Mario,
From the links and your description, I assume that you have an Amatuerradiokits case with the audio amplifier.  If that is correct, then the data that I have shows a TA4225 (not a TA4425) audio amp IC as the audio amp.  That is a 5 terminal device, not 3.  That board is very cramped, so it could be that the silk screening is really pointing out the TA4225 5 pin socket and not the 3 holes that are close by.

Attached are the 2 pdf files that I have for the audio amp.

My guess is that the 3 hole location is for the onboard "volume" control that is really a maximum volume control as the front panel volume control is used to adjust the volume in operation.  You should have a blue 3 terminal variable resistor that goes into that location.

Please verify the above before you start any modifications or soldering.  If you need more help, I would suggest that you post a picture of the board and the location so that we can better help you.

73
Evan
AC9TU

Hello Mark,

Am 16.08.2020 04:26, schrieb Mark - N7EKU:

Hi Mario,
Go to the Wiki section of this website, then to uBitx Topics, then
uBitx Assembly. We hide it really well here ;-)

I found this one [1]. The wiring diagram is for ubitx v5. I do own an ubitx v4. What is the difference between the v4 and the v5?

You may also need to do a small fix on the audio amp since I think
most v4's have biasing issues there. Check this post and the
accompanying thread as it covers it well:
https://groups.io/g/BITX20/message/53356

thanks for the info.

Links:
[1] https://groups.io/g/BITX20/wiki/5696

73

Mario Koppensteiner
OE5MKE

Hello curt,

Am 16.08.2020 02:16, schrieb Curt via groups.io:

Mario
Hfsignals has builder info, but you have to click the link for
previous versions.

I tried this already.

You didn't say which case, maybe from amateurradiokits.in? see if they
still have info, at one time they also had a website at ubitx.com

Sorry. I bought the 4.3 inch Metal case [1].

Blending rig and case instructions takes some patience. v4 isn't a
follow exact instructions kit, but a homebuild adventure. I suggest
building first with lcd, then later changing displays.

So there is no follow exact instructions guide?

Links:
[1] https://amateurradiokits.in/product/ubitx-nextion-case-for-4-3-inch-display/

[...]

73

Mario Koppensteiner
OE5MKE

Hello bitx20 List,

I bought the uBitx Nextion Case for 4.3 Inch Display [1] case.

I got a note that there is the LA4425 transistor missing. I did a internet picture search about this transsistor and found this [2]. This transistor does have 5 terminals. On the PCB there are 3 holes and not 5. Please provide me a picture of the PCB with the LA4425 transistor soldered in.

Can you suggest a source in the internet to get the LA4425 transistor?

Links:
[1] https://amateurradiokits.in/product/ubitx-nextion-case-for-4-3-inch-display/
[2] https://i.ebayimg.com/images/g/s9MAAOSwHnFVxLbm/s-l640.jpg

73

Mario Koppensteiner
OE5MKE

Am 15.08.2020 23:52, schrieb Mario Koppensteiner:

Hello Viktor,

Am 15.08.2020 23:55, schrieb Viktors Miske:

Mario, give this site a shot;
http://ubitx.net/

I tried this site already.

[...]

73

Mario Koppensteiner
OE5MKE

DEAR REED,  EVAN, and the group,
       Good day. Thank you very much for your kind helps. Now I have solved the issue and uploaded REED software. The rig is working now.
   Thanks a lot for all guidance from the group and especially Reed and Evan.
Regard and 73
MUTHU
VU2LMN

Dear All,
    Good Day. In continuation of my above message No. 81273, I am glad to inform the group that the problem has been solved now. I have done the required calibration on the touch screen available in the Settings Menu. After carrying out this, the touch screen started working and the Transmission also works in LSB/USB mode.
    Really UBITX is a wonderful gear to learn a lot.What we have learnt is tiny and what we have yet to learn is to a size even greater than the globe. UBITX and this group  offer good opportunities to learn.
Regards and 73
MUTHU
VU2LMN

Hello,

I've posted a few times on here about my kit-projects AGC.  I'm thinking that I've never really had it working right, and am hoping I can get some help.  Here's my setup, and here are my symptoms.

