RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown

[joeyjoejoe]

It might be best to look at options that can work with 1.6mm boards as these are cheap for fab houses.

If we start getting off the beaten path, things get expensive pretty fast...

I'll take a look.

[texaspyro]

It might be best to look at options that can work with 1.6mm boards as these are cheap for fab houses.

Almost all the cheap fab houses off 0.8-1mm boards for the same price as the 1.6 mm boards.

[TopLoser]

2x25 1.27mm pitch, intended for mounting on the edge of the PCB, so 1 row of pins per side of the board

Don't know the exact plug part number.

I suspect this means the PCB is 1.0mm or 0.8mm thick.

Are you sure about that? Looks like a good old fashioned 2x25 0.1” pitch connector on the one I’ve got.

[joeyjoejoe]

2x25 1.27mm pitch, intended for mounting on the edge of the PCB, so 1 row of pins per side of the board

Don't know the exact plug part number.

I suspect this means the PCB is 1.0mm or 0.8mm thick.

Are you sure about that? Looks like a good old fashioned 2x25 0.1” pitch connector on the one I’ve got.

Oh crap, you're right! Good to know 0.6-1.6mm at least for PCBWay is the same price.

[Rerouter]

Could well be. I was working off the xray image. (Dont have the hardware myself)

[TopLoser]

It’s 2x25 0.1” pitch on the scope, interface lead and pcb take it down to smaller pitch cable so I guess it may well be a 0.05” pitch connector on the active probe pcb...

[Rerouter]

I would base it on the smaller the ribbon the less cumbersome it is to use. A 0.05" ribbon cable for 50 wires is about the size of an IDE hard drive ribbon.

Edit:
Did some checking based on images, its quite clearly using 0.025" or 0.635mm pitch ribbon wire between the scope and pods. Nice and standard, and also reduces the amount of connectors it could be.

So for each pod of 8 channels, there is (ground, 4v, +2.5, -2.5, Vref, 8 differential pairs) at minimum 21 signals, do we want to make these devices purely compatible with what is already in place, or make it designed around 2 seperate 8 channel pods? e.g. have a little breakout board at the scope end to 2 plugs for the pods?

I was thinking something like the Hirose ST40 series connectors, most likely the 24 pin one, but as they don't have prefab cables, Its probably not a good option for a projec tlike this. the scope end is 0.1" 2x25, shall we just make both ends the same? or do we get creative with smaller ribbons or more flexible wiring? by using a little adaptop board that plugs in at the scope?

[madmac]

In testing the LA input with a LVDS driver I noticed that channel 6 has a lot of crosstalk when unterminated. The remaining lines are all quiet.
It would be good if some else could confirm that it is a layout issue inside the scope not a fault on my unit. To get live update on the LA short pins 1 and 2 (the right most pins) on the 50 way connector and press the LA button. With nothing connected I get this issue.

These pins seem to have a little bit of protection and go directly to one of the ASIC's which I guess is why they are not hot pluggable.

With the SN75LVDS389 connected it works correctly.

[Rerouter]

At a glance, some of the differential pairs in the scope are far closer than others,
https://www.flickr.com/photos/eevblog/44893153125

So i could imagine some pairs being more noise effected than others. Not to mention once they disappear into internal layers Its hard to say what happens.

[dren.dk]

I just finished my first stab at the 4-layer + single sided version of the board.

All components are on the top layer along with almost all of the signals.
Layer 2 is a solid ground plane.
Layer 3 is a mostly solid -2.5 V plane for heat sinking, because somone noted that the chips were about 60 degrees in the Rigol pod.
Layer 4 busses the power and other common signals between channels.

I have not yet done anything about the silkscreen, though I might as well just hide all the references and values because there's no room for them:)

The channels will need to be labeled though.

I'm still not entirely happy with the crampedness of parts around the ICs I could only make around 1 mm worth of space there, so any rework is going to be a bitch.

I slapped a 50 pin 0.1" IDC connector on the board because that's what's in the scope and with the size the parts take up there's really no reason to save space there.
The board ended up at 86x62 mm.

I used through hole connectors because I like robustness.

Everything is online here: https://gitlab.com/dren.dk/mso5k-la-pod

[joeyjoejoe]

I would base it on the smaller the ribbon the less cumbersome it is to use. A 0.05" ribbon cable for 50 wires is about the size of an IDE hard drive ribbon.

