RX-Currentconsumption too high (180mA/5V-USB)

[Rolf, DK9DQ]

Currentconsumption is too high after possible short circuit (180mA/5V-USB).

A super good kit: !!!Congratulations to the developers!!!!

Hello uSDX-friends,
unfortunately there was possibly a short circuit between the motherboard (J4) and the RF-board during the first power-up (7.5V; currentlimiter 200mA). (!!! Not all hints observed !!!)

Error description: At 5-12V; current: 180-200mA ( 2-3V current: 0 mA)
- Display: All display values okay, the higher the voltage the darker the display gets
- Menu works
- Loudspeaker works
- Relay switching
- Receiving is oK.
- Transmitting in CW is okay, but the displayed output is a bit too low (200mW instead of 700mW);
SWR-measurement is perfect.
- Powerconsumption with and without RF-board is almost identical high.

When operating from the USB-port, the display is brightest, but the current is also 180mA).

My assumption:
The current through the voltageregulator U2 is too high (170-200mA depending on the operating voltage).
So U2 internally regulates the operating voltage down to protect itself! The display gets darker. U2 is not needed for the operating voltage via the USB port. So far okay!

But why is the current about 100mA too high? Hm !!!
... or is the possible short circuit not the reason for the increased current?

Who has an idea?
- What can I measure or test to locate the fault????

Best regards
73
Rolf, DK9DQ

[DL2MAN]

99,9% one ore more PA Fets shorted.
Remove RF Board and measure again. it should be 80mA max in that case and gives another hint, that it really is PA Fets.
If so: Remove PA FET(s), connect RF Board again and power up.
If still max 80mA -> It was the PA FETs -> Replace ´em by good ones.
In case of Low Band Board with 3x BS170 -> Buy way more and sort them for best matching equality of values. Solder in 3 equal ones and watch for polarity. Not all BS170´s have the same Pin-Out as the original ones.

73 Manuel; DL2MAN

[Rolf, DK9DQ]

Hello Manuel,
thanks for your quick tip!

But the current with and without the RF board is almost the same (Rx-5V-USB/180mA).
The error is a bit tricky, but that is for me also the attraction of our common hobby.
Not always easy, often you have to use your mind !

73
Rolf, DK9DQ

[Rolf, DK9DQ]

Hello friends of the (tr) uSDX !!!

The solution of the problem

After a longer operation with 5Volt via the USB input,
the display became warm/slightly hot at one corner.

I examined the boardside of the dislay exactly and discovered a very fine
soldersplash between two traces of the 30pin-databus to the display.
I removed the soldersplash mechanically and everything is okay now ! (smile !!!)

I think the soldersplash was caused by desoldering C3 + C4.
Now the device works better than I expected.

Thanks to the developers DL2MAN and PE1NNZ

73
Rolf, DK9DQ