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bitx40 not transmit on ssb #bitx40help #bitx40 #ssb


sv5fri@...
 

hello,

My bitx40 not transmit when use mic but when use CW transmit  normally  and my output power is 5watt on dummy load.
 
please any idea about my problem.

73 de Yiannis, SV5FRI


 

Yiannis,

Please check your wiring polarity to the mic element. The one connected to the body is -ve (ground).
The element may be defective also.

I hope the RX is fine.

Raj, vu2zap.

At 21/12/2020, you wrote:
hello,

My bitx40 not transmit when use mic but when use CW transmit normally and my output power is 5watt on dummy load.

please any idea about my problem.

73 de Yiannis, SV5FRI


sv5fri@...
 

Dear Raj,

I have check the polarity of mic and is ok.
Also reciever is ok.

I want check the transistor Q12 but what is measurement  must be have.


 

Let us know what voltages are on E B C of Q12 ?

At 21/12/2020, you wrote:

I want check the transistor Q12 but what is measurement must be have.


sv5fri@...
 

Hi

I have measurement the Q12 transistor and the results are below
 
in receive mode C,B,E it was 0Volt
in transmit mode it was
C=13,2 volt
B=2,4 volt
E=0 volt
 
Maybe  something going wrong with Q12.


Jerry Gaffke
 

Yup, looks like either Q12 is not conducting, or perhaps R16 is shorted.
Probably a problem with Q12.

The emitter voltage should be around 0.7 volts less than the base voltage
when an NPN transistor is in the active region.
So should see around 1.7 volts at the Q12 emitter.

Seems odd that Q12 would fail.
Emitter (and collector) current when operating normally is only about 1.7volts/470ohms = 4ma,
it's not working very hard.

Jerry, KE7ER


On Tue, Dec 22, 2020 at 11:38 AM, <sv5fri@...> wrote:
I have measurement the Q12 transistor and the results are below
 
in receive mode C,B,E it was 0Volt
in transmit mode it was
C=13,2 volt
B=2,4 volt
E=0 volt
 
Maybe  something going wrong with Q12.


Jerry Gaffke
 

The node RX in the schematic only has 12 volts on it during receive,
the TX node has 12 volts on it only during transmit.

Note that Q12 is powered from RX, so it is only powered up during receive.
If the receiver is working fine, you do not have trouble with Q12.
Perhaps you are looking at a different transistor than Q12 when doing your measurements?
Perhaps you are looking at Q22, which is used only during transmit?

Whatever transistor you are looking at, it doesn't seem to be working.

Jerry, KE7ER


On Tue, Dec 22, 2020 at 12:12 PM, Jerry Gaffke wrote:
Yup, looks like either Q12 is not conducting, or perhaps R16 is shorted.
Probably a problem with Q12.

The emitter voltage should be around 0.7 volts less than the base voltage
when an NPN transistor is in the active region.
So should see around 1.7 volts at the Q12 emitter.

Seems odd that Q12 would fail.
Emitter (and collector) current when operating normally is only about 1.7volts/470ohms = 4ma,
it's not working very hard.

Jerry, KE7ER
Hide quoted text

 


On Tue, Dec 22, 2020 at 11:38 AM, <sv5fri@...> wrote:
I have measurement the Q12 transistor and the results are below
 
in receive mode C,B,E it was 0Volt
in transmit mode it was
C=13,2 volt
B=2,4 volt
E=0 volt
 
Maybe  something going wrong with Q12.


Rubens Kamimura
 

Hello everyone,

My uBITX v4 does not transmit strange waveforms.

Does anyone have the patterns (of the voltages and) of the AC and DC waveforms at the oscilloscope test points?

Merry Christmas and a less complicated 2021.

fraternal 73
Rubens
py2pvb

Em seg., 21 de dez. de 2020 às 10:28, <sv5fri@...> escreveu:

hello,

My bitx40 not transmit when use mic but when use CW transmit  normally  and my output power is 5watt on dummy load.
 
please any idea about my problem.

73 de Yiannis, SV5FRI


sv5fri@...
 

Dear Jerry,

I have check again the transistor and is Q12.
Also the receiver working very well


Yiannis , SV5FRI


Jerry Gaffke
 

Yiannis,

My mistake, you are correct.
I didn't read the title, assumed this was a uBitx.

It probably is a burned out Q12.

Note that Q12 is an MMBT3904, not the BC849 shown in the bitx40 schematic.
The MMBT3904 is a surface mount version of a 2n3904, which you could also use.
The leaded 2n3904 might be easier to obtain, and could be soldered to those nearby resistors..

The schematics show a BC849 only because Farhan 
did not have a symbol handy for an MMBT3904 when he was drawing up the schematics.
Though a BC849 would probably work, as would many other small NPN transistors.

Jerry, KE7ER


On Tue, Dec 22, 2020 at 03:41 PM, <sv5fri@...> wrote:
Dear Jerry,

I have check again the transistor and is Q12.
Also the receiver working very well


 

Yiannis,

The collector voltage is at supply and emmiter at 0 means transistor is not
working as Jerry said. Before you change it (2N3904 and not BC849) please
resolder the EBC junctions.. sometimes the solder gives way.

Raj


At 23/12/2020, you wrote:
Dear Jerry,

I have check again the transistor and is Q12.
Also the receiver working very well
[]


sv5fri@...
 

Hi again,

I have try to resolder the transistor without result.
 
Now I waiting the new transistor   where I have ordering

Thanks 

73 de Yiannis, SV5FRI


sv5fri@...
 

Hello,

Finally the problem with transmit fixed.
I have replace Q12 with a new and transmitting on ssb working perfect.