Resistor of an agilent oscilloscope DSO-X 2012A PS,doubt! - Page 1
Forum section: electronics / repair

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 13, 2016, 10:47:48 pm
content: http://i63.tinypic.com/2h81ws3.jpgI don't know if it's value is 2031 or 2021. Can anyone help me?IT is of a keysight 2000 series, DSO-X 2012A.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 13, 2016, 10:54:37 pm
content: More images:

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 14, 2016, 12:14:34 am
content: If the resistor was in the series E96 or E192 then it could only be 200, 203, 205, 208. With the trailing 1 as the multiplier.As it seems to be part of the rectifier its value may not matter too much.Do you have any closeups of the other blue resistors? Once that will show the font of the 3s, 5s etc.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 12:21:19 am
content: Quote from: HackedFridgeMagnet on November 14, 2016, 12:14:34 amYes,I made a closeup and nothing looks like that number,please say me,what is E96 or E196.It is linked to the pin 1 of Q1 that is a mosfet P12nm50

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 12:26:32 am
content: I am not sure but,sometimes I see a number 2 on that resistor.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 14, 2016, 03:11:03 am
content: https://en.wikipedia.org/wiki/Preferred_numberthats for the series.Resistors normally come in a series of exponentially increasing numbers. what series they belong to is often dictated by their tolerance.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 14, 2016, 03:34:47 am
content: Quote from: SAUL BRITTO on November 14, 2016, 12:21:19 amSo its attached to the gate of an N channel Mosfet.2k does seem an unusual value to me. Not sure if it in series or a shunt from the gate to the source.Have a look what resistor is in a similar position in regards to Q3.It may be in parallel withQ3Q2 in which case they should have similar gate topologies, including resistor values. (as part of PFC?)Also look for shorts on all the semiconductors nearby.edit: meant q2 but third semi from left on heatsink.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 03:52:26 am
content: Quote from: HackedFridgeMagnet on November 14, 2016, 03:34:47 amThis resistor on the gate of Q1 ( In short) as you can see, there is smoke on the foto of PCB.This resistor on the image is measuring 246 Ohms it is linked to another resistor of 5.1 Ohms on the gate of Q3 ( there is one 5.1 Ohms resistor on the gate of Q1 too) I will try to make another image for you.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 04:02:07 am
content: Here are the images I hope you can understand.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 04:10:38 am
content: So its attached to the gate of an N channel Mosfet.2k does seem an unusual value to me. Not sure if it in series or a shunt from the gate to the source.Yes you are right, it is attached gate/source of Q1.That other semiconductors are one diode and two IRF840.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 04:27:58 am
content: Quote from: HackedFridgeMagnet on November 14, 2016, 03:34:47 amI think 2k is a strange value because it is measuring 246 Ohms "on board"Just if it changed for less than your original value. But,as it is in parallel with the shorted mosfet...Maybe this is the effect caused by the short.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 05:12:17 am
content: Removed that "smoked" Tr and measured the resistor again, it measures 1.15 mega Ohms.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 14, 2016, 09:18:19 am
content: Because it such an expensive bit of equipment It might be reverse engineering a schematic of the section. Including all known values and chip types.I dont think I can help anymore without this info.Apparently in parallel mosfet circuits it is very important to match the gate drive circuits but if there is only 1 of that type of mosfet on the board then I dont think the exact value can matter very much.Just for the record, is there any sign of previous work done on the board? This is always something to watch out for.EEVBlog does a teardownhttp://www.eevblog.com/2011/02/15/eevblog-144-agilent-2000-x-series-infiniivision-oscilloscope-teardown/at 2:00 can see the board but it has 4 semiconductors mounted on that heatsink?

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 01:56:43 pm
content: Quote from: HackedFridgeMagnet on November 14, 2016, 09:18:19 amHI. Yes it has 4 semiconductors on that heatsink and there are 4 more on the other side of the board and no, no sign of previous work,it looks original.I have a "service manual" for this unit but it doesn't help as you can hope,we just can find things like trubleshootings,no electric schematics.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 03:00:25 pm
content: It would help a lot if someone had a photo or a layout or any information about this card, I think it would solve this problem quickly.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: November 14, 2016, 09:00:29 pm
content: I've found a diode and was thinking it was a Tr but,no!Looks like JV3 isn't a transistor but a diode in SOT-23 BAT54http://www.s-manuals.com/ru/smd/jvhttp://www.s-manuals.com/pdf/datasheet/b/a/bat54_series_taitron.pdfIf I am right,no more than a Schottky diode in three terminals, one is NC.

author: Vinchi
author_rank: Newbie
timestamp: January 20, 2017, 05:44:55 pm
content: Hi!I also have a broken DSO-X 2012A.I have attached the power supply image with resistor.Was you able fix your oscilloscope?

