Category: Repair

Tektronix’s TDS/DPO7000 series Mechanical (Chassis) Design is Evil

Repair

I thought the TDS500~800 series design is already frustrating to service. But TDS7140 (or DPO7000) takes the cake. Whoever the a**hole designed the chassis made it a f*cking lettuce wrap. It’s not even an onion that you can predictably guess how you’d approach it.

To get any meaningful access to the insides, you MUST first remove the plastic front panel bezel, which is a fragile part that if you didn’t get the plastic hooks right, you’ll break it when you try to force anything. The service manual is not helpful. Likely written by somebody with a ‘fuck it. somebody’ll figure it out’ attitude.

This can be seen by the service manual giving an exploded view diagram without a precise order-of-removal dependency graph, nor the decency of telling you where each hook is and which of them are slides that must not be pried open like hooks. This is basically is tricking people to break the front bezel because those who didn’t know this already won’t know until they shine a flashlight to investigate the geometry around the hooks before releasing the front bezel.

It’ll make much more sense if you see the insides of the released front trim/bezel:

Not to mention that that black (lower) Acq front panel trim was double-sided taped to the BNC panel because it’s so easy to f*ck up the plastic to get access to the insides of the unit. The bottom trim is supposed to come out first (because there are no hooks) but I wiggled the upper part out first, luckily without damaging the bottom hooks, because of the silly double-sided tape used for the lower trim.

None of these shit was mentioned in the service manual. It basically said “there are some hooks in the front panel, pry them open and pull it out. Good luck!”. Mixed with a flimsy, non-intuitive chassis design, it’s pretty much telling outsider to break the front trim.

I really couldn’t believe some f*cker who’s a delight to deal with would design a case with an insane order of disassembly so I read the vaguely worded manual over and over again to see if there’s a step I can skip to get partial access to the PC motherboard inside. I couldn’t find any so I gave up and follow the painful disassembly order and realize the design was indeed evil and fully intended to shove it up the a$s of whoever that tried to repair the unit.

The service manual is also very unhelpful that they first told you to remove all the knobs yet the rest doesn’t depend on it. The real first step is to remove the front plastic trims. Nonetheless you need to remove the carrying handle because it’s bolted to the right side of the sheet metal.

The take away is that the Mushu-chicken lettuce wrap is that the top and left side is one sheet metal, while the right and bottom side is another sheet metal in one straight piece. What’s really frustrating is that you cannot just move the top-n-left half cover in isolation because it’s sandwiched by the right-n-bottom half cover, which in turn it’s bolted down by the screws that are obscured by the front trim:

This is madness!

HP/Agilent/Keysight doesn’t do this kind of abusive design that reeks evil. I should start charging more if people sends me a Tektronix to fix if I have to deal with the damned disassembly maze.

Another bit that shows whoever wrote this damned service manual doesn’t give a shit is the instruction to take out the 2-in-1 CD+HDD bracket. A normal person who dealt with Agilent Infiniium unit would expect the 2-in-1 bracket should come out on its own in one piece. This is not the case for this damned Tektronix scope.

Here is all the information available from Tek on how to do it (which is both incomplete, misleading and confusing):

Should not have used the word slide. Should use the word pull because the HDD+CD combo bracket is trapped in the unit so there’s only one way to get it out: by pulling. You can’t slide it from the sides as the sides or the top of the CD drive bracket are covered.

Figure 6–20 is just an exploded diagram, which covers everything taken apart without explaining the order and dependencies, which is essential because this damn thing was designed in a way that you wouldn’t have intuitively guessed the order by just looking at it.

Turns out after you removed all the screws that seemed relevant, the HDD+CD combo bracket won’t come out because it

The manual is surely misleading because if you just need to take the HDD+CD combo bracket out, you don’t need to take out the 4 #0 Philips screws. This is something you can do after you pulled the CD drive bracket out, but first you have the remove the two T-15 at the front of the CD bracket, which made it look like it was the bracket of the HDD+CD bracket combo, so you wouldn’t suspect the whole thing hinges on you pulling the CD drive bracket out first.

Tektronix certainly doesn’t have good excuses for these lame design with lousy documentation. Even with cost savings in manufacturing materials, it just doesn’t justify the labor. This is just taking shortcuts in design and it shows the lack of forethoughts and purely poor judgement.

This scope is lame everywhere. It really showed the people designed it either divided it into too many teams or they simply don’t give a shit. There’s no reasonable excuse for this other than laziness. The hard drive interface was converted twice! It takes an IDE drive, converts it to an SATA drive, then plugs into a board that converts the SATA to IDE back again just to fit the form factor.

