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By now a number of builders have reported low output. This seems to be a distinct trouble as opposed to being a one-off report. Let's analyze and fix this.
I would start my asking if anyone who has seen just ?2 watts output and has an oscilloscope to report the following while transmitting a loud 'HAAAAALOOOWW!' 1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor) 2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510 3. RF peak to peak at the drain of IRF510
let's go from there
- f
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Dear Farthan
my RF out is 2 watt the following are voltage Pk to Pk with CRO
1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor) 450 mv
2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510 is 85 mv
3. RF peak to peak at the drain of IRF510 is 1.5 volt 4.Driver Q14 base 250 mv collector 500 mv 5.pre driver transister? q13 base 20 mv collector 1100mv
transformert5 & t6 checked for short circuit of winging and cleared with tooth pick.
Till no improvement
idle irf current increased to 200 ma
Adjusted 100 R R136 pot to maximum at that time power output 2 watt .
Soundar
vu2rjw
On Tue, Nov 22, 2016 at 9:12 AM, Ashhar Farhan farhanbox@... [BITX20] <BITX20@...> wrote:
?
By now a number of builders have reported low output. This seems to be a distinct trouble as opposed to being a one-off report. Let's analyze and fix this.
I would start my asking if anyone who has seen just ?2 watts output and has an oscilloscope to report the following while transmitting a loud 'HAAAAALOOOWW!' 1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor) 2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510 3. RF peak to peak at the drain of IRF510
let's go from there
- f
|
the predriver is the culprit. carefully pry away the wires of the predriver's transformer, they are probably shorting somewhere.
- f
On Tue, Nov 22, 2016 at 1:07 PM, 'Soundararajan Ra.' vu2rjw@... [BITX20] <BITX20@...> wrote:
?
Dear Farthan
my RF out is 2 watt the following are voltage Pk to Pk with CRO
1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor) 450 mv
2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510 is 85 mv
3. RF peak to peak at the drain of IRF510 is 1.5 volt 4.Driver Q14 base 250 mv collector 500 mv 5.pre driver transister? q13 base 20 mv collector 1100mv
transformert5 & t6 checked for short circuit of winging and cleared with tooth pick.
Till no improvement
idle irf current increased to 200 ma
Adjusted 100 R R136 pot to maximum at that time power output 2 watt .
Soundar
vu2rjw
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q13 collector voltage is 1.1 volt?
c134 is connected in mid winding voltage at the point is 550 mv checked for short circuit find no shorting pre dreiver base voltage is 20 mv is it correct. voltage at c6 is 65 mv and c1li junction is 20 mv
On Tue, Nov 22, 2016 at 1:14 PM, Ashhar Farhan farhanbox@... [BITX20] <BITX20@...> wrote:
?
the predriver is the culprit. carefully pry away the wires of the predriver's transformer, they are probably shorting somewhere.
- f
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Farhan and friends,
I would additionally suspect an SMD cap going bad - just in case. You can
check the RF voltage at both ends of the coupling caps in the power 3
stages and it must be almost the same.
Raj
At 22/11/2016, you wrote:
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?
q13 collector voltage is 1.1 volt????
c134 is connected in mid winding voltage at the point is 550 mv checked
for short circuit find no shorting
pre dreiver base voltage is 20 mv is it correct.
voltage at c6 is 65 mv and c1li junction is 20 mv
On Tue, Nov 22, 2016 at 1:14 PM, Ashhar Farhan
farhanbox@... [BITX20]
<BITX20@...
> wrote:
- ????
- the predriver is the culprit. carefully pry away the wires of the
predriver's transformer, they are probably shorting somewhere.
- - f
- On Tue, Nov 22, 2016 at 1:07 PM, 'Soundararajan Ra.'
vu2rjw@... [BITX20]
<BITX20@...
> wrote:
- ????
- Dear Farthan
- my RF out is 2 watt the following are voltage Pk to Pk with CRO
- 1. RF peak to peak at hot end of the R136, (the shiny preset near the
driver transistor) 450 mv
- 2. RF peak to peak at the R150, the 47 ohms resistor at the gate of
IRF510 is 85 mv
- 3. RF peak to peak at the drain of IRF510 is 1.5 volt
- 4.Driver Q14 base 250 mv collector 500 mv
- 5.pre driver transister???? q13 base 20 mv collector
1100mv
- transformert5 & t6 checked for short circuit of winging and
cleared with tooth pick.
- Till no improvement
- idle irf current increased to 200 ma
- Adjusted 100 R R136 pot to maximum at that time power output 2 watt
.
