Author Topic: Anritsu MS2651A repair (need service manual) (Read 19649 times)

jkf1000 · « **Reply #25 on:** June 28, 2016, 10:34:22 pm »

Thanks for checking that for me. exactly the signals I expected to see if measured from pin 13 and 14. ( On a working machine ) Time for me to order a new chip as I have no regular pulses on my unit so no timing control for later stages. The other possibility with mine is corrupted data from the CPU or bad 3 state transceivers between the CPU and the ACRTC chip. I am flying a little blind on this without data so its a process of elimination based on best guess and logical signal paths. I will report back with any progress but it may take a while to source the parts.

I just hope that if or when I restore my display there are no further issues with my machine lol.

Did you check your backup battery and run a full calibration sequence with your machine as I suggested earlier? It may give you more of a direction to go in if it does not resolve your level problem. If I can return the favour with measurements from my unit let me know and report back with any findings and progress you make. Karl.

jkf1000 · « **Reply #26 on:** June 28, 2016, 10:42:36 pm »

I will check the IF for you but it wont be until tomorrow evening at the earliest. Please bear in mind also that until my display issue is resolved I cannot determine that my machine is working 100% Karl

jimon · « **Reply #27 on:** June 28, 2016, 11:06:29 pm »

Self cal doesn't do much, either mixers are completely dead or either something is really strange.

Basically my current situation is just crazy:
- Did "All Cal", it went fine. And actually I've checked what happens if you just remove cal input from main attenuator - the device doesn't care, there is simply no "calibration failed" errors (or I was not able to trigger them any way possible)

- Did preset -> All, and I'm getting straight line over 0 dBm on whole spectrum
- Device reports >+4 dBm (sometimes +300 dBm) over all spectrum
- If I provide some input signal, spectrum around this signal jumps down to ~-50 dBm
- Noise level (can you really even say +4 dBm is a noise level???) jumps between different levels when I switch between different RBW.
- Backup battery is doing fine, minor level of oxidation is present though.

Not having tools to properly test 1st and 2nd mixers (I don't even understand wiring of them) makes me sad

For now I just want to know what works and what doesn't.

jkf1000 · « **Reply #28 on:** June 28, 2016, 11:19:37 pm »

Study and try and understand the block diagrams in the manual. They are our only source of information at the moment. Assuming that my unit is functioning 100% as far as the RF stages is concerned, between both our units we should be able to resolve both units as both appear to have completely unrelated faults. Karl

jkf1000 · « **Reply #29 on:** June 29, 2016, 07:27:12 am »

One other thing you can try is to hold in the Preset button for 5 to 10 seconds while powering up which boots the unit into a default condition according to the manual. Karl.

Falkra · « **Reply #30 on:** June 29, 2016, 09:18:01 am »

Quote from: jimon on March 30, 2016, 09:07:37 pm

Does anyone have an idea where to look for service manual ? Tried to google it, but was not so lucky.

Is this what your are looking for ?
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Anritsu/MS2601A_J_SM.pdf

jimon · « **Reply #31 on:** June 29, 2016, 10:48:03 am »

Quote from: Falkra on June 29, 2016, 09:18:01 am

Quote from: jimon on March 30, 2016, 09:07:37 pm
Does anyone have an idea where to look for service manual ? Tried to google it, but was not so lucky.

Is this what your are looking for ?
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Anritsu/MS2601A_J_SM.pdf

MS2601 is a bit close, but different:
- Modules layout is different, 2651 have almost everything RF related in one block, with external local oscillator board.
- 2651 uses 4.xxx GHz between 1nd and 2st mixer when 2601 is uses 2.5214 GHz
- 2651 IF is 110.695 MHz and 2601 is 21.4 MHz
- YTO \ VCO controls looks to be different
- etc

jkf1000 · « **Reply #32 on:** June 29, 2016, 03:35:41 pm »

If your unit is responding to an input signal, assuming that it is displaying the correct signal frequency, that suggests to me that it is not a mixer issue and is more likely to be a leveling issue. Maybe a failed AGC or ADC. Does it display your input signal at around the right signal position on screen? Does the signal level displayed on screen match the output level of your generator?

jkf1000 · « **Reply #33 on:** June 29, 2016, 10:27:06 pm »

I have had a probe around the RF board and not been able to find the 110.7Mhz signal but there are 16 pins on the connector that I am not able to probe. There is a very good chance that it will be on one of the unreachable pins. I found the 100Mhz reference and the 12Mhz mixer signal (on the connector marked X2) but that was all.

