Re: It stopped transmitting

Soundararajan Ra.

Yes .measured rf voltages i am getting 200 mv compared with working one 500 mv on my cro in c132 .all stages up to q4 base only 30 % of working one .
During comparison i am using same mic ,same power supply .
Further i have go.
It was working for few minutes and suddenly dropped output below 1 watt.

On Jan 4, 2017 5:42 PM, "Raj vu2zap@... [BITX20]" <BITX20@...> wrote:


Your Q13 seems fine! See else where.


At 04-01-2017, you wrote:


I my case
predriver q13 collector voltage 10.4
base voltage 3.4
emitter is 2.8
while supply voltage is 12v
i am facing very low output .
should i have replace q13 ?

On Wed, Jan 4, 2017 at 12:21 PM, iam74@... [BITX20] <BITX20@... > wrote:

Very nice, Jerry.

I still wonder about the phasing, however. And the impedance matching.


---In BITX20@..., wrote :

Ashhar says it's a 2n3904, and that the schematics are incorrect about it being a BC849.
Fairchild has a 2n3904 in a SOT23 with a "1A" marking.
I suspect there's quite a few other manufacturers, and that somebody is appending an "M".
(Fairchild is now part of OnSemi, which has it's own 2n3904 in a TO92)

I don't have a Bitx40 yet.  But from Arv's post of 19583, all the transformers are "trifilar using 10 turns of twisted together wire" on FT37-43 cores.  (That post is well worth re-reading.)  With one of the three wires left unused at T5, seems it has to be 2:1 center tapped, and not a 4:1 winding ratio.  I assume we're talking the latest Bitx40 schematic up on

If the phasing was wrong it should be very obvious.  Two of the wires from T5 are connected together, that's the center tap and has a trace to C134.  One of those center tap wires should come from one end of the trifilar bundle, and the other center tap wire should come from the other end of the trifilar bundle. Â

If there was trouble in that stage, I'd verify with an ohmmeter that the two free wires of T5 are not connected to any of the four wires that have traces to them.  And of course, look for shorts and cold solder joints.

Jerry, KE7ER

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