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2017, 10:46:14 pm
content: Quote from: Vinchi on January 20, 2017, 05:44:55 pmWow ! Thank you so mutch Vinchi, this will helps me so mutch! I will try to fix the scope and tell you the result. What's the problem with your scope?

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 21, 2017, 11:03:02 pm
content: Quote from: Vinchi on January 20, 2017, 05:44:55 pmCan you say me what's the refference of Q1?

author: Vinchi
author_rank: Newbie
timestamp: January 22, 2017, 09:15:27 pm
content: My scope has same symptoms as this one:The power supply for my scope shows 13 VDC so it is ok, i think the problem could be with Windows CE boot. Who had the idea to put windows on the oscilloscopeI think you can fix your scope easy by installing open frame 13vdc 200-250W power supply from Mean WellWhich value you need to know?

author: Vinchi
author_rank: Newbie
timestamp: January 22, 2017, 09:26:29 pm
content: Another image.Does the scope provide power to USB host device when it starts to boot?In my case i think there could be some problem with some voltage regulator or step-down converter chip. May be power problem for graphics chip.

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 27, 2017, 05:49:00 am
content: Quote from: Vinchi on January 22, 2017, 09:15:27 pmHey guy, did you look the screen voltage? maybe a LCD problem...

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 27, 2017, 05:57:04 am
content: Quote from: Vinchi on January 22, 2017, 09:26:29 pmMy scope is completely dead! I need to fix the P.S at first to know how it will reacts

author: SAUL BRITTO
author_rank: Frequent Contributor
timestamp: January 27, 2017, 06:02:19 am
content: Quote from: Vinchi on January 22, 2017, 09:26:29 pmYes, see the the PWM if it does not have a smoked component.Lets think as if it was a notebook mobo, maybe this is a good way to solve the problem.I don't know what kind of technology is used in this screen, common LCD or LED.

author: zgr
author_rank: Newbie
timestamp: September 07, 2017, 08:04:00 am
content: Quote from: SAUL BRITTO on January 27, 2017, 05:57:04 amHi SAUL BRITTOI have a same problem with you. Q1 transistor and 2K resistor are dead. Before i will change them, your experience is very important for me. Did you have a chance fix the P.S. and try to open oscilloscope ? Does change the Q1 and 2K resistor enough for fixing?

author: Jurkstas
author_rank: Newbie
timestamp: October 07, 2017, 06:00:36 pm
content: Quote from: SAUL BRITTO on January 27, 2017, 05:49:00 amHi, I replied tothis topicwith a very familiar symptom. My scope lights one more LED before halting. LCD voltage is down, because it is disabled. I assume it is only enabled later in boot process. Have you found anything more about this issue?

author: Eclipze
author_rank: Contributor
timestamp: September 28, 2019, 08:55:36 am
content: Sharing on a related issue I had just now...DSO-X 3024A power supply failed. Didn't turn on... nothing, no lights, not even the fan running.On the rear of the power supply board, noticed signs of the group of 4x 22kohm resistors overheating (blackened mask). Noticed the solder was cracked. Resistance of the resistors themselves was fine, however not with respect to the PCB pads. Re-soldered the pads and the oscillocope powered up as usual. Perhaps one of those soldered joins failed and caused the overheating of the others... until another joint cracked. Repaired, although would have preferred to replace the resistors. Added a small heatsink.

author: drvtech
author_rank: Regular Contributor
timestamp: January 06, 2020, 06:04:06 pm
content: I stumbled on this thread when I looked up the part number of the PSU in my DSOX2014A. Thought I'd add my two pence worth for future readers. The PSU had gone pop and shorted out the mains input. When I opened it up the main reservoir cap had bulged and it measured about 5uF out of circuit (should be 100uF). Also found Q1 was short. Replaced both parts and PSU came back to life.Some odd snippets of info:- Q1 is the PFC switch. It should be an STP12NM50. I fitted an IRF840 as that's all I had and I needed the scope today. IRF840 is rated 8A and has higher Rds so I'll have to change it for the correct part ASAP. And I WON'T be leaving it plugged in! Those 22k resistors that Eclipze mentioned are also scorched on my unit and it looks as though they supply the bootstrap voltage to the PWM chip, which explains why his wouldn't start up at all.When I bought this scope it was partly on the strength of Dave Jones's tear down and I had always assumed that the mains switch was a real mains switch which turned off the supply. It is now apparent that it does not so all those years (about 8 ) of leaving my scope plugged in have meant that it was sitting there with 400V on the reservoir cap. No wonder it dried out.Anyway, hope the above is usefulDrV

author: mngiggle
author_rank: Contributor
timestamp: November 04, 2022, 02:30:44 pm
content: Landed here for the same reason with an MSO-X 3054A scope; bulging cap, plus scorch marks around the FETs. (Although it looks like ours is mechanically switched, so maybe it's not just sitting plugged in that's the problem.)