Softrock rxtx ensemble TX Opamps Stage problems. Please help me.

EA4B

I have been completing several stages with satisfaction according to the instructions on the website wb5rvz.org. Last week I finally had the possibility to start the receiver when I reached the RX_OpAmps part.

With great surprise and satisfaction, I verified how well it worked in the bands that I have selected for its construction: 17m-20m-30m, with great reception also in 15 m, 40 and 80 m, even in the om broadcasting band.

A few days ago I decided to continue and I have completed TX_OpAmp and there I am having problems.

The voltage data that had to be obtained when measuring the voltage of ICs U6 and U7 (double operational TLV2462CD) does not correspond to what was expected, the values ??being much lower than expected, the two circuits U6 and U7, give exactly the same measurement sequence voltage on its pins:
From PIN 1 to PIN 3 it should be 2.5v and the measurement I get is 1.75v
PIN 4 is the only correct 0v (ground)
From PIN 5 to PIN 7 it should be 2.5v and the measurement I get 1.72v, 1.75v and 1.76v respectively
Pin 8 should be 5v and the measurement I get 3.52v

I have gone through the entire assembly without success to find out if there was any confusion in the resistor values ??or any short or ground fault.
In the end - big mistake - I estimated that it could be a failure of the voltage regulator of the power supply, so I replaced the voltage regulator TL78L05 (U9 in the Softrock diagram), without any result. This was not the problem.
I decided to check how the inputs and outputs of the 7805 voltage regulator behave and I find this surprise:

? With the 7805 output pin in the air, without soldering on the board, I measure: PIN 1 (input) 12.3v and PIN 3 (output) 5.5v
? With the circuit connected on the board in place: PIN1 (input) 5.1v and PIN 3 (output) 3.5v

CONCLUSION: The source voltage drops when the 7805 regulator circuit comes into play. The 7805 heatsink gets very hot, plus the Dividers Stage components get hot too, including the U5 divider IC (74AC74 Dual D FF). As a result the softrock rxtx receiver has stopped working and I don't know how to solve the problem.

I would appreciate your help to solve these problems and continue with this interesting project.

Thank you.

José María, EA4B

#88840

On 11/10/2021 12:05, EA4B wrote:
I have been completing several stages with satisfaction according to the instructions on the website wb5rvz.org. Last week I finally had the possibility to start the receiver when I reached the RX_OpAmps part.
With great surprise and satisfaction, I verified how well it worked in the bands that I have selected for its construction: 17m-20m-30m, with great reception also in 15 m, 40 and 80 m, even in the om broadcasting band.
A few days ago I decided to continue and I have completed TX_OpAmp and there I am having problems.
the values ??being much lower than expected, the two circuits U6 and U7, give exactly the same measurement sequence voltage on its pins:
 From PIN 1 to PIN 3 it should be 2.5v and the measurement I get is 1.75v
PIN 4 is the only correct 0v (ground)
 From PIN 5 to PIN 7 it should be 2.5v and the measurement I get 1.72v, 1.75v and 1.76v respectively
Pin 8 should be 5v and the measurement I get 3.52v
I have gone through the entire assembly without success to find out if there was any confusion in the resistor values ??or any short or ground fault.
In the end - big mistake - I estimated that it could be a failure of the voltage regulator of the power supply, so I replaced the voltage regulator TL78L05 (U9 in the Softrock diagram), without any result. This was not the problem.
I decided to check how the inputs and outputs of the 7805 voltage regulator behave and I find this surprise:
? With the 7805 output pin in the air, without soldering on the board, I measure: PIN 1 (input) 12.3v and PIN 3 (output) 5.5v
? With the circuit connected on the board in place: PIN1 (input) 5.1v and PIN 3 (output) 3.5v
CONCLUSION: The source voltage drops when the 7805 regulator circuit comes into play. José María,
The voltage data that had to be obtained when measuring the voltage of ICs U6 and U7 (double operational TLV2462CD) does not correspond to what was expected,

These voltages are fixed by the R21/R22 divider but as you found the 5 volts is low on pin 8.

