Rohde & Schwarz SMIQ06B Repair - 6GHz board Level Preset Error - Page 1
Forum section: electronics / repair

author: smgvbest
author_rank: Unknown
timestamp: June 24, 2017, 05:07:34 am
content: After following DaJMasta's Repair log for his SMIQ06B I'm finally getting started on repairing mine.for his repair log see here ->https://www.eevblog.com/forum/repair/rohde-schwarz-smiq06b-repair-log-6ghz-board-alc-error/50/Like DaJMasta I got mine of eBay with a stated status of a Level Preset error but output is stable and with-in .5dBm of requested value.I do not have a SA or Scope that can go to 6.4Ghz but I can go to 3 Ghz on my frequecy counter and if I put a divide by 4 between the SMIQ and my SA I can at least see the signal but can not use it for amplitude checks.I have a E4418A and can check power and in deed it's is in the 0.5dBm range and the Level Preset is the only error reported.I produced two items to help troubleshoot thisI cleaned up and stitched the E6GHZ Service Manual and it is available herehttps://drive.google.com/open?id=0B0n5ltUlE8YHZ1laejFma245V00I hopeI also created a excel spreadsheet to log Test data which you can get herehttps://drive.google.com/open?id=0B0n5ltUlE8YHbjlQUG4yNlJuNlUi hopehere's a screen shot of the spreadsheet. the TP's are not in numeric order but in order of the signal path from left to right.this helps make it clearer where the problem is located. (at least I think so)My initial thought based on the test point data available in the diagnostic menu indicated a problem in the IF900 path somewhere around or before N4.I connected up some test points as seen here and measured bias voltagesTP Value ActualN39 4.9 ± 0.1 4.67V91 4.7 ± 0.1 6.28N3 4.8 ± 0.1 4.95N4 4.8 ± 0.1 4.92V91 is suspect and I found one of the SHF-0186-K (datasheet herehttps://drive.google.com/open?id=0B0n5ltUlE8YHZlZrWkRvQXV6NEEI have the SHF-0186 on order and should be here this weekAlso N39 is a bit low 4.8 to 5.0 is specified value in the service manual. the service manual though is for a 01 version and I have a 02So as I am writing this up I decided with all the test points wired up I'd run a full calibration the bloody thing calibratedDoing some quick tests in the 0-3.3Ghz range its within -0.16dBm on my un-calibrated E4418Ain the 3.3-6.4 range it is now off 2dBm.So thinking about this I am still going to replace the V91 as it's voltage is very high. and at that point I will also re-run Level Preset Cal + ALC Table Cal.and see what changes if anything.I do plan once this part is fixed to also tune the various voltages on the unit.here's some various images I took while working on itThis is the area i'm focusing on. the amp marked H1 is the V91This shows N3/N4 which is after the mixer in the IF900 section.View of top of the unitView of bottom of the unitPower reading at 3.301Ghz. Soon as i go above this it goes about 2dBm offclose up of the hybrid output sectionclose up of the hybrid input ampPic to remember how the connections go to the E6GHZ boardHere's N4 - This is the last amp before the Test Point that was the first one out of toleranceJust because it looks neatThis has all the inputs/output on the back, I want to move them to the frontQuestion?The rigid coax for the main output. appears long enough to be moved from the rear to the front panel. but I would have to re-bend the coax to make it work. will doing so mess anything up?edit: made a few updates and hopefully you can see the images now.my next planned update is after i get the v91 replaced hopefully this week (waiting on part)

author: DaJMasta
author_rank: Super Contributor
timestamp: June 24, 2017, 05:46:40 pm
content: Good to see! Though for whatever reason, I'm not seeing the pictures.It's my understanding that bending rigid coax is not necessarily the end of the world, but it should be avoided. The idea is that bending it introduces small changes in its performance (though I imagine these are most significant at much higher frequencies), and while they had to bend it at the factory, they then characterized the response of the unit with those initial bends compensated for. The risk being run is that you won't be able to calibrate out these later bends in the instrument - and in the case of the final output line, the SMIQ's self tests won't compensate for it either because it doesn't have a detector right on the output.I got a small amount of bend in the two that directly attach to that front end board, but I think this is largely unavoidable. I accidentally bent the long one with the ferrites going to the output by not being careful of what my fingertips were doing when lifting the instrument - but I gently bent it back to position and while the output was probably effected, I have not noticed any differences. I'd imagine that big bends (like a 180) are more likely to kink and change the dimensions of the conductor more, being more likely to cause a problem. While it's not a guarantee... maybe put the signal through a similar length low loss flexible or semirigid cable and see if the output level differs from what's coming out the back. If there's no big difference, then maybe the bandwidth isn't so sensitive and maybe rebending the rigid (avoiding hard angles) is viable.

