp: August 25, 2016, 09:02:15 am
content: The latest version of the firmware is 2.41 (2015-11-02). Super unlikely that that's the cause however, but shouldn't hurt to try if you're out of options?Also from the Keysight website:After your oscilloscope's firmware is updated, check the calibration status: press  > Service > User Cal Status. If "Results: OK" is displayed, you do not need to recalibrate. If calibration is required, press the Start User Cal softkey.Edit:Did the seller offer you any warranty of their own? Many do if you encounter issues within the first week or so.

author: Kilrah
author_rank: Unknown
timestamp: August 25, 2016, 09:05:26 am
content: You should really complain with the seller ASAP.

author: tautech
author_rank: Super Contributor
timestamp: August 25, 2016, 09:07:35 am
content: Quote from: matthieu.e on August 25, 2016, 07:21:03 amI'm not familiar with the UI of your scope, all I know is those that I sell there is an internal Self Cal features in the UI for both the scope and the AWG.So if we want the calibration of the AWG to be corrected we run the self cal feature for the AWG only.So can you get any waveform from the AWG or does the self test fail disable the AWG?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 09:20:35 am
content: Thanks for your answersI have done the "hardware self test" and the result is OK. I have not done yet the "user calibration" because it require connection between the different channels.I have not any signal on the generator output. When I launch it , there is the error message.I don't know is there is a calibration menu for the AWG.

author: idpromnut
author_rank: Unknown
timestamp: August 25, 2016, 12:38:51 pm
content: Did you try and measure the AWG BNC with a DMM to see if there is a DC voltage on it? Perhaps there is something not right, and this will tell you right away if something on the AWG output pathway is blown.

author: GEuser
author_rank: Frequent Contributor
timestamp: August 25, 2016, 12:42:49 pm
content: Try a dummy load on bnc ?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 01:37:31 pm
content: Hi,Thanks for the advices.When I come home I will try with a load and measure the DC voltage at the output.

author: EEVblog
author_rank: Unknown
timestamp: August 25, 2016, 01:45:28 pm
content: Quote from: blueskull on August 25, 2016, 07:47:21 amThat was fixed before they even shipped the first units 5 years ago.But about 6 months ago my MSOX3000 gave an acquisition memory checksum failure or some such. Keysight replaced it with the 3000T

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: August 25, 2016, 03:13:16 pm
content: The best thing you can do if you're seeing an error is to call our call centers. You get right to an applications engineer with minimal hassle; I've even called in with questions from time to time.Also, I'd contact the seller.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 25, 2016, 04:44:08 pm
content: Quote from: blueskull on August 25, 2016, 07:47:21 amSo from a field of 5 cases you conclude the MSOX Series has "design bugs"? Seriously?While I'm not a huge fan of the limitations of the DSOX/MSOX Series, we have lots of DSOX/MSOX3k(A/T) and DSOX/MSOX4kA out in the field, and aside from the occasional defect and some excessive noise issues with some DSOX/MSOX4kAs the scopes have proven to be as reliable as one would expect from a HPAK product.QuoteSo you believe the MSOX has "design bugs", but you still want to buy one because your hope that the one you buy somehow won't have these "design bugs"?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 04:56:30 pm
content: I come back home and done some measurement.On the ouput BNC I have :- 0V DC- 0V AC- 100 Kohm impedance- no signal at all in high impedance or 50ohm, same with a load.I check the calibration in the menu: it's OK.The demo (demo 1 and demo 2) PIN show waveform. Are they link to the generator function ?Is there any high rez photo of the board on the forum ? Where should I start to investigate ? Thanks.BTW I contact Keysight France by mail, I will see if they respond me.

author: TheSteve
author_rank: Unknown
timestamp: August 25, 2016, 05:00:42 pm
content: You can find some good photo's here from Dave's teardown:https://www.flickr.com/photos/eevblog/albums/72157626631250619

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 08:20:18 pm
content: Seem to be a difficult problem to solve because no one know about it. Am I the only one to have this problem ?There is no schematic to help and try to investigate...I have no voltage on the BNC output so it could be a resistor sensor problem.Any ideas to progress ? Thanks

author: TheSteve
author_rank: Unknown
timestamp: August 25, 2016, 08:43:23 pm
content: I've never heard of or seen anyone post about this issue before. Hopefully looking at the pictures you can find something that is out of place or doesn't look correct. If you do disassemble the scope feel free to take some good quality pictures and post them so we can take a look as well.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 09:08:48 pm
content: Hi,I took some pictures. I saw nothing special. Any idea where I should investigate ?

