Rigol MSO 2202A input circuits damaged - Page 1
Forum section: electronics / repair

author: Dieter
author_rank: Newbie
timestamp: March 18, 2017, 01:59:06 pm
content: Rigol MSO 2202A input circuits damagedBy accident, the input impedance was switched to 50 Ohm and a Voltage of about 60 Vpp applied at the same time to both channels . The fist resistors after the BNC sockets are damaged such that the value can no longer be identified. Batronix (I bought the rig from them) could only offer to change the whole motherboard at cost of € 1.300.--. They even cannot help me with a schematic diagram and even worse are unable to give me the value of the resistors in question.Can anyone help and me with an information to this problem?

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: March 18, 2017, 02:30:42 pm
content: You can find tear down photos of the DS2000 on Daves Flikr account:https://www.flickr.com/photos/eevblog/sets/72157631618295437I believe that the mso2000 could be roughly the same.

author: Dieter
author_rank: Newbie
timestamp: March 18, 2017, 04:34:10 pm
content: Hi,thank you again. Meanwhile I found the right picture showing a similar design. However the resistor I was looking for is marked "51X" which obviously is a number and not a resistor value. Any Idea how I can translate this number ?Thank in advance.Dieteralternative my mail: pivi@aon.at

author: Carrington
author_rank: Super Contributor
timestamp: March 18, 2017, 04:44:08 pm
content: Easy 51X is 33.2http://www.hobby-hour.com/electronics/eia96-smd-resistors.php

author: Monkeh
author_rank: Super Contributor
timestamp: March 18, 2017, 04:48:36 pm
content: Quote from: Carrington on March 18, 2017, 04:44:08 pmErr, 33.2.I'd be willing to bet the rest of the termination is a little unhappy, and possibly the relay, too.

author: Carrington
author_rank: Super Contributor
timestamp: March 18, 2017, 04:59:29 pm
content: Yes, check my previous post.I noticed it two seconds later.

author: Carrington
author_rank: Super Contributor
timestamp: March 20, 2017, 03:57:41 pm
content: Hello Dieter!I received your PM, I will try to help you, as far as I can.First I recommend you to review this post:https://www.eevblog.com/forum/projects/project-yaigol-fixing-rigol-scope-design-problems/msg890966/#msg890966I'm pretty sure it's going to be very useful to you.Also, I think that you should post here some pictures from your MSO2000A (front-end) here, as well. Just to compare.Cheers.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 20, 2017, 04:00:34 pm
content: Do the inputs still work in non-50R mode ?

author: Dieter
author_rank: Newbie
timestamp: March 20, 2017, 07:48:52 pm
content: thanks to everybody for trying to help me. I am sure together I will get my scope back to work. Tomorrow I will post several pictures from the front end lay out.Only channel 1, and only 1MOhm setting, detects signals but the amplitudes are too low. I will change the resistors and if necessary the relays as the next steps.

author: Carrington
author_rank: Super Contributor
timestamp: March 20, 2017, 08:47:19 pm
content: Quote from: Dieter on March 20, 2017, 07:48:52 pmToo low on AC & DC mode?

author: Dieter
author_rank: Newbie
timestamp: March 21, 2017, 05:44:27 pm
content: made some experimental measurements today before taking the scope apart in order to make some images that i will post later.Signal applied to scope from a waveform generator:wave form: sineU = 2Vpp, f= 7, 14, 30, 100 Mhz........scope displays: 20mVpp on all "f"5Vpp 45mVpp10Vpp 90mVppamplitude unchanged 7 to 100 Mhzsame amplitude coupled A or Dchannel1: however the displayed sine wave is not stable, it moves up and down slightly at appr. 10Hz.Surprisingly also channel 2 works today giving very similar results. Maybe fiddling around on the rig has changed something.up to this test channel 2 was dead.