author: smgvbest
author_rank: Unknown
timestamp: June 24, 2017, 08:47:02 pm
content: i tried from another computer and google is saying no permission so I'll try to figure that outedit: hopefully images are fixed, sorry about thatWhat you posted is pretty much what I understood also on the rigid cables.

author: smgvbest
author_rank: Unknown
timestamp: June 27, 2017, 01:56:41 am
content: Replaced V91 and now the bias voltage is 4.65 which is good.recal'd it and 300Khz to 3.3Ghz is still in the <0.052 range but the >3.3Ghz range is off as much as 2.4dBm now.Basically the IF900 section is still my focus. going to go back and look at the other bias volts for everything upto N4 in the LO900 pathwill update again once I have the change to wire up the test points.V91 biad now looking better6.4Ghz @ 0dBm not quite rightDooh, I only have a 8481D power probe, good for 4.4Ghz as I recall. so not sure how accurate that reading really was.

author: technogeeky
author_rank: Frequent Contributor
timestamp: June 27, 2017, 02:37:46 am
content: Quote from: smgvbest on June 24, 2017, 05:07:34 amYou absolutely shouldnotbend (and especially not re-bend) a rigid coax. Always substitute flexible coax (if necessary, tape the coax down in many places to keep it from bending and rotating) while troubleshooting.Also, bends do not need to be extreme (like 90 degrees or near 180 degrees) to change the properties of the rigix coax. Even small bends (above 10 degrees or so) can introduce small ridges on the internal circumference of the cable which will change the properties significantly.

author: smgvbest
author_rank: Unknown
timestamp: June 29, 2017, 02:41:36 am
content: Just ran some checks now after replacing V91, seen below.with this change N4 bias is now high @ 6.276Vdc so my next item will be to pull N4 and replace it.hopefully tomorrow evening I can get to that point. Once replaced I think I will run all the diags again and check them to reset my baselinehere's all the points I measuredN38 SNA486 4.9 ± 0.1 4.950N39 SNA486 4.9 ± 0.1 4.994V20 BFP450 4.4 ± 0.1 4.417V87 BFP450 4.4 ± 0.1 4.416V91 SHF-0186-K 4.7 ± 0.1 4.650N3 SCA-4 4.8 ± 0.1 4.960N4 SCA-4 4.8 ± 0.1 6.276

author: DaJMasta
author_rank: Super Contributor
timestamp: June 29, 2017, 04:24:33 am
content: Wow, with readings like that we may just have twin failures between the two units. Wonder how common that is.The pics work now and the macro shots are nice!

author: smgvbest
author_rank: Unknown
timestamp: July 01, 2017, 04:53:21 pm
content: Maybe/Maybe notSo I replaced N3 and N4 and they are both slightly high now.I replaced them with the MMG3012NT1N38 4.9 ± 0.1 4.950N39 4.9 ± 0.1 4.977V20 4.4 ± 0.1 4.411V87 4.4 ± 0.1 4.403V91 4.7 ± 0.1 4.670N3 4.8 ± 0.1 5.003N4 4.8 ± 0.1 5.104it's pretty level from 300Khz to 3.3Ghz on the output but is going from 0.7 - 2.3dBm in the 3.301 to 6.4 Ghz range so thinking something is still not right in it.Attached is a screen cap of my spreadsheet for referenceThe values in the IF900 section have cleared up but now the "Level ahead of filter bank" TP2409 and "Level ahead of AM Mod." TP2410 are showing off somewhich brings N25 and V92 into play so I pulled the board and add a few more test points to measureN25 MGA82563 3.4 ± 0.2 3.038 LOWV92 SHF-0186-12GHZ 7.1 ± 0.1 7.147 OKI really don't cherish the thought of replacing N25, such a tiny part but is out of tolerance.plus have to find some and digikey has them and of course ebay

