CMU200 PSU erratic ON/OFF - Page 1
Forum section: electronics / repair

author: BeO
author_rank: Contributor
timestamp: April 18, 2017, 07:33:22 pm
content: HelloI am new on this forum , I try to learn RF and built a Ground Radar as projectI have purchase in 2016 on Ebay UK , one CMU200 which have failed , power supply have failed , thanks to Ericmax on this forum for repair tips BUT after repairmy actual situation is :my CMU 200 -02 : it's start normally and works fine regarding both spectrum and generator but it auto switch off when it wants by a similar way I press the one ON/OFF button ( shutdown in progress and now it s switch off at the bios screen levelI have all the power supply green LED OKI have change the TI SOIC 10 on the main board in case off but no change regarding the auto switch offI have check the ON/OFF button , soft PCB is OKI have check all connectors , nothing wrongI have remove signal group cards ''option'' to eliminate possible ''short'' but the defect is still the sameNow ( 20 April ) after several power ON power OFF trials ;PSU start OKGreen LEDs on base board are OKBUTI go straight from orange to green led on the front panel ( ON/OFF ) , and nothing startI am very disappointed by R&S multiples failures cases , and the fact that the maintenance manual is not availableBeO

author: BeO
author_rank: Contributor
timestamp: April 23, 2017, 09:27:46 am
content: HelloI have succeed to locate a copy of the service manual , problem seems to be the lithium battery flat on the computer board , I will run a disassembly and battery identification to order a new , there is two battery model possible on in 3.6v and one in 3VI will post the result soonThanksBeO

author: richnormand
author_rank: Unknown
timestamp: April 23, 2017, 09:04:30 pm
content: You might want to go through this thread about PSU issues.Not the main theme but several replies do seem to address some of your problems.https://www.eevblog.com/forum/repair/rohde-schwartz-universal-radio-communication-tester-cmu200-psu-issues/As far as the "service" manual all I have is pretty generic and not that useful as it only includes high level flowcharts.Is yours including actual schematics?I collected quite a bit of info on the CMU200 so let me know if you want to get in touch. Also in that thread, and another one I started on the RxTx module, you will find links to people that know a lot more about the CMU200 that I do.PS: does BeO refer to beryllium oxide?

author: BeO
author_rank: Contributor
timestamp: April 24, 2017, 10:31:23 am
content: Hellothanks for your feedbackmy CMU have start to generate self ''automatic shutdown'' more and more quicker so the explanation regarding battery fail looks reasonableI have switch PSU from my other CMU200 ( I enjoy problemssso that a ''250'' which works on my other CMU200/30 , nothing change same defect . green led OK , no startI will try to track on/off button on the computer boardI agree regarding the service manual that not a detailed service manual , th ereal serice service manual with all schematics and circuits is the ''module service manual## I try to loacte one copy , but as this ''module service'' is a true internal doc from R&S that look difficultThis afternoon I try to change the battery and restart the CMU200/02 and will post regarding the resultBeO

author: BeO
author_rank: Contributor
timestamp: April 24, 2017, 05:49:57 pm
content: HelloAfternoon progressI have change the Lithium battery for a new one ( CR2032 ) as the installed one was clearly deadNO changeBut when I have manipulated the CMU200 , the defect have changed as self restart trials. shutdown .... , front panel keyboard shows to be very sensitive effect around On/Off and F1 touchafter to have disassembled the front panel the flexible PCB was corroded on one track between on/off and F1 touchI have switch the flexible PCB by using the flexible PCB of my other CMU200 (30 ) and now the CMU200 works fineFlexible PCB of the keyboard looks very sensitive to corrosion as the membrane is very thin and area arround on/off / F1 is stressed by numerous useAs conclusion now my CMU200 / 02 works gainI now search to locate a spare flexible PCB in good shape to complete my CMu200/30 and solve boot problemI have a signal unit available which was removed from another CMU200 if that can help someoneBest RegardsBeO

author: RF_fanatic
author_rank: Regular Contributor
timestamp: June 24, 2017, 10:16:50 pm
content: Just read your topic for first time. Indeed your behaviour sounded like a foil issue. It is a often occuring problem, most of the time manifested by a shut donw when pressing other buttons on the row on the bottom.I have seen replacement units for the front foil, made by a chinese (?) guy. He copied the foil on a very thin PCB board including an added flexible part for the connector. That would be an option as foils are very hard to find!But I can'n'r recall where I found it. I know it were CMU for sale for which he had made the above boards

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 29, 2017, 09:22:23 am
content: There are replacemant PCBs available on Taobao:https://world.taobao.com/item/544961277461.htm?fromSite=main&spm=a230r.1.14.194.76bf523nb9jsk&ns=1&abbucket=17#detailBut i didnt order one yet.

author: BeO
author_rank: Contributor
timestamp: July 07, 2018, 08:20:23 am
content: HelloThanks for the linkI have order one from R&S the cost is 170 EuroRegardsBeO