Author Topic: RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown (Read 99916 times)

oliv3r · « **Reply #125 on:** February 02, 2019, 02:30:54 pm »

ah, right; ok so I really like the breakout board; what connector are you intended to use? I remember there was talk about HDMI cables earlier which make a lot of sense I suppose, but then your short.

I wonder if it would make sense to 'downgrade' to 4 bit pods then. Seeed studio's boards are super cheap even for 4 layers, and if you have 4 bit pods, you still would get 10-ish pods per order (if you use the full 50 x 50 for a pod. If you'd go with 2.5 x 2.5 per pod (very small though) you could put 4 pods on a pcb and thus you'd get 40-ish pods per order!

Rerouter · « **Reply #126 on:** February 02, 2019, 02:49:37 pm »

a 8 channel 4 layer pod is only 34x33mm in size, and thats with single layer loading and 0603 components. so you really don't gain anything by going to 4 channel pods.

the breakout board i am currently working on is 65x15mm for reference so far.

there is enough room for 4 pods and 2 breakout boards on a 100x100mm pcb, but that leaves the end user the guillotine them out.

so yep, if you wanted, 20 pcb sets could be had for about $37 posted.

The current ribbon me and dren are working towards are 0.025" or 0.635mm pitch ribbon cable, the same stuff they use on the more professional gear, (very flexible)

oliv3r · « **Reply #127 on:** February 02, 2019, 07:13:23 pm »

Going to 4 bit pods could not be so much as for size, but price as well of course. And cables. If a HDMI type A connector is used as a cable for example, which has 4 differential pairs if i'm not mistaken. USB-C connector is 24 pins, but unless you put reversing logic in it, I think you effectivily end up with the same amount, 4 differential channels (the other pins would be unused to allow for connector reversal.

If a 4 bit pod would even be smaller (due to the single LM) and cheaper, it's up to members to decide if they want 1 or all 4. Also scale of economics may be achiveable by group-bying the parts 'kickstarter' like or something?
Just a thought is all...

Rerouter · « **Reply #128 on:** February 02, 2019, 10:47:01 pm »

All i can say oliv3r is, I have posted my current design files only a few posts ago, the software is free (Kicad) and the layout I have used can be cut in half or doubled, the only thing they would need to do it is fiddle with the output connector, and run there own breakout board for whichever esoteric connectors they please.

Noy · « **Reply #129 on:** February 03, 2019, 11:12:17 am »

Which connectors/cables do you want to use on the DUT side?
I was thinking about using DSlogic shielded fly wires from my DSLogic but there are some passives used in them.
So i have to buy another set of cables and dismount/mount 0Ohms.

Do you have better ideas?
I think the shielding is good for highspeed signals?

wulfman · « **Reply #130 on:** February 03, 2019, 08:25:58 pm »

I doubt shielded will make a diff most of the wires going to the DUT will not be tightly grouped, just left flying.
Testing will show the truth.

stj · « **Reply #131 on:** February 04, 2019, 03:24:34 am »

this is all good, but:
does anybody have a link to images of the internal board in the 1000z series scopes?
that really needs to be cloned.

all the teardowns i'v seen where on the 1054z that does not have the function.

joeyjoejoe · « **Reply #132 on:** February 06, 2019, 06:30:02 pm »

For those working with it, the LMH7324 is now in the official KiCad repository - if you're working off GitHub, just do a git pull to get the latest. If you're not working off GitHub, you should be

Noy · « **Reply #133 on:** March 01, 2019, 04:28:11 pm »

Any News here?

dren.dk · « **Reply #134 on:** March 01, 2019, 04:34:58 pm »

Yep, I received my boards, stencil and all the jellybean parts from jlcpcb on Monday and ordered the expensive parts from Mouser on Tuesday:
https://photos.app.goo.gl/MEetU1SV5LrNyh2t5

One of the parts in my Mouser order is backordered and it's the one part that I have not managed to find anywhere else:
https://www.mouser.dk/ProductDetail/200-ESQ12523LD

BTW, talking over the design with a friend, I ended up sticking a murder of de-coupling 0402 caps on the bottom of the board, because it would be a shame if I left it out and it turned out to be needed.