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 25, 2016, 09:11:11 pm
content: another one

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2016, 09:12:21 pm
content: I'd try to retrace the circuitry (starting from the plug) and see where it is sourced.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: August 26, 2016, 03:30:56 am
content: I did a little digging around the office today, and found that we've seen this once before (that we know of) when someone accidentally tried to drive a signal into that connection.It's not really designed for that, and generally falls under the "user error" fault category.I'll see if I can talk to R&D about what specifically triggers that warning, but no guarantees I'll get an answer in the next few days (or at all).

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 07:39:09 am
content: Hi Keysight_DanielBogdanoff,Thanks you a lot for taking time to ask about this problem. That would be a great help to know what component or area is in fault.I don't think I will be the last to have this problem and it will help a lot for the future.I saw a component which look like a TVS diode (in sot23 package) after the two relays. So if I'm right the BNC output can't be damage by an high voltage at the input.What you said sound right, perhaps someone tried to drive a signal into that connection. That produce a inrush of current and break something.nctnico, yes I will try to retrace the circuit.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 06:29:37 pm
content: Hi,I have done some voltage measurement (they areon the picture linked). I don't know if there is something wrong.There is no RF signal on the test point.Can you give me your opinions about the voltage ? Thanks.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 06:40:06 pm
content: I make a list of the chip list (on the picture linked)- MAX9201:Low-Cost, 7ns, Low-Power Voltage Comparators :https://datasheets.maximintegrated.com/en/ds/MAX9201-MAX9203.pdf- AD8184:700 MHz, 5 mA 4-to-1 Video Multiplexer :http://www.analog.com/media/en/technical-documentation/data-sheets/AD8184.pdf- Relay Axicom IM43 :http://www.farnell.com/datasheets/1717896.pdf- TI062:Low-Power JFET-Input Operational Amplifiers:http://www.ti.com/lit/ds/symlink/tl062.pdf- TI HB94 = SN74AHCT594:8-Bit Shift RegistersWithOutput Registers :http://www.ti.com/lit/ds/symlink/sn74ahct594.pdf/not sure ??- 74ACT08:Quad 2-Input AND Gate :https://www.fairchildsemi.com/datasheets/74/74AC08.pdf- TI LM333A 08AN0TM:can't find the data, if you have a idea ?TI062 is a AOP, it power supply seems to be OK : V+ =13,2V V-=-14V GND=0V. IN+= 3,5V IN=3,5V and output is 11V.I don't know how is the AOP schematic but perhaps there is a problem on IN- or IN+. What do you think ?The two 5V on the second relay seem not good too.

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2016, 07:15:03 pm
content: LM333:http://www.ti.com/product/LM33311V on the TL062's output doesn't sound right. Is this chip driving the output? You could try to remove the chip using hot air and see if the 11V goes away. I'd also check the SOT23 device above the TL062 and see if the other end it connected to a power supply rail (I expect it is a zener or TVS diode though and the other end is connected to ground).

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 07:19:58 pm
content: Yep +11V on the aop output seem strange. Perhaps a fail on IN+ or IN- ? It is difficult without schematic.I don't think LM333 is the old voltage regulator but I can't figure for now.I don't know what are the two sot23 chip. At first look I was thinking of a TVS diode but the two upper pin are not connected to ground.

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2016, 07:46:31 pm
content: Try to measure what is on the SOT23 devices. If it isn't a voltage over 11V it cannot produce the 11V on the TL062's output and you can eliminate the devices as a possible source of trouble.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 07:50:17 pm
content: nctnico,You are talking about the first or the second sot23 chip ? I have already mesure the voltage on the first sot23. There is 13.2 and -11V on the upper PIN.You think I should desolder the first sot23 chip ? Thanks ?

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2016, 07:57:17 pm
content: I'd start by desoldering the parts which are the easiest to desolder. Still I highly recommend to use a hot-air station to avoid damage to the board.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 08:20:45 pm
content: I will try to desolder component in second timeI would like to understand better the fonction and have more advices.I don't have a hot air station, so I think it will be difficult to desolder component...

