Products > Test Equipment
Rohde & Schwarz CMU200
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richnormand:
Loopback Rx/Tx tests:

I would make sure loop cables is hooked up in front (good quality cables needed)
I would check the various flat cables to the unit.
I would check the SMA lines under the mainboard are connected connecting to the Tx/Tr module and that it is well seated in the main connector.

Lots of info in this thread:
https://www.eevblog.com/forum/repair/rohde-and-schwartz-cmu200-rxtx-module-issues/
_Wim_:

--- Quote from: capt bullshot on July 09, 2021, 05:43:17 pm ---Loopback tests  (1->4 / 2->3) require an external cable connection between the mentioned ports (just in case you didn't notice that).

--- End quote ---

Indeed, but as there is quite a bit of cross-talk between the channels, this can be confusion because your actually seeing a signal, but it is just to low...
arno:
Dear all,
thanks for so many replies. I unplugged the front RF module from the RXTX-board and connected both SMA connectors. Then, in RF1 internal loopback test, I saw around -30 dBm, but ONLY in Bd (I assume band) 5, between 2.2 and 2.7 GHz. The rest is still dead. Also, I do not see any RF power from the TX out.  ::)

Edit: opened up the RXTX-unit. There are no visible damages, like broken caps or something, just some dust.

Thanks
Arno
arno:
Dear all,

sorry for the long break, I was quite busy and could not work on my CMU. Luckily I found a replacement RXTX-Board and the unit is fully working, again!   :clap:

Thank you all for your help!

Arno
richnormand:
Hi arno,
just sent you a pm.
Cheers
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