2018-02-26

Toshiba Canvio Basics external HDD

Cheap external USB 3.0 HDD - 2.5", 1GB.




 MQ01ABD100 HDD.
VIA Labs VL711S USB to SATA bridge.

Pros:

  • cheap (~$50 in 2015 or so) 
  • still works (albeit lightly used)

Cons:

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. Sometimes image might get really weird:





 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 (A25L020). 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) - this might be just coincidental.
 PAM8007 - class D power amplifier, 2 x 1.5W @ 4Ohm, 10% THD, 5V supply.



 Audio quality is very poor as nothing separates the front and the back of the speaker. Perhaps some piece of plastic is missing from this unit? Otherwise this would be just poor design - sacrificing audio quality for like a dollar.

Monitor is using PWM for brightness control - it is working with 240Hz frequency right after brightness is reduced below 100%.
 I've changed scaler chip for new one (from 2016) bought on ebay for ~$4. Although I've used hot air old one was rather hard to desolder. Also, despite used some protecting aluminum foil I've blown away 2 or 3 0402 SMD components near the chip - be careful when setting air flow.
Replacing scaler did not seem to make difference - monitor is still randomly shuts off, so my next planned step is replacing Flash chip. I have now new chip soldered and I've added piece of 3M thermal tape and small radiator just in case, but I think replacing Novatek was not necessary.
Update: Pm25LD020 finally arrived ($1.50 for 5 pieces) and then I realized I have no programmer for these low voltage chips (pickit2 with flashrom did not work for me), so I also ordered CH341A-based flash programmer ($2.50).
After desoldering original A25L020 I wasn't able to read anything making sense from it - it is possible I have overheated it, but I've used firmware from https://www.elektroda.pl/rtvforum/viewtopic.php?p=15640144#15640144 (iiyama ple 2274hds-b2 25l020.bin) and it seems to work. For programming I was using CH341A.
I don't see any problems with monitor at the moment.
This seems to be frequent problem with this model, but if you have to spend money to fix it keep in mind that this is not top of the line device - vertical viewing angles are pretty poor, PWM frequency is low (240Hz), speakers are just disgusting.


 LED driver: OZ9998BGN, controlling 4 LED strings, up to 160mA per string, external PWM dimming input. My guess is that PWM frequency is controlled by scaler firmware thus might be not possible to change.
(low quality schematic comes directly from datasheet)

 LD7576AGR - power supply controller

 SMK0965 - N-channel MOSFET, 650V, 9A.

 SP1060 - dual Schottky diode, 60V, 5A per leg
APM8005 - dual N-channel MOSFET, near LED driver chip

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.
NiMH cells (1.2V) seems to work fine, so semi-discharged primary cells would work also. Consumed current = 6uA.

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.