I find it very strange that they would choose to route a high frequency signal through a 0.1 header then on via a board to board interconnect. I can only guess that it has very effective guard traces around it or it is buried in one of the inner board layers between ground planes.

The only way you will see more is by making some sort of extender cable as you suggested before using an ATA type connector. One thing I did notice is that from the 32 0.1 header connections, at least 17 of them are just ground which leaves only 15 for supply, signal and control signals.

If there is anything else I can check for you just ask. Karl.

jimon · « **Reply #34 on:** June 30, 2016, 08:20:16 am »

Hm it's strange that you have 12 MHz around X2 (Looks like it's directly coupled to YIG), I don't think it's a reflection from the mixer ... or it might be?
I got the extension cable, and indeed top pins are mostly ground and power, will check lower ones.

jkf1000 · « **Reply #35 on:** June 30, 2016, 02:18:33 pm »

I have ordered a new chip for the video circuit, unfortunately none available locally so will take a few days from the USA. I no longer trust the HongKong/China marketplace for anything branded, I have had too many fakes in recent months. In the meantime I will pull the old chip and just fit a PLCC socket to make life easier. There is still the possibility that it may be one or both of the octal transceivers between the CPU and video chip so may change those as a matter of course while waiting.

Jimon, I will update with any progress. and let me know if you need anything from me as far as measurements. the 12Mhz was found by scoping the back of the X2 multi connector not at the X2 coaxial connector, sorry if that caused any confusion. Karl

jimon · « **Reply #36 on:** June 30, 2016, 05:34:28 pm »

Ok good news, AGC is f**cked after CAL procedure, so full reset (by holding preset button on power up) helps a lot! Basically SA is unusable after CAL.
Some bad news, something somewhere is f**cked as well, by default I get a peak in 48 MHz when nothing is connected :/ And when I provide 100 MHz on input - I get peak at 148 MHz ... well at least mixing works somewhat, so what is it? YIG or VCO out of tune?

jkf1000 · « **Reply #37 on:** July 01, 2016, 07:59:05 pm »

I have no idea about the 48Mhz, I can only guess that it is a mixing product but dont have the block diagram to hand to look at the frequencies involved. It may be you have a failed filter or similar. I will look into the block diagrams and see if I can work it out for you but it does look as if you are heading in the right direction with what you have learned so far, Karl

khach · « **Reply #38 on:** July 04, 2016, 03:10:43 pm »

Quote from: jimon on June 13, 2016, 09:01:03 pm

3) This is the closest thing between YiG and input ... but is it really 1st the mixer? It sure doesn't look like one :/

Yes, thats is a star mixer. IF input of mixer is RF input of analyzer.

jimon · « **Reply #39 on:** July 06, 2016, 04:05:49 pm »

Got delivery today ... jeez I would say having the right tools for the job is a number one requirement everywhere ... so looks like X4 output (top of RF module) is coupled directly to ... I don't even know what to .. looks like unfiltered output of second mixer or something, and good news are my new epic EIP 545a is able to pick it up!
Bad news are:
- the screw on pic is a fine tune for resonant frequency of VCO ... I'm getting range a bit around 3.95 - 4.08 GHz
- I have no idea which frequency should be there, I guess either 4110.695 MHz as specified (but the screw doesn't go that far), or 3999.995 if it's direct VCO output (4110.695 - 110.7).

UPD: from X4 there is 1 strong signal around 4.0xx GHz and another one around 8.0xx GHz
UPD: managed to get readings from X2 in zero span mode:
cf 3ghz = 6985.03 MHz
cf 100mhz = 4166.53 MHz
cf 0hz = 4070.67 MHz
cf -100mhz = 4008.9 MHz
Sounds correct regarding the diagram (4.1 - 6.6? GHz), but I don't know if margins are ok, 6985.03 - 3000.0 = 3985.03 MHz on first IF when there is a filter for 4110.695 ... :/

jimon · « **Reply #40 on:** July 06, 2016, 08:44:00 pm »

khach, woah thanks, first time see mixer like that! =)

jimon · « **Reply #41 on:** July 06, 2016, 09:18:15 pm »

Ok, I've finally found where the IF out from RF module! This is LND11 port visible from one side of a module. This output is barely amplified (there a pot on other side), noise level is around 50 mVpp, and 0dbm is around 120 mVpp.

jkf1000 · « **Reply #42 on:** July 06, 2016, 10:12:35 pm »

It looks like our RF boards are pretty much identical but there is a difference in part numbers so not sure what if anything may be different in the operation. Mine is a Anritsu A1001 322U12943b (Y2)

Just measured mine from the same LND11 point and this is the wave form that I got on a single shot capture. It was a real pain to get it to trigger as there seems to be a lot of noise and other signals at that point. I have the trigger set just at the top of one of the peaks. If I just let the scope run the signals on screen are very messy.

