R&S SMV03 repair - need help with the handles - Page 1
Forum section: electronics / repair

author: 1design
author_rank: Regular Contributor
timestamp: November 23, 2021, 02:57:53 pm
content: I acquired a R&S SMV03 signal generator of off ebay, it was listed as powers on but nothing on screen.I was hoping for a power supply issue, or something down that line. Once the unit arrived, things didn't look good...the handles were removed from the instrument and the calibration stickers covering the rear screws were all broken. Someone has unsuccessfully tried to repair the unit and we all know what that could meanOnce inside, I saw that all of the screws holding on the main board shield have been unscrewed and a lot of the front panel and LCD screws were missing.The previous attempt was not only unsuccessful but also VERY sloppy.After probing around the STN LCD PCB, I came to the conclusion that the HW works:Turning the main knob triggered data to be sent to the LCDAll the H and V driver lines were happly bouncing back and fort in a periodic wayData was written to the RAM with every button pressAll RAM data/address pins were workingI continued my investigation by removing the STN matrix from the controller and there laid the issue. The ribbon connecting the matrix to the control PCB has deteriorated to the point of only contacting on one line, this was also the only line showing up on the LCD.After fiddling about and cleaning all the surfaces and re-seating the ribbon multiple times I was able to get 6 lines to work. This showed that the device was actually working, only the LCD was damaged.Encouraged by my latest find, I attached an SA to the output and low and behold, a signal appeared. This was pretty much spot on at 0dBm, 1GHz. There was a substantial amount of phase noise present, fuelling my concerns about the state of the main bard, since the shield has been removed in the past.I ordered a new LCD, which is readily available from E-bay, if you don't mint spending some $/€.After connecting the new LCD I was greeted with the R&S logo and the generator GUI...HURRAH!The GUI also revealed the source of the excessive carrier noise, both AM and FM modulations were turned on with no signal on the modulation inputs.So, in summary, I now have a working SMV03. Regarding the missing hardware, I was able to measure the remaining screws and order additional parts to fill in the missing ones.The only HW I need help with are the handle screws.Does anyone have a piece of R&S gear and would be so king to measure the size and length and tell the type for the handle screws?Thank you!If you have any questions about the instrument or repair, please feel free to ask.

author: eurgenca
author_rank: Regular Contributor
timestamp: November 24, 2021, 04:09:28 pm
content: Hello.I have SML03 I think that is the same. If you still need info I can do that for you tomorrow when came in office.

author: 1design
author_rank: Regular Contributor
timestamp: November 24, 2021, 07:05:21 pm
content: Hi eurgenca,thank you! The case is the same for both units as the SMV03 is just an SML03 with added IQ modulation.

author: eurgenca
author_rank: Regular Contributor
timestamp: November 25, 2021, 08:20:36 am
content: Hello.Here you go.

author: prbsrv.ru
author_rank: Newbie
timestamp: November 26, 2021, 04:22:01 am
content: Hello, EurgencaI am engaged in the repair of spectrum analyzers Rohde Schwartz, Agilent, Anritsu, Keysight. There are similar bolts for your devicehttp://www.prbsrv.ru/

author: 1design
author_rank: Regular Contributor
timestamp: November 26, 2021, 05:30:34 am
content: Thank you, I ordered an M4x16 Extra-Wide Truss Head Phillips Screw. It has a 1mm narrower head and is 2 mm longer, nevertheless, it should work.

author: CrazyTiger
author_rank: Regular Contributor
timestamp: November 27, 2021, 04:21:25 am
content: Based on my experience with SMLI would suggest changing the power supply unit capacitors and the power supply cable harness to the mainboard as a preventive maintenance, the 12V line tends to pull current and you will notice discoloration on the PSU 12V line connector, and slowly it will make the LCD run dimmer and cause intermittent error on the unit.For LCD I changed mine with a LED back light type,it runs a cooler and and its super bright, up better than the original. The price was a bit steep but its worth it. Purchased mine from here:https://www.rfshop.it/en/rohde-schwarz-sml-sml03-sml02-smr-smr20-smr27-lcd-display-spare-part-sp12n002/

author: 1design
author_rank: Regular Contributor
timestamp: November 29, 2021, 05:23:30 pm
content: I checked the power supply voltages with my scope and they all look clean and within the service manual specifications.On my unit I did not see any discoloration on the supply connectors or brittle cable insulation due to overheating.I looked at what it would take to remove the power supply and replace the capacitors:Remove output stage 2/3GHzRemove IQ modulatorSince this would require removing all of the semirigid and soft cabling, I opted not to do it right now.Better not to put unnecessary stress on all those connections if not strictly necessary. The battery is currently sitting at 3.05V and will not be replaced.Regarding the backlight, since I just bough a new LCD with CFL backlight for 130$, I will leave it as is. It should be good for the next 10 yearsThe unit has 65000 hours and 196 power cycles, must have been used in an ATS. The LCD probably died a while back and no one cared/noticed.I am actually surprised that the PSU is still doing well and there is no ripple from drying capacitors, nevertheless will keep an eye on any strange behaviour.Here are a few pictures of the unit:TOP:BOTTOM:Output module, IQ modulator and option B5 board: