John measure Q90 base to emitter junction, if close to zero it has shorted. I measured about 500ohms. This will cause no output and loss of receive and it is still in circuit during receive.

CW-KEY is doing exactly the same thing.
When transmitting CW, CLK2 is programmed to be at the transmit frequency, CLK0 and CLK1 are shut down,
and a Nano IO pin drives 5v on CW-KEY to unbalance the mixer.

Jerry, KE7ER

On Wed, Jan 13, 2021 at 10:30 PM, Ashhar Farhan wrote:

On my bench is a new rig coming up that is built for high performance, hybrid sdr capabilities.

When do we get to learn more?

Tom, wb6b

On 01/19/2021 08:22 PM, Evan Hand wrote:

Frank,

It is not clear to me what you are asking. If you have a uBITX then the
method that Bob describes is the easiest. If your question is how to do
that, then here is the way that it is done in the v3 and later,
displaying the v6 schematic:


The way that works is that the first mixer (T1 and T2) is being
unbalanced by a 5 volt signal from the Nano on the CW-KEY line. This
forward biases 2 of the diodes in the mixer and allows the LO signal
that has been changed to the frequency that is to be transmitted to be
applied to the amplifier stages.



It should be noted that the power output will be the full power for that
band.

To get less than full power out, you can vary the voltage from 0-5v. TP13 (it looks like TP13 anyway) would be a good place to inject that variable voltage, you'd probably want to use a diode and resistor in line.

I did that on my B40 and it worked well. I put the pot right on the front panel.

Vince.
--
K8ZW http://www.metalworkingfun.com http://www.hamradio.fun

What is the emission type / signal characteristics of this "FT8"?

Thanks,
Rafael

Just set CW keyer to hand-key and key the radio, you'll get a continuous
CW for tuner adjustment. I'm adding a "TUNE" button in my ubitx v6
interface code for this.

Rafael

Frank,

It is not clear to me what you are asking.  If you have a uBITX then the method that Bob describes is the easiest.  If your question is how to do that, then here is the way that it is done in the v3 and later, displaying the v6 schematic:


The way that works is that the first mixer (T1 and T2) is being unbalanced by a 5 volt signal from the Nano on the CW-KEY line.  This forward biases 2 of the diodes in the mixer and allows the LO signal that has been changed to the frequency that is to be transmitted to be applied to the amplifier stages.  



It should be noted that the power output will be the full power for that band.

The other way would be to use FT8 software or similar to generate an audio tone that can be adjusted in level for the power needed to activate the tuner.

A third option would be tu use CW-TONE or generate a tone on the unused A7 pin to feed the mic input through a variable resistor.  This would take modifiying the Nano code.

Of the three, I use either the CW or Audio tone from FT8 software.

73
Evan
AC9TU

A question of curiosity about FT8 and the level of power being used, I have a uBITX v6.2 with a usb dongle running approx.5-7 watts into either a  cobweb, 20m hexbeam, or a 20m delta loop, all antennas are run through a tuner and average < 1.1 swr at the digital freq.
I have made contacts and the average report I get back is anywhere from -13 to-26db
I am curious what everyone else is doing and seeing
thanks in advance

Is it still available?  I am looking for a uBitz.

--
Frank, KG9H

This past weekend, I went back in time and reviewd posts back to 2018.

About half way through I started taking notes but... I did not take any notes on how to unbalance the balanced modular to get a signal out for using a tuner.

Anyone have that info available?  

If I recall the ham disabled a resistor causing an imbalance and a steady signal came out which he used to tune his tuner.  He turned it on and off with a toggle switch.

--
Frank, KG9H

The wires for volume control must be ok as the volume does adjust and all the wiring connectors match the photographs I had previously taken.
That being said it does seem likely that something must have been touched or dislodged while I was working possibly one of the many coils or even heat transferred to the wrong component while de-soldering.
I will check all the connection's around the PA transistors and look for touching wires on the coils as the video suggested and let you know the results.

73
John M7CPT

Yes, get the receiver working first.

Here's an old video Farhan created to show how to take a meter of wire as an antenna to
pick up local QRN around the house, and strobe that wire to each stage of the receiver
progressing back from the audio amp until you reach a point where it no longer
makes scratchy noises in the audio.  That tells you about where the problem is.
    http://bitxhacks.blogspot.com/2016/12/troubleshooting-bitx40.html
The video is about the old Bitx40, but should work on the uBitx too.

Though first look for obvious stuff.  Maybe a wire broke off of your volume control?
Maybe a wiring harness got plugged back into the board wrong?
Are the RX stages getting 12v power? 
Note that the audio amp is powered from "12V", other receiver stages from "RX", but only when receiving.
    
If you replaced the PA transistors and now the receiver doesn't work,
sounds like you must have touched something else in the process.

