Anritsu MS8604A as generic SA & repair - Page 1
Forum section: electronics / testgear

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 10, 2018, 04:38:57 pm
content: Just wanted to throw this out there. Amongst the stuff I have inbound to check and sell, I have a few Anritsu MS8604A's. As a "Digital Mobile Radio Transmitter Tester" it's probably close to useless (maybe a few things like occupied BW still have some use) but what caught my attention was the fact it has a "generic" SA inside. A 8.5GHz one. So, browsing through the spec sheet (there isn't all that much info out there, this is what I got:Good-100Hz to 8.5GHz. 8.5GHz is nice, obviously, but 100Hz makes it usable for audio as well. Which a lot of machines don't support- VBW down to 1Hz- 40dBm inputNot great- ANL < 112dBm doesn't seem stellar?Wut?(frequency) accuracy +/-2.5% I don't get this? It has a pretty decent 10MHz reference, so 2.5%? Of what?(RBW) accuracy +/- 20% what now?So, your thoughts? Yay or nay as generic SA?

author: Mr Nutts
author_rank: Regular Contributor
timestamp: December 11, 2018, 09:32:46 am
content: Have you seen this?https://www.eevblog.com/forum/testgear/anritsu-ms8609a-13-2ghz-spectrum-analyzer-short-review-(work-in-progress)/msg1014488/#msg1014488Quote from: Wuerstchenhund on August 29, 2016, 07:19:43 pm

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 11, 2018, 09:45:19 am
content: I haven't! Thanks for that. Searched for 8604 but not 8609. Doesn't seem to be the same family, though. The 8604 is a fair bit older and seems to be monochrome.But if his review is anything to go by, seems like a full fledged SA inside. So yay!

author: Mr Nutts
author_rank: Regular Contributor
timestamp: December 11, 2018, 10:57:11 am
content: I can ask the author next time I'll contact him with questions but I think his point was that all "MS" are real spectrum analyzers.Your instrument is probably just a predecessor of the one in the review

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 11, 2018, 11:18:40 am
content: I miss him toosay hi from me.Anyone else with some experience or input?I'll add more info when I get to checking her out..

author: nctnico
author_rank: Super Contributor
timestamp: December 11, 2018, 12:42:11 pm
content: I think this is a mostly an analog swept YIG oscillator machine (hence the 2.5% frequency accuracy and minimum RBW of 10Hz). Not useless but definitely less versatile compared to a modern SA with an minimum RBW of 1Hz and USB storage.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 11, 2018, 03:19:04 pm
content: So... that's not something I misunderstood? You're looking for a 100MHz signal and it might as well say it's 102.5MHz?That's pretty nasty.. Still don't get it, though.. All the 2G cell stuff is in essence a bit of SW sauce over an SA so I don't get how you'd get to pass/fail criteria on anything with that kind of uncertainty..

author: nctnico
author_rank: Super Contributor
timestamp: December 11, 2018, 03:30:09 pm
content: Quote from: Ice-Tea on December 11, 2018, 03:19:04 pmAFAIK it is 2.5% of the span. So if you are looking at a 100MHz spike with a span of 10MHz then the error is 250kHz.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 11, 2018, 03:33:23 pm
content: Ah, that makes sense. And makes it quite OK. If you reduce the span (which you would if you don't want to wait forever to refresh anyways) the error decreases.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 18, 2018, 11:55:38 am
content: Last time I was this happy to unpack a unit I just turned it on.Got smarter though

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 18, 2018, 03:00:32 pm
content: That.. was easy!

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 19, 2018, 11:58:27 am
content: Or not. It turned on, worked perfectly, went to the loo, came back and the screen was gone.Frack.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 19, 2018, 07:56:53 pm
content: Several hours of dissasembly, cleaning connectors, inventing new curse words I come across this fellow:Provides the HV for the EL display. Looks a bit crusty on the bottom left side so I zoom in on it and... hello!Yep. Shoddy solder and a crack. Display is up and running again, even though there's now a bad line in it. May have something to do with the way the flex from the row and collumn drivers are bended?? That's not pretty. But that's a job for tomorrow!

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 21, 2018, 03:09:25 pm
content: So, just to make sure, I took the 'good' flux (toxic looking, feeling and smelling) to town on that slab of bad looking solderjoints.No dice.Heated up the hot air gun, got some mild flux on column drivers corresponding to the bad line.No dice.So, I drag soldered over the suspected culprits... (and cleaned it up off coarse)No dice.At this point, I was kinda done. So I started to put humpty dumpty back together again. As I have bad experiences with putting a unit completely together, I do interim checks to see if everything still works. As soon as I put back the EMC enclosure and the earth connections to the two EL driver boards...it worked. I'm sure I'll think this is funny somewhere in the future, but not right now.

author: tautech
author_rank: Super Contributor
timestamp: December 22, 2018, 12:22:20 am
content: Is C27 leaking ? The surrounding conform coating looks dodgy like you sometimes see around leaking caps.Hook it out and test it.

author: nctnico
author_rank: Super Contributor
timestamp: December 22, 2018, 12:24:20 am
content: Quote from: tautech on December 22, 2018, 12:22:20 amWell spotted. Leaking electrolyte is probably also the reason why the solder joints look so bad. If C27 is leaking I'd replace all the capacitors on the board. Preferably with good quality low ESR capacitors.

author: tautech
author_rank: Super Contributor
timestamp: December 22, 2018, 01:20:24 am
content: Quote from: nctnico on December 22, 2018, 12:24:20 amThe ‘flag’ is dull and pitted SMD solder fillets.....whenever spotted and localised.....look harder !

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 22, 2018, 03:56:31 pm
content: Oh! TBH I never suspected a leaking cap. But it makes a lot of sense as I already wondered how they could have passed inspection looking like that (even when taking aging into account).Put her back together & on eBay but I'll replace c27 at least.Thanks guys!

author: nonlinear
author_rank: Contributor
timestamp: January 05, 2019, 12:31:55 pm
content: These units (as well as their brothers MS2701A) suffer from capacitors leaks.Places are LO1 (YIG drive PCB) , LO2 (DRO PLL PCB) and sometimes (worst case) - synthesizer PCBs.