2021-09-30

Trust GXT 105 Izza USB mouse

Cheap (prices starting from ~$8) fashionable USB gaming style mouse.
Switchable 800-2400 dpi, though it seems like wider range when tested.



Not quite matching picture on the box and some other pictures I've found on the Internet - side panels mounted with screws and style of these side panels is different. They are purely for decoration and I would not recommend as plastic underneath would not survive repeated reassembling - some glue might be needed then.

As there are some holes under big sticker on the bottom side (see cross cut below) I though at first this is where screws are hidden, but they are under feet.


Fortunately mouse is easy to disassemble after removing these four screws at the bottom.
Single all-in-one chip: SPCP180-126.
PCB marking: TY_V300_SPCP186 20180906.

Piece of steel adding weight.



I do not recognize brands of these switches.

There is some space for extra switch under DPI +/- button and there are also two pegs sticking from top part of the shell. Perhaps there was some variant using it.

Mouse was completely dead when I've received it, it was probably product returned to Amazon. Surprisingly this was easiest fix ever - USB cable plug was not attached properly.

H13 scroll encoder.
Three RGB LEDs seem to be some kind of "smart" 2-pin diodes, perhaps pulse controlled: https://www.youtube.com/watch?v=gxdgRHmOuIo
Special switch for mouse wheel.
Other minor issue: scroll wheel was slightly blocked by pieces of cable insulation (I've cut it off).

Mechanically this mouse seems similar to https://mysku.ru/blog/aliexpress/67695.html - same scroll wheel, similar top shell made from two kinds of plastic.
 

2021-09-29

Inphic P-M1 wireless mouse

 Cheap wireless mouse.

Built-in rechargeable cell (14500, 500 mAh nominal), noiseless, wireless. Charged with micro USB cable, small USB radio receiver is included.




Optical sensor: KA8. Poorly documented, but apparently identical to PAW3204DB and even better documented MX8650.
LED is emitting infrared.

BYKC68MS - not a lot info on this, but this seems to be somehow popular in this type of peripherals.
PCB: BYKC_M1-VER1.1
Two main microswitches (left and right) are unusual and almost noiseless.
Currently not working - I see almost no activity except for periodic pulses on one of the crystal legs and maybe something when powering on, otherwise sensor data lines are idle. Swapping crystal and adding 30 pF capacitors to it did not help.

Other mouse with very similar circuit and even similar, quiet mouse button switches, T-WOLF Q13: https://mysku.ru/blog/aliexpress/67695.html.

2021-09-26

Grundig KSC 35 radio clock - teardown and repair

Small radio with clock and alarm, quite typical in form and functionality.
FM PLL tuner. All functions controlled through pushbuttons.
10 station presets, 16 volume levels (including 0/mute).
Retail price: somewhere between $15-$20.
No signs of life when received and as it weights literally nothing I though at first that this was just an empty shell.
 External switch mode power supply, 5V/0.55A.
2 AAA cells for clock and station memory backup. Measured current consumption: 10 uA with some hard to measure spikes every second. This is quite reasonable and allows leaving cells inside even if radio is unplugged for a long time (some older radio clocks consuming few mAs from 6F22 battery might actually deplete it in one day when unpowered).

Quite easy to open - four screws at the bottom (two hidden under rubber feet) and few small latches. Easy to open without leaving any marks.


7-segment LED display - 4 digits and few extra LEDs to signal alarm state. This is also main board of the device.

Reason of failure: buttons board broken in half. Given factory-new device state I would assume that this was transport accident.
Extra screw holes might be a sign that same shell was also used or intended to be used with different electronics, maybe leaving less empty space inside.
Radio chip: 1580H - cannot find documentation.
Clock/control - unknown blob.
Audio amplifier: 8002A.

Board was glued together with epoxy glue and traced repaired with wire and solder.
To strengthen the board I've glued steel U-shaped rail the edge (probably part of laptop optical mechanism in previous life). Not too elegant but probably stronger than originally.
Cable strain reliefs (heat shrinking tubes) were added to power cord and antenna.

Audio quality is not impressive - I guess typical for this class of equipment.

2021-09-11

Casio fx-82super calculator

Quite old scientific calculator, according to https://www.calculator.org/calculators/Casio_fx-82SUPER.html both introduced and discontinued in in 1989.
One issue important for me is a lack of hexadecimal mode.
 Easy to open - 4 screws and latches places near battery compartment.





Looks like original cells, with expiry date of 1997. Not a sign of leakage and still full nominal output voltage.