Jerry, KE7ER

For a clone Nano, do a web search for "nano ch340"
You don't want the headers soldered in place because they would be soldered on the wrong side for plugging into a Raduino.
Examples:
    https://www.amazon.com/ELEGOO-Arduino-ATmega328P-Without-Compatible/dp/B0713XK923
    https://www.banggood.com/Geekcreit-ATmega328P-Nano-V3-Controller-Board-Improved-Version-Module-Development-Board-p-940937.html

For the display, search for "1602 lcd", or maybe "1602 lcd HD44780"
You want the parallel interface for the v3 uBitx, not one with the i2c backpack.
Though if using it on other projects, the i2c backpack version is easier to wire up to the nano.
Examples of parallel interface:
    https://www.amazon.com/HiLetgo-Display-Backlight-Controller-Character/dp/B00HJ6AFW6
    https://www.banggood.com/2Pcs-1602-Character-LCD-Display-Module-Blue-Backlight-p-1370817.html
    https://www.taydaelectronics.com/lcd-display-16-x-2-blue-character-with-backlight.html


Ordering from China through Banggood can take a month, but usually cheaper than a distributor here in the US.
Tayda is cheap and has a warehouse in the US.  Some Banggood items are stocked in the US.

Maybe get two or three of each, they are fun to play with and you can make them do other useful stuff.
Having a couple Nano's allows you to program new code while leaving the one with the old code on the shelf..

Jerry

Thanks, do you know where I could buy a display or arduino? I've looked but I can't see a source.

Thanks—I will look into all of that. I tested the 510s with a method found on the web alternating connections with a digital ohmmeter. I also tested the new ones before installing them. I also have not determined where the stove came from—none of the parts appeared charred.

Did you figure out where the smoke was coming from?
The IRF510's are a good first guess, but could also have been a board trace, or L8,L9.

I find that going out of the room can bring my nose back to where it can smell a faint wiff of burning epoxy.
Then perhaps a soda straw from board to nose to help pinpoint where the smell is coming from.

Or, when I first shut down, immediately press the board with my hand to figure out what got hot.

Jerry

It is possible that those IRF510's are now drawing too much current for your power supply,
and this is causing the "cycling white-out of the screen".

Did you figure out for sure that the old IRF510's were damaged before replacing them?
If they did get damaged, it was probably heat.  They were likely too hot to touch when they failed.

Did you figure out why the IRF510's smoked?  That should not have happened.
Perhaps you were running for long periods of time at 10W in digital modes, and didn't have an adequate heat sink?
Perhaps the antenna system presented more than a 2:1 SWR?   (Due to heat, IRF510 damage would not be instantaneous) 
Perhaps you fed your rig well over 12v to get a little bit more power?  (Damage due to IRF510 heat)

The gate bias required varies with each IRF510, they are not manufactured to be exactly the same.
That's why we have RV2 and RV3.
Did you adjust RV2 and RV3 for the new IRF510's, 100ma quiescent drain current on each?
A good way to determine if IRF510's are damaged is to attempt setting quiescent drain current, 
if you succeed then they are OK.

A good way to blow out your new IRF510's is to just turn the rig on and try transmitting
without first setting RV2 and RV3 properly.

My suggestion on how to proceed:
Make sure your power supply is 12v, and has a 3A fuse.
Adjust RV2 and RV3 for minimum gate bias (minimum is fully clockwise, this is backwards of most such knobs in this world)
Power up, see if you are back to the display working properly, and hearing the driver when attempting to transmit.

Then follow the instructions on hfsignals.com to set the gate bias on each IRF510, specifically:
  Monitor power supply current, I'm guessing on the v6 it might be around 300ma on receive, 500ma on transmit with zero gate bias.  (Could somebody confirm?)
  With PTT pressed and no audio into the mike, adjust RV2 counterclockwise very slowly until supply current increases by 100ma.
  Then adjust RV3 counterclockwise till the power supply increases by another 100ma.

You must turn RV2 and RV3 slowly, nothing will happen till about 4/5'ths of the way around when drain current will suddenly shoot up.
You can measure the gate voltage with a DVM, watch it rise from 0v to 5v as you turn the pot, current suddenly shoots up at about 4v on the gate.
to transmit.

If rotating RV2 and RV3 fully clockwise does not bring back the display and the signal from the driver, then remove the 12v supply on the IRF510 drains.
On older rev uBitx's there were two 12v supply wires into the main board, one for the IRF510's and one for everything else.
Unfortunately v6 only has one wire, you might try unsoldering one end of L8 and L9 instead.
I hope that if there is a v7, it will again have a separate 12v supply wire for the IRF510 drains going into the board.

Once 12v to the IRF510 drains is removed, you can turn the rig on and try transmitting.
The IRF510's won't be getting hot, or drawing so much current from your power supply that it fails to give 12v.
But you should be able to see the gate bias of each IRF510 rise from 0v to 5v as you turn RV2 or RV3 counterclockwise.

Tell us what you learn when you try the above.

Good Luck,
Jerry, KE7ER

Skip
I thank you for that