Spectrum Analyzer - Rigol DSA815

[TurboTom]

The discoloration around the thermal tab of U1211 (LM317EMP) is a clear indication that this voltage regulator got hot. My guess would be a short circuit on the 15V rail, most probably the result of a broken tantalum or cracked MLC capacitor. Find the short, (ideally with a thermal cam) and replace the culprit... But if there's still some warranty time left, just have the instrument fixed or replaced.

Edit: Btw, what's that ugly stuff on the PCB near TP1201?

[auato]

I have my DSA815 open, and also measure 36 V in the unplugged state.

Edit: At the test point TP1209 I measure 15.00 V.

Peter

Thanks Peter I just wanted to ask you about this 15V… So, it seems that the voltage regulator is not working correctly indeed at Vin I have 17V and 0 on all other pins.

Thanks @TurboTom really I couldn't notice earlier this discoloration around the thermal tab of U1211. Unfortunately it is no longer covered by warranty

[TurboTom]

The LM317 series of voltage regulators is short circuit / overload protected. So I wouldn't expect it to be broken in your DSA. Please check resistance from TP1209 to ground with a multimeter -- I'ld predict you will find a dead short. Now comes the difficult part: finding the damaged component that shorts this rail. The easiest approach is feeding a low voltage (sub 1V) at considerable current (>0.5A) into that rail by an external laboratory power supply and observing the PCB with a thermal camera -- you will find the culprit to get warm. If you haven't got a TC, you may spray some IPA (isopropanol) on the PCB and observe where it evaporates first.

If you don't find a short on the 15V rail, U1211 may have failed after all, just replace it.

I'm pretty positive that this DSA can be fixed without too much hassle.

[auato]

The LM317 series of voltage regulators is short circuit / overload protected. So I wouldn't expect it to be broken in your DSA. Please check resistance from TP1209 to ground with a multimeter -- I'ld predict you will find a dead short. Now comes the difficult part: finding the damaged component that shorts this rail. The easiest approach is feeding a low voltage (sub 1V) at considerable current (>0.5A) into that rail by an external laboratory power supply and observing the PCB with a thermal camera -- you will find the culprit to get warm. If you haven't got a TC, you may spray some IPA (isopropanol) on the PCB and observe where it evaporates first.

If you don't find a short on the 15V rail, U1211 may have failed after all, just replace it.

I'm pretty positive that this DSA can be fixed without too much hassle.

Ok a thermal camera is really cool but I don't have one of it and it also looks like a bit expensive.  I only have some alchool spray and flux

[auato]

Edit: Btw, what's that ugly stuff on the PCB near TP1201?

Yes, it looks like that foam rubber also Peter has. @TurboTom you have a good eyes

[buble_lab]

@tv84 - thank you for your help and BLESS this thread.
All options on mine.

[auato]

update:
today I completely pull out the board, desoldered that IC LM317 on the 15V rail, checked the impedance between the rail and ground (short circuit of 0.5 ), injected 1.0V then 2.5V from an external power supply and with my hand I noticed a llight warming in a particular area under the shield. At 2.5V the current was 1.5A. As the heating was barely noticeable, I increased the voltage to 10V. At 10V the current moved from 1.5A to 5A and you can see what is happened:

https://youtube.com/shorts/IYQJwg59dvw?feature=share

Removing that tantalum cap (47uF-35V), the consumption dropped to 0.1A. I don't know if the voltage regulator LM317 is still OK and if it's necessary a replacement of that tantalum cap as I have some new 47uF caps but at 16V.

[auato]

update:
removed shorted tantalum cap

https://youtu.be/brQo1g0AJbo

[eloso]

Interesting things, tantalum caps.  They do get a horribly bad press and you're not alone in suffering a failure.

I spoke to a contact who designs electronics modules for spacecraft around 5 years ago. He told me that there was no problem in using tantalum caps for mission critical modules as long as they were good quality and they were specified correctly.

Since then I have done some reading and where a design specifies a tantalum I would tend to replace with a tantalum. There may be a reason why that particular component was selected and some voltage regulators , especially LDOs can be very twitchy about the exact characteristics of their output capacitors. To high an ESR = problem and too low an ESR = problem.   Go with the manufacturers datasheets.  I do know that a common mistake is using caps of insufficinetly rated voltage. For example for a 12V circuit it would be easy to think that a cap of 16 or 25V would be ok. But that might actually be incorrect. The cap manufacturer should publish a derating curve and it might be indicated to double or triple the rating for some circumstances. It is never ok to use a 16V tantalum with, for example a 12V rail.

