Option Hacking the Tektronix TDS 420A | Hacker News Reader

Option Hacking the Tektronix TDS 420A

tomverbeure.github.io

Oscilloscope options are famous for being trivial to enable, and I think Rigol finally did the right thing by just selling the scopes "pre-hacked", enabling the options that everyone was gonna enable on their own within minutes of unboxing the thing anyway.

Debates rage endlessly about whether the manufacturer is in the right to lock-out certain features or sell low-end scopes at a loss or a zillion other business questions. But the fact of the matter is, the clientele for this particular product is _hardware engineers_, and hardware engineers seem to take a stronger view than most, that if they bought it, they own it, they're going to use it.

Particularly in the case of this old Tek that hasn't been sold in decades, I think anything that keeps it out of the solid waste stream is great.

For many scopes the process is simply to "run backdoor command X", "run keygen Y" or "overwrite byte ZZ of the EEPROM", it's unusual to see a cool fully documented reverse engineering effort on a model previously unexplored, which is why I submitted this article. Interestingly, since the manufacturers' revenues come from selling to enterprise users under service contracts, they usually don't care about a hardware hackers or two on the web at all.

Agreed, the depth of the writeup is a refreshing change. Thank you for submitting it!

I love these stories about hacking around hardware to enable features in the software. I'm impressed when seeing engineering decisions of leaving ways to upgrade boards to the next level of options.

It's a good series of articles to read, they show good technique in how to do the reverse engineering process.

For those interested Tom also has a few really good posts on leveraging the Yosys framework for simulation.

I like the way the author says PAL/NTSC video triggering is obsolete, when it's used every day for timing purposes in a broadcast facility.

I'm surprised to hear that, having been a volunteer at an e-waste recycler several years ago when entire truckloads of NTSC equipment came in. Over the span of about 8 months, I think three or four separate local studios upgraded to digital and completely ditched NTSC. Waveform monitors, U-Matic decks, switchers and effects consoles, you name it.

Who's still using CVBS, and for what?

Does the e-waste recycler assess whether the incoming hardware is still functional and should be preserved, or is it required (by contract) to destroy / recycle the hardware?

Both, depending on who they contract with. If it is manufacturers that are trying to control their secondary market you have to provide proof that gear was scrapped (usually, for instance by extracting some critical component and returning those as proof of scrapping). When gear is at the end of its service life and is returned in bulk lots of various bits and pieces of equipment there is an assessment made whether all or part can still be sold on the secondary market (typically: ebay lots).

Wipe the data, resell anything they can find a market for, recycle the rest.

> NTSC Waveform monitors

NTSC waveform monitors and vectorscopes are amazing instruments. For example, only with them you can see the true color (pun intended) of the STMPT color bars on TVs - the iconic staircase waveform [0] and its corresponding curve on the vectorscope [1]. They are how the color bars were intended to be viewed.

During my recent hunt for test equipment, I was still able to find a lot of waveform monitors and vectorscopes in usable conditions. Unfortunately, I couldn't find any reason to buy one - it will be a complete waste of money and room space since these instruments have became totally useless with zero utility. You don't even have a signal to probe anymore, unlike a vintage computer or an oscilloscope which can still be used and even serve a practical need... To think about it, they'll continue to be stored in an abandoned warehouse collecting dust and rust indefinitely until someone sends them to a metal scrapyard.

It's really sad.

[0] https://i.stack.imgur.com/cIQVf.png

[1] https://www.danalee.ca/ttt/images/7/vectorscope_bars_big.jpg

There are enough folks around the vintagecomputing community, there must be a parallel world of vintage studio gear, eh? Someone's gonna be nostalgic enough for the NTSC/VHS look someday, to pay top dollar for original hardware.

Anyway, I noticed something about the parent comment that I missed earlier -- "for timing purposes". Huh, like I guess the concept of genlock probably still exists, and they're probably passing around a test pattern or black frame or something just as a common sync reference signal?

(For similar reasons, a lot of telecom gear uses a 1.544Mbps "all ones T1" signal for sync, even if there isn't a real T1 circuit anywhere.)

Nobody broadcasts PAL or NTSC anymore.

but movies are still 24000/1001 fps

Well sure, but that's just the frame rate. These triggering modes are about specific components of the NTSC/PAL broadcast signal, and that is indeed obsolete.

Did these CRT-based digital scopes have fully rasterized graphics for the plot or do they somehow use an analogue sweep?

The former, I’m pretty sure. I’ve never heard of a “hybrid” display on a digital scope. Interestingly, though, there are sometimes deliberate simulations of analog behaviors on the digital display.

Stranger things have happened!

https://patents.google.com/patent/WO1999034394A1/en

http://www.industrialalchemy.org/articleview.php?item=882

Yeah, those are cool! I do seem to remember analog scopes with auxiliary digital displays on the screen for measurements. But not the other way around, digital samples displayed with a vector CRT beam.

There’s an HP spectrum analyzer that does this.

There are bunch of Tek scopes of the era (the TDS 700 series etc) for which you can buy kits that replace the CRT screen by an LCD panel.

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