R&S CMU200 TXLO3LEVD ERROR - Page 1
Forum section: electronics / repair

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 12, 2023, 09:56:26 am
content: i have an error on my cmu200self test on the rxtx boardTXLO3LEVD -0.200 | 0.200 | 1.02VThe device works perfectly, this is the only errorSuccessfully passes all testsINTERNAL RF LOOP PATH 11->4/2->3 RF LOOP PATH 1I tried to search for information about the cause of this error for a long time without successI would appreciate it if you could get information about the reason for this error

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 14, 2023, 07:10:17 am
content: the error

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 17, 2023, 02:06:26 pm
content: Dear Customer,Ticket 507061 has been resolved.The resolution proposed is:Dear DavidThe 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 regardsWinfried JansenIf 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 supportFirst of all, thank you very much for the responseI don't need a fixMy field is repair and calibration of laboratory equipmentThe 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 repairThis is something that every company should respect in our day.And it's a shame that you are in the same category as AppleGreetings David Azulay

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 17, 2023, 05:38:19 pm
content: photos of the rxtx boardI removed the SAW FILTER836.5MHZWith the HAKKO FR801 hot air stationI will order these filters1842.5mhz836.5 mhzB69813-N1847-B476 PCN RX Filter 1842MHz SMDB39841-B4122-U410 836MHz SAW Filter SMD

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 23, 2023, 11:53:04 am
content: i order the lilter B39182-B4139-U410 1842.5MHz SAW Filter 50 Ohm SMD B69813-N1847-X475 PCN RX Filter 1842MHz SMD B39841-B4122-U410 836MHz SAW Filter SMDand theIDE CF Adapter CF to 2.5 IDE 44pin Adapter Card 2.5''44pin Male CF Compact FlashPCMCIA TO CF CompactFlash Card - Laptop CF TO PC Adapter Reader Converter2.5" IDE Hard Drive Laptop Female to 44Pin Male HDD SDD SATA Adapter Converter

author: pico61
author_rank: Contributor
timestamp: March 13, 2023, 11:33:26 am
content: 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.

author: Mkpirulo
author_rank: Contributor
timestamp: June 17, 2024, 07:05:04 am
content: 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?ThanksMichael