So what do I think of the FNIRSI-1014D 100MHz Digital Oscilloscope now that mine is working "properly"?
 
 

Photo Linuxslate.com.  Test setup with  FNIRSI-1014D and Kooltech Signal generator.
 
Well, If you want the short version of this review, note that I put the word "properly" in quotes.
 
I cannot recommend the purchase of the FNIRSI-1014D given the gross and apparently on-going quality control failures, firmware issues, and problems that I and others have reported.
 
I purchased mine locally, so I could have returned it to the store where I bought it from.  Others would have to deal with sending it back to China, and possibly issues with language and different attitudes in different cultures about returns and or refunds.  Even in my case, asking for a refund from a local small business run by people I consider friends would have been at least a bit awkward.  As mentioned I am thankful that I am able to make a repair like this, and for the help from Nercy Eletrônica.  I realize that repairing brand-new merchandise is not something everyone can or would want to take on, and nobody should have to.
 
The concept of trust when it comes to test equipment should also not be overlooked.  Trust is the reason Fluke, Tektronics, Hewlett-Packard, and other companies charge premium prices for their products.  Engineers, technicians and lab managers continue to gladly pay those prices because they know they are getting a product that not only works, but also produces results they can bank their careers on.
 
I would strongly suggest that even budget or casual hobbyist users spend the extra $40 to $70 for a similar unit such as the Hantek DSO2D10.
 
If you want to accept the risk of hardware failure and/or inaccuracy, purchasing (and possibly repairing) a vintage or surplus CRT oscilloscope is another, and IMHO opinion better, option for those wanting an oscilloscope without spending thousands of dollars on brand-new lab equipment*.
 
That said, I am now happy with mine, and I intend to keep it.  I may even go as far as to say that having to fix it boosted my sense of ownership.  It contains (a little) of my own work.  It is unique.
 
i also have to give it credit for a bright and crisp screen.  At least until you encounter one of the firmware bugs, the user interface looks very nice, and is intuitive to navigate.
 
The FNIRSI-1014D is also small and easily portable.  Since it includes a fold-down handle, and is powered by USB, all that is needed is a portable phone charger (battery pack) -- and perhaps a bit of double sided tape -- to make it a truly portable oscilloscope that retains a full-size screen.  Current draw is about an amp, so it would run for several hours from a 5000mah phone charger.
 
Given that the repair was quick (I literally had the back off for less than 15 minutes) and did not incur any significant additional cost, I still feel that I got a good deal.  I like it's features, appearance and portability.  
 
I will not however, blindly trust it, or ever rely on it for a critical measurement.  I will always look at that 7" LCD screen with suspicion.
 
*NOTE:  CRT Oscilloscopes employ lethal voltages, as well as other hazards including CRT implosion risk.  Repairs/adjustment should be attempted only buy those with the requisite skills.

UPDATE
 
It appears that FNIRSI has at least attempted to post a new firmware for the FNIRSI-1014D Digital Oscilloscope.
 
There is an entry for a Version 3.0 Firmware dated 06 October 2021 on thier Support Page.
 
However, this link does not result in a file actually being downloaded for me.
 
(EDITED)
 
By editing the URL, I was able to get a file.  More news on this development once I have a chance to investigate more.
 
(UPDATE:  Firmware Installed.)
 
First, the link to the Firmware does not work on Google Chrome (and probably not on Chromium, Edge, etc.)  The link works fine with Firefox.  The following link will work with Chrome, but be warned that it appears that I am bypassing some sort of signing key by doing it this way.  Use the following link at your own risk:
 
https://newwezhanhkoss.oss-cn-hongkong.aliyuncs.com/contents/sitefiles3602/18014 148/files/71398..rar?Expires=1636160238
I am not in control of or responsible for the above link.  This is an edited version of the actual location that the FNIRSI support page redirects to. Again, use of the above link should not be necessary if you are using Firefox.  You should get a file of 3,120,794 bytes.
 
Once you download and extract the file, you will see that there are 2 firmware versions -- One for an "old" screen, and one for a newer screen.  This explains one of the issues that others have experienced in the past.  Apparently, there have been 2 different LCD screens used in the FNIRSI-1014D.  Each screen requires some different values in the firmware.  If you use the wrong one of the 2 provided firmware files, nothing bad will happen to your FNIRSI-1014D.  You will just end up with an offset screen.  If this happens, it is easily corrected by simply loading the opposite firmware.
 
Loading the firmware is easy, fast, and very straightforward:

• Simply connect your FNIRSI-1014D to a PC with the "A" to "A" USB Cable (a cable that should technically not exist.)
  
• Put the FNIRSI-1014D in USB Export mode.  (MENU ---> USB export)
  
• Copy one of the FSI-1014.bin files to the FNIRSI-1014D's volume (8 Gig drive)
  
• Optional, suggested step, at least on Linux:  Open a terminal, and type the command:
  Code:

  sync 
  
  

  This is a very old unix trick that insures the file is written out to the FNIRSI-1014D's storage (all storage) even if the drive/device is not properly unmounted or ejected.  Be sure to wait for the command to complete, but it should be almost instantaneous for this file.
  
• Properly "eject" or "unmount" the FNIRSI-1014D's storage.
  
• Disconnect the USB cable from the FNIRSI-1014D.
  
