Author Topic: Advantest U4941 Portable Spectrum Analyser repair. By Fraser  (Read 15441 times)

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Offline Fraser

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #50 on: November 13, 2016, 11:48:41 pm »
Thanks Bitseeker.

That may explain the quality issues.

Fraser
 

Offline bitseeker

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #51 on: November 13, 2016, 11:53:51 pm »
Indeed. Would be nice to know which devices they built.
I TEA.
 

Offline Fraser

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #52 on: November 13, 2016, 11:59:08 pm »
The hunt for knackered capacitors continues....... this time the front panel assembly.

I found more SMT capacitors and guess what ? ..... they are all leaking  >:(

I have removed them all to check for damage but thankfully no corrosion present.

I have been so fortunate that none of the electrolyte leakage in this analyzer has caused serious corrosion. I am surprised as PCB track corrosion is normally commonplace when the capacitors leak.

Pictures of the front panel attached. With capacitors and after capacitor removal. Replacing the capacitors is not that much hassle or time consuming but this is the first time I have had to replace virtually all the electrolytics in a piece of equipment.

Fraser
 

Offline bitseeker

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #53 on: November 14, 2016, 12:05:53 am »
I have been so fortunate that none of the electrolyte leakage in this analyzer has caused serious corrosion. I am surprised as PCB track corrosion is normally commonplace when the capacitors leak.

You can say that again. It reminds me of the old Tek TDS scopes with tons of leaking caps. I guess you acquired this machine just in time to recover it before serious damage ensues.
I TEA.
 

Offline Fraser

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #54 on: November 14, 2016, 12:11:29 am »
In case anyone is wondering how I know the capacitors are leaking and that it is not flux residue.....when removing these capacitors some were so corroded on the leads that they virtually fell off the board and there was a collection of corroded metal where the leads had one been. A quick sniff test also confirmed leaking electrolyte. Once the capacitor is removed, the remnant leads left on the PCB can be seen and the corrosion on their surface is very obvious. They are a very dark grey colour and easily peel off of the solder pad as corrosion eats away the solder joint interface. You can often see the lead corrosion is visible where it just pokes out past the insulator plate that sits between the capacitor case and PCB. Sometimes there is wet electrolyte under the capacitor, other times the electrolyte has dried to a yellow dusty material. Wet or dry, the electrolyte really pongs when heated with a soldering iron.

I should have taken a photo of the corrosion evidence. Apologies, I was too keen to clean everything ready for the new capacitors to be fitted. If I find another corroded set of leads I shall take a picture.

If in doubt, replace. It saves problems further down the line and may even improve an instruments performance if the capacitor has fallen out of specification due to age.

Fraser
« Last Edit: November 14, 2016, 12:14:37 am by Fraser »
 

Offline Marcel G

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #55 on: March 07, 2017, 12:44:45 pm »
Maintenance: enter shift + 5 = Maintenance Mode

Input password: enter 27466
 

Offline Fraser

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #56 on: March 07, 2017, 01:17:16 pm »
Many thanks  :-+ :)

Fraser
 

Offline Ken1173

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Re: Advantest U3641 Portable Spectrum Analyser repair.
« Reply #57 on: November 17, 2017, 04:41:46 pm »
Hello, I have an Evan Adventest U3641 with a PPL error. Can you give me any guidance on how I should try to stay down? I noticed you check the dc-to-dc converters. Did you pull a card and hook up an external power supply directly to the 12 volt rails? if you did pull the card and hook up the power supply this won't harm anything on the card? Thank you for any and all help.
Best regards,
Ken McGrath
 

Offline Fraser

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #58 on: November 17, 2017, 07:56:34 pm »
I pulled the DC-DC converter card and applied power to its input via the labelled connections on its edge connector. From memory I had to supply a bias to the enable line that controls the DC-DC converter modules. I believe this line is common tonall of them.

I was then able to check the output from each DC-DC converter. No load was needed as the converters are quite happy to operate without a load. All electrolytic capacitors were replaced. If the PLL has electrolytic capacitors on it, they are likely failing, or have failed.

Fraset
 

Offline eb4fbz

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Re: Advantest U4941 Portable Spectrum Analyser repair. By Fraser
« Reply #59 on: January 26, 2018, 08:50:56 am »
Hello Fraser, great work replacing all electrolytic caps! I've had a similar experience with a R3271 some years ago  :-DD

I've read on the Anritsu Yahoo group that you had a booting problem after this replacement, probably due to backup battery loss. Were you able to get it back to life? I'm about to start to replace capacitors on U3661 and i'm worried about this booting issue.
 


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