author: smgvbest
author_rank: Unknown
timestamp: July 02, 2017, 08:29:40 am
content: Before replacing that one component I decided to check the LO4200-6O00 path outThose amps are in bold belowComponent No. Device Type J:c/mA 0/V ActualN38 SNA486 4.9 ± 0.1 4.950N39 SNA486 4.9 ± 0.1 4.977V20 BFP450 4.4 ± 0.1 4.411V87 BFP450 4.4 ± 0.1 4.403V91 SHF-0186-K 4.7 ± 0.1 4.670N3 SCA-4 4.8 ± 0.1 5.003N4 SCA-4 4.8 ± 0.1 5.104N15 SNA486 5.25 ± 0.1 4.103 <<N17 SNA486 5 ± 0.1 4.075 <<N14 MGA82563 2.8 ± 0.2 2.950V90 SHF-0186-12GHZ 7.1 ± 0.1 7.050N25 MGA82563 3.4 ± 0.2 3.038V92 SHF-0186-12GHZ 7.1 ± 0.1 7.147N15/N17 Both the SNA486 are about 1v low and look to have been replaced before.This path feeds in to U9 which mixes the IF @ 900Mhz and the LO @ 4200-6000Mhz (talking like I know what I'm talking about)The IF path seems much better after replacing the N3/N4 there.I also noted that when checking the BIAS on V90 i saw a ~1dBm loss on the outputI'm going to replace N15/N17 first and see if there is an improvement base on that.

author: smgvbest
author_rank: Unknown
timestamp: July 07, 2017, 01:59:18 am
content: OK, so here's a really dumb moment. My previous tests where without the shield in place and the budge wire attached. I decided to give it a full test and removed all the wires. re-assemabled the board shields including all those screws and put it in.with the shield in place and the previous repair done it passed all tests and calibrates. no more level present error.Also the output levels are now <0.6dBm in the 3.3 - 6.4 Ghz range. it's not very linear though. with a low of ~.25dBm and high of 0.6dBm which is likely my power sensor which is only rated for 4Ghz. I'm trying to find a good deal on a E4412A sensor but no luck so far.I think before I really look at part replacement I should attempt to tune the voltage references, bias and other levels first that are with in my equipments ability.

author: smgvbest
author_rank: Unknown
timestamp: August 20, 2017, 03:01:44 am
content: Finally got ahold of a better power meter (Agilent U2001H) and took some reading with it.It's pretty flat upto 6.4Ghz varying around .20-.35dBm across the entire range of -40dBm to 16dBm so I don't see that I actually have any other repairs to be done.If I didn't mention it already I've also moved all the connectors back the front. I used a semi-rigid cable for the main RF for now. I did find a piece of hardline and just need to solder the ends on it for a permanent cable.time to button it up and call it repaired.

author: DaJMasta
author_rank: Super Contributor
timestamp: August 20, 2017, 05:09:22 am
content: Grats! Nice to have the connectors in front when it's on the bench too - anything special to mount them in front, or is it the same board/just panel mount connectors?

author: smgvbest
author_rank: Unknown
timestamp: August 20, 2017, 02:29:12 pm
content: nothing special really. just allot of work to reroute the BNC's from the back. the main RF connector hardline cable needs to be replaced. That was my question on bending them. I thought I might be long enough to make it but would require multiple bends to do it. decided to not bend it and replace with RG401 for now. it does have some RF suppression on the existing cable that is not on my replacement.Though I guess this means my E4418/8451 is out of cal.

author: BFX
author_rank: Frequent Contributor
timestamp: August 21, 2017, 12:00:01 pm
content: Great repairYou remind me that I have to fix my old HP8559A 22GHz spectrum analyzer

author: rastro
author_rank: Frequent Contributor
timestamp: August 24, 2017, 09:46:47 pm
content: Quote from: DaJMasta on June 29, 2017, 04:24:33 amI think the N3 and N4 on this PCB are a weak point. I had the same repair on an SMIQ6 a few years ago. The board in my system had different MMICs for the N3/N4 and it looked like they where original to that PCB. This suggests that RS may have noted problems with this component.Also I gambled on an untested 6GHZEXT on ebay which also turned out to have an issue with the N3. I also found an old repair log from a German blog which had focused on the the N3/N4 as a culprit.BTW I swapped EXT PCB's between an SMIQ4 and an SMIQ6 - they seem to be to be interchangeable.-rastro