As soon as I have all the bits I'll fry up a batch and let you know about it.

Noy · « **Reply #135 on:** March 07, 2019, 12:59:18 pm »

Hi, can you please provide your mouser project cart?
Which tolerance class 1% or even better for the resistors?
Which condensator C0G or X7R?
Some of the measured values in the schematic aren't E series..?

dren.dk · « **Reply #136 on:** March 07, 2019, 01:15:43 pm »

I ordered almost all of the parts from https://lcsc.com so they could be shipped with my pcbs from https://jlcpcb.com.

The Mouser order contained:
https://www.mouser.dk/ProductDetail/926-LMH7324SQ-NOPB
https://www.mouser.dk/ProductDetail/649-221121-00026T4LF
https://www.mouser.dk/ProductDetail/855-M50-3301342
https://www.mouser.dk/ProductDetail/200-ESQ12523LD

I picked X7R caps and 1% resistors.

I've attached the BOM export from LCSC.

I see now I ordered 200 extra LEDs by mistake, good thing they were so cheap:)

nimish · « **Reply #137 on:** March 07, 2019, 10:19:56 pm »

Quote from: dren.dk on March 07, 2019, 01:15:43 pm

I ordered almost all of the parts from https://lcsc.com so they could be shipped with my pcbs from https://jlcpcb.com.

The Mouser order contained:
https://www.mouser.dk/ProductDetail/926-LMH7324SQ-NOPB
https://www.mouser.dk/ProductDetail/649-221121-00026T4LF
https://www.mouser.dk/ProductDetail/855-M50-3301342
https://www.mouser.dk/ProductDetail/200-ESQ12523LD

I picked X7R caps and 1% resistors.

I've attached the BOM export from LCSC.

I see now I ordered 200 extra LEDs by mistake, good thing they were so cheap:)

Assuming this works do you plan on assembling these for sale?

dren.dk · « **Reply #138 on:** March 08, 2019, 07:26:13 am »

That's a hard question.

The raw BOM cost at 10-off numbers is around 100 EUR and that's without hooks and cases.

The sale price a PLA2216 is 300 EUR, so there's certainly room for saving a bit of money, but at low numbers the cost of assembly, shipping and other overhead quickly eats up any savings.

For me it looks as though it's viable to build my own as long as I count the time spent as hobby-time.

If I were to count the time spent as work-time I'd probably have to jump to a production run of at least 1000 units assembled professionally, possibly with custom cases and probes, but that's a huge investment that I have no way of making.

One option to fund the production run would be to set up a kickstarter to ensure the customers are at hand before starting the factory.

Another concern is that I suspect there aren't enough cheapskates with MSO5k scopes in the world that would be willing to plunk down 150 EUR for a knock-off LA probe.

All of this applies to my current design which is more or less a straight clone with a slightly cheaper, but equal performance, comparator chip and the split-pod physical layout.

The connectors and comparators make up 85% of the BOM cost out of that about half is the comparators part.

To make a truly low-cost alternative someone would have to put in the legwork to attack the BOM cost at the expensive end:

1.a: Connector cost could be slashed by finding the parts at the source in .cn in stead of Mouser, I suspect waltzing down to any market and browsing stalls in the pearl river delta would yield massive savings:)
1.b: Another option could be using off-the-shelf consumer cables, but I don't know of any modern standard with 8 LVDS pairs, ground and 4 extra power wires, so that's probably not going to happen.

2: Lower performance comparators must exist, but likely with single-ended output, so one would have to find a cheap LVDS transmitter to pair it with.

bmx · « **Reply #139 on:** March 09, 2019, 05:42:47 am »

That's exactly what I had in mind since the beginning of this thread: Is the rigol price really high? No sure, considering it comes with ``quality`` hooks.

It's pretty hard to find good hooks that don't cost a finger each.
After initial disassembly of the pod, everyone noticed quality components inside, compact design, etc. I'm not quite sure at all rigol makes profit on those probes. All in all, fpc, board, case, cables, hooks, labels, lead time, packing and shipping, it's not worth it.

