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Finally got back to troubleshooting my BITX40 transmitter failure. Using Randy K7AGE voltage chart, the only stage that had bad DC voltages was Q9, with just a few milivolts on the base, emitter and collector. What I don't understand is that Q9 is used in both transmit and receive and yet my BITX40 receiver seems to be working.
Any thoughts, and also any suggestions on how to "test" Q9?
Thanks, Roy WA0YMH
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Hi Roy
I had a problem of the Si5351 getting to the mixer. Turned out my Q9 was shot. I happened to have some on hand.
73
Ken VA3ABN
On Mon, Mar 20, 2017 at 6:51 PM, Roy Appleton <twelveoclockhigh@...> wrote: Finally got back to troubleshooting my BITX40 transmitter failure. Using Randy K7AGE voltage chart, the only stage that had bad DC voltages was Q9, with just a few milivolts on the base, emitter and collector. What I don't understand is that Q9 is used in both transmit and receive and yet my BITX40 receiver seems to be working.
Any thoughts, and also any suggestions on how to "test" Q9?
Thanks, Roy WA0YMH
|
Also Ron, the transistor is a 2N3904 but in a SMD package as a? mmbt3904.
73 Ken
On Mon, Mar 20, 2017 at 6:51 PM, Roy Appleton <twelveoclockhigh@...> wrote: Finally got back to troubleshooting my BITX40 transmitter failure. Using Randy K7AGE voltage chart, the only stage that had bad DC voltages was Q9, with just a few milivolts on the base, emitter and collector. What I don't understand is that Q9 is used in both transmit and receive and yet my BITX40 receiver seems to be working.
Any thoughts, and also any suggestions on how to "test" Q9?
Thanks, Roy WA0YMH
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Farhan had to use the BC849C footprint in the schematic, but the part is actuallya? mmbt3904.
73 Ken
On Mon, Mar 20, 2017 at 8:43 PM, Roy Appleton <twelveoclockhigh@...> wrote: Oops, I just ordered a 100 BC849C off of eBay! Back to the drawing board!
Roy WA0YMH
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Ken, thanks for the info, now I'll have a 100? mmbt3904 also!!! ?:-))
Roy, WA0YMH
On Mar 20, 2017 7:50 PM, "Ken" < chase8043@...> wrote: Farhan had to use the BC849C footprint in the schematic, but the part is actuallya? mmbt3904.
73 Ken
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IF Q9 is bad some RF from Raduino will get through to the next transistor
and RX will work.
I had a 1K open in the 3rd VFO stage and 3904 blown!
Raj, vu2zap
At 21/03/2017, you wrote:
toggle quoted message
Show quoted text
Hi Roy
I had a problem of the Si5351 getting to the mixer. Turned out my Q9 was
shot. I happened to have some on hand.
73
Ken VA3ABN
On Mon, Mar 20, 2017 at 6:51 PM, Roy Appleton
<
twelveoclockhigh@...> wrote:
- Finally got back to troubleshooting my BITX40 transmitter failure.
Using Randy K7AGE voltage chart, the only stage that had bad DC voltages
was Q9, with just a few milivolts on the base, emitter and collector.
What I don't understand is that Q9 is used in both transmit and receive
and yet my BITX40 receiver seems to be working.
- Any thoughts, and also any suggestions on how to "test"
Q9?
- Thanks,
- Roy
- WA0YMH
|
I too had some trouble getting external VFO sigs through to the mixer.?? I suspected a bad Q9, but turned out that the transistor was good. (Check the voltages without the Raduino connected.)?? You might have to remove C91 and/or C92.?? On my 40 meter rig, with an analog VFO running at around 5 MHz, I had to remove C91 to get sufficient signal through to the mixer.? On my 60 meter BITX, with an Si5351 running at around 17 MHz, I removed BOTH C91 and C92.?? 73? Bill? N2CQR
On Tuesday, March 21, 2017 12:29 AM, Raj vu2zap <vu2zap@...> wrote:
IF Q9 is bad some RF from Raduino will get through to the next transistor
and RX will work.
I had a 1K open in the 3rd VFO stage and 3904 blown!
Raj, vu2zap
At 21/03/2017, you wrote:
Hi Roy
I had a problem of the Si5351 getting to the mixer. Turned out my Q9 was
shot. I happened to have some on hand.
73
Ken VA3ABN
On Mon, Mar 20, 2017 at 6:51 PM, Roy Appleton
<
twelveoclockhigh@...> wrote:
- Finally got back to troubleshooting my BITX40 transmitter failure.
Using Randy K7AGE voltage chart, the only stage that had bad DC voltages
was Q9, with just a few milivolts on the base, emitter and collector.
What I don't understand is that Q9 is used in both transmit and receive
and yet my BITX40 receiver seems to be working.
- Any thoughts, and also any suggestions on how to "test"
Q9?
- Thanks,
- Roy
- WA0YMH
|
Bill you are right!
I have had such experiences when RF is present the meters show low or
wrong voltages. In BITX40 also, I shorted the external VFO pins and then
checked and later found fault at the 3rd stage.
Disconnect the external OSC and then check voltages Roy.
Raj
At 21/03/2017, you wrote:
toggle quoted message
Show quoted text
I too had some trouble getting
external VFO sigs through to the mixer.?? I suspected a bad Q9,
but turned out that the transistor was good. (Check the voltages without
the Raduino connected.)?? You might have to remove C91 and/or
C92.?? On my 40 meter rig, with an analog VFO running at around
5 MHz, I had to remove C91 to get sufficient signal through to the
mixer.? On my 60 meter BITX, with an Si5351 running at around 17
MHz, I removed BOTH C91 and C92.?? 73? Bill? N2CQR
On Tuesday, March 21, 2017 12:29 AM,
Raj vu2zap <vu2zap@...> wrote:
IF Q9 is bad some RF from Raduino will get through to the next transistor
and RX will work.
I had a 1K open in the 3rd VFO stage and 3904 blown!
Raj, vu2zap
At 21/03/2017, you wrote:
Hi Roy
I had a problem of the Si5351 getting to the mixer. Turned out my Q9 was
shot. I happened to have some on hand.
73
Ken VA3ABN
On Mon, Mar 20, 2017 at 6:51 PM, Roy Appleton
<
twelveoclockhigh@...> wrote:
- Finally got back to troubleshooting my BITX40 transmitter failure.
Using Randy K7AGE voltage chart, the only stage that had bad DC voltages
was Q9, with just a few milivolts on the base, emitter and collector.
What I don't understand is that Q9 is used in both transmit and receive
and yet my BITX40 receiver seems to be working.
- Any thoughts, and also any suggestions on how to "test"
Q9?
- Thanks,
- Roy
- WA0YMH
|
Raj vu2zap