author: smgvbest
author_rank: Unknown
timestamp: September 01, 2017, 01:42:25 am
content: Well, here's an update.After working great for a while I am now getting the same ALC error DaJMasta had.Freq is spot on and very stable. but startying at the 3.3Ghz range i get from -2db to +2db depending on which band it's in.i'm going to re-run my speadsheet to see what's changed if anything from the last run. it's still usable but no longer repaired

author: rastro
author_rank: Frequent Contributor
timestamp: September 01, 2017, 07:26:22 pm
content: Quote from: smgvbest on September 01, 2017, 01:42:25 amWhen you replaced the MMIC did you change the bias resistor to accommodate the substitute part? The bias resistor(s) are located on the other side of the PCB from the MMIC's. I changed the resistor values to accommodate the substituted replacement amp. The original bias resistors (SMD) where double stacked on my 6GZEXT PCB - Parallel aided.-rastro

author: smgvbest
author_rank: Unknown
timestamp: September 04, 2017, 02:57:34 am
content: Hi,No I did not change the bias resistor. how did you determine the correct value for the replacement bias resistor?

author: DaJMasta
author_rank: Super Contributor
timestamp: September 04, 2017, 05:05:07 am
content: Well, I guess I hadn't used it as much, but mine seems to be exhibiting the same error now - smaller variation from what is set than before, but still a failure on the ALC.Looking into it a bit though... according to the schematic, the bias resistors shouldn't need to be changed. The replacement MMG3012NT1 is rated at 82mA nominal supply current and has an absolute max of 300mA, while the schematic indicates an 80mA supply at both amps... I could be missing something, but voltage and current should be correct in that instance.Clearly it's not working, but maybe the schematic is different from the built board (not the first time) and maybe it's something else. On the schematic, the resistors on the bias for both N3 and N4 total 30 ohms, which at 80mA should be a 2.4V drop from the 7.5V supply, plus whatever resistance there is from the inductors... which seems to be right in line with the indicator and our testing of those points.I've got a new instrument open for a fix at the moment, but looking at the test points from the screen, TP2409 is only 10-40mV down from my original recorded results, but TP2010 is 40-270mV down. While the prime suspects may still be N3 and N4, it may not be happening at those... hard to tell. I'll be going back to give it a look eventually, but at my usual working speed, it could be a couple months.

author: smgvbest
author_rank: Unknown
timestamp: September 05, 2017, 12:02:09 am
content: [quote author=DaJMasta link=topic=90644.msg1294184#msg1294184 date=1504501507I've got a new instrument open for a fix at the moment, but looking at the test points from the screen, TP2409 is only 10-40mV down from my original recorded results, but TP2010 is 40-270mV down. While the prime suspects may still be N3 and N4, it may not be happening at those... hard to tell. I'll be going back to give it a look eventually, but at my usual working speed, it could be a couple months.Sorry to hear you're experiencing the same.But I have to admit I got a laugh out of your 'usual working speed' comment. That is so me also.I finished the repair of the SRS PS350 and have been tracking down a undocumented circuit in it. to no avail so far. loose it under a resistor divider.I'll get back to SMIQ hopefully soon.do wish someone would out the service kit up on ebay. sure would be easier LOL to troubleshoot.

author: rastro
author_rank: Frequent Contributor
timestamp: September 05, 2017, 01:38:42 pm
content: Quote from: smgvbest on September 04, 2017, 02:57:34 amDaJMasta is probably correct. This may not need a different bias resistor based on the MMG3012NT1 datasheet I downloaded. Table-4 shows a typical current of 70mA with a maximum of 82mA. Then by using figure-6 it seems you can derive the collector current based on the collector voltage. So 5.0V and 5.1V collector voltage is in the 60-70mA range according to the graph.The part I used was different and did require different bias resistors. To determine the bias resistor I used the datasheet to find the typical bias current. After replacing the MMIC I removed the original bias resistor(s) and hooked up a DMM (DC amp setting) in series with a 500-ohm multi-turn pot (using only 1 leg and sweep arm). I adjusted the pot to reach the appropriate current. I took the test rig out off the PCB and measured the resistance of the pot to determine the correct bias resistor value.-rastroAlso thanks for posting the additional documentation excel and schematic cleanup.

