Category Archives: Repair

Tagarno Magnus HD UNO – No video output repair Service

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I recently scored a Targano Magnus HD UNO microscope but the video output was broken in around a month. The system sill had a pulse as I can hear the button beeps as expected when I tried the operator keypad. Just no video output at all so it had nothing to do with the optics of the microscope.

There was no superficial, visually identifiable problem as as burns or yellowing. The microscope just quit outputting video quietly. The board was pristeen and didn’t seem to have been reworked

I was able to identify the problem and fixed the microscope (regaining video output after quite board level surgery), though it’s a huge huge pain to open it up because the screws were too tight and I stripped a couple of screws trying to open it up.

These are discontinued models (now they primarily sell ZIP). I suspect FHD UNO is the same if it has the same problem. If you have a Tagarno with a similiar fault, I can try repairing it (electronic faults only). To fix no video output, it’d be $1000 + you pay all overheads. If it’s some other problem, I might give you a quote (no fix no charges).

Please reach me at owner+blog@humgar.com if you’re interested in having this repaired.

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TL866CS and TL866A recovery mode

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I was playing around with my TL866 programmer trying to refresh the firmware and needed to get to the recovery mode. However, it seems like the recovery mode info on http://www.autoelectric.cn/en/note.html is incorrect for 2014 design (the one I have). I tried the 240\Omega as recommended with a decade box and it doesn’t work .

Usually my guess that if somebody is going to set a recovery mode in a micro-controller to be enabled with some hardware path to the power supply rail with a small resistor, it’s just saying that he wants you to pull the pin high.

The said pin is a digital I/O line so I took it as a GPIO pin used for input (I might be wrong)

I measured the voltage of the said regulator with a decade box. Interesting that if I flip the resistance while the unit is on, it occasionally remembers the last state when I plug it in again! (EDIT: There is a Schmitt Trigger buffer in between. The buffer type says ST for RC1. Doh!)

Here are some of my measurements with a decade box:

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54855A/54854A Oscilloscope won’t power on

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Recently I got a 54855A oscilloscope sent back to me for service under the 1 year warranty I underwrote for most of the unit I’ve sold direct. The unit would not turn on at all after sitting for a long time.

I looked up the forum and it turns out other people had this problem with a certain generation of Infiniiums and sometimes changing power supply or motherboard would disturb the setup a little bit and the unit might power on again. When I tried to do that, the unit does boot a quite few times but the problem randomly came back again. This is frustrating as it’s a heisenbug. I almost thought I was done when the unit worked consistently for a week then it comes back. It just looked like something component was acting borderline and disturbing the setup and got it to click.

In the past I had 54830s that’s ‘fixed’ by changing either one of the motherboard or power supply, but turns out that those were flukes, but I didn’t get lucky with 54850s this time.

The customer gave me time to troubleshoot deeper instead of just getting something to work as a fluke by just blindly changing modules which might break down again at a random time if it’s a gravitating aging problem (i.e. if you figured out a problem, it tends to be a wave of manufactured gears that’ll trip on the the same issue as they age). So I spent a whole month troubleshooting through reverse engineering the circuit and nailed down the cause and the fix.

There’s a lot of mixed info going on in the forum with different modes of failure, but those might not be the real cause, as replacing components disturbs a set up that wasn’t supposed to be in that state in the first place and the unit is prone to get trapped into a bad state when the unit ages. The real fix is to plug the path to the bad state in the first place instead of rocking the boat hoping the new combination doesn’t trigger the bad state.

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

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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.

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

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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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