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 08:40:54 pm
content: I manage to desolder the first sot23 without dommage with a metcal SMTC-005 tip.There is no change. I have the same voltage on the unpopulated PIN of the sod23 and the 11V is again here on the AOP output.Any idea to continue the investigation ? ThanksYou are right , I have to a hot air station, it is useful.

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2016, 08:46:02 pm
content: You can try to lift the output pin on the TL062 or remove it completely and replace it because it is not an expensive chip.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 09:21:44 pm
content: Yes, here it is the voltage on the board without the sot23 chip and with the aop output lift up.I run the scope and the error message is still there. Perhaps I should put back the sot23 chip ?

author: TurboTom
author_rank: Super Contributor
timestamp: August 26, 2016, 09:23:18 pm
content: Since both inverting and noninverting inputs of this TL062 are at 3.5 volts, it seems this opamp is in balance with the 11V at the output. Since all the circuitry at the inverting input (pin 2) is referenced to ground or AC coupled, I would have a close look at the noninverting input (pin3), maybe try to pull it to ground via a resistor (1kR should do) and see if the output changes. The OPAMP may still be the culprit but to me actually it doesn't look very likely. Then the job will start to get ugly...Can you check DC resistance across the two output inductors since there seems to be a slightly different voltage at the signal gen output and the node in between? What kind of instrument are you using to measure the voltages?All the best,Thomas

author: TheSteve
author_rank: Unknown
timestamp: August 26, 2016, 09:25:28 pm
content: Is that a TL062 or a TL061?

author: TurboTom
author_rank: Super Contributor
timestamp: August 26, 2016, 09:28:37 pm
content: You are correct, Steve, the output amplifier circuitry looks like it's a single opamp, so it's more likely a TL061.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 09:29:54 pm
content: TheSteve, I think it is a TL062 but difficult to see on it. Will look at it again.TurboTom, thanks for the advice , I will try tu pull it down with a resistor. You are right I don't know why there is not the same voltage across the inductor. It should be the same. No ?I am using a fluke 177 ta make the voltage measurement. Why ? Thanks.

author: TheSteve
author_rank: Unknown
timestamp: August 26, 2016, 09:46:11 pm
content: Based on the wiring I don't think it can be a TL062. If I was working on the unit I'd remove the TL061 and see if the error goes away and if there is still 11 volts on pin 6.If that doesn't yield any clues then I think you need to start at the output and trace the signal path backwards until you find something that just doesn't make sense.

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 09:50:15 pm
content: Something not make sense. The first inductor have 460 Kohm impedance, I think it is a fail ?I don't see a relation between the problem and that. What do you think ?I look closer to the chip. I think it is not a ti062 or 63. It is write :3091TI 06ZGRJ7I can't find information on it.

author: TurboTom
author_rank: Super Contributor
timestamp: August 26, 2016, 09:59:03 pm
content: So I guess the inductor has released its magic smoke, acting as a fuse and possibly (hopefully) preventing further damage... Some "special agent" must have supplied substantial voltage to the signal generator output, forcing quite some current through the inductors and probably through the clamping diode (which apparently survived since the inductor was faster to blow). For a general test, you can just jumper the broken inductor (or put a 10 ohms resistor into the circuit instead -- if you haven't got a suitable spare inductor that is). If the error is gone after that, voila! If not, the search goes on...Cheers,Thomas

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 10:28:17 pm
content: Thanks you all ! It is a success ! I saw the self problem at the beginning but I don't know with I go investigate on the chip.The high voltage message make me search for a high voltage...So the self is blow, I have to solder a new coilcraft in place and re assemble the scope. The self should act like a low pass filter here. I'am very happy to solve this problem.No message at booting and a nice signal on the scope. It was a long electronic evening.

author: TheSteve
author_rank: Unknown
timestamp: August 26, 2016, 10:31:31 pm
content: Very nice! Even if all of the electrons are falling out

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2016, 10:32:54 pm
content: Cool! Now fix the text being upside down :beer:

author: matthieu.e
author_rank: Regular Contributor
timestamp: August 26, 2016, 10:36:03 pm
content: Yep time to play with this little scope in the right side :beer: