Re: QCX mini died


howard winwood G4GPF
 

this is one problem that anyone using a lipo to power ANYTHING, is there ability to supply ridiculous amounts of energy in a very short time.
LiPo’s do not take prisoners.
Dig out the old soldering iron I guess LOL.
you have my sympathy.

On 23 Jan 2021, at 16:18, Fredi HB9BHU <hb9bhu@...> wrote:

Hi
 
I have build my QCX min 20 m Version straight foreward. Super design, super assemlby manual! It was a lot of fun to biuld it - thank you Hans!
I could carry out the alignement exactly as described in the Manual. Ecerything worked fine on my workbench an the laboratory PS; 5W out @ 13,8 V  and very sensitive RX.
But ready for the first SOTAactivation, I plugged in my Lipo 4S battery ... and bang! After first inspection I found a damaged L6 and the LM1117-5.0 has shortet the input to the output :-(!
Despite I followed the instruction to an dditional 100uF capacitor at the 12V input, I it looks like there this is not enough protection if one use a very low impedance voltage source like a LiPo battery! 
Now I afraid, I am ahead of a lot of SMD repair work. Therefore I have two questions:
1.) Has anybody experience with the repair of a dead QCX mini caused by a faild LM1117-5.0, where 13,8 V got fed into the 5 V rail? Is it a better advice to build strsight away a new kit instead of dealing with all those faied comopnents?
2.) Aside from a better regulator like 78M05, is there anything one shoud do externally to avoid high current peaks during power-up, like a coil in series?
 
73 de Fredi, HB9BHU

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