ROHDE & SCHWARZ CMS33 Radio Tester, with Avionics options Review, Strip-down, Analysis walk & talk.

[@GumbyRoffo]

CMS 53 here , ex Mil , thanks for the in depth video , clearing out so many cobwebs for me .

[@djm384]

Thank you for this interesting video! And congrats to your brilliant assistant He agrees with your schematics and components values!

[@johnmatthews6878]

Many thanks for your interesting and informative video. I came across your video after "Googling " CMS, 52 looking for help. I`ve now subscribed. You`ll be pleased to know that within the first 2 minutes of your video you have cured one the problems I had with the FM demod setting parameters. Yes, you`ve probably guessed , I was trying to test an FM radio and, now I know, that somehow the CMS 52 had reset itself to default and was in AM mode. I just find it a little strange that you have to go into Rx mode and set up the FM mod there to actually get the TX mod settings to work and no indication ,other than a study of the Rx settings as to which mod carrier the set is set to. If I may, just a question about one of the parameters you mention concerning the automatic switch to Tx mode should you operate a radio Tx whilst actually in Rx mode. I`m still a little unsure as to whether or not this a built in parameter or is it a user setting? I can`t find any info about it and I`m afraid of damaging the delicate input if I try it without knowing. Yes, I do agree with your "rant " concerning the vulnerability and lack of protection of the Rf power input. What a shame, is it built in redundancy or just complacency, I wonder? Also, I do agree with you concerning the lack of customer service from R & S and the pricing of spare parts which is , as you say, nothing short of extortionate. I myself have two CMS 52 840.009.52 , one of them which ,thanks to you , is now back in full working order. The other one, which has sat on the shelf for a few years, appears to have suffered the fate of the RF power input scourge. I received it with the power input module removed and the the ceramic 26dB attenuator removed along with a note saying that the Rf power input had been exceeded by a trainee and it was not cost effective to have it repaired. I have checked under magnification and the ceramic substrate of the attenuator appears to be undamaged. There doesn`t appear to any overheat or visible damage to the components. I can see the two dots which ,as you say, could be pin diodes and what I think are a couple of s.m capacitors. Do you think it`s possible to repair the Rf power module? or am I wasting my time?, obviously, due to availability and/or cost the R&S route is not an option. I`m a 75 year old enthusiast and would love to get this thing working again, now that I've been inspired by your article. I`d very much appreciate your views and any advice you can offer. Kind Regards Johnm

[@rfmanrfman4536]

Hi if the 26db ceramic attenuator pad is not physically damage i.e cracked, i would check its attenuation by sweeping it on a spectrum analyser with a track gen. you can solder coax cables to the rf in & rf out port on the ceramic attenuator use the heatsink lugs on it for RF signal ground for connection of the coax braid, if it reads 16db between rf in & out then its good, there is also another attenuator pad on it too as mentioned in the video, this is a 10db pad measure that separately again it should read 10db attenuation, PS if you don't have a spectrum analyser with a track gen you can use a spectrum analyser with a signal generator, choose a VHF test freq of 100 MHz at 0 DBm then setup the spectrum ana to the same frequency & measure the attenuator output port to measure it. if after testing you find the attenuator is correct then it will most likely be the shortly diode which is one of those two black dots you refer however i would find this unlikely, to check that reassemble the attenuator back into the RF main attenuator metal case & shoutout installing it back in the test set instead connect a radio transceiver of any power up to 50watts use a volt meter / multi meter on DC & connect the black probe to the metal body & the red probe to the feed thru capacitor there are two however one of them will / should produce a DC voltage only when the RF power is applied, if no voltage is present then the attenuator substrate which is under the black epoxy dots is blown & would be irreparable. if however DC voltage is obtained when RF power is applied on one of the two wires from the feet thru capacitors then your attenuator section / module is working & the fault is elsewhere probably on the board with the blue potentiometer which is for setting the RF power analogue DC set, You can use your other instrument to do these checks. all the best.

