no lights ethernet yellow led not blinking, U17 very hot, 1.7V after FB28

[Jean-Pierre FERLAY]

After 2 months of good working, my HL2 stopped working suddenly, the 4 leds are off. All voltages are correct but the 2.5V measured after FB28 drops to 1.7V when Ethernet is connected and U17 becomes very hot. I tried a factory reboot according the procedure but the HL2 remains dead. I suspect a FPGA failure.

What can I do now ? Could I send it for repair or exchange  under warranty ? Thank you for your help.

BR Jean-Pierre F5LOL

[Jean-Pierre FERLAY]

The FPGA has a short (0 ohm) measured between 1V2 and 2V5. What can I don now ? 

[Steve Haynal]

Hi Jean-Pierre,

If you are comfortable with surface mount components, can you remove FB28 and see if the heating and drop in 2.5V goes away?

73,

Steve

kf7o

[Jean-Pierre FERLAY]

Hi Steve, 

I have remove FB28 with my hot air tool. Now the short between 2.5V and 1.2V remains 0 ohm, but the 1.2V drops from 2.1V to 1.18V and the 2.5V drops from 2.34V to 1.13V. The HL2 seems to work as before RX and TX, all bands CW and SSB, the TX power and modulation are OK. I didn't check all the functions but all seems to work fine. I suppose that removing the 2.5 Vlvds from the FPGA modify somethings but what ? could you explain me please. What shall I do now ?

Thank you very much.

73 Jean-Pierre F5LOL

[Steve Haynal]

Hi Jean-Pierre,

I was hoping by removing FB28 we could determine in which portion of the circuitry (FPGA side, power supply side) the short between 1.2V and 2.5V is. I didn't expect this to fix anything.

There are some unsupported add on boards which apply power to Vlvds. Have you installed any board which connects to Vlvds?

Between which points are you measuring the 1.2V to 2.5V short? Are you using the test points show on this wiki page?

https://github.com/softerhardware/Hermes-Lite2/wiki/Hardware

Now that FB28 is removed, can you measure any short between 1.2V and 2.5V twice, once withe the 2.5V point at each pad of the FB28 footprint? This may tell us on which side of the now open circuit the short is.

73,

Steve

kf7o

[Jean-Pierre FERLAY]

Hi Steve,

Thank you again to your support.

I haven't install any board connected to Vlds. I have only the main board + the filter board + the I/O connector board connected together.

I used the points of the wiki page to check the voltages and resistances.

The short is between 1.2V and the side of FB28 connected to DB1(Vlvds). There is 8.2 ohm between 1.2V and GND or  Vlvds and ground.

Br

73, Jean-Pierre F5LOL