Re: Basic board test: 130ma @ 12.5 volts #ubitx

hirosmb <hirosmb@...>


Very much appreciated for your detailed explanations.

// hiro, JJ1FXF

2018/07/15 3:18、Jerry Gaffke via Groups.Io <jgaffke@...>のメール:

Not stupid.

It's not in the instructions.
Also, the photo clearly shows no Raduino plugged in.
Seems Farhan wrote that 7 months ago, and this has all since slipped his mind.

There's nothing that would be damaged if a uBitx main board were powered up
without a Raduino plugged in.  

Looking at the Raduino connector on the uBitx main board schematic near the bottom of this webpage:
there are signals for  T/R, TXA,TXB,TXC, CLK0,CLK1,CLK2, CW-KEY, and CW-TONE.

The relay driver at Q15 for T/R won't have any current going into the base,
so that transistor won't be on.  The rig will not be trying to transmit.

Likewise for the LPF band-switching relays at TXA,TXB,TXC.
Though if some of them were on we don't really care.

Perfectly fine that the three clocks are dead, that won't hurt anything.

CW-KEY won't be unbalancing the first mixer because there's no current going in there.
Doesn't really matter anyways because T/R does not have us in transmit mode.

CW-TONE is fine if there's no current going in. 
And would be fine if 5v was applied there anyways.

You might think we could have damage if T/R was somehow injecting current
into Q15, which would power up the transmit amp with inappropriate LPF filters selected by the relays.
However, with all clocks dead, won't have any RF energy going out anyway.
And if there was RF, the IRF510's powered at 12v would be fine (at least for awhile) with the high SWR.

I'd recommend you follow the WireUp instructions as originally written up.
Follow the example in the photo, and do not plug in the Raduino.
I don't see anything wrong with that.
If it were a problem, then we would probably have lots of failures when
blowing new firmware with the rig powered on, no reports of such failures.

I'm much more concerned with the false sense of protection from reversed supply leads 
provided by the recommended reverse diode and no inline fuse, that's a recipe for disaster.
We have several threads on this, search for "reverse polarity" here:

Jerry, KE7ER 

On Sat, Jul 14, 2018 at 08:51 AM, Don - KM4UDX wrote:
Hum.....the build instructions say NOTHING about plugging in the raduino BEFORE the current test.  So I didn't plug the board in -- and did the test per instruction. 

If if this is an important caution, why not just say..."plug in raduino then do test".  Why leave us to guess and be stupid? 

So so I was stupid. 

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