Not to mention that the 44-pin to SATA adapter is a ribbon inside the caddy, which means it’s not carefully designed that you can slide the drive in. You have to pull the short cable out to plug it into the drive and push the bulk back in. It’s easy to mess the ribbon cables up with this design. It just screams the people who designed it hate their job.

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All in 1 Mini Card Reader Manufacturing Flaw (Bad USB connector)

Electronics, Repair

Recently, I’ve bought this CF card reader on eBay but it doesn’t detect at all.

Picture 4 of 7

I looked closely into the connector with a loupe and realized that the mini USB conductor was molded incorrectly. The center middle pin was pushed down because extra plastic was deposited above it:

The seller refunded in full but I figured that if the connector is malformed at the molding stage, buying it from another seller is not going to make it work, and the other form factors/connector configurations are inconvenient, so I tried my luck and see if there are exact matches for the connector they’ve used. Turns out it’s a 56 cents connector (price for 1 piece) available in Mouser (UJ2-MBH-1-SMT-TR):

In bulk, this connector can be bought for $0.22. For something that’s selling for $5/pc, the Red Chinese manufacturing had to go cheap to shave a few cents that ended up turning finished products into total trash. Most people are not electronics/troubleshooting savvy enough to figure out this shit, and the labor cracking the piece up and the SMD rework can easily buy 20pcs new. I just happened to have the tools (Metcal hot tweezers) so I can desolder the bad connector in seconds, but average users do not have that luxury so the neutered USB card readers go straight into trash.

We need more products NOT made in China!

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Crack open wall wart (power brick): hot air method (READ or risk more damages!)

Repair

The power brick that came with my U1620A order has a rattling noise when I shook it. I suspected a piece of soldered cracked and was wandering inside so I chose not to power it on as it might short something. So I had to crack open the wall wart, which turns out many people have little luck open it up non-destructively.

Just prying it open by force with a screwdriver will ruin the plastics. I needed to somehow soften the glue first and work into it (like using a cutter) to dislodge/cut the glue. Rubbing alcohol doesn’t work that well. The glue is quite stuff so it’s not the easily dissolvable kind.

After some experimentation, I used my hot air station and set it to a temperature right below it melts the hard ABS plastic outside (143 deg C, max air flow), and carefully pried it after taking the heat away.

WARNING: Do not pry while the hot air is blowing as the ABS plastic might be slightly softened! The hot air might overshoot in its temperature feedback) so you might accidentally remold it. When working at the borderline temperature that barely soften the ABS plastic, the second you take the hot air away the plastic cools back (hardens) enough for you to pry.

Out of practicality, I heat up one edge at a time, then focus on 1/3 of the area at a time get an entry point prying one hook open at a time. It takes a lot of patience.

After I got all the 4 sides pried open for some reason I couldn’t release the case and it felt something was stuck in the middle. Turns out the wall wart I have happened to have a center screw hidden from plain sight under the label. The label quality was so good that just pressing it around with a pair of tweezers won’t find the screw hole (because of the tension). I used hot air (at the same 143 deg C) to probe with tweezers to locate the screw hole. I cut a hole in the label for the screw hole because it’d be a pain to use hot air to get the label off in one without ruining it and be able to put it back like new.

Bonus discovery: molded plastics have some memory!

I dented the ABS plastic case during prying (before I thought of using hot air), but I discovered this magical temperature (143 deg C) actually heals the plastic when I blow it in a direction that undoes the dent! The small (like 2mm) dents magically smooth itself out and went back to rough where it was before I screwed it up (pun intended)!

Yes, for molded plastics, small dents caused by prying and bumping, heating it up to the temperature right before it softens will return it to its near original shape without external forces!

Of course, do not go past the softening temperature (143 deg C). If you heat it to a melting temperature, the plastic will lose its memory so you need to apply external force to beat it to the shape you wanted (which is a pain in the butt and it requires a lot of post-processing to get it to look like original).

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Agilent DSO6000 series was internally called 54670/54680?

Humgar LLC, Measurement Equipment, Repair

Architecturally, the DSO6000A series shares common designs with 54830 series oscilloscope and 54640 series oscilloscopes. I noticed the Acq board numbers for my DSO6052A start with 54672 and the my M/DSO6104A starts with 54684. Looks like the 5467X means 500Mhz and 5468X means 1Ghz while the X is the number of analog channels.

