Bitx40 Circuit Diagnosis How To?
My first Bitx40 kit suffered through my attempts to learn to desolder smd components and various hack attempts.? I did the c113 removal and subsequent replacement, replacing the 100 ohm resistors with 220 ohm to reduce drift, L4 attempted repair and replacement, subsequent replacement with the Raduino and replacement of the audio potentiometer.? So there are many ways that this radio could be messed up.? There may be multiple problems.
The symptoms are no power on transmit: the relay clicks but no power shows on my swr/power meter, low audio volume and audio works for a few minutes then fades out.
I went through the Tips and Mods Q voltage table and compared my radio's voltage readings.? My radio has an odd difference in Q1-Q2-Q3 and Q4-Q5-Q6. Each of these sets are three transistors that should have the same reading or very close to it.? In my case Q1 voltage while receiving is significantly higher than the other two (Q2-Q3). Q4-Q5-Q6 have a similar pattern while transmitting with Q4 being about 23% higher than Q5 and Q6.
For example:
Collector Voltage Receiving, battery power at 12.2V
Q1: 10.73
Q2: 8.70
Q3: 8.70
According to the Tips sheet, these should all be at about 9.8V.
I have gone through the board looking for solder bridges and testing resistances but have pretty much reached the end of my knowledge of circuit diagnosis.? Any advice would be appreciated.
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Re: Possible PA low output problem. Problem SOLVED
That 900ma quiescent is an awful lot, the IRF510 would be getting hot. ?Hfsigs/WireUp recommends 100ma.
On Thu, Feb 9, 2017 at 10:27 pm, noel pakihi wrote: 4. Wound the PA bias trimpot to fully clockwise. ?Adjusted slowly to fully anticlockwise and got 0.9A ?with? ? ?no modulation. ?Speaking very loudly, output watt meter on ATU jumping between 5 and 7 watts into dummy load.
?
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Re: Possible PA low output problem. Problem SOLVED
even NXP make , the marking code is L44 or V4, while for vishay make it is L44
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Re: Possible PA low output problem. Problem SOLVED
The item used is? series diode pair? BAT54S. if NXP make, the marking code might be V4. ?if vishay ( ? )the code is L44 ? Perhaps the marking code depends on the maker of the device but part number is BAT54S.
?regards ?sarma ?vu3zmv
On Thursday, 9 February 2017 5:12 PM, Lawrence Galea <9h1avlaw@...> wrote:
Are you sure the forward resistance is 80K¦¸? In that case it's way way out and the diode is no good and it is no wonder that you were not getting enough output. Just for info, before writing this I took a bunch of 1N4148's from a bag that I had bought cheaply from ebay and checked them with a DVM on the diode test position. The forward reading is around 950 and no back resistance reading as they are silicon diodes. Someone else inanother comment said that the diode is marked IL440 which according to Vishay?consists of a GaAs infrared emitter optically coupled to a silicon planar triac chip with a non-zero crossing network.
I am sure that Farhan can clear this up
On Thu, Feb 9, 2017 at 4:03 AM, Randy Hall <listk7age@...> wrote: Tom
Outstanding. I would just leave the dual diode out and make it like your other radio.
Did you notice that you had carrier without the mic plugged in? I have seen a couple of postings about having carrier without the mic.
Keep up the good work and reporting your findings.
Randy, K7AGE
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Re: Possible PA low output problem. Problem SOLVED
Sharma and friends,
As I understand L4 marking is Bat54S , I also realised that there is no I(L) or l(L) because that line is the marking for the cathode!
Cheers
Raj
toggle quoted message
Show quoted text
At 10/02/2017, you wrote: vu2zap,
? thank god that it was not RD16 to cost you more.
Incidently , can you please readout the actual component? marking on the? BAT54S. I suppose, that? for example NXP, make device, L suffix id BAT54 and V4 suffix is BAT54S
sarma
vu3zmv
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Hello,
This email message is a notification to let you know that a file has been uploaded to the Files area of the [email protected]
group.
File: Fred1_Bitx40_Box.dxf
Uploaded By:
Fred Finster
Description:
First Rough Draft file of Fred1_Bitx40_Box 6" wide x 6" depth x 3" high for CNC Plasma burning. Review the .PDF or .SVG file to see the layout of the controls and the display. The speaker will mount in the Top Piece of the enclosure and will have the Metal Grill speaker cut out for a 4" speaker.
I have not created the TOP piece yet. I might move the Volume control and RF Gain Control up to the TOP of the enclosure box.
Welcome you changes and requests. You have the parts Kits in your hand. I don't have any and would like some help in measuring and deciding a layout for the controls.
Place comments here. /g/BITX20/message/21402?p=Created,,,20,2,0,0::recentpostdate%2Fsticky,,,20,2,60,4314155
You can access this file at the URL:
/g/BITX20/files/Enclosures_Metal_or_Plastic/Metal_Box_files/Metal%20Box%20Files/Fred1_Bitx40_Box.dxf
Cheers,
The Groups.io Team
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Good morning gentlemen.? I know that the PA of the BITX40 can handle 12V to 24V input.? My question is what can the rest of the board handle.? I have a 4 pack holder for 18650 batteries, and with them freshly charged they are at 16.5V output.? I don't want to burn up the board.? Does anyone know for sure what the circuits will handle?