The 7805 heatsink gets very hot, plus the Dividers Stage components get hot too, including the U5 divider IC (74AC74 Dual D FF). As a result the softrock rxtx receiver has stopped working and I don't know how to solve the problem.

You need to find out what is loading the regulator.
I do not think any of the ICs should get particularly hot. Use an eyeglass (Loupe) check all your soldering, maybe a solder splash or whisker.
Carefully lifting pin 8 with a pin or needle might show a bad IC but an error is the most likely fault.

73 Alan G4ZFQ

73 Alan G4ZFQ

#88843

If the 74AC74 is running hot, then make sure it is not installed backward, or has a solder bridge on the pins.

Mike W6MXV

Show quoted text

-----Original Message----- 
From: EA4B
Sent: Monday, October 11, 2021 7:05 AM
To: [email protected]
Subject: [softrock40] Softrock rxtx ensemble TX Opamps Stage problems. Please help me.

I have been completing several stages with satisfaction according to the instructions on the website wb5rvz.org. Last week I finally had the possibility to start the receiver when I reached the RX_OpAmps part.

With great surprise and satisfaction, I verified how well it worked in the bands that I have selected for its construction: 17m-20m-30m, with great reception also in 15 m, 40 and 80 m, even in the om broadcasting band.

A few days ago I decided to continue and I have completed TX_OpAmp and there I am having problems.

The voltage data that had to be obtained when measuring the voltage of ICs U6 and U7 (double operational TLV2462CD) does not correspond to what was expected, the values ??being much lower than expected, the two circuits U6 and U7, give exactly the same measurement sequence voltage on its pins:
From PIN 1 to PIN 3 it should be 2.5v and the measurement I get is 1.75v
PIN 4 is the only correct 0v (ground)
From PIN 5 to PIN 7 it should be 2.5v and the measurement I get 1.72v, 1.75v and 1.76v respectively
Pin 8 should be 5v and the measurement I get 3.52v

I have gone through the entire assembly without success to find out if there was any confusion in the resistor values ??or any short or ground fault.
In the end - big mistake - I estimated that it could be a failure of the voltage regulator of the power supply, so I replaced the voltage regulator TL78L05 (U9 in the Softrock diagram), without any result. This was not the problem.
I decided to check how the inputs and outputs of the 7805 voltage regulator behave and I find this surprise:

? With the 7805 output pin in the air, without soldering on the board, I measure: PIN 1 (input) 12.3v and PIN 3 (output) 5.5v
? With the circuit connected on the board in place: PIN1 (input) 5.1v and PIN 3 (output) 3.5v

CONCLUSION: The source voltage drops when the 7805 regulator circuit comes into play. The 7805 heatsink gets very hot, plus the Dividers Stage components get hot too, including the U5 divider IC (74AC74 Dual D FF). As a result the softrock rxtx receiver has stopped working and I don't know how to solve the problem.

I would appreciate your help to solve these problems and continue with this interesting project.

Thank you.

José María, EA4B

#88844

If you could put a picture, more eyes would see more - maybe we'll find the fault.
Of course, if the error is visible.

-- 
Gyula HA3HZ

#88845

Good Morning Group,

I have built hundreds of the RXTX boards and usually the freshly built board will play right with first application of power.  That is because I do my initial trouble shooting with good lighting and a magnifying glass.  As I do careful inspection of the just built board I ask myself questions about is the right component mounted with the right orientation and soldered in properly with no solder bridges.

The extra hour of careful inspection often saves multiple hours of trouble shooting a powered up board. :-)

Best regards to the group.
Tony, kb9yig

Show quoted text

On Oct 12, 2021, at 3:20 AM, HA3HZ <gyula@...> wrote:

If you could put a picture, more eyes would see more - maybe we'll find the fault.
Of course, if the error is visible.

