Electronic guru help - MLCC capacitors on DNA75c

[Vapaneezer Scrooge]

One of my Therion BF DNA75c has a fault, it overheats while not in use, I've stripped the board out and the only damage I can see is a tiny surface mount capacitor showing signs of burning out.

I will photograph mine if required but here's a similar faulty one I found on Bing images, in fact it's the exact same capacitor that's gone on mine which is causing the 2 large chips IRO 1627 (Inductors?) to heat up quite a lot.

Problem is I don't know what the capacitance of the capacitors are to try and replace it, or even if I can buy one?
I can't test it in the circuit so any advice appreciated as it's a wasted DNA75c at the moment.

 

[flearider]

can you not just take a reading of the one next to it ? multi meter on each side ?
or shoot a e-mail to evolve

 

[domejunky]

Open a ticket with Evolv, it'll cost about £7 to send it back to them, they'll send you a new board for free

 

[Vapaneezer Scrooge]

can you not just take a reading of the one next to it ? multi meter on each side ?

I can't without un-soldering it as it's in a circuit.

Open a ticket with Evolv, it'll cost about £7 to send it back to them, they'll send you a new board for free

Its well beyond the warranty and I bought it used, won't they charge me? done some more digging and it looks like a 1206 capacitor perhaps they can tell me the capacitance?

 

[Deleted member 58360]

There are ways of testing a capacitor in circuit...

I chose to build an esr meter as part of my ham test, one of those would at the very least show if the cap has failed. It's not a very complicated build, or you can buy them relatively cheaply now.

Might be something to consider if customer support can't help?

 

[Vapaneezer Scrooge]

There are ways of testing a capacitor in circuit...

I chose to build an esr meter as part of my ham test, one of those would at the very least show if the cap has failed. It's not a very complicated build, or you can buy them relatively cheaply now.

Might be something to consider if customer support can't help?

Nice one, I didn't know they existed, there's been several times I could have used one.

Will this one do the job if I use 2 x male/male pin dupont cables for probes?
https://www.fasttech.com/products/0/10043277/9295500-digital-transistor-tester-capacitance-esr-meter

 

[Deleted member 58360]

Nice one, I didn't know they existed, there's been several times I could have used one.

Will this one do the job if I use 2 x male/male pin dupont cables for probes?
https://www.fasttech.com/products/0/10043277/9295500-digital-transistor-tester-capacitance-esr-meter

I don't see any reason why it wouldn't. Caveat that I've not tried one like that and mine has far fewer features

Be aware that adding cables and probes may affect the readings - I built mine so I can calibrate the display (just a swingy needle on mine) to account for different leads and even position (it'll read a capacitance on stuff like shotgun speaker cable).


Oh, and I'm sure you're aware but I'll mention it anyway - it may tell you if the cap has failed but not the reason for failure. The cap may be the cause or it may be a symptom (although a cap is usually the cause tbf).

It also obviously won't be able to tell you what the cap should be if it's failed - so unless you have another board or other source of that information...

 

[Vapaneezer Scrooge]

Useful info thanks, I do have another board to compare.

I will try a few different cables to see the variation difference.

Regarding the reason for it's failure the problem has been reported a few times as battery draining while in standby, the board is constantly drawing power while its not in operation until I found someone fixed it by replacing the defective capacitor though it seems strange it's in the same position so I think I will drop Evolv a ticket to see if they can advise.

I don't suppose you know what the IRO 1627's are? are they inductors? these are the components that are getting hot and drawing power.

Thanks for the advice, much appreciated

 

[Deleted member 58360]

Don't know what those components are offhand, the numbers aren't hitting anything right now... They do bear a resemblance to inductors though.

If that cap is say a part of a resonator circuit and has failed short, then the associated inductor would just effectively be a resistive element and get hot.

I can't say whether that's the case though, or what might have caused it, or why it's constantly drawing power - a cap 'blocks' DC but if failed short it'll allow it to pass, but if it's part of the power circuit (pwm for chip or screen power?) it might explain the symptoms and the reported fix.

 

[Vapaneezer Scrooge]

Okay that makes sense to me - thanks for your time.

Capacitors are cheap and the ESR Meter will come in handy so little to loose, I get more enjoyment from fixing things myself so I will take a shot at it.