author: smgvbest
author_rank: Unknown
timestamp: September 05, 2017, 08:01:05 pm
content: Happy to give back to the community.ok so it was the brute force technique. i was wondering if there was a magic methodI'm not sure when I'll get back to it. The output power is stable once selected. it's just off by varying amounts. if I really need a exact power level I can hook it up the power meter and get it dialed in so not dead, just walking with a limp

author: charlyd
author_rank: Frequent Contributor
timestamp: February 20, 2022, 09:47:00 am
content: Hi a lot of thumbs up for DaJMasta, Smgvbest & Rastro for doing all the investigation.as i followed both topic(s) and took my 6Ghz apart i found out the different components are used in my SMIQ06Bi wanted to share these pics with you all figuring out where the problem lay in the output level

author: smgvbest
author_rank: Unknown
timestamp: February 20, 2022, 07:16:44 pm
content: Quote from: charlyd on February 20, 2022, 09:47:00 amTook me a minute to figure out you zoomed in on the photo to show N3/N4those were replaced and not sure with the correct componentsN3/N4 are DC-3Ghz MMIC Applifiers and if substituted they may need to BIAS network redone to work correctlyI replaced mine with MMG3012NT1 (thanks DaJMasta)

author: smgvbest
author_rank: Unknown
timestamp: February 20, 2022, 07:27:15 pm
content: by the way, the evil ebay has one seller with themeBay auction: #https://www.ebay.com/itm/132863299750?_trkparms=ispr%3D1&hash=item1eef4510a6:g:PKUAAOSwXHxb9QZA&amdata=enc%3AAQAGAAACkPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSHYXPhGXR5uguexJBeHwfgU%252FMAp%252BmZYsUr3k34eAw%252BVmA2J4dFbFW47fHDX2MRUlN52XzvUv9Ss9gy%252BCxXorxZGAzwOhnsK5xpcXT9QUB%252BPCQGYe4auJblKNGu8kgx3Y3Au4zo53hMlY2SAHFassn9b%252FOg8cOxgFc6ls%252Fu7TE288vpuYQMR4vBp7fK4zfArN1yGAw3BdHhk97Db4QAMyDK805HqAgXnyWjwVSOnfsl1JePkdq0SixHuOLtkSBVKhpOPKnRhtMRxIGHeC4aGKskUoUAnfE95vA6zNq16PyQKmUED47tvCAr%252BoYj0HZIEWnYi6jFsmfwsNaOb%252FEcWLZJjRcECFV2AiFx4v83hwJxsu416iHooxLQDvdsRBpBcJh8%252Fl4DUImawWl8ywf7WnRKyIoCRWDd2tn7nR0O3fICz%252FDDJuB16n%252B4wmek6N7MeQsME6fMlZVH9w0LpenapuSkSe1iaucIfGldpdJWtq%252FUHSosy02lAA02cXfp3gctrvHnTxdoiIeGmBClrtNHurTUFdvHqvftnv1wFa%252BQ48JStQIsTVMECBQtM6eX3wVReULuz0s2rFsOVixNYZRB6vsdtuuW8A8hX3Vsi%252F9WnQptByIGnAJK11esfVXJwwryvIV27IJaleWMZ5E86%252FpZzpWfbzVU2fuKk9xdrnty6g59%252BIrHOE%252BwjpBFyyn3zCA2Z%252FtHcZmIbBcP0wjcx%252FPZmg1XRGNFIwGHo5IZEsJxgnXfy7ZWSWiI2QzqVKeVnOcZ5s%252FtZGmmBSbrKATJ10lNLZB9IP2YxeWJDSJ7KAfucIZjSrwd9UAUFPE80SHnpdDclzs%7Cclp%3A2334524%7Ctkp%3ABFBMgu2FjuNfbut very high costyou could make an offer and see what they'll takeLinks seems to not be workingjust search for the part number, there's 1 hit for it

author: rastro
author_rank: Frequent Contributor
timestamp: February 21, 2022, 09:08:38 pm
content: Reply to charlyd:what type are the module connectors. so i can maybe make the extension board/cable.A: I think the cable use a standardIDE maybe 40 pinDupont Cables (1X32 and 2X64). I also used some of the pins (usually used on PCB's) to make male connector to fit on the system backplane. I was not able to attach a picture on the eevblog message replies so left it here.There is also 2 RF cables which you should be able to get on eBay. SMA to IPX???note: corrected error calling it an IDE cable; also additional cable description.

