Topics

#calibration #v5 #calibration #v5

Tony Vandenborn
 

Hello all

My v5 is not working correctly. I have Nextion 3.5" and CEC V1.20. What I did: connected the uBITx to a dummy load, and using my Icom IC7300 in spectrum mode I managed to position both sidebands where they should be, more or less 2.5 kHz broad. CWL and CWU are both around the carrier frequency, resp. round 700 Hz below and above carrier frequency. I achieved this with the Memory Manager; master is at 140000, USB cal on 11054900. On transmit in SSB I only have 200-300 mW out; in CW 600 mW. Now I have not yet set the quiscent current of the PA - that no concern at this moment. But I have NO RECEPTION. On my antenna, tuned at 7074 FT8 for the Icom I have 59 + sigs on the Icom. On uBITx almost nothing to hear.

Wat I tried: putting a signal generator on 12 and 45 MHz. The touched the input of the resp. filters with a piece of wire: works fine - they are live. When I try the earlier described procedure with the audio spectrum analyzer, I have a flat spectrum 50 - over 20 000 Hz, so impossible to use that tuning help. I think there is something wrong with the DBM at the input: T1/T2, D1/D2. Has anyone alreaady had loose or bad contacts at these components? The clock CLK#2 is present (500 mVpp, checked with oscilloscope). Anyone has a suggestion ? The uBITx is already mounted on a (aluminum) chassis, if not necessary I'ld prefer not to remove it from the chassis: the final transistors (well insulated) use the chassis for cooling. One more thing: on connecting an antenna the noise from the speaker doesn't change. All help or suggestions would be highly appreciated !

Tony ON6NT

Evan Hand
 

Tony,
I have not seen many posts with issues around the first mixer.  I have read about issues with L1-4.  I would start by using a length of wire as an antenna at TP1 and at TP2 to see if there is an increase in the noise of the receiver.  I would also try touching the volume high connection on the volume control to verify that the audio stage is working to verify the audio amp.  Do you hear the sidetone on CW?  Since you have a signal generator, you could also verify the audio amp by injecting audio into TP21 or at the wiper of the volume pot.

You can also verify that there is continuity from the antenna to TP1.

One last idea, verify that Q90 is not blown and shorting the signal at TP2.

I would first verify the audio sections are working, as no sound at all is very suspicious.

Above are just ideas.  I have not experienced the issues as you have described them.

Good Luck and Happy Hunting.
73
Evan
AC9TU

Tony Vandenborn
 

Hello Evan

Thank you very much for the help, I really appreciate it.
The antenna connector, as well as TP1 and TP2 are both 'hot': with a small antenna connected to the signal generator, I can receive the generator signal with a 30 cm piece of wire, and even with my ...finger. I don't have an idea on the output power of the generator: it is an antenna analyser, that can be used a generator. So I would assume that the signal chain to TP1 or T1 are fine. The audio part is ok: touching the volume pot gives hum, and the side tone on CW is fine.

Then I checked Q90. On transmit I measured (with the oscilloscope) collector 12 V, base 4V, and emitter around 3.5 V. Seen the resistor divider on the base 1k/470E that looks fine to me. I also measured once again supply currents: on receive 230 mA, in SSB 630 mA (modulation doesn't barely change this current), and in CW key down some 1.2 Amps. 

I just tried something else: the antenna input is connected to the dummy load. With the generator at 48.6 MHz, and the uBITx at 3.6 MHz, I receive the generator loud and clear. But when I touch TP13 and/or TP14, absolutely nothing changes: no cracks, no hum, signal doesn't become weaker or stronger - nothing happens, no matter if I touch TP13 or 14 or not... Is my conclusion correct: the first DBM works fine, but there is something wrong around Y1... ?

Thanks again !

Tony ON6NT

Evan Hand
 

OK, Q90 is OK.  Can you clarify if you are connecting an antenna to the radio to test the BFO?  The BFO tests will not work with a dummy load.  You need to have some sort of wire or antenna connected to get the background static.

With the rig off, you can check the continuity of the antenna to TP1 with a DVM set to read ohms.

So far your first diagnosis seems to be the most likely.  Try injecting a low-level signal (less than <500 mv)  into TP1 at the frequency of the uBITX dial and see if you can get a tone tuning back and forth.  You can then go to TP13 and inject a 45MHz  frequency and do the check again.  Last would be an 11.058 signal at TP16 and check again

One last thing I should have had you check right off, are you sure you have the correct file for the v5 uBITX from GitHub?  If you loaded a v3/v4 file, you would have the same symptoms.  The second IF is at a different frequency, and though you have adjusted the BFO correctly for starters, the Clock#1 would not be at the correct value, causing the signal to be filtered out in the 11.059 MHz SSB filter.  CW would still be OK, as that does not use the second mixer.

I will open up my v5 and see if I can get any more data for you.

73
Evan
AC9TU

Allen Hill
 

Hi Evan, I'm not sure how many thanks you get for your work except the few I see sprinkled here. But I'd like to say a hearty THANK YOU for all the effort you put into these responses. I have to say I've learned quite a bit just by walking behind you through the big foot prints you've created.I

Keep up the good work!

