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DIY Logic Analyzer Probe and Pods for Siglent (and LeCroy) scopes

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FrancisM:
Thomas,

I learned what deskew is with my first digital scope some years ago. And I saw you using it while testing your probe earlier in this thread.
A friend of mine is amused to tell me that most of my gear is running close to DC, so I will leave it at 0ns.

This morning, I made some further testing on a Z80 cpu board. And as almost always, it started with a bad electolytic on the PSU. The +5V is a buck converter (L4960) and it's output cap measured less than one tenth it's original value, not speaking about esr. There was a lot of garbage on top of the 5V and it's probably the only issue. After replacement, the ripple was down to a decent value. The thing runs at 100kHz and I used a Panasonic FR.
So far, so good.

I was told the board fails to read temperature of a sensor. I can see an ADC0844 and some opamps connected at it's inputs. There's a span adjustment like in the datasheet and the opamps make the zero shift. It's a four layer board and I have no manual but the sensor seems to be connected to ch1 and ch2 through two opamps.

I connected your probe to the ADC data and control lines. Once triggered, the timings are clean but a read always outputs a 0FFh even with the sensor(PTC) connected. I then triggered on a write to get the mux mode control byte. It reads 04h wich is not what I expected. It translates to channel 1 in single ended mode while I thougt it to be in diff mode. The board doesn't seem to initialize as it should, probably an external missing stimuli. It will be replaced where it comes from with everything connected to it.

I had fun playing with my scope.

All the best,
Francis

oz2cpu:
great, yes Z80 speeds is quite a facter away from this scope capeabilities,
but you are having fun, and learn how to use it as hardware and software debugger,
the more you dig into the z80 board, you be amazed how easy it is to find and fix all the problems.

pzw:
I guess I was one of the lucky people getting one of the last sets! The PCBs look great, and well assembled!
One small hint for whoever will decide to make their own PCB; The inner layers of the PCB with the edge connector will be exposed when the edge is sanded under the correct angle. Not that it will create any issue, since I do not see how the exposed copper can short out anything. But if the internal layers are made about 1.5 - 2.0mm shorter at the edge connector end, this inner layer will never be exposed.

Now I am on the hunt for an old DVI cable, or maybe I just need to buy a new one ;-) .

Thanks again to @on2cpu for the nice PCBs and quick shipment!

oz2cpu:
Fantastic usefull comment
if anyone like to take this up in the near future
and maybe dont own an Altium license, just pm me,
all files , gerber, and altium, are in the thingiverse link.

techneut:
My pcb's arrived today and they are looking good. I'm waiting for the slow boat from China for the components and in the mean time checking out other scart cables for coax. We still have a lot of them at work.

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