[@johnmatthews6878]

@@rfmanrfman4536 Hi many thanks for your reply and the detailed info it contains. I`ll have a go at trying to get it set up as you suggest ,although I don`t know if I`m quite clever or confident enough to do it. But we`ll see how it goes and I'll let you know the outcome. Just in passing, There was a guy, on the net, in France, who was selling one of these divider modules, but when I enquired it had already been sold. Just out of curiosity more than anything else I found a parts enquiry form on the R & S web site and enquired about the module part and the full attenuator unit. I`ll see what, if anything, happens. LOL. In the past I`ve had the same kind of response as you!

[@xavierguzmanjr5495]

@RFMAN Thank you for a very educational video! You mentioned during the video that the test set can be set up to switching automatically between TX-Test and RX-Test. I looked in the operating manual but could not find it. Would you mind pointing out where this feature can be enabled? Thanks.

[@rfmanrfman4536]

Hello, On the CMS33 because it doesnt have the Duplex option as standard, when you go the the RX Signal Generator screen & are generating a receive signal into a radio tranceiver under test if you then key the radio into transmit the radio test set automatically flips to TX test on its own. upon ceasing transmit on the radio the test set then automatically flips back to RX test. This is all automatic & you dont need to press any buttons on the test set as far as i am aware. In the video you will see i have the radio in receive mode monitoring the signal from the test set then when i press the TX button on the radio the test set detects the presence of TX RF power entering it then it flips to TX test without me having to press a button on the test set itself.

[@xavierguzmanjr5495]

@@rfmanrfman4536 Thank you very much for your explanation. I am currently away from the tester but will follow your points as soon as I am able and report back. Thank you again!

[@xavierguzmanjr5495]

@RFMAN - I just tried your suggestion and it worked as promised. Thank you!

[@ATOMSCOLLIDE]

Great video and very informational. I was wondering if you happen to have any idea where to source a replacement LCD ? Also would you happen to have a copy of the manual you would be willing to share? Thanks in advance and great video again

[@youtubehobbyists]

10+ years ago, I bought one directly from R/S, it costed AUD 1500. Later on I found out if you're handy enough, the polarised film in the LCD can be changed to restore the LCD...

[@Aligreta]

Hello Very nice video. In my case i own cms52, problem here is to find rear panel standoffs and upper side foot seems almost imposible 😂

[@TheGmr140]

Very good video 😊😊

[@nomanaslam6208]

How to repair display board model( CMS 54 ) display lights On but never show anything please tell me how to repair Thanks

[@satine3211]

I have three of these here, with various issues... Would you happen to have the service manual for this unit? Or is it all stored in your brain? In which case: can I have that? :D

[@rfmanrfman4536]

I do have the Service Manuals, however the issue with ALL Rohde & Schwarz kit is getting spare parts especially the RF substrates as these are bespoke parts you can only get off a spares broken one or you will have to go to R&S to buy from them, if so then get ready for a major shock, i was quoted £680 for a 50 ohm load resistor , plus 20% tax plus £50 handling fee. R&S gear has design floors, whilst they live on the name of best quality i have found them not to be any better than a Marconi or HP test set, infact other brands are far easier to repair so best of luck to you with your test set but hopefully my videos will help you out.

[@sbelectronicaindustrial6652]

Hi, Very, very Good Video...👍👍

[@luke1147]

Was a long video but great to see all the possibilities and menus as well as the internal structure. I'm looking forward to the next videos.

[@IZ0MTW]

I’m watching at the video and is super interesting. One thing I’d like to mention is that we on board our civilian aircraft (B737NG)don’t have the clarifier on the HF radio. Only an RF gain labeled sensitivity. In fact sometimes our radio has dirfted over time and I can notice it, being used to ssb communications (I’m a licensed ham operator too)but there’s nothing I can do unfortunately. Amazing, isn’t it?! Thanks for all the valuable informations you provide on this and other videos you make!

[@ЭндиДюфрейн-ь3я]

я вот себе купил CMU 200 но так хочу CMS53 (((