I've got a uBITX v5 with the kit-projects AGC, preceded in the RX path by the kit-projects BCI filter.  I've taken a photo of the AGC board, below.  As I've noted in a previous post, I also have a G4HUP buffer tapped off of the Q12 emitter.  In addition, I've got an audio buffer and preamp for a line out tapped off the VOL-H.  So I can imagine there is some signal loss.  However, that still doesn't (in my mind at least) explain what I'm seeing.

Also, I do have a 1K audio taper pot wired up as an RF gain control.  It appears to work fine, although I always leave it at its max setting (if I decrease it, signal strength decreases appropriately; I just haven't found occasion to use it in practice).  The RF gain pot is wired to the AGC via two lengths of RG-174.  The shields of both are soldered to the pot body, which is grounded to the chassis.  The shields are NOT grounded at the AGC end.  So I think I have installed this properly, though I understand this has been a source of problems for some folks.



The red, green, and blue wires are wired to the switch per the kit-projects instructions, as is the black wire (which is NOT ground, but rather corresponds to the purple wire in the instructions).  I've got a connector that goes to the Raduino A7 ADC for the S-meter, and the yellow wire is the audio input.

I will note that I have no real way to calibrate this thing.  However, I have done a couple of different things to attempt to "force" some AGC action, with no luck.  I will note that I am generally using 40 meter FT8 (7.074 MHz USB) as my "test signal".  There are some very piercing signals, that the AGC doesn't seem to do much of anything with.

Basic Setup:  AGC audio input from VOL-H ("per the instructions")

In this case, I generally see very low signal strengths, even with strong FT8 signals.  The KD8CEC firmware reports ADC values in the range of 20-50 (I understand that this has been divided by 4).  Using my DVM to measure the DC voltage at A7 / the control voltage, it looks to fluctuate between 0.1-0.3 VDC.  As I understand it, this DC voltage is way too low to cause any AGC action.

Next Setup:  AGC audio input from my line out

I have a TL082 configured with one half as a basic buffer, and the other half as a 20dB (100x?) amplifier (reference the TL082 preamp on this page http://rason.org/Projects/opamps/opamps.htm).  I normally adjust the gain control (a trim pot) to provide a reasonable audio level for my sound card--this is actually the whole reason I got the AGC in the first place, to control the audio for digimodes. 

Here's where it gets a little weird.  If I adjust the gain to 0, then the A7 ADC registers about nothing... pretty much what I expect.  However, as I increase it, the control voltage increases above what it was in the "basic" case, but it really never gets above 0.3-0.5 VDC even on those same strong FT8 signals.  Even if I max the gain control on the preamp output.

The strange thing here is that if I max the gain control and run that to my sound card, the sound card at its 0dB gain setting (which is line-level) is completely clipped/flat-topped.  So I would assume this is somewhere around 0.7 Vrms on the audio, which according to the ND6T write-up on the AGC, should yield about 3 VDC on the control voltage... but I'm still only seeing 0.3-0.5 VDC!  And no AGC action that I can discern.

Last Case:  Direct DC control

This initially led me to think that the audio wasn't getting properly amplified by Q1 (the 3904, or whatever it is) in the AGC circuit.  So I tried applying 3 VDC directly to the "Common" pad on the AGC, with the switch in the "Slow" position.  When I do this, I see the expected value on the Raduino ADC (reports ~155, i.e. (1024/4)*(3V/5V)).  However, again there is no apparent AGC action (and in this case, I would have thought it was forced to do it).

So, any thoughts?  What am I missing, or what did I break?

Regards,
-Rob KC4UPR

Ulrich

Okay a more careful read I see you have a recent v6. I imagine an email to hfsignals reporting quality issue may get you a replacement pot, otherwise the value and taper should be listed on the parts list.

Many of us modify our ubitx, is the YL a new ham? Nearby hams might help with parts.

Hoping you will soon be pleased with your work.

