Lecroy WR64MXi teardown...

[TunerSandwich]

I was doing some upgrades and general service on my WR64MXi, and thought you all might like to see some pics of it's guts.  I will add some closer views and further tear down the front panel, as I go through cleaning/maint and upgrades.  Enjoy. 

front panel controls and display (will add pics of what's under the hood, as I get to that section)

front end/inputs/processing (rear panel)

front end/inputs/processing (front panel)

AC/DC (main) PSU

Lecroy bus input card

Main motherboard (for OS and applications) notice the interesting daughter card, which acts as a bridge, between the MOBO and the front end main board

[mcinque]

 

What a huge PSU section!

[kizzap]

In the last picture, can you point out the "daughter-card"? The only two boards I see are the main PCB and then a generic DDR ram stick 

[free_electron]

In the last picture, can you point out the "daughter-card"? The only two boards I see are the main PCB and then a generic DDR ram stick 

put on your other glasses grampa.
it's the one in the forefront witht the bix xilinx chip on. fan left , xilinx chip then grey flatcable coming to front.
look above the xilinx chipo : see that big black pinstrip connector ? that looks like a PC104 / pci version to me

[TunerSandwich]

What a huge PSU section!

It powers all of the intermediate busses of the system...so needs to provide ATX power, as well as the bus for the input processing and front end.....it's a beast for sure.  I am a bit concerned about the density, and fact that it lives in a rather hot environment.  I can't imagine those electrolytics are going to last a decade more. 

It does have very nice discreet daughter cards and very nice input filtering.  I will show it in depth a bit more.   When it's assembled it has a nice isolated/ducted fan and shroud....

I shudder to think how much that thing is going to cost to replace when it goes.  It's also way too dense/complex to repair in house (unless I get really lucky).

[TunerSandwich]

In the last picture, can you point out the "daughter-card"? The only two boards I see are the main PCB and then a generic DDR ram stick 

[kizzap]

In the last picture, can you point out the "daughter-card"? The only two boards I see are the main PCB and then a generic DDR ram stick 

put on your other glasses grampa.
it's the one in the forefront witht the bix xilinx chip on. fan left , xilinx chip then grey flatcable coming to front.
look above the xilinx chipo : see that big black pinstrip connector ? that looks like a PC104 / pci version to me

In the last picture, can you point out the "daughter-card"? The only two boards I see are the main PCB and then a generic DDR ram stick 

http://i123.photobucket.com/albums/o282/madgreed/2014-11-25002.jpg
http://i123.photobucket.com/albums/o282/madgreed/2014-11-25001.jpg

* kizzap books an appointment to get his eyes checked.

I still think it was blended in rather well...

[jeremy]

On the rear panel of the frontend, what are those strange unmasked serpentines for? Something thermal? I imagine the grey stuff on the BGA fanout is some kind of thermally conductive tape?

[PA0PBZ]

I still think it was blended in rather well...

I agree, I had to look twice to find it. Stealth daughter card...

[Wuerstchenhund]

I am a bit concerned about the density, and fact that it lives in a rather hot environment.  I can't imagine those electrolytics are going to last a decade more. 

I wouldn't worry too much, the caps should be fine. Most of the heat is dissipated via the chassis, and the rest through the fan. The caps are also spec'd appropriately for this environment.

I was a bit shocked when I noticed that the PSU of my 64Xi is made by Cherokee, but they seem to produce pretty reliable stuff these days (they certainly haven't in the past).

I shudder to think how much that thing is going to cost to replace when it goes.

Why replace it? Just send it in to LeCroy for repair.

It's also way too dense/complex to repair in house (unless I get really lucky).

It's densely packed but I don't think it's a very complicated design. These PSUs are much more straight forward than say the dreadful Eaton PSUs in the HP 54542 scopes.

[TunerSandwich]

I am a bit concerned about the density, and fact that it lives in a rather hot environment.  I can't imagine those electrolytics are going to last a decade more. 

I wouldn't worry too much, the caps should be fine. Most of the heat is dissipated via the chassis, and the rest through the fan. The caps are also spec'd appropriately for this environment.

I was a bit shocked when I noticed that the PSU of my 64Xi is made by Cherokee, but they seem to produce pretty reliable stuff these days (they certainly haven't in the past).

I shudder to think how much that thing is going to cost to replace when it goes.

Why replace it? Just send it in to LeCroy for repair.

It's also way too dense/complex to repair in house (unless I get really lucky).

It's densely packed but I don't think it's a very complicated design. These PSUs are much more straight forward than say the dreadful Eaton PSUs in the HP 54542 scopes.

The ducting/fan system on the PSU is quite nice....I can tell it works well, by how much heat this thing kicks off 

Despite ratings and quality of those caps, I still fear their longevity....that is a pretty dense PSU, with a lot of discreet heat makers in it 

This scope is probably going to see A LOT of use....thankfully the environment is very well controlled. 

I never get lucky enough, when something fails, for it to be anything..other than the most burred surface mount BGA or QFN type device....I will gut the PSU a bit further tomorrow and have a look closer....it's certainly a bit on the sloppy side....

In general the wiring/routing in the MXi is a bit "sloppy"....it seems they could have done a lot better w/o all the delicate flying leads ETC.....the use of Kapton tape in the front panel/display area is a bit funny....either way it all comes together, just a bit surprised by how dense the entire design is.  I honestly wouldn't have minded a slightly bigger footprint, for some decreased density and better cooling.  An extra 3 inches in depth would have allowed for a much easier service access and cooling options....but it works...

