Recently we have started research why USB FLASH disk can work and USB DTT tuner never. Well the fault is on USB LIMIER BOARD. There are 4x resistors 5R6 instead of small inductors (wires). Than there is FUSE F wrongly set to 5R6 too instead of 0R fuse.
All the resistance are cause of (+5V) voltage fall. In case of really small currents like 10-50mA than all the serial resistance is causing very small voltage fall - like in case of 50mA current and serial resistance of all resistors is about 17 Ohms (5R6+5R6+5R6) the voltage fall is U=I . R /U=17 . 0.05 = 0.85V / that means if your USB stick power consumption is 50mA than the resulting voltage on your drive is 5-0,85=4.15V . Well so far so so. But in case of DTT USB stick there are different currents depending on the type. We have measured 3 different dongles. 2 of them very cheap and one expensive. The expensive one had USB current about 200mA and the very cheap ones had 320mA and 410mA. So now it is clear why your DTT can not work at all with the board USB current limiter. Similar situation is with USB WiFi dongles. The solution is on the pictures.

Tested with USB DTT with 320mA current on USB power. Working very well. The pdf manual says the limit of the IC USB limiter is 0,6A to 1,2A - it is set internally but any USB device should not consume more than 0,5A so must be OK for almost any USB device except of USB HDD.

Datasheet Sipex Chip



Solution A) is simple - remove the limiter board and connect the USB port wire directly to main board. See the picture.
It is fast but your DC-DC inner power converter is exposed to a danger of short circuit. We have tested that short circuit on this +5V area is safe but still dangerous to some external voltage could cause the DC-DC converter faulty.



Solution B) install an USB HUB with external power supply.

External HUB Power Supply



Solution C) is also simple and the correct one. Short all 5R6 resistors by any wire on your USB limiter board and add 2x 100uF/16V to C6 and C7 - those capacitors are like a buffers to any short circuit at output of the limiter board to protect the IC Sipex SP2526A. See the pictures below.

And one more,

Admin

More precise photos about a part not possible to see in the photo published,

Thank you to Giacomino,

TS