EEVblog #879 - R&S HMO1202 Scope Bandwidth Hack Investigation

Dave investigates how the front end bandwidth limiting works on the Rohde & Schwarz 1202 series oscilloscope.
Is the bandwidth limit set just by the LMH6518 front end Variable Gain Amplifier chip through the SPI bus?

See the extended 50 minute version here that has much more detail and mucking around trying to get the R&S1202 to probe itself.

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[DrTune]

I bet R&S are very grateful for your insights :-)

[johndrachenberg]

"Hoy!"
I also say this at the start of every video. :) Please never stop this tradition.

[EdEditz]

Geeess, it boggles the mind. Somebody had to sit there and think all this stuff up when designing a scope like that. Well, there'd be a team I bet but still. Amazing engineering.

[Mr.Laidukas]

Great video Dave! At last not a review, not a mailbag but real stuff :) Its not that I don't like reviews or teardowns but there are so many of those on your blog... Please make more videos like this one + design/build video :) it's bin a while I wait and wait for you to star new build/design or finish some old ones that you have started in the past like PSU.
P.S. in this type of probing situation I use even thinner enameled wire (magnet wire), less likely to tear off PCB trace with them.

[Pieh]

14:20 EEVBlog PSA: Never probe your own clacker, always get outside assistance

[lpopuuw]

But what about the sampling rate? Would they not decrease that for the lower bandwidth scopes? I sure would.

[chrisridesbicycles]

When it comes to solder little wires to probe chips, I often apply a little solder blob on the end of a insulated copper wire, put this next to the pin I want to probe and use a bigger soldering tip to heat up the whole wire and make a connection to the pin like that. This proved to work reasonably well down to 0.5 mm pitch QFPs

[peteabc]

When you use both channels on this scope, are they both 300MHz? The brochure mentions something about 2x1GS/s or 1x2GS/s.

[GiGaSzS]

I really hate it when companies deliberately limit features. If the manufacturing and developing costs are the same, why not make only better version!?
And if companies would still argue that the cost of limited products is indentical to full blown, I have a good antiargument: How much does it cost to make special limiting software+hardware!?

!!! Such decisions are only slowing down development and progress of electronics !!!

[carstensraspiarduinounddd]

I am not convinced that only hacking that chip would do. So if you feed a 300MHz signal into a scope which "thinks" it will only get 100MHz signals it will still only sample with an apropriate sample rate of xx Gsamples/s. So if you hack the input it will get a 300MHz signal through but with the same sample rate which may be undersampling?

[ABaumstumpf]

Lovely - that solder-blob mirror ~ 9:00 .

[bytefree]

Perhaps this analog attenuation is needed for noise considerations, to start with, but the limit could be anywhere else on the application FW of the scope. They are processing all the data digitally, so a digitall filter is likely to happen appart from the analog one.

[SITIMPE]

Hello. In 20:33 what is he doing and the states changed?

[electronicsNmore]

The price range is certainly "reasonable".

[pvc]

Now put in a tiny 6 pin attiny and done :) BTW. Does this scope have JTAG or something like that accessible? If it has then maybe it can be just soft modded.

[Jordanma]

Does it fail to trigger because the LMH6518 is not outputting anything during an SPI access? Should hook a probe up to the OUT aux and see if it doesn't trigger when it is switching bandwidth.

[johndrachenberg]

Isn't there some sort of solvent or acid you could use (@ 11:40) to dissolve the solder mask but not harm the traces or PCB? Just a tiny drop on that via would probably be immensely easier than trying to melt / scrape it away.

[zerbt]

Can you hack another oscilloscope, for educational purposes ;)

[TheTruthSentMe]

If they don't have any model going higher than 300MHz bandwidth, why put in a 900MHz chip? Couldn't you save cost here?

[KyleRepinski]

25:15 isn't the bandwidth limit changing as you change the timebase as well?