• Turn the FNIRSI-1014D off and then back on.
  
• The startup screen will appear twice, followed by a very basic horizontal progress bar.  The bar should complete within about 20 seconds. The FNIRSI-1014D will reboot by itself, and the Firmware file will be gone from the FNIRSI-1014D's storage.  Of course, Make sure power is not interrupted during the actual update.
  

Note that you may even be able to upgrade from your phone, but you must use an USB OTG cable or adapter, and the included "A" to "A" cable.  Connecting the scope to a phone or tablet with a normal "A" to micro USB or "A" to USB-C cable will not (and should not) work, since it will not put the phone/tablet into OTG mode.
 
On reboot, the new firmware will display the version number.
 
I have not fully tested the new firmware, but I can tell you a few things that are definitely not fixed:

• Pictures saved to the scope's storage are still not correct when they are viewed in a PC image viewer.  They are displayed correctly in The GIMP.  It seems to be some sort of .bmp meta data or encoding problem.  YMMV depending on the app you use to display the files.
  
• A power cycle is still needed to clear a garaged display after using USB export.
  
• Bugs/Awkwardness in navigating the Signal Generator settings.
  

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I Blew Up  (and Fixed ) My FNIRSI-1014D
 
--- Back Story ---
 
I was working on my latest tube amplifier build (Detailed Here).  Channel 1 was connected to the Left Speaker output (across a dummy load).
 
I was probing inside the amp using Channel 2.  What I think happened is that the probe slipped off of the point I was attempting to measure, and the small ground ring near the tip of the probe contacted the HV feed to the Pre-Amp/Phase Inverter Power Source (about 360 VDC.)
 
So this would have created a path through the shield on the test lead I was holding, through both BNC's on the FNIRSI-1014D, out through the other test lead, and to the speaker (-) terminal (which is referenced to ground inside the amp).
 
As you will see if you peruse the Other Builds and Projects section, I build my own SMPS's for tube amplifiers.  To power (4) 7591a tubes, it takes quite a bit of power -- in terms of both voltage and current.  If what I describe above is in fact what happened, a lot of joules would have gone through that path.
 
I should say a couple of other things:
 
1.  I was being careful, and that is why I was not injured.  Fingers were safely away from all points with a High Potential. Probes slip -- it happens.
2.  There was no arc, flash, or sound.  The amp continued to work normally.
3.  If the tip of the probe had contacted B+ (or any other HV source in the amplifier), it should not have damaged anything.  The probe was set to x10, so I should have been able to probe up to 400V with no problem.  In fact checking for ripple on the output of this type of PS is something I do with this 'scope often.
4.  I was not using the signal generator function at the time.
 
--- Symptoms ---
 
As mentioned, I am assuming that there was a momentary (nearly instantaneous) current path within the FNIRSI-1014D from the Channel 2 ground to the Channel 1 ground.
 
As soon as this happened, I observed excessive (beyond full scale) noise on both channels.  Both channels would indicate nearly 100 volts of noise even with the ground clipped to the tip of the probe.  Changing the volts/division knob would change the appearance of the noise, but excessive noise was present regardless of scope settings.
 
Other functions continued to work normally (Sweep, settings, menus, etc.).  Power cycling the scope did not result in any change.  Performing the "Base Calibration" succeeded, but did not have any affect on the displayed noise.
 
--- Repair ---
 
Upon opening the FNIRSI-1014D, there was no obvious damage (even under magnification).  I opened both inputs' shielded areas, but did not observe any damage there.
 
Given the fact that the symptoms looked similar to the noise seen if the scope is not properly grounded to the item under test, and also knowing that the scope should be capable of handling any voltage present in the device under test being applied to the input, I decided to have a look around the return path.
 
Each input, and the Signal generator have a common network of resistors and capacitors connected to the BNC shields (ground or return connection).  Since the signal generator was not in use or connected to anything at the time, I suspected it was un-damaged.
 
There are 2 surface mount resistors as part of this "network" on each return.  Testing these components in the area of the signal generator with a ohmmeter showed these to be low value (10 and 100 ohms) resistors.  Using my phone as a magnifying camera, I was able to confirm the marking indicated these values.
 
These resistors showed open in the area of both Ch 1 and Ch 2 inputs.
 
To be perfectly open, I do not feel that this oscilloscope is worth the time or cost of ordering replacement SMD (SMT) components. I determined that there was sufficient room to solder through-hole devices in this area.  The result may not be pretty, but all measurements in this area are now the same within 4 decimal places as measurements in the area around the signal generator.
 
I did the "Base Calibration" again, and it succeeded.  Using the separate signal generator as a test, the FNIRSI-1014D seems to be as accurate as it ever was.
 
Note that these are 1% metal resistors, which should be accurate, and hold their value over time almost as well as the SMD components.  I am confident that the failed components are permanently failed fully open, so I left them in place.
 
A dot of glue would help hold the components, but since I don't plan to use my FNIRSI-1014D in a high-vibration area. I am sure that it is fine as-is.
 
Note that any significant potential applied from one probe return to the other -- even instantaneously -- could cause this same failure in the FNIRSI-1014D.
 
I do also want to note that I am sure that any of the vintage oscilloscopes that I have owned would have not suffered any damage had the same thing happened.