[i4004]

I shudder to think how much that thing is going to cost to replace when it goes.

why would it go?

which caps in the psu, if japanese, they can last.
if they go you can put japanese caps then...

[alex.forencich]

On the rear panel of the frontend, what are those strange unmasked serpentines for? Something thermal?

Looks like high speed differential microstrip.  Probably connects the output of the front end to the ADCs.  Some people remove the solder mask over microstrip traces to get a more uniform impedance (solder mask variations will not affect trace impedance when you remove the solder mask). 

[TunerSandwich]

On the rear panel of the frontend, what are those strange unmasked serpentines for? Something thermal? I imagine the grey stuff on the BGA fanout is some kind of thermally conductive tape?

[TunerSandwich]

On the rear panel of the frontend, what are those strange unmasked serpentines for? Something thermal?

Looks like high speed differential microstrip.  Probably connects the output of the front end to the ADCs.  Some people remove the solder mask over microstrip traces to get a more uniform impedance (solder mask variations will not affect trace impedance when you remove the solder mask).

 If I have time I will remove the heatsinks on those BGA devices and we can have a look at the p/n....the traces carry over to the front board

[Lukas]

Anyone got some idea why they need these crusty looking coaxial cables all over the place? Sampling clock distribution maybe?
Are these dark things on the underside of the BGAs ferrite dampers? Interesting to see them in such place...

[T3sl4co1l]

Those are definitely microstrip, but vanishingly low impedance... trace widths like that would be reasonable on a two layer board, but...?!  I'm guessing they were going for 50 ohm differential (~25 ohm each), but geez... and why?...

It bothers me more that they didn't bother to finesse the soldermask cutouts -- it's all angular and blah!

Tim

[jeremy]

Thanks tunersandwich, this is very interesting! Would be cool to see under the heatsinks if you get a chance.

I also find it odd that the copper is not gold plated, yet it looks quite good and unoxidised. Is there lacquer on the board? Although if there was, that would probably defeat the purpose of having the bare microstrip.... Does the unit live in a humid climate?

edit: also, it just occurred to me that they are in fact not length matched....

[T3sl4co1l]

I've got at least another board with unplated copper,





(Note, second pic is at a right angle to the first; note the bigger and smaller empty holes, and the common hole with a brass insert.)

This is a HP/Compaq 8510W motherboard; this area is between the Northbridge and Super IO chips.

I would assume they used a somewhat more reactive flux in the solder paste, relative to the recommended low activity flux, RoHS paste and gold plated boards, that are most common for assemblies.

The copper parts look coppery, but remember, a bright copper surface is... well, *bright*!  Almost as bright as the brass.  So there's more than a few years of tarnish on there (almost five, in this case, actually).

Tim

[TunerSandwich]

Anyone got some idea why they need these crusty looking coaxial cables all over the place? Sampling clock distribution maybe?
Are these dark things on the underside of the BGAs ferrite dampers? Interesting to see them in such place...

That coax looks pretty far from crusty.  It's well terminated and routed.  I will trace them and try to get an idea of what they are doing....I have a feeling something to do with ext trig and other front end duties, but I haven't really investigate.  Will have a look...I am curious now that you brought it up.

The pads on the back of the main BGA in the cluster, are silicon and have a rough texture....seems like isolation, rather than thermal.....I will lay it in the chassis and see what they might line up with.....

the two BGA clusters are obviously driving or processing channel pairs.  1-2 + 3-4.....the main BGA cluster with cooling fan has to be post a/d and acquisition.....I wouldn't be surprised if that BGA clusters traces lead back to the ribbon cable connections, that go to the PCi bridge board.....I will beep those out and see where they go.....

[marshallh]

Any pictures of the acquisition section?

[TunerSandwich]

Those are definitely microstrip, but vanishingly low impedance... trace widths like that would be reasonable on a two layer board, but...?!  I'm guessing they were going for 50 ohm differential (~25 ohm each), but geez... and why?...

It bothers me more that they didn't bother to finesse the soldermask cutouts -- it's all angular and blah!

Tim

They carry over to the front of the board and disappear under the passive heat sinks.  Let's lift those and remove the i/o board and see....

[TunerSandwich]

Any pictures of the acquisition section?

specifically the i/o?

[Wuerstchenhund]

That coax looks pretty far from crusty.  It's well terminated and routed.  I will trace them and try to get an idea of what they are doing....I have a feeling something to do with ext trig and other front end duties, but I haven't really investigate.  Will have a look...I am curious now that you brought it up.

If I remember right the coax is for the internal calibration signals for the 50ohms and 1Mohms paths. This is used when the scope stops acquisition and goes into calibration cycle to compensate for temperature variations and changes in the signal path.

On these scopes there's a setting to disable internal calibration for thermal compensation but will still re-calibrate when larger changes in the vertical setting are made.

[TunerSandwich]

Front panel USB plus SigGen/Test/Cal out



CH input topside...notice the interesting resistive divider at the top left?



CH inputs topside



CH inputs bottom side



There is where our "crusty" coax leads to/from....it terminates on more of the same traces as the backside of the board...the traces run up the board under the cans, through routed channels....3 cans, 3 coax.....not about to bother lifting the cans off....but I think the auto cal circuitry is the best bet for those sections



Topside of processing board, with the inputs/acquisition board removed....love the hirose board to board connections....will possibly pull those heat sinks off tomorrow and expose the BGA clusters