This post was last edited by AfengA on 2023-4-30 21:59
My friend's fascia gun broke down not long after using it. I was too lazy to go to after-sales service, so I asked them to repair it to see what the problem was. I had repaired one a long time ago, so I took this opportunity to see if there were any design differences between this model and the previous one.
First look at the appearance of the packaging
The marked battery capacity is 2000mAh. Wait until you disassemble it to see if it is falsely labeled.
The instructions are as follows
Judging from the voltage, it should be 2 batteries connected in series
The manual says there are gear switch instructions, gear introduction and charging instructions. The current problem is that it cannot be turned on. When charging, the power indicator light is not on. When charging, press the power button and the charging indicator light flashes green.
There is not a single screw visible on the exterior of this fascia gun. It took me several days to find out how to disassemble it.
The disassembly points found are that the upper and lower plugs need to be pried open, and the anti-slip sheet on the palm also needs to be pried open, both are snap-on structures
There are screws hidden under the anti-skid sheet on the palm. Fortunately, the screw holes are under the anti-skid sheet I removed the first time, otherwise I would have to remove the anti-skid sheet on the other side.
The buckle of the lower plug is like this
There are switch buttons, charging ports, gear indicator lights and charging status indicator lights on the lower plug.
The button cap is fixed with glue, and the LED indicator has a light-shielding structure.
Buckle structure of the handle anti-slip sheet
I originally thought that I would have to pry the gun head hard, but just as I was about to exert force, the gun head cap was unscrewed. If the structure was like this, it would be easy to disassemble.
The gun head cap also hides the body fixing screws
The upper cap of the fuselage cannot be unscrewed by looking at this line, so you still have to pry it off, and great force will work miracles!!! The upper cap still has the fixing screws of the fuselage hidden in it
The top cap was pried off rather badly
At this point, all the structural parts of the fuselage have been dismantled. Let's take a group photo first.
The next step is to remove the screws of the body. There are 7 screws in total, all of which are hidden. It is really difficult to disassemble the machine without knowing the method. It took several days to complete it (in order to reduce the damage to the appearance, after all, people will use it after it is repaired)
The internal photos after disassembling the fuselage show a circuit board, a battery, a motor, and the mechanical structure of the gun head.
The motor model is HT-J2-W BLDC4012
The battery capacity is really 2000mAh, 14.8Wh, 7.4V, and it is not falsely marked.
To troubleshoot the problem, I removed the battery.
When the power supply is plugged in, the circuit is normal, so I unpacked the battery and tested the battery. One battery has a normal voltage.
The other section is not normal, only 0.4V, the problem should be caused by this.
So, I used the battery removed from the broken power bank to replace it. The capacity of my old battery is larger than the original one.
Because there is no spot welding machine, the original nickel sheet was retained and soldered using solder.
The battery pack uses a 2-string lithium battery protection board (similar to the one shown below)
Wrap the replaced battery in the original protective packaging.
Next, let’s take a look at what’s on the control panel.
The chip with silkscreen 5082E is a boost charge management
IC for dual-cell lithium batteries
ZCC-ZCC5080E.pdf
(986.07 KB, downloads: 0)
Three-phase six-arm full-bridge inverter circuit for BLDC
There is a TSSOP24 chip with the silk screen removed on the board. Judging from the circuit structure, it should be an MCU. The rest are resistors, capacitors, transistors and the like.
Analysis of the fascia gun damage problem: This fascia gun uses a 18650 lithium battery to drive the motor. Because the current is high during operation, the charging IC cannot realize the method of charging and discharging at the same time. In addition, the battery uses two strings and is equipped with a charge and discharge protection board. Once overvoltage or undervoltage occurs, the battery protection board will disconnect the input and output. Because one battery is faulty, the battery protection board has been in an undervoltage protection state, so that the control board has no power supply, so it cannot be turned on. When charging, the power indicator light is not on. When charging, press the power button, and the charging indicator light flashes green.
Summarize:
First of all, the structure is made of plastic, and the feel is OK. It would be better if the anti-slip pad on the palm was replaced with rubber. The appearance looks very simple, and the screws are hidden under the decorative shell, but it is almost impossible to disassemble it without damage. I guess they didn't consider disassembly when designing it. The fascia gun market is very competitive now. I guess if there is an after-sales problem, they will directly replace it with a new one. If it is repaired on the spot, it will be violently disassembled and the shell will be replaced.
Let's talk about the electronic solution. The overall solution is relatively mainstream. The battery charge and discharge management and BLDC control circuit are relatively clear. The battery used is a bit poor and broke down after little use. The silk screen of the BLDC control IC was polished off. Another model I repaired before was more impressive. It didn't polish the silk screen. The main control used is the 8-bit MCU N76E003 of Nuvoton. I heard that the latest solution is that the MCU integrates charge and discharge management and MOSFET gate drive, which has higher integration, simpler circuits, and more advantages.
Let's talk about the functions. The fascia gun I disassembled this time is almost the same as another one I repaired before. They both have power indicators and gear indicators. The gear output power is constant, and the output will stop when the resistance is too large. But it is not as good as the one I use at home. The one I use at home can detect the motor resistance. When the resistance of the gun head increases, the output power will be adjusted dynamically to increase the output power. The output will stop when the resistance is too large to prevent the motor from burning out.
Disassembling the machine is too difficult so I didn’t record a video. Here’s an installation video.
Installation video:
WIN_20230416_21_48_23_Pro
https://www.bilibili.com/video/BV1hh4y1W719/?vd_source=379505f5c723a533bd2f5f97bf385084
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