This is ‘confirmed’ by a slip up in the documentation (user guide) which they forgot to update the model number in their vector graphics:

I think I’m getting a hang of Agilent’s oscilloscope’s hardware to do deep level board repairs as I have various model to compare. I used If you need yours repaired, please reach me at 949-682-8145.

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Stanford SRS PS350 High Voltage Power Supply Repair

Measurement Equipment, Repair

I received two PS350 power supply units that one of it has sparks when output is enabled and the other just won’t output anything at all.

The only repair info I found is from one of my favorite youtube channel the Signal Path. However, his unit has a much easier problem: the solder joints cracked because PS350 uses the metal case as a shield that are subjected to mechanical stress.

However, after difficult troubleshooting, I realized one unit has a fried resistor in the HV section, and a few core MOSFETs shorted.

The other unit is much more difficult: not only the HV capacitor is blown, resistor is blown, diodes shorted (won’t be able to detect it by probing in-circuit because of the capacitor ladder), PCB trace to the feedback path vaporized (without that the voltage will rise uncontrollably until something’s fried), and a bunch of MOSFETs, transistors and regulators ICs needs to be replaced.

Likely both units are broken because the users switched polarity without turning the HV section off (and let the voltage bleed out). This is very important and the markings on the case already warned the user NOT to do so.

You absolutely must NOT change the polarity while the output is live because the components in the HV section are marked for 4~6kV, so there is little room for a voltage spike past the operating voltages. The act of switching out the polarity (by mechanically swapping the pins through the dial switch at the back) doubles the voltage stored in the capacitors in a voltage multiplier ladder, so you are almost sure to crack the HV capacitors and likely the HV diodes.

Since I’ve developed experience for repairing SRS PS350 by reverse engineering some of the circuit sections, I welcome request for repair evaluation (no fix, no fee). Please call me at 949-682-8145, or meet me at www.humgar.com.

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Data Precision 8200 Repair Service

Electronics, Repair

I just bought a big lot of Data Precision 8200 and some Analogic AN3200 DC Voltage/Current Calibrators with a bunch of hard to find (unobtainium) genuine parts (relays, switches, hardware, regulator and amp ICs, whole modules, transformers) that that I believe it’s the leftovers of a closed down repair shop.

That means I’ll have all the materials needed to service and upgrade Analogic / Data Precision 8200 that you are unlikely to be able to find elsewhere.

Data Precision 8200 is the official unit to field adjust TDS 500~800 series oscilloscopes as the automation software (GPIB) was hard-coded to this model. Nonetheless, I find it a reliable reference for verifying oscilloscope performance and adjusting my multimeters as well.

Call me at 949-682-8145 for a repair quote or if you are interested in buying a unit. GPIB and 1kV option can be ordered for extra, either with the unit or service upgrade.

 

 

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

Measurement Equipment, Repair

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 been 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 board/unit 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 has 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 don’t expect their products 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 dumb autoscale mechanism that doesn’t even detect all channels and show you all relevant signals.

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.

I have spare parts to repair MDO4104C, MDO4054C, MDO4034C, MDO4024C

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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Agilent N9340B Handheld Spectrum Analyzer Repair and Teardown

Electronics, Measurement Equipment, Note To Self, Repair

I received an Agilent N9340B 3Ghz Handheld Spectrum Analyzer with a note that it passes all self-tests but does not respond to input signals. I took the gamble that it’s the RF input connector got disconnected somehow.

I opened up the case and noticed that the 40Mhz cable was unplugged, so I was half-correct. I connected it and got a signal at the precise frequency, but the amplitude doesn’t look quite right. It’s around -20dB off. When I scanned it across the full 3GHz band, I noticed the amplitude roll-off when I scan below 800Mhz, and I got very little signal left when I get to somewhere near 10Mhz.

I tried running a user calibration with a 50Mhz CW source but it failed amplitude calibration. Apparently the unit is not fully working. No self-test errors though.

So I opened up the unit and the RF section. The front side of the board doesn’t have any visible signs or unusual smells, so I suspected the improper gains is caused by the input attenuator HMC307:

I was about to order the chip, but because of the lead time, I decided to just take a picture of everything and analyze it off-line:

After removing the screws holding the N-type terminal so I can get to the back side of the board for taking pictures, I noticed the RF in connector just fell off the board with the pad:

That means the RF in is not touching the board! I resoldered the connection after I put the board and the connectors back to the RF module slab. Once I put unit back together, I turned it on again and everything works perfectly! The power level is flat and within 1dB of what my 8648C pumps out. I did the user amplitude calibration again, it passed, and everything was spot on!

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