Thanks Jason
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Re: Possible PA low output problem. Problem SOLVED
Yes, but RD16 are much more robust. Regards Lawrence
On Fri, Feb 10, 2017 at 1:00 PM, Mvs Sarma <mvssarma@...> wrote: vu2zap,
?thank god that it was not RD16 to cost you more. Incidently , can you please readout the actual component? marking on the? BAT54S. I suppose, that? for example NXP, make device, L suffix id BAT54 and V4 suffix is BAT54S sarma
vu3zmv
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Re: Possible PA low output problem. Problem SOLVED
vu2zap,
?thank god that it was not RD16 to cost you more. Incidently , can you please readout the actual component? marking on the? BAT54S. I suppose, that? for example NXP, make device, L suffix id BAT54 and V4 suffix is BAT54S sarma
vu3zmv
On Fri, Feb 10, 2017 at 12:28 PM, Raj vu2zap <vu2zap@...> wrote:
I had wierd problems and instability.
My 40M antenna unused for a long time was showing high SWR - a new Balun
fixed that issue. But not the power and instability in the IRF.
Finally figured out it was a bad cable that I had soldered from ant
output to a BNC linked to my antenna. This cost me an IRF!
That was that and the rig works beautifully as intended by
Farhan!
Never assume what LOOKS ok is OK but it may not be OK like my
case!!
Cheers
Raj
At 10/02/2017, you wrote:
Don't assume low power out is
due to a bad diode pair.
The two issues at Q13 mentioned below can both cause a "Possible PA
low output problem" that would be indistinguishable from a bad diode
pair in the modulator.? Also could be a a damaged IRF510, perhaps
from driving a high SWR load with 20v on the drain, or setting the bias
control beyond 100ma quiescent.? Or the microphone connector got
shorted out.? Or transformer wires shorted or broken.? Or about
half the remaining parts in the rig experiencing some sort of
failure.
On Thu, Feb 9, 2017 at 12:19 pm, Jerry Gaffke wrote:
- Regarding post 19730, there's a couple issues a bit further down that
we need to keep track of.
- 1)? Q13 is dissipating an awful lot of heat for a Sot23, may
need to adjust the emitter resistor there.
- 2)? Having your Bitx40 hooked up to an antenna while some nearby
antenna is transmitting at high power can blow Q13, may need Raj's dual
diode plus lamp fix.
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Re: Possible PA low output problem. Problem SOLVED
As a fix using 4148 diodes is ok.? If you want the same package then a BAV99 is dual 4148's in same smd footprint. BAV99 are high speed switching diodes.
The BAT54 pair used on the board are ultra high speed Schottky diodes with lower forward voltage than 4148. A suitable replacement Schottky diode would be 1N5711.
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Rob G4NQX
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Re: Possible PA low output problem. Problem SOLVED
Correction - his freq 7.1350mHz ?- my DDS 7.1352mHz ? ?Sorry
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Re: Possible PA low output problem. Problem SOLVED
Success! After completing mod had my first QSO. ?Distance 724km - time 1735 AEDT - his freq. 1.7350mHz - my DDS 7.1352mHz steady my ant 10m end fed with 9:1 un-un bal - My RST to him 59+ - his rst to me 36, some QRM/QRN, narrow bandwidth but rock solid. Cheers - Noel
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Wrong links in daily summary
I switched yesterday to the daily summary option for receiving group information - and as soon as the first message arrived I found that all the links contain an error, e.g.:
- the "https//" is not necessary and makes the link unusable. Is it groups.io or the BitX20 group issue?
--
73,
Greg DL3GJ FISTS #17694 / SKCC # 15874 / GQRP #15403
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Re: Possible PA low output problem. Problem SOLVED
I had wierd problems and instability.
My 40M antenna unused for a long time was showing high SWR - a new Balun
fixed that issue. But not the power and instability in the IRF.
Finally figured out it was a bad cable that I had soldered from ant
output to a BNC linked to my antenna. This cost me an IRF!
That was that and the rig works beautifully as intended by
Farhan!
Never assume what LOOKS ok is OK but it may not be OK like my
case!!
Cheers
Raj
At 10/02/2017, you wrote:
toggle quoted message
Show quoted text
Don't assume low power out is
due to a bad diode pair.
The two issues at Q13 mentioned below can both cause a "Possible PA
low output problem" that would be indistinguishable from a bad diode
pair in the modulator.? Also could be a a damaged IRF510, perhaps
from driving a high SWR load with 20v on the drain, or setting the bias
control beyond 100ma quiescent.? Or the microphone connector got
shorted out.? Or transformer wires shorted or broken.? Or about
half the remaining parts in the rig experiencing some sort of
failure.
