Pure Evoke H4 Not Powering Up - Damaged Component?

[Grotsoft]

Hi,

I'm looking to repair a Pure Evoke H4 DAB radio.

Nothing's happening on power up, the battery is showing 3.9V but, again, nothing happens when trying to power up from it either.

It looks like my SO pulgged in a 21V PSU rather than 12V PSU at some point.

Physical examination of the board shows what looks like a damaged (diode?) tied to one of the battery input pins.  I've attached a picture of the component, it's the black rectangle at the top of the picture.

My question is:

1. Is this a diode?  (It has two parallel lines at one end.)

2. Does anyone have a circuit diagram of this radio?  I've had a look through dozens of sites.

thanks
Stewart

[Manul]

It is likely a diode (could be also a zenner diode), thats true. Does it look damaged? It is not clear from the picture. It could be more then one damaged component, don't forget that. Do you own a multimeter? Soldering station/iron?

[Grotsoft]

It is likely a diode (could be also a zenner diode), thats true. Does it look damaged? It is not clear from the picture. It could be more then one damaged component, don't forget that. Do you own a multimeter? Soldering station/iron?

It does look damaged, you can see what looks like some bulging on the top.

I have a full set of electronic tools, just not much experience with surface mount components (valves and MCUs are more my thing).

I used the diode test mode of my multimeter on that component (in situ) and got 0.5V one way and 0.6V the other.

[Manul]

In that case it is most likely good. Overstressed diode will usually fail shorted. Bulging to me looks like residue of some glue / conformal coating. Proceed with tracing and measuring power path and power rails of the circuit, switching converters, linear regulators, etc. Is some rail shorted?

[Grotsoft]

Thanks Manul, I'll dig in.