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Bitex40 power output.

 

Dear
In my bitx40 during testing upto three qso power output about 7 watt .Then suddenly no output ,when i measure drain current of IRF 510 on mic disconnect conditions it was 90ma and with speaking current about 110 ma.
I thought IRF may qrt .
I changed new irf 510 (ST make) adjusted rvi1preset in mic out condion drain current was 70 ma at maximum rvi1 position and when i speak current s only 120 ma .my sx200 swr/power meter at 20w range reading is 3to4watt.
is it correct or what is to be done to raise the power.
Your suggestions welcome.
Thanks in advance.
73s
Soundar
VU2RJW.
 

on tx, when you are not speaking into the mic, the current.draw of the PA power line should be about 100ma. adjust RV1 for that much current.
- f


On 28-Oct-2016 10:55 am, "'Soundararajan Ra.' vu2rjw@... [BITX20]" <BITX20@...> wrote:
?

Dear
In my bitx40 during testing upto three qso power output about 7 watt .Then suddenly no output ,when i measure drain current of IRF 510 on mic disconnect conditions it was 90ma and with speaking current about 110 ma.
I thought IRF may qrt .
I changed new irf 510 (ST make) adjusted rvi1preset in mic out condion drain current was 70 ma at maximum rvi1 position and when i speak current s only 120 ma .my sx200 swr/power meter at 20w range reading is 3to4watt.
is it correct or what is to be done to raise the power.
Your suggestions welcome.
Thanks in advance.
73s
Soundar
VU2RJW.
 

Thanks for the reply .
RV1 is in maximum position ,but current is not raising above 70 ma gate source voltage is 5 volt.
Soundar.


On Oct 28, 2016 11:24 AM, "Ashhar Farhan farhanbox@... [BITX20]" <BITX20@...> wrote:
?

on tx, when you are not speaking into the mic, the current.draw of the PA power line should be about 100ma. adjust RV1 for that much current.
- f


On 28-Oct-2016 10:55 am, "'Soundararajan Ra.' vu2rjw@... [BITX20]" <BITX20@...> wrote:
?

Dear
In my bitx40 during testing upto three qso power output about 7 watt .Then suddenly no output ,when i measure drain current of IRF 510 on mic disconnect conditions it was 90ma and with speaking current about 110 ma.
I thought IRF may qrt .
I changed new irf 510 (ST make) adjusted rvi1preset in mic out condion drain current was 70 ma at maximum rvi1 position and when i speak current s only 120 ma .my sx200 swr/power meter at 20w range reading is 3to4watt.
is it correct or what is to be done to raise the power.
Your suggestions welcome.
Thanks in advance.
73s
Soundar
VU2RJW.
 



On Thu, Aug 17, 2017 at 11:29 AM, Soundararajan Ra. <vu2rjw@...> wrote:
Dear om.Farhan
I got one bitx40 nearly a years back and output power decreased day by day .
Three times replaced Q13,14 and 15 but no result
Finally found that? the R141? resistor value going on increasing and? found 123ohms as on today.
?connected a lead type 10E? CF resistor? across R141 and getting good power output.
With 13.4 volt DC input my Diamond SX 200 showing the reading 12 watt maximum forward power in 20 w range.
I had lot of discussion with Raj in this process.

Thank you Raj.
DE
Soundar
VU2RJW
?


On Fri, Oct 28, 2016 at 11:47 AM, Soundararajan Ra. <vu2rjw@...> wrote:

Thanks for the reply .
RV1 is in maximum position ,but current is not raising above 70 ma gate source voltage is 5 volt.
Soundar.


On Oct 28, 2016 11:24 AM, "Ashhar Farhan farhanbox@... [BITX20]" <BITX20@...> wrote:
?

on tx, when you are not speaking into the mic, the current.draw of the PA power line should be about 100ma. adjust RV1 for that much current.
- f


On 28-Oct-2016 10:55 am, "'Soundararajan Ra.' vu2rjw@... [BITX20]" <BITX20@...> wrote:
?

Dear
In my bitx40 during testing upto three qso power output about 7 watt .Then suddenly no output ,when i measure drain current of IRF 510 on mic disconnect conditions it was 90ma and with speaking current about 110 ma.
I thought IRF may qrt .
I changed new irf 510 (ST make) adjusted rvi1preset in mic out condion drain current was 70 ma at maximum rvi1 position and when i speak current s only 120 ma .my sx200 swr/power meter at 20w range reading is 3to4watt.
is it correct or what is to be done to raise the power.
Your suggestions welcome.
Thanks in advance.
73s
Soundar
VU2RJW.

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Soundar VU2RJW wrote...

Three times replaced Q13,14 and 15 but no result
Finally found that the R141 resistor value going
on increasing and found 123ohms as on today.
Thanks for posting that. I just checked R141. According
to the drawing, it should be 10 ohms. I'm measuring
almost 60 ohms there. It won't be surface mount, but
I'll see if I can find anything close to 10 ohms here.

Bonus... R141 has a "burnt" look to it and I can't
read the number on it.

Good timing. My hot air soldering station finally
showed up two days ago. That should make things a bit
easier.

PS - I previously replaced Q15 and then Q13 (with a
TO-92 2N3904) with the same results as you. I do
have a 2N2219A (Q14) here but hopefully it isn't
needed. R142 looks OK (close to 1K) but R143 reads
low (300 ohms or so) but that's measured in the
circuit with it still connected from the base to
the collector.

