My first 7" Android Tablet

7" size just fit into pocket.

The soul of the tablet : 4G NAND flash memory, 64Mx2 = 128M ram ~horrible!

LCD cable

Unsolder are for addition 4G nand.

1800mA 2cell 7.6V lipo

WiFi antenna on the right top.

Model : HSG X5A

Spec: Telechip 8902, 4G nand, 256M ram

Firmware: 2.1 update

Repair Canon EF lens Err99

The cable is now secure with tape to avoid future pulling and fracturing.

The iris mount has the cable exit area "rounded" to remove the right angle on the lip.

Site of fracture as from the small impression on it. The pinhole is puncture to confirm location of fracture.

My Canon EF lens showed this well known Err99 while I was on my long trip to Europe. That was desperate as the problem worsen progressively. Eventually, the camera stops working whenever the lens is zoomed and is fired.

There are lots of reason for Err99, including ring contact, jammed shutter, jammed iris (aperture)....

After returned to my home country, the lens was disassembled. The iris was tested and they seems to have no mechanism binding. The iris works intermittently. Bingo, that should be the broken cable. The cable is visually normal ....hey..except where it exit from the iris mount..there is a impression caused by pulling the cable against the iris housing. Cannon is stupid to allow this happen as the impression cause the thin copper to fracture. Mine counts only around 4,800 shots in 4 years.

Since I got no replacement cable on hand. I decided to confirm the fracture and solder it myself.

Hairpin connectded ohm-meter confirmed the fracture. After careful sanding and solder, the lens now works flawlessly.

Repairing Euron-320 HDTV VCR Power supply.

The replace blown capacitors with dots on it.

Euron HDTV VCR broken down after 1.5 year usage. All instrument light does not lit up. Some ticking noise on power up. Likely somehow of short circuit. On opening up the case. 3 capacitors will blown. With the tanned marking on the circuit board, likely due to overheat , caused by poor design (as the HD still spins and the heat can be felt from the ventilation slot on standby mode).

After changing the capacitors, the circuit board can still not power up. The small tickling noise can still be heard. Likely the short circuit has not yet found out. On removeing the power supply to the harddisk. Bingo! the unit can now be powered up normally.

With ohnmeter checking, the Zener diode (Someone said not zener, ..I forgot ) guarding the voltage input is burnt as well, causing a short circuit. The diode is removed and the unit works nicely...at least for antoehr 4 months.

Now the harddisk list everthing in it. Um....I forgot to check the ventilation fan.. a small , low power fan rated 0.16A and 5V ~1W. I was so stupid that I miss the non-spinning fan. I replaced th fan and it still does not spin and I suspect the old fan is stuck by dust and burnt the supplying transistor as well (some sort of temp. driven fan).

Eventually, I replace with another old 320G harddisk and plug a 3.3V computer fan (for video card) instead.

Hope it works for another 2 years...

ChangeSun 90mm motor fan unit

Motor fan unit using outrunner 1900kv. Running at 6s with amp drawn 70A, the thrust is over 2.6kg. Almost 1.6g/W in benchtesting. My F18 now make a speed record of 180 km/hr.

Quadtwirl gyrotor revived !

My old quadtwirl is revived after its maiden 2 years ago. The torsional weakness is now solve with a piece of 1cmx 1cm balsa running along the fuselage.

Motor now upgraded from 100W to 250W outrunner that runs at 3s/ 20A with a 11x4.7 propeller. THe elevator will be mixed as Delta to provide more roll control. If I were to strengten the rotor, I would insert CF rod + tapes need the rotor blade root.

Converting 220V Hot glue gun to 12V

The heating element : Nicrome wire pressed to the contact slab (solder will melt ! ), the heating resistor 3.6K @220V, which generate rather constant temperature, and the insulating wrap.

These will be replaced by a 2-5W 8 Ohm resistor powered by 2-3s lipo.

SAPAC F16 with 70mm EDF

Now redo the power system with 70mm EDF at 700W. EDF unit from OK Model Tahmazo 3600kv inrunner. Speed now getting close to satisfaction. Needs to reduce the exit nozzle to get extra speed.

F18 90mm Nose strut

The shock absorbing strut works perfectly and one can actually see the nose sinks as the plane lands at nose high angle.

Much lighter that the stock retract and easier to the retract servo.

Bae Hawk shortened nose gear

Shortening the front nose gear makes her never bouncing on landing.

The wire needs some dremel to lock the control arm in position. Now she lands like sticking a magnet !

SAPAC 70mm EDF revive

Very agile and predictabel control F16. Recently upgraded from 400W EDF to 800W. The performance is excellent.

Lightex film is ironed onto the wing, to reduce drag. Lightex on foamy is suprisingly good in reducing drag.

With OK Model inrunner EDF, this F16 flies like composite model.

Eflite Haw - Test flight with Flap modification

The flap is added to slow down the plane on descend.

Smart looking nose strut.

The A4 Sky Hawk is much faster and needs extra attention to fly.

DX7 Switching 3.3V power supply

DIY a 3.3V switching power supply from a 12V to 5V USB car adapter. My DX7 can now run 40% more air time.

Eflite Hawk Flap Modification

Changsun nose strut with "shock absorbing" spring.

This Hawk flies so nice but needs lots of attention when landing. The relative high speed on landing also makes her bouncing. How nice to add flap to slow her down and avoid stall. Simply adding reflex does not make a good solution for perfect landing.

The flap modification is pretty straight forward by cutting along the aileron to the wing root. A servo can be easily attached to the fuselage and a link control.

OK Model A4 SkyHawk Modification

The fastest model of this class with small wing area and high wingloading.

The relatively easy to stall on banking turn is partly explained by the high pressure at wing bottom is stolen into the cheating hole under the fuselage. Therefore, transparent sheet was added to act as guard to prevent high pressure air sucked into the EDF.

Test flight confirmed no easy stall on high bank angle turn, which happens easily on high bank angle turn from downwind to headwind direction.

She is now back to service and flying experience gives more fun than worry.

Eflite Bae Hawk

Very nice finish and scale The intke is small and the profile helps to reduce drag.

Stock motor runs at 60A @14.2V ~840W.

The fixed landing gear produce much drag. Will be modified to electronic retract soon, after I can handle the landing behaviour of this bird.

Will add flap to make landing more easy. She bounces too much with the stock landing gear.

Maiden flight. No trim in and 70% throttle only. She really needs flap to slow her down.