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.





Citizen SR-260 calculator

 Popular scientific calculator - I've seen it in use around 2003. Apparently replaced by model SR-260N.


Case is slightly flimsy - perhaps because I don't have other part, cover.
Two alcaline GPA76 cells.
Two screws on the back and few latches around - rather easy to open.







2021-09-04

Energizer CHVCM-EU charger

 Simple NiMH accu charger.

2 charging channels (2 x 2 AA/AAA), relatively low charging current, no detection of fully charged accumulators, just 11 h timer. Might be useful for complementing modern chargers that sometimes seem too smart refusing to charge.
Open circuit voltage on each channel: 11.6V.


Transformer: outputtting 7.7V RMS and 5V RMS.


Visible corrosion damage - these pictures were taken after cleaning. Fortunately PCB traces does not seem to be broken. Two electrolytic capacitors were replaced as they seemed to be corroded, though their capacitance was fine.

Strangely only one problem was found: not working LED in first channel.

Timer: HCF4541.