author: Twoflower
author_rank: Frequent Contributor
timestamp: March 21, 2017, 07:59:13 pm
content: Your values seem to indicate that you haven't setup your scope correct. It seems you are using 10x probes with a 1x setting in the scope. It does nothing but tell the scope to multiply the measured voltages and voltage/div by 10.And that makes me wonder what happened. You seem to use a 10x probe, that means on the termination resistor is 'only' 6V. The input is rated in 50Ohm mode to be 5V RMS, so a 6V wouldn't kill the front end immediately. Or did you connect the signal direct to the BNC connector?EDIT: I'm still jet-lagged. So it is not 10x but more in the 100x region. Which would be rather odd for a wrong setting (even since the scope allow a 100x setting too). So probably you should just ignore my post.

author: technogeeky
author_rank: Frequent Contributor
timestamp: March 22, 2017, 04:19:11 am
content: I have more pictures (and non-macro pictures, if somehow they would be helpful) from repairing my scope front-end also. Granted, it's only a 1054z but it's the same manufacturer, and assuming "CH2" is essentially oscilloscope input (and not the RF input) it should be similar enough damage.See the attached pictures.Note:In damage-01, the traces (from input to a 75R, to square pad, to relay) appear in-tact but they are not.In damage-02, you can see the debris from the 75R resistor "fanning out" between a input ground pad and the square grounding pad.In repair-01: For the repair, I simply bypassed the curved ground-shielded trace there; it was ripped halfway out. The pads for the resistors were also heated off. I used some30 AWG silicon multistranded wireI had laying around. I glued the wire and the resistor down in place (with glue stick glue... ugh!).In possible-remaining-damage-01: I noticed that, at some angles, this trace from signal pad to relay looks damaged too. However, since I have tested the scope's input as pictured and have found no errors, flaws, or extra noise (up to about 10 MHz for fast signals, 300 MHz for sinusoidal ones)... I am just going to leave that as-is.I suspect I did what was suggested here (and what you may have done): I think I may have mistakenly put a powerful source (in this case, a handheld radio with outputs 60Vpp or RMS, I forget... but a lot) straight into the scope input with a BNC.Also note: this is clearly not a good enough fix in general. The original trace was embedded in a ground plane, and this is not. I suppose you could have used some very small coax cable (like what's used with SMA) and grounded the outside.

author: Carrington
author_rank: Super Contributor
timestamp: March 22, 2017, 12:18:28 pm
content: Quote from: Dieter on March 21, 2017, 05:44:27 pmWas the signal applied a sinewave? Do you get the same relations for a DC signal?The 60V you applied by error were DC or AC? If AC, high frequency?Find the affected parts should be easy, just follow the path. But avoid links/images/schematics from the non-A versions, because it's input stage is slightly different to A versions. However, I don't know if there are different variants for the A versions, that's why we need images/pictures from your oscilloscope PCB (front-end).https://www.eevblog.com/forum/projects/project-yaigol-fixing-rigol-scope-design-problems/msg890966/#msg890966The information contained in the link above should be enough to find/replace the faulty parts, assuming that both are the same variant.However, the capacitors are a different history, and maybe a big problem, because we don't have any reference, so fingers crossed.Do you have problems to found the relationship between the electrical scheme and the components in the pcb? SMD marking codes, etc...For semiconductors this link may help:http://www.ecadata.de/mysuchneu/ecadata.php?F_SPRACHE=1What components have you checked?Also, are the vertical position knobs responsive?Edit 1: Wrong link.

author: Carrington
author_rank: Super Contributor
timestamp: March 22, 2017, 12:20:08 pm
content: @technogeekyWow, almost volatilized!

author: Carrington
author_rank: Super Contributor
timestamp: March 22, 2017, 12:53:07 pm
content: Non-A version, avoid it. I post it just as a curiosity.Note: The yellow and black values correspond to different Non-A revisions.

author: Bud
author_rank: Super Contributor
timestamp: March 22, 2017, 01:20:32 pm
content: Use the schematic in the link Carrington provided. Should be a no brainer to isolate the fault.