- Soundar
- vu2rjw
- On Tue, Nov 22, 2016 at 9:12 AM, Ashhar Farhan
farhanbox@... [BITX20]
<BITX20@...
> wrote:
- ????
- By now a number of builders have reported low output. This seems to
be a distinct trouble as opposed to being a one-off report. Let's analyze
and fix this.
- I would start my asking if anyone who has seen just ??? 2 watts output
and has an oscilloscope to report the following while transmitting a loud
'HAAAAALOOOWW!'
- 1. RF peak to peak at hot end of the R136, (the shiny preset near the
driver transistor)
- 2. RF peak to peak at the R150, the 47 ohms resistor at the gate of
IRF510
- 3. RF peak to peak at the drain of IRF510
- let's go from there
- - f
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AsharNow that you mention it ... "?RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor)" ...
I think that I resolved an issue that I was having with my BITX 40 meter version 3.? The receive is great but the transmit was?unintelligible.? I set it up with a dummy?load on the antenna, shorted out the transmit switch, and put the mike by an AM BC radio (on my favorite station).? Just experimenting, I found a small adjustment to R136 fixed the problem. ?
Now, as to the power output, I did see that the BITX was drawing about a half amp at 12 volts (with the famous?'HAAAAALOOOWW!')?That's?6 or 7 watts, conforming to the specs. ?
I have an?oscilloscope, so I will measure the peak to peak tonight.? I?can't wait to install the rig in the enclosure!
W3TTT Joe ?
On Mon, Nov 21, 2016 at 10:42 PM, Ashhar Farhan farhanbox@... [BITX20] <BITX20@...> wrote:
?
By now a number of builders have reported low output. This seems to be a distinct trouble as opposed to being a one-off report. Let's analyze and fix this.
I would start my asking if anyone who has seen just ?2 watts output and has an oscilloscope to report the following while transmitting a loud 'HAAAAALOOOWW!' 1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor) 2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510 3. RF peak to peak at the drain of IRF510
let's go from there
- f
|
Tried for short circuit in the predriver transformer but no luck .
I am getting 1.1. Volt at q13 collector but at center tape suppose to 1.5 instead getting 700 to 800 mv ..1mfd capacitor c134 alright .
Today planning to remove the transformer and rew
ound with new wire and see any raise in power.
On Nov 23, 2016 1:14 AM, "Baruch Atta baruchatta@... [BITX20]" < BITX20@...> wrote:
?
AsharNow that you mention it ... "?RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor)" ...
I think that I resolved an issue that I was having with my BITX 40 meter version 3.? The receive is great but the transmit was?unintelligible.? I set it up with a dummy?load on the antenna, shorted out the transmit switch, and put the mike by an AM BC radio (on my favorite station).? Just experimenting, I found a small adjustment to R136 fixed the problem. ?
Now, as to the power output, I did see that the BITX was drawing about a half amp at 12 volts (with the famous?'HAAAAALOOOWW!')?That's?6 or 7 watts, conforming to the specs. ?
I have an?oscilloscope, so I will measure the peak to peak tonight.? I?can't wait to install the rig in the enclosure!
W3TTT Joe ?
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"Baruch Atta baruchatta@... [BITX20]" <BITX20@...> wrote:
> Ashar
> I think that I resolved an issue
> Now, as to the power output, I did see that the BITX was drawing about a half amp at 12 volts (with the famous?'HAAAAALOOOWW!')?That's?6 or 7 watts, conforming to the specs. ?
>
Class 'A' amp as in BITX, is only approx 50℅ efficient,
Baruch Atta, so that might be 50% of 6 watt! :D
+ there's additional loss in heat that with 510.
& not to mention exiter also consumes some. :P
?++++++++++++++
Mr. F is 'on the way'? for push-pull...
Sun getting more bad day by day? :(
++++++++++++++
Soundararajan, it's just 3 to max 4-5 turns on slim-pencil. Short it if 510 starts ringing...
U replaced / reused 5 mm ECM from mobile- earhone? 10mm available now a days in VU R all low gain type, here thousands to throw frm my junk,
Can also be paralled...
Did plot BPF wth external signal source?
As 'Guru' say better to find reason for low...
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sandeep,
the bitx is AB1. not class A
On 23-Nov-2016 10:55 am, "Sandeep Lohia sandeeplohia12@... [BITX20]" < BITX20@...> wrote:
?
"Baruch Atta baruchatta@... [BITX20]" <BITX20@...> wrote:
> Ashar
> I think that I resolved an issue
> Now, as to the power output, I did see that the BITX was drawing about a half amp at 12 volts (with the famous?'HAAAAALOOOWW!')?That's?6 or 7 watts, conforming to the specs. ?