Unless someone reports on quality inspection of the rest of the rigol probe (plastic, leads, heat resistance, hooks, ..) as a $5 piece of crap.

joeyjoejoe · « **Reply #140 on:** March 09, 2019, 04:02:09 pm »

I think the biggest opportunity missed here is the ability to design a simple low cost 4-8 channel version.

dren.dk · « **Reply #141 on:** March 13, 2019, 04:47:06 pm »

I have just assembled the first set of pods and breakout board: https://photos.app.goo.gl/qMiUNHk9Tk6krjD9A

Holy hell, those 250 parts by hand at 0603 was hard without going insane.

I ended up sticking 48 0402 10 nF caps on the back, so each of the 12 power pins per IC has a super-local decoupling cap.

I still want to play around with a cheaper and lower performance frontend.

MegaVolt · « **Reply #142 on:** March 17, 2019, 12:10:28 pm »

Input band at the probe 200 MHz. Perhaps changing the input chains can raise this band to 500? Sampling frequency allows.

felix ch · « **Reply #143 on:** March 18, 2019, 02:03:37 am »

Quote from: dren.dk on March 13, 2019, 04:47:06 pm

I have just assembled the first set of pods and breakout board: https://photos.app.goo.gl/qMiUNHk9Tk6krjD9A

Does it work as you expected?
If so, I'll going to make it.

Thanks for you a lot!

dren.dk · « **Reply #144 on:** March 18, 2019, 08:38:58 am »

Not quite.

Good news first:
* I have verified all the output voltages on the breakout board without the pod, so that's nice.
* I have also verified the connections from the breakout to the pod and that there are no shorts.

Then the bad news:
* I fucked up the charlieplexing for two of the LEDs, so that will require either a new board or some bluewires.
* I'm seeing -2.5V on Vref when the pod is plugged into the scope, which should not happen as nothing but high-impedance inputs are connected to Vref and no shorts to any power rail.

dren.dk · « **Reply #145 on:** March 22, 2019, 08:20:28 pm »

Close inspection of the board file revealed that the problem was that I fucked up and overlapped the -2.5V and +4V zones so they ended up shorted.

The good news is that the MSO5k has a nicely robust set of power supplies for the LA probe, they survived the abuse just fine.

I've created a new board and I'm just waiting for another layout for the same order before sending it out.

The changes are:
* Fixed the Charlie plexing fuckup.
* Fixed the power rail short.
* Moved the parts away from the edge, so there's less risk of damage when depanelizing.
* Wired the ISP tracks out to the panel frame, so it's easy to program without fiddling with the annoying SOIC clip.

johnmx · « **Reply #146 on:** March 22, 2019, 08:35:16 pm »

Quote from: dren.dk on March 22, 2019, 08:20:28 pm

Close inspection of the board file revealed that the problem was that I fucked up and overlapped the -2.5V and +4V zones so they ended up shorted.

Always run the Design Rule Check before sending the design for production. Most people don't care about this tool, but I think it is essential.
I am only happy when it returns 0 errors.

thm_w · « **Reply #147 on:** March 22, 2019, 10:00:27 pm »

Quote from: johnmx on March 22, 2019, 08:35:16 pm

Always run the Design Rule Check before sending the design for production. Most people don't care about this tool, but I think it is essential.
I am only happy when it returns 0 errors.

Wow, that is wild that people would not care, it should be run as default function when generating gerbers. Of course the best is live DRC, but that is probably much harder to implement software wise.
Good to know it didn't blow the Rigol, but I'm thinking to add some 1A fuses on the 4V/2.5V rails, just in case.

dren.dk · « **Reply #148 on:** March 23, 2019, 09:26:17 am »

I certainly always run DRC before tapeout, but in this case it generated a single warning that didn't sound dangerous and when I went over the board I could not see any problems at all, so I figured that it was a false positive.

Good thing 4 layer boards are so cheap now, so it's only a 50 USD lesson:)

BTW: Someone warned against having decoupling caps on the bottom of the board because it would be too hard to assemble, but that was really not a problem at all.

voltsandjolts · « **Reply #149 on:** March 23, 2019, 09:43:53 am »

Maybe they meant it is more hassle for automated assembly and reflow - all components on one side would have to be glued in place?


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Author Topic: RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown (Read 99916 times)

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