--
73 Keith VE7GDH
Karl Schwab
 

I am trying to trouble shoot low power output on my friends BITX-40 that he built a couple months ago (latest version?) with a VOM after he lost full power.? It now, barely, moves a low range watt meter!? I bought one also at the same time and mine is working fine.? I did the voltage checks and toroid connections, that Jerry, KE7ER, had posted and got seemingly, similar?results.? My friend had replaced Q13 with a 2N3904, but no change.?What might I (we) do next?? Receive, however, is good.? 73, Karl, KO8S




On Thursday, August 17, 2017 12:05 PM, Keith VE7GDH <ve7gdh@...> wrote:


Soundar VU2RJW wrote...

> Three times replaced Q13,14 and 15 but no result
> Finally found that? the R141? resistor value going
> on increasing and found 123ohms as on today.

Thanks for posting that. I just checked R141. According
to the drawing, it should be 10 ohms. I'm measuring
almost 60 ohms there. It won't be surface mount, but
I'll see if I can find anything close to 10 ohms here.

Bonus... R141 has a "burnt" look to it and I can't
read the number on it.

Good timing. My hot air soldering station finally
showed up two days ago. That should make things a bit
easier.

PS - I previously replaced Q15 and then Q13 (with a
TO-92 2N3904) with the same results as you. I do
have a 2N2219A (Q14) here but hopefully it isn't
needed. R142 looks OK (close to 1K) but R143 reads
low (300 ohms or so) but that's measured in the
circuit with it still connected from the base to
the collector.

--
73 Keith VE7GDH
 

Do check R141 with that VOM, see if it is still 10 ohms. ?It runs awfully hot, have had several reports of it burning out.

I recorded AC measurements with a scope here: ?/g/BITX20/message/22764
and here: ?/g/BITX20/message/21027
Randy did this list of DC readings: ? ?/g/BITX20/files/K7AGE/BITX40%20Voltage%20Measurments.pdf
If you just have a VOM, you're probably not checking my AC numbers. ?

The DC readings should be radically different than those on a good rig if Q13, Q14, Q15 blew or if an emitter resistor went out.

Check current from "12v PA" with PTT down, quiescent should be around 100ma, if you don't see that then the IRF510 or something
between its drain and the 12v supply is blown. ?Or the ~4v bias supply into the gate has failed. ?

Be careful about tweaking the IRF510 gate bias voltage at RV1
Rotating counterclockwise increases the bias and thus the IRF510's drain current to its recommended quiescent of 100ma.
which is counterintuitive. ?You will smoke the IR510 if you turn that pot a bit too far.
?
The AC signals after Q13 are plenty big to see with a simple diode RF probe into a VOM.

Here's a compendium of various troublshooting and modding issues,
though I think the above pretty well covers your situation.
? ??/g/BITX20/message/31456

Jerry


On Thu, Aug 17, 2017 at 12:55 pm, Karl Schwab wrote:
I am trying to trouble shoot low power output on my friends BITX-40 that he built a couple months ago (latest version?) with a VOM after he lost full power.? It now, barely, moves a low range watt meter!? I bought one also at the same time and mine is working fine.? I did the voltage checks and toroid connections, that Jerry, KE7ER, had posted and got seemingly, similar?results.? My friend had replaced Q13 with a 2N3904, but no change.?What might I (we) do next?? Receive, however, is good.? 73, Karl, KO8S
?
 

Karl KO8S wrote…

I am trying to trouble shoot low power output on my friends BITX-40 that he built a couple months ago (latest version?) with a VOM after he lost full power.
Thanks to Soundar VU2RJW, I looked at the 10 ohm R141 and found it had gone to a higher resistance. I replaced it and I'm back on the air again. I was just about to post a note with more details and a few pics.

--
73 Keith VE7GDH
Karl Schwab
 

Yes gentlemen; checking resistor R141 to be 10 ohms, is one of the first things that I did and it checked okay.? Please keep the trouble shooting ideas coming, I really would like to get this BITX-40 on the air for this Sunday at 7:00p on 7.277!? 73, Karl, KO8S


On Thursday, August 17, 2017 7:32 PM, Keith VE7GDH <ve7gdh@...> wrote:


Karl KO8S wrote…

> I am trying to trouble shoot low power output on my friends BITX-40 that he built a couple months ago (latest version?) with a VOM after he lost full power.

Thanks to Soundar VU2RJW, I looked at the 10 ohm R141 and found it had gone to a higher resistance. I replaced it and I'm back on the air again. I was just about to post a note with more details and a few pics.

--
73 Keith VE7GDH
 

Hi Karl,
I had the same problem with my 40 and after pulling out the transformer, checking all voltages etc, I found that it was the VFO injection. ?Check the voltages on Q7, Q8, Q9 against the chart. ?I think on mine Q8 was dead.
Andy
KM4TRT
Karl Schwab
 

Thanks Andy, we'll try what you found.? 73, Karl, KO8S


On Saturday, August 19, 2017 10:16 AM, KM4TRT via Groups.Io <garello@...> wrote:


Hi Karl,
I had the same problem with my 40 and after pulling out the transformer, checking all voltages etc, I found that it was the VFO injection. ?Check the voltages on Q7, Q8, Q9 against the chart. ?I think on mine Q8 was dead.
Andy
KM4TRT


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