I wonder if you can identify  the manfacturer of the capacitor in question ? It would be interesting to know.   I'm no expert but I would replace it with another tantalum from a top quality manufacturer and of a voltage rating as least equal to the one removed.  Maybe real experts will comment.

No anti-tantalum / pro-tantalum flame wars please !

Cheers


Eloso

[auato]

I wonder if you can identify  the manfacturer of the capacitor in question ? It would be interesting to know.

Unfortunately I am not able to identify the manufacturer.

Frankly speaking the machine is running without that cap and I dont' know if it is also necerrary to find a good replacement for it. I have to buy online some generic of them because I only have some 47uF-16V that, honestly, I dont' want to use on a 15V rail.

[oddbits]

Hi all , can someone please send me in the correct direction ?.  Just bought a 815 tg , and the past couple of days reading this forum, but my old brain is not taking it in.

815 DETALS
      MAINBOARD 00.09
      RF BOARD    00.05
      DIGI BOARD 00.05
      FIRMWARE   00.01.19
      BOOT           00.01.04
Can someone tell me if this one can be done and if so by software or short ?. 
Any info would be greatly appreciated .  thanks in advance..

[buble_lab]

Read Reply #1087 from tv84 on this thread.

Hi all , can someone please send me in the correct direction ?.  Just bought a 815 tg , and the past couple of days reading this forum, but my old brain is not taking it in.

815 DETALS
      MAINBOARD 00.09
      RF BOARD    00.05
      DIGI BOARD 00.05
      FIRMWARE   00.01.19
      BOOT           00.01.04
Can someone tell me if this one can be done and if so by software or short ?. 
Any info would be greatly appreciated .  thanks in advance..

[oddbits]

Yes all done and many thanks to tv84 , you are a star , 

[Lanman100]

Sent a PM. Thanks!

[egloni]

I am new in this forum
I bought recently DSA815 -TG

Version of Main Board: 00.09
Version of Radio Frequency Board FPGA: 00.05
Version of Digital Board FPGA: 00.05
Version of Firmware: 00.01.19
Version of Boot: 00.01.04

If anyone can help me
To enable VSWR

[IRB]

Noob question,  is there a way to mirror the DSA screen onto a pc  WITHOUT taking control of it

If you control the DSA815 via SCPI, the local operation is automatically locked. You can unlock the operation via SCPI command. But if you want to read and display e.g. a trace all the time, this does not work with simultaneous local operation.

Peter

I wrote a screen grab via USB, in VB6. I posted it a while a go. It does take control of the analyzer. Then the user needs to press the ESC key at the bottom left of the keypad. I did try to code a release, it goes in to remote when communicated with. I tried sending the "ESC" key that did not work for me:
:SYSTem:USERkey:KEYCmd <key_value>{,<key_value>}

Last I tried it works on the RSA5065 and the DSA-815.

I added TCP option in Rev E below...
   

[IRB]

I tried sending the "ESC" key that did not work for me:

With every firmware version the SCPI command should work:

:KEYB:KEYV ESC

From version 01.12 there is a separate one for local operation:

:SYST:COMM:BRMT 0

Peter

Peter
Thank you for the information. 
I do not have the DSA-815 in front of me.  I tried both commands on my RSA5065-TG, sorry to say neither one seems to have worked.

I wonder if that has to do with the fact that I am using the USB?

[IRB]

Sorry, the commands are for DSA815, I didn't add that.

Peter

Here is an updated zip of the exe. Updated with two buttons one with the :KEYB:KEYV ESC and the :SYST:COMM:BRMT 0.

I hope they work, as I do not have the DSA815 near me.

Someone please let me know if one or both work.

I added TCP in Rev E below...

[Kean]

Here is an updated zip of the exe. Updated with two buttons one with the :KEYB:KEYV ESC and the :SYST:COMM:BRMT 0.

I hope they work, as I do not have the DSA815 near me.

Someone please let me know if one or both work.

While I wasn't able to grab a screenshot for some reason from my DSA815-TG over TCPIP (maybe a problem with my VISA install?), those two buttons both worked to release the remote connection (remote mode entered separately via Tekbox EMCview software).

