External power supply damaged board?


#41

Here are a few more images of the board in case anyone can spot any other components.


#42

Hi @jslatten,

It looks like power switch is burned out.


#43

Zack,
Where is the power switch located?


#44

Hi @jslatten,

It is IC25, check the picture.


#45

Is there any way to bypass the power switch or test whether it is in fact burnt out?

I feel like any sort of testing or repairs may be a lost cause at this point…


#46

I believe if you solder blob R167 it will bypass IC25 and give direct 5v(USB) power to VVC_INT


#47

Thank you so much @KBBF5 and @Zack . I can’t believe its actually working again. I solder blobbed FR38 and R167. Not sure what the repercussions of doing this are yet so if anyone has any ideas please let me know. Less than 15 mins of work and I’m back in business. Here’s a screenshot on 20m


#48

Darn, and I just purchased a new LimeSDR a couple of weeks back figuring it was not going to be possible to fix. Wonder what I should do? It hasn’t shipped yet, so might be able to cancel it but then again I’m not sure if my current unit is a ticking time bomb due to these incorrect fixes…Please advise…


#49

Can’t advise on the implications of the fix, but with two boards you could use one for master clock and the other slave for 4x4 MIMO.


#50

@andrewback Yeah, I figure I’ll just keep it as I’m not sure at this point what is working correctly or not. Having a bit of trouble with transmit at the moment so I may compare to an undamaged board.


#51

@jslatten

Any problems with your R167 FR38 fix? I had also “bricked” my power supply and now desperately trying to get it to work.


#52

Not that I know of…honestly I haven’t done extensive testing, but receive and transmit both work. If you’ve damaged your board by putting too much voltage/current through it its worth a try to perform this fix.


#53

I really wish this topic was solved since I will be trying external power supply and really don’t want to toast a lime. jslatten, did you check if your power supply and usb had the same ground reference or that one was floating? This is a common way for creating smoke as you did.
As for a USB that does not supply voltage/power, this would be one in Accessory mode. I’m not sure what other constraints this might add. I was planning on using host mode and have a fire tablet control my lime.


#54

One other possibility comes to mind. Could you check the resistance across C273? This may be hard to do since the USB chip is connected. I’ve seen this happen when ceramic caps get very small cracks and the inner layers short. This could explain the the damage and voltages you measured.


#55

I have a similar issue. FR38 was burned. I think it came through the external power supply. Is there a way to see if the Cypress FX3 is also burned?


#56

Check to be sure the polarity is correct. Also, check if it is AC or DC output. Either of those could damage it.


#57

Polarity I aready checked. The LEDs are not blinking anymore and the FX3 gets really hot. I saw, that the FR38 was burned. I jumpered the FR38, like @jslatten. But it had no influnce. now I want to check if the FX3 chip has also a issue.