73
KI4QCK



On May 16, 2020, at 1:38 PM, Evan Hand <elhandjr@...> wrote:


OK, Q90 is OK.  Can you clarify if you are connecting an antenna to the radio to test the BFO?  The BFO tests will not work with a dummy load.  You need to have some sort of wire or antenna connected to get the background static.

With the rig off, you can check the continuity of the antenna to TP1 with a DVM set to read ohms.

So far your first diagnosis seems to be the most likely.  Try injecting a low-level signal (less than <500 mv)  into TP1 at the frequency of the uBITX dial and see if you can get a tone tuning back and forth.  You can then go to TP13 and inject a 45MHz  frequency and do the check again.  Last would be an 11.058 signal at TP16 and check again

One last thing I should have had you check right off, are you sure you have the correct file for the v5 uBITX from GitHub?  If you loaded a v3/v4 file, you would have the same symptoms.  The second IF is at a different frequency, and though you have adjusted the BFO correctly for starters, the Clock#1 would not be at the correct value, causing the signal to be filtered out in the 11.059 MHz SSB filter.  CW would still be OK, as that does not use the second mixer.

I will open up my v5 and see if I can get any more data for you.

73
Evan
AC9TU

Tony Vandenborn
 

Hello again Evan-

Alleluia ! It is working ! There were some bad solder joints in the vicinity of Q10, Q11, and Q12. After soldering them again I noticed right away that the set was working: a real increase in noise when connecting the antenna. And now for the alignment of the power transistors, and further finetuning the master and the BFO.

I can only agree with Allen: a big THANK YOU for the help. Thank you, thank you, thank you very much !

By the way: I do have a Kenwood TS120V and an Icom IC7300. But I enjoyed very much building the uBITx. I already have a 3.5 Nextion display installed, the next step is building an S-meter.

73 from Belgium
Tony, ON6NT

Evan Hand
 

You are welcome, though it was you who found the issue.

This is the first time that I have heard of a v4 or later having a solder issue.  I hope that Ashhar Farhan is seeing the emails and has HF Signals look into the issue.  You could also send an email to HF Signals telling them what you found.  The version 5 is no longer in production, so not sure if there is anything that they could do about it at this time.

Enjoy the rig and the tinkering with it.  That to me is the most fun.

73
Evan
AC9TU

Don - KM4UDX
 

Evan is one of the best and most helpful  uBITX diagnosticians in the known universe..

I too follow his posts. I read them like a master class. 

Don
Km4udx

Evan Hand
 

All of you are giving me more credit than is due.  If you would read as many of the posts here as I do, you would gain the same or more knowledge.  It is the advantage of being retired (lots of free time).

There are others on this board that are more knowledgable than I, they have other jobs or commitments such that I get in the first post.  I would head anyone that does provide another point of view, as they may have the first-hand experience that I do not.  I do try to point out my limits so that if another does provide input you can judge for yourself.

Again, Thank you for the kind words.
73
Evan
AC9TU

Tony Vandenborn
 

Hello Evan

As told, my radio (v5) did work, but intermittand. The sensitivity was very, very low. I've been aligning during days, and days, and days...
Today I once more checked the receiver. Audio part: ok. 11 MHz to test points 16 and 17: nothing happens. Than checked TP18 with a 50 MHz oscilloscope: a poor 11 MHz signal, some 50 mVpp, very distorted. Same on pin9 of the Raduino board, and the right hand side of C4. Beautiful 11 MHz (600-700 mV sine) on the left hand side of C4 (oscillator chip side). Removed Raduino from the chassis, checking C4 with magnifying glass: is was broken (see pic). Replaced it with a (wired) cap, and yessssss: it was clear by hearing the noise already, the miracle happened. Could receive FT8-sigs on 7074 USB with my finger as antenna...

And now finally for the alignment !
Thanks once again Evan !

73's from Belgium - ON6NT
 

Evan Hand
 

Good find on your part!  Glad that you found the issue.

It seems like there are more manufacturing issues cropping up recently than I have seen in the past.  The problems do not seem to me to be from shipping or miss handling on the part of the customer  As stated before, I hope that Ashhar Farhan is reading these posts as there may be some systemic problems that need to be addressed.  Cracked parts and poor solder joints should not get through testing, let alone be there in the first place.

73
Evan
AC9TU

 

Congrats on the trouble shooting!

At 23/05/2020, you wrote:
Hello Evan

As told, my radio (v5) did work, but intermittand. The sensitivity was very, very low. I've been aligning during days, and days, and days...
Today I once more checked the receiver. Audio part: ok. 11 MHz to test points 16 and 17: nothing happens. Than checked TP18 with a 50 MHz oscilloscope: a poor 11 MHz signal, some 50 mVpp, very distorted. Same on pin9 of the Raduino board, and the right hand side of C4. Beautiful 11 MHz (600-700 mV sine) on the left hand side of C4 (oscillator chip side). Removed Raduino from the chassis, checking C4 with magnifying glass: is was broken (see pic). Replaced it with a (wired) cap, and yessssss: it was clear by hearing the noise already, the miracle happened. Could receive FT8-sigs on 7074 USB with my finger as antenna...

And now finally for the alignment !
Thanks once again Evan !

73's from Belgium - ON6NT