[IRB]

Here is an updated zip of the exe. Updated with two buttons one with the :KEYB:KEYV ESC and the :SYST:COMM:BRMT 0.

I hope they work, as I do not have the DSA815 near me.

Someone please let me know if one or both work.

While I wasn't able to grab a screenshot for some reason from my DSA815-TG over TCPIP (maybe a problem with my VISA install?), those two buttons both worked to release the remote connection (remote mode entered separately via Tekbox EMCview software).

The program was not written for TCP. I wrote it for USB control.  I have not tried to connect my unit via the network port.

Does the top box fill in if you click the Find and Connect button?

The top box I know is the address of the analyzer I get back from the API. 


Thank you for the feedback.

[Kean]

The program was not written for TCP. I wrote it for USB control.  I have not tried to connect my unit via the network port.

Does the top box fill in if you click the Find and Connect button?

OK.  No the Find and Connect button didn't work.  I typed in TCPIP0::192.168.xxx.yyy::INSTR and then clicked the buttons.
As I use EMCview for a lot of my measurements, I don't often need a screen grabber but it might be useful occasionally.

[IRB]

The program was not written for TCP. I wrote it for USB control.  I have not tried to connect my unit via the network port.
Does the top box fill in if you click the Find and Connect button?

OK.  No the Find and Connect button didn't work.  I typed in TCPIP0::192.168.xxx.yyy::INSTR and then clicked the buttons.
As I use EMCview for a lot of my measurements, I don't often need a screen grabber but it might be useful occasionally.

The save file has better clarity then the image shown in the program.



I added a option button to switch between USB and TCP, then added the code behind it... If the TCP port is open selecting USB will Close it. 

Start the program:
   For USB  Click the Find and Connect, the USB address should fill in the top text Box, click the Grab Screen Image button


   Select TCP       Set the IP     the Subnet does nothing    Leave the ports alone(Unless you have changed them)    Click OK to use the IP and Ports.
   Click the Find and Connect to Open the Port ( an *IDN? is sent)  then click the Grab Screen Image button.

There is no save for the IP so it will need to be set when the program is re-started.
A number (file size) will show up in the text box next to the Read button, if the image does not appear I will need that number to correct the program.
For the RSA I know it's "1843254".

Please let me know if this works on a DSA815, as I mentioned I only have the RSA5065 near me to try.

[IRB]

hi @ll

Noob question,  is there a way to mirror the DSA screen onto a pc  WITHOUT taking control of it

I have Ultra Spectrum and Ultra Sigma installed,   tried some other pieces of softwares  no luck, some of them relies on Libusb drivers, and don't detect the DSA ??

While tring to answer a question for Frex about the web control interface on RSA3000/5000
https://www.eevblog.com/forum/testgear/new-rigol-real-time-spectrum-analyser/msg4911775/#msg4911775

I do not have the DSA815 near me, but when I connected to the Rigol RSA5065 through the web browser, the unit did not go into "RMT" mode so all the function were available on the unit.   I do not know if the RSA815 has the Web Control Feature.

You could get a HDMI usb capture device, I have no affiliation to this I just searched amazon.com:
https://www.amazon.com/Capture-Papeaso-Editing-Streaming-Teaching/dp/B0BFBN4K8H

[Kean]

@IRB I did some quick tests again with my DSA815 via Windows 10.

With Rev D of your program and connected via USB cable
- The Find and Connect button seems to work (DSA815 shows Rmt) but the Grab Screen Image button does nothing other than the app seems to hang for a few seconds.
- I can use either the Send ESC or Send BRMT0 buttons to exit Rmt state back to Local control.

With Rev D of your program and connected via TCPIP by manually typing: TCPIP0::192.168.xxx.yyy::INSTR
- Exactly the same as with USB, so your program did support TCPIP via VISA but the screen grab seems to be incompatible.

With Rev E of your program
- I get an error that MSWINSCK.OCX is missing and cannot run it.  Wow VB6 & OCXs, that brings back bad memories!
- This isn't something I want to search for let alone install on my Win10 machines, but it shouldn't be needed as mentioned above.  VISA takes care of the comms layer.
- Because I think you only added the file size display in Rev E, I cannot tell you what the response is for the DSA815.

[Kean]

Forgot to mention, regarding your comments re assisting Frex...
The DSA815 has a web page, but does not include a Web Display or Control Feature - just some info and network config pages.
It also doesn't have HDMI output, unlike the RSA3000&5000 models.