>
Class 'A' amp as in BITX, is only approx 50℅ efficient,
Baruch Atta, so that might be 50% of 6 watt! :D
+ there's additional loss in heat that with 510.
& not to mention exiter also consumes some. :P
?++++++++++++++
Mr. F is 'on the way'? for push-pull...
Sun getting more bad day by day? :(
++++++++++++++
Soundararajan, it's just 3 to max 4-5 turns on slim-pencil. Short it if 510 starts ringing...
U replaced / reused 5 mm ECM from mobile- earhone? 10mm available now a days in VU R all low gain type, here thousands to throw frm my junk,
Can also be paralled...
Did plot BPF wth external signal source?
As 'Guru' say better to find reason for low...
|
I performed some transmissions test Yesterday night, I can confirm the values declared: 100 - 90 mA in RX mode, almost 385 mA pressing PTT and over 1.1 A when modulate. Clear audio. I measure over 7 W output on my wattmeter. Fine job. I planning to add a fan to IRF510 for temperature controll. Thanks. Giuseppe, ik8yfw
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Dear mr farhan Realy unble to solve my problem removed predriver transformer and rewound . Ground to collector 1.1 v collector to centret tap .5 volt (both supposed to be added and to get 1.5 v) But CT to ground is .5 volt (c134). At 100R preset getting .5 v so insufficient drive voltage . Getting 2 watt out put at antenna. I am blinking ,what next 7 do. One more option for me is to order one more kit. Soundar Vu2rjw. On Nov 23, 2016 4:41 PM, "ik8yfw@... [BITX20]" <BITX20@...> wrote:
I performed some transmissions test Yesterday night, I can confirm the
values declared: 100 - 90 mA in RX mode, almost 385 mA pressing PTT and
over 1.1 A when modulate. Clear audio. I measure over 7 W output on my
wattmeter. Fine job. I planning to add a fan to IRF510 for temperature
controll. Thanks. Giuseppe, ik8yfw
[Non-text portions of this message have been removed]
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Recieved my bitx40 about a week ago. Assembled, it recieves pretty well but is at the bottom of the band. 7.000 up to around 7.200. Since it doesnt tx cw, is there a way to adjust rx/tx to the upper portion of the band (in the US) where phone is? Currently only get about 75kH of phone portion of the band (7.125-7.200)
Also, tx power is only a few hundred mW at a regulated 12v. Saw this on my watt meter amd confirmed it with a dummy load and my oscilloscope. Any suggestions on cause?
Thanks.?
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I followed the suggestion in a post here. I carefully adjusted C93 clockwise and now I have 7080-7300. I don’t know if that’s how its supposed to be done and I am still getting the mic hooked up to try transmit. But I am getting the receive coverage I want. If I have to, I can just change it back. Mark K3MRK ? ?
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From: BITX20@... [mailto:BITX20@...]
Sent: Thursday, December 01, 2016 8:51 PM
To: BITX20@...
Subject: [BITX20] Re: LOW tx output? ? Recieved my bitx40 about a week ago. Assembled, it recieves pretty well but is at the bottom of the band. 7.000 up to around 7.200. Since it doesnt tx cw, is there a way to adjust rx/tx to the upper portion of the band (in the US) where phone is? Currently only get about 75kH of phone portion of the band (7.125-7.200) Also, tx power is only a few hundred mW at a regulated 12v. Saw this on my watt meter amd confirmed it with a dummy load and my oscilloscope. Any suggestions on cause?
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Anymore ideas on the low power problem?
Only getting milli-watts. Adjustment of the bias pot seems to have no effect on the supply current.
A loud HALLO only gets a small flicker on the power meter.
I've looked at the driver transfomers. I can't see any shorted leads Any chance of a stage by stage diagnostic aid please? I don't have ready access to a scope so DC measurements only preferred or a ?pointer towards a simple RF probe I can build.
DDS VFO ready to go.
Regards
Mike.. G4KXQ
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toggle quoted message
Show quoted text
On Wed, Dec 7, 2016 at 2:04 PM, mikewogden@... [BITX20] <BITX20@...> wrote:
?
Anymore ideas on the low power problem?
Only getting milli-watts. Adjustment of the bias pot seems to have no effect on the supply current.
A loud HALLO only gets a small flicker on the power meter.
I've looked at the driver transfomers. I can't see any shorted leads Any chance of a stage by stage diagnostic aid please? I don't have ready access to a scope so DC measurements only preferred or a ?pointer towards a simple RF probe I can build.
DDS VFO ready to go.
Regards
Mike.. G4KXQ
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Soundararajan Ra.
Raj vu2zap