Author Topic: Advantest U4941 Portable Spectrum Analyser repair. By Fraser  (Read 15439 times)

0 Members and 1 Guest are viewing this topic.

Offline cvanc

  • Frequent Contributor
  • **
  • Posts: 595
  • Country: us
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #25 on: November 12, 2016, 10:20:13 pm »
Very much enjoy reading about your efforts.  Well done and thank you.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #26 on: November 12, 2016, 11:32:43 pm »
It was not as interesting as I had hoped. Failed capacitors and a MOSFET are pretty run of the mill repairs really. No delving into the RF Voodoo this time I am sorry to say.

I tested the analyzer and it is working perfectly. The chap who sold it to me is also pleased that I saved the unit from 'parting-out' or the scrap heap. A good result 🙂

Fraser
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #27 on: November 12, 2016, 11:34:23 pm »
I also have a couple of Advantest R4131 Spectrum analysers that are in the repair pile. Those will also be documented on this forum when I get time to work on them.

Fraser
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #28 on: November 13, 2016, 07:32:19 pm »
As the sharp eyed will have noted, this repair is not yet complete  ;)

I returned the unit to correct operation with the work on the DC-DC module, but that is not the whole story. As I stated at the beginning of this thread, the capacitors on the microprocessor and another digital PCB also looked suspect due to corrosion on the leads. Experience tells me that this is likely caused by electrolyte leakage rather than atmospheric effects (no other surface corrosion was visible on other metal parts or solder joints).

Today I had a few minutes to tack the two outstanding boards. I removed all of the SMT electrolytic capacitors using the twist method and all went well with no adverse effects on the PCB. As expected, several of the capacitors had started to lead around their lead seals. The fluid was starting to pool under them on the PCB but no obvious corrosion had occurred. A lucky escape fot the PCB and testament to the laquer coating quality.

The cleaning and preparation approach for these two PCB's is a little different to that of the DC-DC module as the contamination is far less severe and a full clean process is not justified. The full clean process comes with risk and so should be carried out employing common sense rather than automatically, as I will explain.

The areas of contamination on the two PCB's are limited to directly under the capacitors and no fluid spread could be found further afield. The cleaning process used is as follows:

1. Electrolytic capacitors removed
2. Lead remnants removed with fluid flux and a soldering iron.
3. A good layer of fresh solder applied to ll capacitor pads
4. New solder removed from capacitor pads
5. PCB area around capacitor pads hand cleaned with a Q-Tip and IPA.
6. PCB placed into orbital mixing bath filled with IPA to wash away any contamination on the PCB. Duration 10 minutes for microprocessor PCB and 3 minutes for PCB fitted with Lithium cell.
7. PCB allowed to drip off excess IPA
8. PCB placed into orbital mixing bath filled with De-ionised water. Duration 10 minutes for microprocessor PCB and 3 minutes for PCB fitted with Lithium cell.
9. PCB dries in warm air drying cupboard.

Some readers may wonder why I did not use the Ultrasonic Cleaning Bath this time. Ultrasonic cleaning is justified where heavy contamination exists and where components are relatively robust and without special needs. Using such cleaning technology casually and without due consideration invites problems. The microprocessor PCB contains many sensitive processing components that may, or may not respond well to Ultrasonic cleaning. If they do not respond well, the SA could be effectively trashed by unnecessary ultrasonic cleaning. The other digital PCB contains a AA size Lithium cell. Immersing such in cleaning fluid heated to 40C is not particularly unsafe, but it could lead to unpredictable conduction and electrolytic action between the battery and areas around it. Loss of the supported memory data is also a possibility. The conductivity and purity of the cleaning solution is not known so it is best to play safe with batteries that cannot be removed from a PCB without vital data loss. IPA and De-ionised water present little risk to the battery or memory chip data contents. IPA and clean water are appropriate cleaning mediums for this limited electrolyte contamination scenario.

Please also note that I did not use solder wick on the PCB containing the Lithium battery in order to avoid the risk of shorting out the battery or the power rail that it supports. Common sense stuff really.

Off of the cleaning discussion..... take a look at the number of bodge wires and components on the PCB that contains the Lithium battery. I am both disappointed and amazed to see such a PCB installed in a production issue Advantest Spectrum Analyser originally costing many thousands of Pounds. IIRC they were around £10K  :scared:

To my eye, the PCB contains an awful amount of botchery that should have been addressed by a new revision of PCB. There are even IC's glued on top of others and bodge wires used to connect to them. Floating resistors on the end of bodge wires.... oh dear  ???  Whilst the soldering and wires are well executed, there are too many of them and such would not normally pass testing on a vibration table. The mastic application on the bodges is also poor. Pretty nasty all round really........but it does function so I will not stress about such. It was just shocking to see this from Advantest, a normally high quality equipment manufacturer.

Note: most of these pictures were taken before the PCB's were cleaned in the orbital mixing bath.

Fraser
« Last Edit: November 13, 2016, 07:50:03 pm by Fraser »
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #29 on: November 13, 2016, 07:34:43 pm »
Bodgery detail.....
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #30 on: November 13, 2016, 07:36:49 pm »
More bodge pictures.......
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #31 on: November 13, 2016, 07:37:56 pm »
After a bath, and the removed electrolytic capacitors.

