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eHam Forums => QRP => Topic started by: WU6R on August 23, 2019, 05:07:27 PM



Title: Bitx40 Wired up and it doesn't work!
Post by: WU6R on August 23, 2019, 05:07:27 PM
I finally got around to wiring up my bitx40 QRP radio and when I applied 12v, 2.0 amps from my bench power supply, nothing happens with the bitx40... the bench power supply supply voltage drops down from 12v to 0.49 V, but nothing happening on the Bitx40 display and no sound from the speaker.  I checked the inline fuse and it is working and it did not pop... 

Any suggestions are greatly appreciated.

73,
Mark / WU6R



Title: RE: Bitx40 Wired up and it doesn't work!
Post by: K0UA on August 23, 2019, 08:16:51 PM
I finally got around to wiring up my bitx40 QRP radio and when I applied 12v, 2.0 amps from my bench power supply, nothing happens with the bitx40... the bench power supply supply voltage drops down from 12v to 0.49 V, but nothing happening on the Bitx40 display and no sound from the speaker.  I checked the inline fuse and it is working and it did not pop...  

Any suggestions are greatly appreciated.

73,
Mark / WU6R




It sounds to me like your bench supply that went from 12 volts to .49 volts current limited instantly and dropped the voltage.  How much current is your supply able to supply in total and keep the voltage up?


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: WB6BYU on August 23, 2019, 09:04:34 PM
I agree:  either the bench supply can't provide enough current, or there is a short circuit in the radio
that is drawing too much current for the supply.

Check the DC resistance across the power connector with an ohmmeter.

It might be a blown protection diode, or one installed backwards.


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: WB6BYU on August 25, 2019, 12:47:57 PM
One other place to check:  I got a K2 that had a short in a toroid transformer.
That could cause a short also.  (In this case, it applied voltage to the base of
the finals that turned them on during receive' drawing high current.)

Assuming your bench supply can put out 2A, and you are not keying the
rig into transmit, then a short circuit is the likely problem. 

First, verify that you have the right supply polarity (otherwise the reverse
protection diode will conduct, causing the symptoms you are reporting).
Then follow the positive voltage path through the radio looking for an obvious
short. You might start my disconnecting the supply wires from the finals and
seeing if the rest of the radio powers up.


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: WU6R on August 26, 2019, 11:47:24 AM
I checked the polarity of the power connector and the power supply and it is wired correctly, but my VOM resistance reading shows zero resistance across the power connections... so I'm looking for a blown diode.

Thanks,
Mark


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: WB6BYU on August 29, 2019, 08:55:10 PM
See if there is a shunt diode across the 12V line for reverse voltage protection.
Otherwise it might be a shorted tantalum capacitor (likely at least 10 uF).

Otherwise it could be a stray splash of solder or a shorted transistor.


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: KG9H on August 31, 2019, 05:56:47 PM
You have a dead short.  Ohm it out but before you reconnect remove the DC to the board or switch to verify you have it wired correctly


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: K3UIM on September 16, 2019, 07:01:55 AM
Mark,
Well? What happened? Did you get it?
Charlie


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: K3UIM on September 17, 2019, 09:40:06 AM
Mark,
Well? What happened? Did you get it?
Charlie

Again!!??? We're all interested!
Charlie


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: KH2BR on September 20, 2019, 11:37:05 AM
He either blew him self up or is to embarrassed to reply. We all learn by our mistakes Like me trying to trouble shoot a circuit that did not work. Why? I forgot to apply power.  ;D  Let us know so we can all learn what not to do.


Title: RE: Bitx40 Wired up and it doesn't work!
Post by: K3UIM on September 28, 2019, 05:38:54 AM
He either blew him self up or is to embarrassed to reply. We all learn by our mistakes Like me trying to trouble shoot a circuit that did not work. Why? I forgot to apply power.  ;D  Let us know so we can all learn what not to do.
Judas Priest! You mean I'm not the only one that Murphy's Law kicks in the pants daily??? Wow! Hi
Charlie