Re: Blown by nearby transceiver #bitx40help

Joe Puma

Hey Jerry, I’ve had strange things like his happen to me with other equipment when transmitting even with a little Power like the bitx40.  I’ve zapped the inductors on a SpyVerter and SV1AFN upconverter, fried them completely, the spyverter has board damage too but nothing else, no other components. Heck, I’ve fried the SV1AFN a few times with my 100w radio and finally beyond repair because it killed the mixer and too many things I didn’t have parts for.  My SDR Antenna is near my long wire TX antenna I use for my Yaesu and the bitx40 when I had it. 

It happened mostly when I was tuning up, actually I think only when tuning up. And especially on 160. I’ve watched an inductor burn up right before my eyes when the tuner was chattering. Must of been throwing high voltages everywhere. RF sure is amazing lol. I’m still learning. 


On Feb 11, 2018, at 4:34 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

From the photo, looks like a burned trace from C6 to L3.
From the Bitx40 schematic it's hard to imagine how that might have happened.
That node is isolated from other parts of the rig that might have significant DC power by multiple DC blocking caps.
RF power there should be milliwatts, even with a nearby QRO transmitter.
Even a loose wire with +12VDC on it striking that node would not blow the trace since there is no path to ground.
L3 is a toroid and thus inherently well shielded, I doubt significant RF was coupled directly into L3 somehow.

Could be that all you need to do is fix the trace.
But the cause is totally unexplained, and something with enough power to scorch a trace like that has enough power 
to blow out many other things.  Fixing this might require finding somebody with a scope and bag of spare parts.

Do let us know what parts had to be replaced once you get this fixed.
And any guesses as to how it happened.
For me at least, truly a mystery.

Jerry, KE7ER

On Sun, Feb 11, 2018 at 08:41 am, Gordon Gibby wrote:
Looks like L3, and possibly other series elements in the 40 m filter got way too much voltage. You’ll probably have to use an ohmmeter to test out each connection and see what has become non-conductive.  I suspect Q 13 got fried in the process, and there are two other transistors that would’ve been connected that might’ve been damaged as well from the schematic.  With some care, these can be replaced by ordinary 2N3904 transistors.

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