73 curt

Ulrich

the ubitx was certainly designed for the op of humble means, including youth.  perhaps us hobbyists have purchased many of them.  it is an amazing rig overall.  okay we can wonder if 0.1 uV is exaggerated or more likely the designer has excellent hearing (-:  The receiver clearly was designed with dynamic range in mind.  I expect it hears most everything my K2 hears in most bands.  As delivered the principle need is BFO alignment.  

most of our HF receivers from the past several decades likely have similar sensitivity - its other parameters where they separate.  nonetheless I have numerous CW contacts with my ubitx and I am amazed how well it does on SSB (I got fortunate I think in the particular microphone I found in my leftover stash). 

my ubtix v4 was delivered with a potentiometer, but I also purchased an enclosure kit that contained pots and controls.  my unit does not have an of-off switch in the volume control, so I don't recall if the stock volume pot has that feature.  my power switch is a push button in the back - I suggest finding whatever power switch its op will appreciate. 

does the ubitx in your hands have a commercial looking enclosure?  many came from amateurradiokits.in.  Sunil the proprietor would certainly fill you in on the pot, but it might be difficult to source that particular pot in DL. 

okay this list may be biased but the ubitx is a nice radio adventure.  when we have sunspots again, I am imagining lots of folks enjoying it when its their primary rig.  I have plans to set mine up for WSPR reception.  nothing like this anywhere in its price range - but someday watch for the QSX when it emerges (more assembly required). 

73 curt

I have a BitX 40 that I 3d printed a case for, that sits on my shelf unused - I never really used it after wiring it up.  I figured someone here might be interested in it, as radios are meant to be used!  Message me off-list for details, if you're interested.

~Josh
W0ODJ

David

Its on hfsignals website. There are links there for v3 v4 etc.

I imagine it may be at ubitx.net, and maybe files section here.

Or use search engine ubitx v3 instructions

73 curt

Hello,
Can you please highlight one point. 
On the documentation of µbitx 6 it is noted:
"

12 MHz SSB filter

 The ladder topology is now enhanced with the improvisation suggested by G3UUR. Paralleling up crystals at two ends of the regular ladder filter of Cohn topology really flattens out the response and even improves the losses. We use a six-section ladder filter here as we can afford the slightly higher losses given that we have had enough gain from the preceding stages. Microprocessor-grade crystals are available cheaply and are well suited for the purpose. The lower Q of these crystals results in higher losses. We can handle the higher losses by increasing the gain in the 2nd RF amps that in turn results in slightly lower IIP3 (it is about +5 dbm as measured) at close range. The 12 MHz filter needs 200 ohms termination at both ends. We achieve this through 1:4 transformers that have the robust 50 ohms terminations. Taking care to terminate filters properly is the secret to having a nice sounding radio."

Can you explain to me how the 1:4 ratio of transformers T5 and T6 (The one before and after the filter) is done.
For me all transformers are tricoils between 8 to 10 turns on FT37-43 as noted on the documentation: "All the RF transfomers are 8-10 trifilar turns on FT37-43"
On the diagram we use only 2 windings on the 3 of the tricoil.
There’s probably a technical explanation (?)
Thank's for your's answers

cdt

Hi Muthu,

The calibrations for the radio should be identical between my software version and Ashhar's v6.1. I'm not sure why you would have a working setup on his software but not mine.

There are a couple ways to calibrate the touch screen. One way is to hold down the tuner button before turning the radio on. This method will force you to also do frequency and BFO calibrations.

The second way is to turn on the radio, briefly press the tuner button, rotate the tuner knob until the gear icon is outlined in white, then press the tuner knob button. Repeat the knob turning and button pressing to get to the calibration, then touch screen calibration setting.


Reed

Hey Curt,

thanks for that reference of 0.1µV but it doesn't help with further reference. So it  sounds more like a wish, not reality. An ICOM IC-736 is known to be sensitive and has less then 0.15µV at a SINAD 10dB with Pre-Amp on. The modern IC-7300 has less then 0.16µV, also with Pre-Amp on.

However, I didn't want to talk the ubitx down, I just need some reference to decide, if the unit I have connected to my test-set is now working or still has problems.
And I need a source for the volume / power combination. It has a pin broken off, as I told before and I cannot find a mechanical matching substitute for it. Does anyone know a matching part?

73 de Ulrich