2018-02-04

IIYAMA E2274HDS (PLE2274HDS-B2) monitor

I've got this monitor for free as previous owner gave up on fixing it.
Symptoms: monitor works fine at first look, but after hour or so it may randomly turn off or start showing image with weird colors (e.g. missing one color entirely). OSD menu has often random minor artifacts. It cannot be turned on again using ON/OFF button but with powered off entirely (detaching power cable) for few minutes it starts working correctly again for a random time.




 From the posts on few forums this is common issue with this model and also with larger XB2374HDS and E2475HDS / B2475HDS. Two possible problems are listed: failure of NOVATEK NT68677UMFG chip (scaler) and failure of serial EEPROM (A25L02). Some suggested that main chips are just faulty and need replacement, but my plan for now is just trying to lower it temperature using radiator from old Pentium 4 motherboard north bridge. After testing for a few days this radiator seems to be helping, not fixing all problems (like not powering on after signal going down and then up) but reducing them significantly (hours of work but still need to cut down the power once or twice per day).
 PAM8007 - class D power amplifier, 2 x 1.5W @ 4Ohm, 10% THD, 5V supply.



 Audio quality is very poor as nothig separates the front and the back of the speaker. Perhaps some piece of plastic is missing from this unit? Otherwise this would be poor design.


2018-01-28

Grundig Music 51 radio

Small portable FM PLL radio with clock and alarm - RP 5201 PLL. Retail price: ~$25-$30.

 2 R6 cells for clock / station memory backup (optional), 4 R14 cells or 230V AC for full operation.

 Decent speaker.
 Two keyboard boards connected with single wire pair each - reading keys by measuring resistance.
 This one is incomplete - transformer is missing, otherwise it works fine. Mains socket is couples with mechanical switch disabling internal battery.

Power supply filtering is very impressive for this class of products - there are 3 coils, 2200uF + 1000uF + 2 x 470uF + 6x 220uF + 100uF (one of these might be DC decoupling for speaker actually).
Audio amplifier: "CHMC S75"/"D820"
Microcontroller: TMP86FM29LUG. Toshiba, 8-bit TLCS-870/C series, 32kB FLASH, 1.5kB RAM, 10bit x 8ch ADC, built-in LCD driver, dual clock. Supply current 4.5mA typ, 8-20uA in SLOW/SLEEP modes. UART bootloader.
 Coils on small board resembling hybrid circuit.
 Radio chip.

Both reception and audio quality is pretty decent.
It's worth noting that apart from 2xAA clock/station backup it seems to retain memory with energy from capacitors for a minute or so.

2017-12-10

UB-PB228 powerbank

Small powerbank with single 18650 cell. Branded as "URBAN BEATZ".


 5V/1A input and output, 2200mAh capacity - matches markings on LiIon cell.
 Small mounting screws are covered with sticker front.


 TP4213 from Shenzhen TPOWER Semiconductor. Chinese datasheet exists - 1A max, over-temperature protection, overcharge and over-discharge protection, output over-voltage protection, output overload protection, output short-circuit protection.
Preset 4.2V / 4.35V charge voltage with accuracy of ± 1%.
When charging, LED1 flashes (1Hz?), LED1 is always on when the battery is fully charged, LED2 is always on when discharging, LED2 is flashing when discharging low.
LED2 1Hz flashing = low battery. 
 2200 mAh 18650 cell, SZN = Shenzhen?



PCB markings: EC018_v6.1 2014.6.4

I've received this in non-working condition - it was not holding any charge at all. Few sources suggested resetting CID with screwdriver and although using this cell further might be risky it worked. Cell voltage jumped to 4.09V so CID probably "exploded" during charging.

2017-12-03

$0.99 mini flashlight

Small $0.99 flashlight from ebay.
 Single LED.
 ON/OFF switch at the back. It might be weakest point of this flashlight - it clicks nicely but light gets wobbly if it is touched when powered on. Because of this rubber cap flashlight has also some problems with standing on its back.
 This works with single 18650 AA cell - I've tested it Eneloop (as I have few of them laying around anyway).
 While this flashlight is often advertised as "3W" it consumes roughly 0.2A from 1.3V Eneloop (260mW).
Emitted light is cold. I don't have point of reference but given the small flashlight size (it can be hidden completely in hand) output light stream is satisfying - it's good enough for the trip to basement or to be used as emergency light in bathroom.

2017-12-02

Car USB adapter


 Car USB adapter- 12..24V DC input, 5V/1.5A output with mini USB cable.
 NEC B772P (2SB772) transistor, 34063 switching regulator from ON Semiconductors.