HL2 not booting up at all

[Aaron]

I have a stable 13.8V on a 3 amp fuse.  It booted up initially with lights flashing, then for some reason, I walked away to connect my computer via Thetis, and for some reason, it was not picking up the HL2 via the network.  I went over, and the HL2 had shut down completely.  I restarted my power supply and all was okay with it - output of 13.8V but my HL2 does not seem to power on - no LEDs anywhere.

Is my Hermes Lite 2 defective?

[Aaron]

I will add that I just bought this approximately 1 month ago and just received two weeks ago.  This thing is not working even with a stable 12V 3A power supply dedicated without any daughter boards connected, or a stable linear 13.8V power supply with 3 amp fuse.

[Steve Haynal]

Hi axk5217,

Using a regular volt meter, please measure the voltage at the test points identified on this wiki page:

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

The wiki page says to measure resistance, but use the picture to identify voltage supply points and measure voltages relative to ground with power applied to the unit.

Also, when  power is applied to the unit, is your 12V or 13.8V still at 12V or 13.8V? This is to measure if the power supply is being shorted out and turning off.

73,

Steve

kf7o

[Aaron]

+3V3 and GND - 3.3V measured
+2V5 and GND - 2.5V measured
+1V2 and GND - 0.01V measured
Vbias and GND - 0V measured
Vsupply and GND - 12.08V measured
Vop and GND - 0V measured
Vpa and GND - 0V measured

[Aaron]

Also, yes, voltage is very stable at 12.08V when power is applied. The voltages I've measured are also stable, no drops noted. 

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[Steve Haynal]

Hi axk5217,

There appears to be a problem with the 1.2V supply. The Vbias, Vop and Vpa supplies are only on during transmit.

* With no power connected, what resistance do you measure between the 1.2V test point and ground?

* If you apply some light finger pressure to U16 and the components around it, does the 1.2V supply turn on? This is to check for a damaged or poorly soldered component.

* Please send pictures of the HL2 board around U16, both top and bottom.

How interested/capable are you in possibly repairing this yourself? You can find the warranty information here to see if you qualify.

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

73,

Steve

kf7o

[Aaron]

I will get some pictures tonight of the board.  I did try pressing down on U16 which I believe to be the black component with 6 connections to the board (highlighted in red in attached photo)?  No changes in bootup after holding pressure on U16, but didn't have a chance to measure voltage this morning before work.  I will definitely get some more measurements tonight.

I could repair myself, but honestly I feel it would require some hot air soldering which I am not too sure I should attempt to do this considering it would be my very first time with this setup.

Thanks!

[Aaron]

I would be fine with soldering this on, I just don't want to void any warranties if you know what I mean, should there be something else wrong with the board.

[Aaron]

there is 1 ohm of resistance between 1.2V and ground.

I have put pressure on the components around U16, with no change in voltage.  I am still getting around 0.01V.

Attached photos

[Aaron]

[Clifford Heath]

Often when a power rail goes short, it will be an MLCC decoupling capacitor which has cracked, possibly due to thermal stress or the board flexing. As these are not critical to basic operation, it is possible to remove all these capacitors until the short vanishes. Then fit new ones and you are off and running.

Clifford Heath 

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[Clifford Heath]

Another thing to try first is to apply 1.2V from a current-limited supply, say 500mA. The capacitor which is short will get hot.

Clifford Heath 

[Aaron]

I just got a small benchtop supply that has current limiting features but it applies amps/watts.  I guess I could apply 1.2V and 500mA and feel around the board, a thermal camera would be nice though! Can I feed voltage in at the test points or should I feed somewhere else?

Also, following the circuit for U16, are these the capacitors I am looking at primarily?

[Aaron]

At this point, I just want a working board.  Should I order a new one or are there any potentials for a refund through Makerfabs for this defective piece?  It seems like I am headed down a rabbit hole here lol.

[Aaron]

I will also note that U16 is getting noticeably HOT during testing.  After about 30 seconds, it feels like it is at least 90-100 degrees Fahrenheit.  The other components do not seem to be getting hot like this, perhaps it is the issue or the capacitors leading up to it.

To view this discussion visit https://groups.google.com/d/msgid/hermes-lite/1f1c5914-24eb-420c-a3c0-745870064458n%40googlegroups.com.

[Steve Haynal]

Hi Aaron,

I have sent private e-mail to you regarding a warranty replacement. It is difficult to tell if the short is in a component (maybe even the FPGA) or PCB. A next step would be to start removing components to eliminate the short.

73,

Steve

kf7o

[Clifford Heath]

You're probably best to go with replacement.

However, a short downstream from the power supply chip will make it get hot. It doesn't mean that chip is bad. I inject enough power to make a bad decoupling cap pop, turn brown, or smoke. A thermal camera can spot larger components and power traces as well, but I don't have one of those.

Clifford Heath 

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[Aaron]

I have responded with the order number.

I can try feeding 1.2V into the circuit just to see what happens and/or remove some faulty components.

I do have some ST1S10 chips on the way.  I looked at the capacitor list as well.  I think it would be cool to fix this one, and I do appreciate the help, but I am starting to become a little concerned that this might be something more than just a bad cap or step down converter.  However, it would make sense, since I am getting good voltages everywhere else.  My primary knowledge is IT, but also computer science and I enjoy tinkering around some.  These components are dirt cheap too.  I just don't want to void any warranty if something else is wrong!

[Aaron]

I did replace the step down converter but it was not attached to the board properly....got .3 volts.  All in all, I can't fix it.  I also removed a capacitor and replaced it but still no go.  The step down converter was REALLY stuck to the board, the pad underneath it was absolutely atrocious, it was stuck on good.  The type of solder used on these boards do not melt easily, must be lead free.