6 ms·
Agilent 2000a / 3000a Oscilloscope NAND Recovery
- pandemic_region 2y agoThis guy knows his oscilloscopes.
- deleted 2y ago[deleted]
- salvagedcircuit 2y agoThanks!
- aardvarkr 2y agoI love seeing ridiculously technical investigations like this. It has zero relevance to me but it’s just sooo satisfying to see someone solve a tough problem.
- salvagedcircuit 2y agoThanks! I'm glad you enjoyed it :D
- a1o 2y ago> the MSO adapter can accept low power signals up to 40v, but it offers no input protection when the host oscilloscope is off. Thus, if the DUT (Device Under Test) has a short of some kind near the area of probing, and the host oscilloscope is not powered, there's a good chance you've just damaged the Maxim MAX9201 comparators in the logic analyzer section of your scope! It's worth checking all 10 pins for voltages outside the MSO operational range. Whoa, it's been a long time since I haven't used these tools but I learned now I was very lucky when using because I didn't knew this and didn't check the voltages when using the logic analyzer in the scope I had at the time from Tektronix - which I guess had the same type of limitations.
- salvagedcircuit 2y agoYeah! I was surprised myself when I sifted through the 800+ page manual and found that tidbit. Certainly good to know. Boy is manual a true coffee table book!
- janice1999 2y agoIf you like this kind of content, I highly recommend checking out the Youtube channel 'The Signal Path' [1]. It has some fantastic technical teardowns and repairs of instruments, including really high frequency equipment. [1] https://www.youtube.com/channel/UCKxRARSpahF1Mt-2vbPug-g https://www.youtube.com/channel/UCKxRARSpahF1Mt-2vbPug-g
- hobs 2y agoYou probably already watch him, but Marco is also great when it comes to similar content (he loves his multimeters) https://www.youtube.com/@reps https://www.youtube.com/@reps
- n_plus_1_acc 2y agoI like bigclive. He takes apart cheap electronics from eBay.
- nativeit 2y agoCurious Marc[1] works on a lot of old HP test equipment, and he’s also a Silicon Valley native, frequent contributor to the Computer History Museum, and his channel features an HN regular, Ken Shirriff, who can reverse engineer everything from vintage Russian Soyuz components to uncapped IC packages. 1. https://youtube.com/@curiousmarc?si=pHOewmmWbDDmSSZb https://youtube.com/@curiousmarc?si=pHOewmmWbDDmSSZb
- salvagedcircuit 2y agoWoah, thanks for the comparison. I'm a huge fan of the signal path and marco reps, but I don't think I've gone that far down the volt nut path yet. Maybe I need to fix up a broken 3458a for my next writeup :D
- bloomingeek 2y agoIt's so good and satisfying to see a person ply a trade to success. When I find myself stressed out for some reason, I like to do something I'm well trained at to help my brain kind of reset, which often gives me a different way of looking at what stressed me in the first place.
- salvagedcircuit 2y agoAbsolutely! I find repair to be therapeutic at times, like repairing a stuck or dirty 1970s film camera lens. It's usually a straight forward repair, it just takes a bunch of patience and attention to detail. This repair was far more complicated than that, but it was worthwhile to get another instrument working around the lab.
- hristov 2y agoThis is very interesting. I just have one minor nitpick. Broadcom did not buy Avago, Avago bought Broadcom. They then changed their name to broadcom as it was more recognizable in the industry (while keeping their old stock ticker AVGO as that was more recognizable in the financial industry). This is entirely a tangent but the rise of Avago from a minor second rate spin off from a spinoff from HP to one of the biggest and most profitable companies of the world (and one that is many times the size of current HP), is one of the most unusual mostly untold stories of the modern business world. It is a story of success (by Avago and Broadcom engineers and management) and incredible incompetence (by hp management that let them go for a pittance).
- jjoonathan 2y agoOh wow, I was just transplanting some TC702 amplifiers to save the doubler in an old 50GHz HP signal generator... would that have been designed by these guys back when they were part of HP? https://www.keysight.com/us/en/assets/7018-04165/application-notes/5991-3545.pdf https://www.keysight.com/us/en/assets/7018-04165/application... EDIT: that's registration-walled, but this HP Journal article isn't. https://archive.org/details/Hewlett-Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard https://archive.org/details/Hewlett-Packard_Journal_Vol._42_... The amplifiers in question are blue-colored in the background, and the doubler that uses them is the spiritual successor to the rear-most golden module. EDIT2: yep, the timeline lines up. The HP journals with these amplifiers were early 90s, and "This division became part of Agilent Technologies when HP spun off its test and measurement business in 1999. Later, in 2005, Agilent spun off its semiconductor products group, which became Avago Technologies. "
- CamperBob2 2y ago83650? I've heard those output amps are very unreliable. Been lucky so far with the one in my 8510C rig.
- jjoonathan 2y agoThey've treated me fine -- the broken one I bought that way. YTOs have given me trouble, though. EDIT: obligatory, pictures https://photos.app.goo.gl/KwvnMGm5GyvnmgE58 https://photos.app.goo.gl/KwvnMGm5GyvnmgE58
- cardiffspaceman 2y ago// “You will need an oscilloscope, passive probes, …” That’s my stop. This engineer is determined! Built a test circuit to identify one part.
- salvagedcircuit 2y agoThanks! It was well worth it :D
- fuzzfactor 2y agoIf you're going to do things that other people don't normally do, you might have to build things that other people don't normally build. Not only that, while you're at it, If you're going to build things that other people don't normally build, you might have to do things that other people don't normally do. And it could never end, so way before it's over you could end up with a lot of capabilities other people don't normally have. Plus when you end up like that, of course it's not over, it's just getting started ;)
- salvagedcircuit 2y agoThere's always more to discover! Thanks for the kind words.
- prbs23 2y agoThis is an awesome write up! I have one of these scopes, with exactly this issue after a long period in storage. When I was looking into it a few years ago the failure mode was known but I couldn't find a recovery procedure. I'll need to give this a try when I get a few hours. I have been putting off getting a new scope in hopes that I could repair this issue.
- salvagedcircuit 2y agoThanks! Go for it or contact Keysight to see if they will cover it. Good luck!
- userbinator 2y agoThat NAND flash is a 128MB SLC part rated for 10 years of retention after 100K cycles. It's interesting that the datasheet says ECC is only "strongly recommended" and not "mandatory", but I guess SLC of the time, unlike MLC and later generations of flash where correctable errors are part of normal operation, was reliable enough that some applications didn't bother using ECC at all. It also recommends the 22-bit/256-byte SECDED ECC algorithm which originated in the earliest NAND flash with 256-byte pages and later became popularised by SmartMedia. Flash memory bits wear out after 100,000 to 1,000,000 writes. Thus, file systems must keep track of the number of writes and have a strategy to avoid wearing out storage, such as by moving popular data. —Patterson & Hennessy, P.23 Computer Organization and Design 5E That quote would've been true in the 90s or early 2000s at the latest. These days it's more like 100 to 10K cycles for most mass storage flash, with the majority trending towards the former.
- salvagedcircuit 2y agoThanks for the input! That is a pretty reasonable conclusion. I was surprised there was no mention of wear leveling or garbage collection in any of the spear documentation when that's essentially assumed today. Wild.
- dezgeg 2y agoI assume that's because wear leveling is something that would be implemented purely in software, so there's no much point having such info in a hardware manual.
- guenthert 2y ago> Flash memory bits wear out after 100,000 to 1,000,000 writes. I'd think that applies to (low density) NOR flash memory, not (high density) NAND based ones.
- transistor-man 2y agoThis is an excellent writeup, it's refreshing to see detailed writeups that are quick to load
- salvagedcircuit 2y agoThanks. I like to keep things lightweight :D
- salvagedcircuit 2y agoWoah, this is really cool to see here! Thanks for the post!
- robxorb 2y agoFor anyone interested in the rotary encoder part, and how they work, I found this 7min explainer getting right into the details: https://youtube.com/watch?v=S2BfGMqe3kQ https://youtube.com/watch?v=S2BfGMqe3kQ