Edit:
Did some checking based on images, its quite clearly using 0.025" or 0.635mm pitch ribbon wire between the scope and pods. Nice and standard, and also reduces the amount of connectors it could be.

So for each pod of 8 channels, there is (ground, 4v, +2.5, -2.5, Vref, 8 differential pairs) at minimum 21 signals, do we want to make these devices purely compatible with what is already in place, or make it designed around 2 seperate 8 channel pods? e.g. have a little breakout board at the scope end to 2 plugs for the pods?

I was thinking something like the Hirose ST40 series connectors, most likely the 24 pin one, but as they don't have prefab cables, Its probably not a good option for a projec tlike this. the scope end is 0.1" 2x25, shall we just make both ends the same? or do we get creative with smaller ribbons or more flexible wiring? by using a little adaptop board that plugs in at the scope?

I would keep it simple with a 0.1" 50 pin cable. H3DDH-5006G has a polarizing key and a strain relief and is cheap. Then slap a header on the PCB and call it a day. Could even look for shorter versions as well - I've seen some other companies that have them even shorter.

[Rerouter]

Well if thats the case. 50 pin scsi cables should fit the bill and come in various lengths.

[wulfman]

It looks nice but the output of the Comparators need to be treated as a diff pair all equal lengths. Also on the rigol pod the inputs all show a ground with the signal so at least 32 pins to the board under test. I do like the 50 pin connector, cheap and simple I was however thinking about the use of an 68 Pin Ultra320 SCSI cable that uses twisted pairs. I am in my spare time creating a board like this for my 5000 series scope.  TI makes a 4 channel version of that IC  LMH7324SQ/NOPB  it may make the board a lot easier to manufacture. at 13~ a lot cheaper too. 

[TK]

TI makes a 4 channel version of that IC  LMH7324SQ/NOPB  it may make the board a lot easier to manufacture. at 13~ a lot cheaper too. 

I proposed the LMH7324 but it seems to not have all the required features.

https://www.eevblog.com/forum/testgear/rpl1116-active-logic-probe-pod-for-1000z-series-teardown/msg2090230/#msg2090230

[Rerouter]

Its more as I was trying 2 layers it would be an utter pain to layout. If 4 layers are in the mix I can give it another spin with the lmh7324's

[wulfman]

I been reading the data sheet. It looks like i can make it work. What have i got to loose ?
Boards are cheap, parts are cheap, I have a large order i need to send to my Chinese board house so i might as well send in this one,

[dren.dk]

I initially wanted to use the LMH7324 too, but the pin-out does make it a bit harder to use, because the outputs sit on opposite sides and it's not really that much cheaper at the sub-10 pieces end, because with the LMH7322 you get into price breaks twice as fast.

The layout of the 16 channel pod is somewhat cumbersome due to the ordering of signals in the 50 pin connector and the resulting scramble of inputs.

As far as I can tell the pin-out of the 50 pin connector was all dictated by having a dual-sided load in the Rigol pod.

I think I want to do a new design with a 3 board construction:
* Two identical 8 channel pods, with a sane straight-through layout.
* A simple two-sided converter board which unscrambles the 50 pin ordering and provides two 26 pin connectors for twisted pair ribbon cable such as this: https://www.mouser.dk/ProductDetail/Amphenol-Spectra-Strip/132-2801-026?qs=sGAEpiMZZMsJiFh04Lj2rnHfTmy1h2ypJt6bk8ifWw4%3d


There are a couple of nice properties of the split approach:
* It's the way the adults do it, see Tektronix P6418: https://www.google.com/search?q=Tektronix+P6418&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiOuZ2a9IDgAhUBjSwKHVVECf8Q_AUIDigB&biw=1920&bih=1077 or Agilent 54620-61601: https://www.google.com/search?q=Agilent+54620-61601&client=firefox-b-ab&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwiz2rL784DgAhWBOSwKHX-sCVIQsAR6BAgGEAE&biw=1920&bih=1077
* The layout of the pod becomes nicer because the ordering of inputs and outputs can be the same.
* Hand-assembly, rework and debugging is easier with two separate pods, I think.
* The two smaller pods with smaller cables are easier and more flexible to use than one 16 channel pod with a large cable.
* If someone decides to make a probe for another scope, then it's very cheap and easy to produce a new converter.