I am still waiting for the video chip for mine which should be here in the next few days so have not really done anything with it, but it is still open on the bench if you need measurements. Karl

jkf1000 · « **Reply #43 on:** July 15, 2016, 10:00:42 pm »

My video chip finally arrived (HD63484CP8) but unfortunately made no difference, still no HSYNC/VSYNC control signals so still no display. It looks as if either the information being sent to the chip is being corrupted by a peripheral chip or the CPU itself is not generating the correct data to be sent to the video chip in the first place. I have done a lot of measuring with the scope and DMM and found several ICs on and in the path of the video chip so not sure which direction to go next. I am thinking of starting a seperate thread just for help on the display problem as I am now out of my comfort zone as far as diagnosing further on the digital signals.. Karl

jimon · « **Reply #44 on:** August 16, 2016, 05:25:03 pm »

Got some time to tinker with that big boy, so I learned how to tune and measure : second LO, IF, and now I'm getting 118.7 MHz there!

Apparently first LO was 100 MHz off and is not locking correctly, if I set CF to 200 MHz and than go to 0 Hz with 20-50 MHz increments - it works. If I set to CF to 1-3GHz and than suddenly jumps to 0 Hz - YTO locks (? not sure if it locks at all) around 50 MHz off ... which kinda explain random crap I observed and why DC was off by ~40-90 MHz. Thanks my stupid brain was smart enough not to touch cavity filter screws because I don't have tools to calibrate that at all.

Now I need to understand how the heck YTO PLL is working there, and where the hell are lock signals if any. MS2601 supposedly have LEDs to represent this, and looks like MS2651 have none.

jkf1000 · « **Reply #45 on:** August 16, 2016, 10:43:26 pm »

Still no further with mine but not had much time due to other projects/repairs. I have fitted new SRAMs as they are a known failure point but that made no difference, next stop is probably the video RAM which I found reasonably cheap but a real pain to fit. I have found more information about them at (http://www.ko4bb.com/getsimple/index.php?id=manuals). Download the service manual for the MS2665C model which is very close to what we have and gives a lot more information on the signal paths and board to board connections. There is also a file named MS2650 service manual which contains bits of service info. Let me know how you progress.. Karl

ducus · « **Reply #46 on:** April 18, 2020, 12:50:35 pm »

Hi there,
Did you manage to fix your spectrum analyzer? I have an Anritsu MS2668C with same behaviour like yours. It wass working an suddenly it being to do stange things with amplitude. After recalibration noise flor it is around-20 dbm. Before it was a problem with power supply but i fixed. Do you have maybe the pinout or voltage frim power supply?
Thanx

jkf1000 · « **Reply #47 on:** April 18, 2020, 01:14:37 pm »

Not able to offer any further information for you unfortunately. It does sound like you may have a failed amplifier or attenuator stage. I ended up selling mine as a parts unit. I managed to resolve the display issue which turned out to be a 74 series IC which sat on the data lines from the main CPU so was corrupting pretty much everything else. Turns out that mine had other issue which I don't have the tools needed to diagnose the various stages. Basically you need a working analyser to be able to trace issues on a faulty one.
One thing I have learned from the time spent with mine is not to buy another Anritsu device. There is just not enough service and repair information out there, even for long discontinued products. Karl

ducus · « **Reply #48 on:** April 18, 2020, 02:06:33 pm »

Tanks for reply. It is possible to be one amp, but is more an challenge to fix it. If it will be to sell parts from it i will get more money than i spend buying this one.

jkf1000 · « **Reply #49 on:** April 18, 2020, 03:55:58 pm »

It all comes down to how cost effective the time and potential parts cost will make the repair. No doubt a good analyser when working but when you compare it to a budget Siglent or Rigol unit with 12month minimum warranty and more features it very quickly becomes beyond economic repair. Karl


EEVblog Main Site	EEVblog on Youtube	EEVblog on Twitter	EEVblog on Facebook	EEVblog on Odysee

Author Topic: Anritsu MS2651A repair (need service manual) (Read 19649 times)

Share me