Fraser
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #32 on: November 13, 2016, 07:55:07 pm »
When I find time I will post pictures of the rebuilt PCB's and will take a look inside the RF and synthesizer modules to find any electrolytic capacitors that are used within them. Those will be changed as well. Every SMT and through hole electrolytic capacitor is considered suspect in this analyser as so many have already failed and leaked to a greater or lesser extent. Owners of these analyser's be warned.... you are on borrowed time if you have not replaced the electrolytic capacitors.

Fraser
 

Online SeanB

  • Super Contributor
  • ***
  • Posts: 15345
  • Country: za
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #33 on: November 13, 2016, 07:55:22 pm »
You are right Fraser, bodge city. looks like they made a few hundred of these boards and found they did not work reliably, or something went unobtanium and they had to make a plan to remedy it. You might want to add a little bit more adhesive to those leads, and if you have a conformal coat that you can add to the board to affix them more firmly.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #34 on: November 13, 2016, 08:04:31 pm »
SeanB,

Excellent and helpful comments as always. Thank you.

I have a bottle of brush application conformal coating that I bought for such situations, so will use this on the PCB.

It must have taken some time to modify these boards to this extent. Labour is not cheap in France, where this was made, so I bet there were some interesting meetings to discuss the extent of the bodges and time needed to implement them, in order to remedy the situation. The fact that the bodge wires are not better tied down to the PCB is very surprising and poor practice IMHO. This is, after all, supposed to be a professional field use spectrum analyzer that will likely be subject to rough handling.

I have worked on a lot of Advantest test equipment over the years and have never seen anything like this level of bodgery within them.

Fraser
« Last Edit: November 13, 2016, 08:07:11 pm by Fraser »
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #35 on: November 13, 2016, 10:04:43 pm »
I needed to check inside the RF and PLL modules in order to compile a list of electrolytic capacitors that I need to order from RS. So, a bit sooner than intended, so I am uploading some pictures for your interest.

The bad news is that I have discovered more of those darned dumpy capacitors that leaked so badly on the TDK DC-DC modules. They look OK but will be removed to prevent problems in the future. There are some other electrolytics scattered around the modules that will also be replaced with new stock as all are pretty aged now.

With regard to build quality issues.... they continue. The Japanese certainly build lovely test kit, but this 'Made in France' model certainly has a lot of bodge wires and components on its PCB's. You will see what I mean in the pictures that follow. I will repeat my earlier comment though...... the SA works, so I will not get in a tiz over the bodges.

Enjoy the pictures. I may go into mre detail on their contents later but this is not a teardown thread so such is not really that high on my priority list.

Fraser
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #36 on: November 13, 2016, 10:07:15 pm »
More....
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #37 on: November 13, 2016, 10:11:19 pm »
The following pictures show bodge trimmer capacitors in line with one leg of the 3 legged filters. One filter appeared to have, or almost have, the ground pin shorting to the solder ball of the added capacitor lead  :o Not great me thinks ! More bodges to come......
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #38 on: November 13, 2016, 10:14:57 pm »
More pics, more bodges. Take a look at the additional floating electrolytic capacitors  :o

The last picture shows some pretty suspect reworking of components.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #39 on: November 13, 2016, 10:16:46 pm »
Variable inductors appear to have been added to the board.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #40 on: November 13, 2016, 10:19:29 pm »
Next module... The RF section where the RF Voodoo is resides  :)
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #41 on: November 13, 2016, 10:22:18 pm »
More pics
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #42 on: November 13, 2016, 10:24:40 pm »
More pics......
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #43 on: November 13, 2016, 10:26:58 pm »
More pics.....
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #44 on: November 13, 2016, 10:30:04 pm »
The other side of the RF module that contains a power supply PCB as well as other stuff.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #45 on: November 13, 2016, 10:32:17 pm »
More pics......
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #46 on: November 13, 2016, 10:34:09 pm »
There they are.... the nasty, leak prone dumpy electrolytic capacitors. Not leaking or smelly yet, but only a matter of time I suspect. Out they will come.
 

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 8304
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #47 on: November 13, 2016, 10:48:47 pm »
It was not as interesting as I had hoped. Failed capacitors and a MOSFET are pretty run of the mill repairs really. No delving into the RF Voodoo this time I am sorry to say.

Ah, but even the seemingly boring repairs are useful knowledge in getting a sense for how these things age and what one might be in for when considering buying one.

Speaking of which, I don't think I've ever seen so many bodges in one device. It's a veritable circus of flying components. Rather entertaining.
I TEA.
 

Online Fraser

  • Super Contributor
  • ***
  • Posts: 9167
  • Country: gb
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #48 on: November 13, 2016, 11:11:17 pm »
@Bitseeker,

I agree. It almost looks like a prototype, but sadly it is not  :(

I even started questioning whether this unit is designed by Advantest Japan. The boards all say Advantest Giga. No idea what the Giga suffix indicates. It could be that Advantest bought in the design in an effort to fill a hole in their range, namely a battery powered lightweight colour spectrum analyzer.

Interesting to see, but as you say, it is the greatest number of bodge wires and components that I have ever seen in one piece of production release equipment.

Fraser
« Last Edit: November 13, 2016, 11:13:10 pm by Fraser »
 

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 8304
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #49 on: November 13, 2016, 11:43:18 pm »
Advantest Giga. Interesting. Not much about it, but I did find this:

Gigal Instruments (French) (Google Translate to English)

And a book that mentions Advantest Giga Instrumentation as one of many examples of Japanese firms acquiring businesses in Europe in the 1990's:

Japanese Firms in Europe: A Global Perspective

So, that pretty much confirms your speculation.
I TEA.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf