Tek Evil: Repairing MDO4000C Series MDO4014C stuck at splash screen on start

I recently got a repair evaluation order that took me two intense weeks to nail the problem. It’s a MDO4104C that does not get past splash screen.

Worst of all, the unit failed right within 3 months right after the warranty expired. The unit didn’t show signs of heavy use. In fact, I nailed the problem so I can tell for sure the unit DIED OF NATURAL CAUSES. It’s not the first time I (and other people on forums like EEVblog) bitch about Tek designed their unit to last beyond the support/warranty period. This one takes the cake.


Basically everything in MDO4000C series happens in the main acq board. Anything that goes wrong there you might as well just buy another unit.

It runs embedded linux (uboot) and it’s slow to boot as I always expected from Tek (Keysight/Agilent use VxWorks for their modern embedded scopes and they boot fast).

There are no UART debug consoles anywhere and the only two test points with digital signals that idles high at 3.3V. The data pulses are quite long for the frame, and one of them looked more like clock bus in either SPI or I2C. So no UART. The firmware file mentioned BDI3000, which is a JTAG, which I suspect there’s a 10 pin IDC (ribbon) port on the right hand side of the main acq board, but this is as much as what I can get getting debug info.

There’s a RS-232 driver chip on the peripheral board, but it goes to the ID pin of the VGA port. I didn’t see any data traffic on it on boot.


Getting stuck at the splash screen practically tells you nothing about what’s wrong. The only thing you can infer from it is that the unit powers on and the display/keyboard is good. This is pure evil. HP/Agilent/Keysight designed their products to make it easy to service, and Tek has always a pain to service, and the new ones are no exception.

They don’t even mark the grounds in test hook points. It’s just a bunch of TPXXXX numbers. Apparently they are there for testing the design, not repairing it.


It’s obvious from the way they designed their product to the service manual, Tektronix definitely don’t want any people to do board level repairs: ultimately they want you to blindly send it in for factory repair within the first 5 yr of production, and make you buy a new one if the model is discontinued.

Despite I hated it, Tek has a valid strategy. If a product is cheaply made, even at the cost that it only last long enough through their warranty period, the manufacturer doesn’t even need to bother with board level repairs because it’s cheap for them to just give you a new part instead of figuring out what’s wrong with it.

Putting the frustrating to use UI designs aside, Tek works if you are a company buying the scope for a short 3 yr project. I wouldn’t recommend Tek at all if you plan to buy it for a long haul (because they are not designed to last given ones I’ve serviced), or plan to use it as a daily troubleshooting scope (because their user interface is slow and clumsy).

Tek has a huge following from the analog days when they did things right. Ever since the digital age, the learning curve for Tek’s UI was so steep that inevitably it turned into a customer lock-in where Stockholm syndrome kicks in.

Nonetheless, Tek was a little ahead of Agilent in terms of the MDO concept that correlates time domain measurement with the built-in spectrum analyzer. If that’s a feature that is important to you to the extent that you are willing to live with Tek’s clumsy UI and it might break down right after the warranty expires and it’s nearly impossible repair it yourself, it’s reasonable to go with Tektronix for this one given the lack of functional alternatives. Do NOT get MDO3000 series for this reason though, since the spectrum analyzer and oscilloscope are not time-correlated there’s no material innovation out there. MDO4000 series and up are time-correlated with the spectrum analyzer.

Again, I’m not saying Tek is bad. Tek is just mean towards their customers from a product design’s point of view, when you contrast them with how considerate (nicely thought-out) HP/Agilent/Keysight products are designed. Tek is still much better than the RCCC (Random Cheap Chinese Crap) in every way.


EDIT (2017-07-02): I just got a call this morning from somebody who bought a TDS 220 from me years ago. The BNC connectors broke off and he’s found somebody selling a kit specifically to fix the problems in TDS 200 series. That’s pathetic. I knew the design was obviously flimsy back in the days, but I trusted the Tek engineers knew what they are doing given their brand reputation. Turns out common sense is right. A bad design cannot last even if they had solid parts/manufacturing.

From my experience opening up many Tek and  HP/Agilent/Keysight units so I can compare their mindfulness, I can see that Tek is one of those high pressure companies that cut corners to get stuff out fast with low manufacturing costs. It’s not necessarily a bad thing from a business standpoint, it’s just Tek and HP/Agilent/Keysight operate with very different set trade-offs (or say, philosophy). Apparently Tek’s kind of trade-offs makes their used equipment a terrible choice unless it’s covered by their extra warranty.

Since I deal with old gears, I’m not impressed with the outcomes of used Tek products that I have/had. If I were to buy from Tek, I’d rather lease it since I do expect their product to last beyond their warranty period without multiple breakdowns that are costly to fix. My experience with used HP/Agilent/Keysight gears is that the problems are more predictable, limited to a small area and easy to reach and fix. For example, the caps in power section and CRT driver of TDS 500~700 series starts to fail, and the flyback transformer dies year after recapping the SMDs, and the units were just sitting there, not actively used. On the other hand, early 54600 series are almost always problem free other than an occasional cheap capacitor in the CRT driver drying up. This gave me a very bad impression about how Tek’s made their stuff.

Even if I could lease Tek products on other people’s budget, I still won’t consider until they radically changed their clumsy user interface and autoscale algoritm.

So far I haven’t see the kind of extra attention to detail in Tek products when I put it side by side with HP/Agilent/Keysight. This is how corporate culture reflects in their products: if you treat people well and trust them, they’ll get to all the nooks that managers and processes can’t reach and do it right. Tek just did enough that it will work as marketed, but whatever that’s cannot be objectively claimed in the advertisements, you are on your own.


If you have an oscilloscope that you’d like to send it to me for repair evaluation (no fix, no fee), please call me at 949-682-8415 or email owner@humgar.com.

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