Hacking the Rigol MSO 2072A - Digital Probe RPL2316

[david.m.hewlett@me.com]

 Please note that Rigol has now resolved this issue with me see below post for more information.

Hello all, I managed to get a very good deal on an Rigol MOS 2072A at an estate sale. Unfortunately the digital probe for the logic analyzer is missing in action.

I have reached out to a few rigol dealers and they are slow to get back to me. $pecial order part. I saw one RPL2316 probe it was listed in UK for very close to the cost of a new scope in Canada. ( I am in Canada)  the price was ridiculous. It would be cheaper to buy a new unit and sell it without the cable as a DS2072. See attached quote from Rigol Canada $1700. I can buy the whole scope with the probes for $56 dollars more. Hmmm.  I could buy a top model Saleae or even higher end logic analyzer for less than this. I had a very good opinion of Rigol the price, performance and quality now I feel so abused 😩 .

Does anyone have any info on this probe. It would appear to be passive , just a cable. From my research there seems to be two kinds of digital probes ones with active electronics with differential amps sometime adc and memory. Other have this all in the scope and just need a shielded cable. I believe this is how it is done on this MSO.

I am considering making my own cable. Can anyone provide any information. Pin outs , connector types , confirm that it is just a cable.

Is this just a shielded cable or an active device ?
Does anyone have one to spare at a good price ?
Can this be easily and cost effectively cloned ?

Regards

David.
Ps. this is my first post, hope I posted it in the right place.
I very much appreciate Dave's video blog,  very entertaining and have found this forum to be very useful in the past. CHEERS   
 

[EEVblog]

Insane.
Too new a scope to have any sort of 2nd hand market either, unlike say old HP/Agilent probes.

[david.m.hewlett@me.com]

Yes I just don't understand. When they price something this high no one is going to buy it. Its just like saying buy a whole new scope. Are they concerned that someone could hack a DSO to a MSO.
Hope someone who has the cable can tell me about the cable Pinout and internal parts. I imagine that a few people will break or lose them. If there is no 'magic' I am sure I could make one for a few hundred.

[Ivan7enych]

I am considering making my own cable. Can anyone provide any information. Pin outs , connector types , confirm that it is just a cable.

As I understand, it consists of 16 coax cables, each with 1:10 passive divider circuit (just like in usual 1:10 probe).

[david.m.hewlett@me.com]

If that's the case I only need the connectors, pin outs ,coax and a few resistors.  May Dave could show us his design as part of a take Rigol to the mat eevblog episode I am sure it would be very entertaining 😎 Dave likes Rigol but he has no fear to call them out. They should be shamed for this kind of price gouging.  Come on $1200 for a $200 dollar cable ( thats with a good markup I am sure).

[Ivan7enych]

If that's the case I only need the connectors, pin outs ,coax and a few resistors.  May Dave could show us his design as part of a take Rigol to mat eeblog episode I am sure it would be very entertaining 😎

I don't think David has MSO2072 in his lab now.

I'll try to inspect my probe set and give you pinouts, may be tomorrow.

[david.m.hewlett@me.com]

Great!
I believe the same cable is used in the 4000 series I think I saw him use that once.

[Ivan7enych]

Here it is, pinout is very simple.

Inside the scope each channel is connected to ground with 10k resistor + some capacitor (~20pF). With the coax cable the input capacitor becomes ~80pF.

On the end of coax there's 91Kom resistor + 8pF capacitor, both make a resistive and capacitive 1:10 divider.

When you make a connector (PCI express ?) and solder a piece of coax cable (rg316 or thinner), you will need to measure the capacitance of both the coax and the scope together, to choose correct capacitor value of the divider.

[david.m.hewlett@me.com]

This is great thank you so much this is great. Hard to believe they want more than $1200 us. For this.
Can you measure the length of the cable ?
Do you see any identification numbers on the cable ?

[Ivan7enych]

Cable length is 100cm,

coax diameter is 1.6mm, it's thinner than RG316 (2.6mm) and a bit thicker than tiny RF cables which I often see inside laptops (from wifi module to antenna) (1.2mm).

[david.m.hewlett@me.com]

Thanks I will work on duplicating

[Howardlong]

If it is passive, check that the ribbon coax isn't lossy, high speed passive LA probes typically use coax or twisted pair with distributed resistance, usually in the 100 to 200 ohm range along the length. Sourcing that probably isn't too easy.

FWIW, the probe on the MSO1000Z is active, counter intuitively that is probably cheaper to make than a passive pod with resistive coax or twisted pair.

[Ivan7enych]

If it is passive, check that the ribbon coax isn't lossy, high speed passive LA probes typically use coax or twisted pair with distributed resistance, usually in the 100 to 200 ohm range along the length. Sourcing that probably isn't too easy.

Yeah, it's true, coax appears lossy, with resistance 132om
It's very easy to measure coax itself and RC divider separately, the RC dividers are in the detachable part.

[david.m.hewlett@me.com]

Hello all, thank for the help with this issue.

Michael Rizzo of Rigol USA has come to my rescue with a spare cable.
Michael has also told me he will be working with Rigol to get the pricing down to a reasonable level for this.

GREAT !

Thanks Michael and Thanks Rigol.

And Thanks EEVBlog.