-- 
Gyula HA3HZ

EA4B

#88846

Good afternoon
Thank you very much for your help.
In reference to what was indicated by Alan, G4ZFQ: I have used an eyeglass (Loupe) to check all his solder, maybe a solder splatter or a mustache with no results. I have not raised pin 8 for fear of breaking the IC.
Mike W6MXV, said to check the IC 74AC74 orientation: I think that is correct.
Gyula HA3HZ said that it is interesting to put a photo "more eyes would see more", I agree, so I will send some images of the work.
My sincere thanks to Tony Parque, KB9YIG. I would like to show my great admiration for you.
When I finished the RX OpAmps stage and started up the receiver, it almost felt like forty years ago, the first time I built a receiver with a germanium diode, a capacitor, a coil, and a large wire antenna.
After completing the first part, "PWR Supply" I learned that I would need a magnifying glass and a solder station. 
All the construction phases I have completed successfully, with the correct checks indicated and with a surprising reception - for me - when arriving at the part "RX OpAmps"
In the following link:      I send two small videos with the operation of the Softrock RXTX when I completed the RX OpAmps stage.
In the following link:     I send the board images with the completed job to TX OpAmps. This is where everything stopped working and the wrong voltage problems have appeared.
As can be seen, the work in the area of the power supply is not clean, especially after breaking the original LM78L05 and replacing it with a 7805 "on air"on the underside board. The solders on the u6 and u7 ICs are also not very visible due to an unsuccessful attempt to remove them, but this has not affected the operation of the Softrock RXTX.
I sincerely appreciate your help.
Many thanks.
José María, EA4B

#88847

Unfortunately, it is difficult to determine a fault location from the images because the cut wire ends are long and bent in one direction.
Regardless, I found a reference in the last description that causes a possible error.
I quote:
"I send the board images with the completed job to TX OpAmps. This is where everything stopped working and the wrong voltage problems have appeared.
As can be seen, the work in the area of ??the power supply is not clean, especially after breaking the original LM78L05 and replacing it with a 7805 "on air" on the underside board. The solders on the u6 and u7 ICs are also not very visible due to an unsuccessful attempt to remove them, but this has not affected the operation of the Softrock RXTX. "

I interpret that the 78L05 was ruined, which you replaced with 7805. The reason for the failure was probably the U6, U7 referred to above, if you soldered them upside down, the stabilizer broke down due to the high current consumption, but U6 and U7 also fault. 
You can check this by lifting 5V from U6 pin8 and U7 pin8 from the solder point and then measuring the supply voltage at + 5V.
 If OK, the current consumption of either U6 or U7 or both will cause the fault.
To lift the IC foot, place 'Desoldering Wire' on the foot and heat it with a soldering iron to absorb the tin from the foot. 
Then with small screwdriver you support the foot from the side and at the same time place the soldering iron on the foot without tin. Due to the hot soldering iron, the IC foot now moves away from the solder joint by pushing the screwdriver.
This is approx. There will be a distance of 1 mm, it does not need to be raised higher.

So there is a reason for the failure of the stabilizer IC, you have not eliminated the cause.
If lifting the IC's pins does not clear the fault, continue searching. 
The path of + 5V must be interrupted, similarly one of the consumers that is supplied with 5V must be interrupted.
You wrote that the receiver works, you attached the video, so don't break the receiver's circuit.
Successful error delimitation.

-- 
Gyula HA3HZ

#88848

ps.: You can replace the 'Desoldering wire' with a piece of cable that has a multi-core twist or a coaxial cable shield that absorbs tin well. 
Try this with a separate tin.
You can replace the small screwdriver with a wallpaper cutter, the point is not to cut the IC foot, just lift it off the panel so that it does not come into contact.
Then repair the power supply, if you are ok, you can solder the removed parts one by one. 
Always measure in the meantime. Have a mA meter plugged into the wire on the input side (meaning 12V) on which you can see the current consumption. If the current consumption is high, you can interrupt the power supply immediately.
I note, for example, that I measure all measurable components (RLC) before installing. 
When I’m done with the installation, I check to see if there is a reverse part insertion.
The panel only gets energized when I have checked it over several times and there are calm conditions.
 Important: always measure the input current consumption, the meter must be in it all the time so that you can interrupt the power supply in case of high current.
You also know that the circuits work with ‘smoke’, if the smoke comes out, it will no longer work.  :-D