On Thu, Feb 9, 2017 at 12:19 pm, Jerry Gaffke wrote:
- Regarding post 19730, there's a couple issues a bit further down that
we need to keep track of.
- 1)? Q13 is dissipating an awful lot of heat for a Sot23, may
need to adjust the emitter resistor there.
- 2)? Having your Bitx40 hooked up to an antenna while some nearby
antenna is transmitting at high power can blow Q13, may need Raj's dual
diode plus lamp fix.
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Re: Possible PA low output problem. Problem SOLVED
Jerry, I am back at the farm this week. Counting the days to Monday so I
can be reunited with my pup and Bitx40!!
I have received some 3904 SMTs, I propose to put one parallel on top of
the existing Q13 and see how much that helps!
I found an old commercial Motorola Mic in my junk. Just 4 wires and seems
perfectly suited to this board. These mics
have built in mic preamp and thats helping me drive the final amp crazy!
The IRF draws more than 1 amp and power meter
is showing 10W. Must be distorting but I did not have time to check with
scope. Plan to have a QSO with vu2pop
for a critical report on audio etc. this coming week.
The mic seems something like this but the model number is worn out.
I still on analog VFO and it's holding 10-20Hz drift.
Cheers
Raj
At 10/02/2017, you wrote:
toggle quoted message
Show quoted text
Regarding post 19730, there's a
couple issues a bit further down that we need to keep track of.
1)? Q13 is dissipating an awful lot of heat for a Sot23, may need to
adjust the emitter resistor there.
2)? Having your Bitx40 hooked up to an antenna while some nearby
antenna is transmitting at high power can blow Q13, may need Raj's dual
diode plus lamp fix.
On Thu, Feb 9, 2017 at 12:04 pm, Jerry Gaffke wrote:
- post 19730
?
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Re: Possible PA low output problem. Problem SOLVED
What BITX40 needs is a BAT54S - this version has two diodes in opposite
direction. Anode of one connected to cathode of the other.
Marking may be KL4.. or Vishay L44.. or even ?V4
As some one reported IL440 - looks like Vishay, the extra letters and
digits I and 0 may refer to some manufacture details!
Raj
At 10/02/2017, you wrote:
toggle quoted message
Show quoted text
You'll never see BAT54 printed
on a SOT23, that wouldn't fit.? So they choose an arbitrary 2 or
3? character code to distinguish it from all the other SOT23
products they make.? But there are far more SOT23 types than there
are codes, and different manufacturers that build BAT54's will choose
different codes.? We've seen this before on the 2n3904 transistors,
read post 19730.? The ohmmeter readings taken of the bad part
suggest that it really is a dual diode.
My guess is that the correct part is getting stuffed, but at least one
slipped by QC at the factory, got damaged when soldering it down, or by
excessive current now that the 100 ohm pot has been removed.? If it
is excessive current, perhaps adding a resistor in series with C106 would
fix it.? Adding back R106 if it isn't needed for establishing
modulator balance would best be avoided.? Not yet clear if this dual
diode was a problem on more than one unit.
Jerry, KE7ER
On Thu, Feb 9, 2017 at 11:23 am, John Smith wrote:
- I haven't seen anything marked BAT54.
?
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Re: Possible PA low output problem. Problem SOLVED
My DDS BITX40 is now putting out over 5 watts. 1. Ripped out the double diode. 2. Attached 2x ?1N4148 ?diodes (any 2) with the ring ends connected to the empty solder spots for the right orientation. 3. Joined the other ends of the diodes together and soldered them into the empty hole for the missing trimpot ? ?- centre pin hole. 4. Wound the PA bias trimpot to fully clockwise. ?Adjusted slowly to fully anticlockwise and got 0.9A ?with? ? ?no modulation. ?Speaking very loudly, output watt meter on ATU jumping between 5 and 7 watts into dummy load. That's it. ?No more no less Cheers - ?Noel
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Re: transmitting CW with Raduino Bitx40?
Al, In the Tips n Mods pdf in the first folder in the files section is the wiring colours and their use with the extra code.? It's worth downloading as there's plenty of stuff taken from all the posts since the BitX40 started. ?? In case you don't want to, it's as follows :-
It uses a pushbutton on A3 pin to select
using tap, press, double tap method. Wiring colours used are Brown = CW??
Key ? Red? =
Calibrate and CW tone when in CW Orange = Pushbutton to select Dual
vfo¡¯s,? RIT,? CW Blue = PTT Sense Black = LPF Select ¨C not catered for yet
--
Rob G4NQX
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Re: Raduino USB connector
Make sure your problem isn't caused by the metal fingers in the mini-USB socket. See my post? /g/BITX20/topic/if_raduino_programming_cable/4334102?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,40,4334102?? 73 AL
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Has anyone experienced a problem finding a suitable USB cable for the Raduino? I have several cables here with me and none of them fit. I have more at home but won't be there for another couple of months.
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Raj vu2zap
Greg DL3GJ