author: charlyd
author_rank: Frequent Contributor
timestamp: February 24, 2022, 02:46:10 pm
content: @smgvbest, for sure both N3/N4 are original in place i even looked under the microscope from what i could see.and the unit was sealed when i opened it so i guess it is not really clear visible on my picture but ok.that is why i tried to figure out the components.something with 301 & 802 ? upgraded version Var3the only way to discover is the find out both smd codes.6Ghz moduleVar3[btw i bought a series of SCA4 ampl. so that can not be the problem]

author: charlyd
author_rank: Frequent Contributor
timestamp: February 24, 2022, 02:49:30 pm
content: @Rastro #25 - is that the set cables you used? mmm..

author: rastro
author_rank: Frequent Contributor
timestamp: February 24, 2022, 07:23:36 pm
content: Quote from: charlyd on February 24, 2022, 02:49:30 pmyes..The main cable (pictured) is a*Dupont2X64 PIN adapted down to 1X32 PIN using additional single row Dupont cables and Dupont Male PINS. This is what I put together based on my parts availability.The simpler and cleaner cable solution would be to buy or fabricate a 1X32-PIN Dupont cable with one side with male connector and the side with female connector.* I previously called the cable type IDE in error instead of Dupont cable/pins (my bad)

author: charlyd
author_rank: Frequent Contributor
timestamp: March 31, 2022, 04:07:37 pm
content: i am still looking to find these R&S upgrades..!! anybody???see my post #26

author: charlyd
author_rank: Frequent Contributor
timestamp: June 21, 2022, 01:16:52 pm
content: .....bump.......

author: charlyd
author_rank: Frequent Contributor
timestamp: November 14, 2022, 04:18:14 pm
content: Hi ok it took a while but i opened up my SMIQ for the second time and now my 6GHz board is ontop connected with the right extension leads.immediately a question raise.- do i need to force cool the 6GHZ board. out of his original housing. to get the unit calibration in place. or is it better to put a fan over it.i still have not yet replaced the N3 and /or N4 because i am not convinced they are not ok.. so now i can start taking some measurements.is there any let call it road map ( step to quickly go to the point where my faulty can be found.) i know, some has spended lots of hours above this unit already.maybe those experts know where to probe.what happens exactly:with the housing opened and a forced airflow my Calibration process is succesfull all the way. onces i stop the cooling process my baords gets warmer and when i rerun the calibration if fails on two places. and throws some errors. like " ERROR E6GHZ: IQ : ALC_ON voltage oot " .my LEV PRESET doesnt finish succesfull and my ALC TABLE not. which brings "ERROR 110 Output unleveled; 6Ghz: ALC Failure." but i already replaced the output ampl. on the other board. the primairy course of the error 110. this time it is generated because the ALC Table fails. i guess.any tips from the experts, like DaJMasta, smgvbest or rastro for a quick approach?

author: charlyd
author_rank: Frequent Contributor
timestamp: September 01, 2023, 07:37:50 pm
content: after a long time i found some time to continue on the smiq06B project....i swapped out the N3 and in run DIAG ALL the lev preset is now also succesful but i still see " ERROR E6GHZ: IQ : ALC_ON voltage oot " .and "ERROR 110 Output unleveled; 6Ghz: ALC Failure." but i already replaced the output ampl. on the other board. the primairy course of the error 110. followed by errorr 183 learning failed. so i don t understand...can this have to do all related to a ALC error.any tips

author: KeBeNe
author_rank: Regular Contributor
timestamp: September 04, 2023, 03:54:15 am
content: Hi,disable the Protect mode 2 and activate the debugging, then still that he should not hold on error.The error could also be on the IQ Mod board, check the frequency response at the output of the IQ Mod board, also try if there are differences with S&H modulation.Use the test points for display, this is a good tool.