I wanted to use a female 50 pin board mounted connector on the converter board (like this, but ideally edge-mounted: https://www.mouser.dk/ProductDetail/3M-Electronic-Solutions-Division/6850-4500PL?qs=sGAEpiMZZMs%252bGHln7q6pm1D%2fu5fPR%252bY0EqgFxb8dXZE%3d), now I'm thinking that having a 10 cm bit of 50 lead ribbon going to the scope might be better due to it possibly being lower physical stress on the scope connector and probably cheaper to make too.

[Rerouter]

Well for an 8 channel pod. Feel free to use my 2 layer pcb design. If you have a case in mind i can tweak it.

edit:
Your linked 50 pin connector calls for a 1.6mm PCB,

Edit2: sorry didnt see you where planning on speccing your own loom ribbons, instead of premade assemblies.

Edit3: If your going with custom ribbons to the pods, why not consider the smaller pitch ribbons? really make it a clone of the tek and agilent? It ends up slightly cheaper per foot.
https://au.mouser.com/ProductDetail/3M-Electronic-Solutions-Division/3754-26-300?qs=sGAEpiMZZMsJiFh04Lj2rnGVP%252b060guwueW9iVoIWzc%3d

[dren.dk]

I certainly do want to use a narrower pitch ribbon cable, the only trouble with that is finding connectors that aren't hugely expensive.

The 3M tripolarized series looks nice but it's spendy.

I wonder if anyone makes ribbon to board transition connectors in 0.025" pitch like these for 0.1": https://katalog.we-online.de/en/em/BHD_2_54_BOARD_TO_CAB_TRANSITION_CONNECTOR_6120XX22323

[wulfman]

cable  https://www.cablewholesale.com/specs/10p2-39103.php
connector https://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/8-5174682-7/8-5174682-7-ND/957333

twisted pair high speed. I am sure better than any flat cable

[Noy]

Do we really need such cables?
I think Rigol knows what they are doing...
I thought the main goal was to get a working  equivalent good pod like the original but much more cheaper... Not 350€...

[wulfman]

Well its not much different really about 17$ more
for something that IMHO would work better
but please go on with your design with the 50 pin stuff
I am just playing around with my design.
I have never used the tuned line feature in Orcad and want to explore the
feature. This is an excellent opportunity for me to do so.

connectors https://www.ebay.com/itm/6-Pcs-IDC-Cable-Connector-FC-50P-50Pin-Female-Header-2-54mm-Pitch/311008750065?epid=1339185073&hash=item486990e9f1:rk:4:pf:0
   
cable        https://www.ebay.com/itm/1M-3-3Ft-1-27mm-Pitch-50-Pin-Wire-Gray-Flat-Ribbon-Cable-For-2-54mm-FC-Connector-/172341711789

board connectors  https://www.ebay.com/itm/6-50-Pin-IDC-Box-Header-Straight-Angled-Flat-Ribbon-Cable-PCB-FC-Connector/253520275026?hash=item3b06fc6652:m:m-nK827yuu_e05v_eSwju6g:rk:3:pf:0


so 15 ~ bux appx for the 50 pin stuff

17$ for the 68 pin scsi cable 20 bux for the board connectors.

[Noy]

With the lvds scsi cable you need an additional converter pcb added to the BOM.

[ebclr]

What about change Ground plane to top and make GND a heat dissipation plane, those ic's like to be hot

[TK]

Well its not much different really about 17$ more
for something that IMHO would work better
but please go on with your design with the 50 pin stuff
I am just playing around with my design.
I have never used the tuned line feature in Orcad and want to explore the
feature. This is an excellent opportunity for me to do so.

connectors https://www.ebay.com/itm/6-Pcs-IDC-Cable-Connector-FC-50P-50Pin-Female-Header-2-54mm-Pitch/311008750065?epid=1339185073&hash=item486990e9f1:rk:4:pf:0
   
cable        https://www.ebay.com/itm/1M-3-3Ft-1-27mm-Pitch-50-Pin-Wire-Gray-Flat-Ribbon-Cable-For-2-54mm-FC-Connector-/172341711789

board connectors  https://www.ebay.com/itm/6-50-Pin-IDC-Box-Header-Straight-Angled-Flat-Ribbon-Cable-PCB-FC-Connector/253520275026?hash=item3b06fc6652:m:m-nK827yuu_e05v_eSwju6g:rk:3:pf:0


so 15 ~ bux appx for the 50 pin stuff

17$ for the 68 pin scsi cable 20 bux for the board connectors.

The IDC connector might be too shallow to fit inside the MSO connector