R&S CMU200 TXLO3LEVD ERROR

[DavidAzulay5000]

i have an error on my cmu200
self test on the rxtx board
TXLO3LEVD -0.200 | 0.200 | 1.02V
The device works perfectly, this is the only error

Successfully passes all tests
INTERNAL RF LOOP PATH 1
1->4/2->3 RF LOOP PATH 1

I tried to search for information about the cause of this error for a long time without success
I would appreciate it if you could get information about the reason for this error

[DavidAzulay5000]

the error

[DavidAzulay5000]

    
Dear Customer,

Ticket 507061 has been resolved.
The resolution proposed is:

Dear David

The testpoint for the 3rd local oscillator in the 3rd mixer stage of the TX board delivers a Voltage of 1.02V which is too high. Limit is 0.2V.

Reason for this, perhaps aging or defect of a component.

But we cannot repair the CMU200 any more.

 

With best regards

Winfried Jansen


If you need further assistance on this ticket please login to our Support Center or contact us via email.



David Az <davidazzz8@gmail.com>
   
16:17 (2 minutes ago)
   
to support
First of all, thank you very much for the response
I don't need a fix
My field is repair and calibration of laboratory equipment
The whole problem is that you are one of the only companies that cannot find a schematic for your products .
This definitely makes me avoid purchasing your products in the future.
the right to repair
This is something that every company should respect in our day.
And it's a shame that you are in the same category as Apple

Greetings David Azulay

[DavidAzulay5000]

photos of the rxtx board

I removed the SAW FILTER
836.5MHZ
With the HAKKO FR801 hot air station

I will order these filters
1842.5mhz
836.5 mhz

B69813-N1847-B476 PCN RX Filter 1842MHz SMD

B39841-B4122-U410 836MHz SAW Filter SMD

[DavidAzulay5000]

i order the lilter

[100pcs] B39182-B4139-U410 1842.5MHz SAW Filter 50 Ohm SMD

[50pcs] B69813-N1847-X475 PCN RX Filter 1842MHz SMD

[50pcs] B39841-B4122-U410 836MHz SAW Filter SMD

and the

IDE CF Adapter CF to 2.5 IDE 44pin Adapter Card 2.5''44pin Male CF Compact Flash

PCMCIA TO CF CompactFlash Card - Laptop CF TO PC Adapter Reader Converter

2.5" IDE Hard Drive Laptop Female to 44Pin Male HDD SDD SATA Adapter Converter

[pico61]

I think I have found the reason why the gigafil used on the CMU200, in contact with the microwave absorber, stop working properly!
I have a CMU200 and a few days ago, after turning it on after a long period of being turned off, I noticed that the spectrum analyzer was displaying spurious signals with nothing connected.
After running the selftest I discovered that it gave me an error on the TXLO3LEVD voltage.
After a quick search on the net, I discovered that this is a common error on the CMU200 caused by the microwave absorber sponge which tends to degrade and corrode some Murata Gigafil contained on the analyzer's RXTX board.
So I unsoldered the two filters in question and checked them at the VNA, noting that, in both, the bandwidth was much wider than normal (120 MHz instead of 25 MHz).
It has been written that the sponge corrodes the filters as it degrades but, at least for those of my analyzer, not in such a way as to completely destroy the external copper shell of the filters.
So, I asked myself, what is the reason that generates the malfunction?
Then I looked at them under the microscope, after cleaning them with isopropyl alcohol, to get rid of the sponge residue.
And I made a discovery: as the microwave absorber degrades, it creeps into the side holes of the filter, closing them.
Both filters used consist of three cells. And laterally to the filters there are three large holes on one side and three small holes on the opposite side. In the 1842 MHz filter, for example, small holes have a diameter of about 0.4 mm in diameter. If the conductive sponge closes at least one of these small holes, it behaves like a short circuit of the corresponding cell, distorting the behavior of the filter.
It was enough to unclog the small hole blocked with a copper wire to restore the correct behavior of the filter! Also, to be safe, I kept the filter wet for a few hours in isopropyl alcohol, to remove all sponge residue from the holes.
I hope I have been of some help to those who have similar problems in the future.

[Mkpirulo]

Hi Pico61,

Do you think that the filter needs to be removed to be able to clean the holes. A small sponge tip cleaning tool could work?

I’m attaching details of how these filters are made, Your findings make sense. So you cleaned them and fixed the CMU200? Did you run your VNA after cleaning?

Thanks
Michael