-- 
Gyula HA3HZ

#88849

Hello Jose,
Are you building the 6.3 RX-TX version?  I just built another one last week
to use in another SDR-Cube, and it works great. I have built many 6.3 and
NG versions.
If you can please post a good quality large picture of the area you worked
on. I tried to look at that link you provided but no go.
We can start there.
Chuck
WA6LTV

EA4B

#88850

Hello Chuck,
I upload the pictures here:

/g/softrock40/album?id=269043

73
José María
EA4B

#88851

Hello Jose,
I just got back home. I looked over your pictures. Can you send pictures of
your Power plug area. Also pictures of your Si570 close up.
I see two possible problem areas. I looked over my build like yours and
looks like your diode is wrong. Lets look over your next pictures and see.
Chuck
WA6LTV

Show quoted text

On Wed, Oct 13, 2021 at 4:01 PM EA4B <ea4bmg@...> wrote:

Hello Chuck,
I upload the pictures here:

/g/softrock40/album?id=269043

73
José María
EA4B

-- 
Thank you,
Chuck Nolin
WA6LTV/4

#88852

Hello Jose,
One other thing, looks like your jumpers at "J2" need to be crossed over
not direct.  That isn't the problem here, but I might forget to tell you
later. Also I will send you pictures that might help you
with your build going forward and future builds.
Chuck

Show quoted text

On Wed, Oct 13, 2021 at 8:37 PM Chuck Nolin <wa6ltv@...> wrote:

Hello Jose,
I just got back home. I looked over your pictures. Can you send pictures
of your Power plug area. Also pictures of your Si570 close up.
I see two possible problem areas. I looked over my build like yours and
looks like your diode is wrong. Lets look over your next pictures and see.
Chuck
WA6LTV

On Wed, Oct 13, 2021 at 4:01 PM EA4B <ea4bmg@...> wrote:

Hello Chuck,
I upload the pictures here:

/g/softrock40/album?id=269043

73
José María
EA4B





--
Thank you,
Chuck Nolin
WA6LTV/4

-- 
Thank you,
Chuck Nolin
WA6LTV/4

#88853

The TO-92 78L05 and TO-220 7805 also have different pinouts. So that also needs to be observed. The 7805, if installed reversed will fail short and feed 12v to the 74logic.
This has bitten me more than once.

EA4B

#88854

Thanks Gyula, HA3HZ, for your indications on how to lift the pins of the IC's U6 and U7. I have done so, but the Softrock remains the same, the 5V voltage keeps dropping and I can't find the cause. I have uploaded some pictures where you can see PIN 8 of ICs U5 and U6 separated from the board. I would like to recall that the replacement of the 78L05 was carried out because I thought that the voltage dropped because it had been damaged, but I was wrong, unfortunately I broke it and had to replace it with a 7805 instead.

Thank you Chuck Nolin, WA6LTV / 4, for your guidance. I also attach photos of the Si570. This afternoon I checked that the oscillator works perfectly, connecting the Softrock to the USB cable of the computer, starting the CFGSR software and tuning the output frequencies of the Si570 with an hf radio. The jumpers of J2 i'll correct at the future.

Thank you Ismo, OH2FTG, for your indication about the 7805. Before mounting the 7805, I read its technical data sheet and also checked -outside the Softrock- that its operation was correct.
I would like to recall that the receiver was working perfectly at the end of the RX OpAmps part, but it all broke the moment I completed the TX OpAmps part.
In the TX OpAmps stage, I have checked with a multimeter the value of the resistors, they are all correct, but the values measured in R21 and R22 is does not correspond to that of the real resistors.  The resistor on the board R21 and R22 are 2.21K, but I measure 1.1K.
Also in the Dividers stage, the same thing happens, the resistors R13 and R14 do not correspond to that of the real resistors. The resistors on the board R13 and R14 are 10K, but I measure 5K.
The values of these resistors are divided by two in the circuit. Is this correct, or is it the consequence of a fault in another part of the circuit?
I have uploaded new images of all these comments. There are here: /g/softrock40/album?id=269060

Thank you very much for the help you are giving me.
73,
José María, EA4B

#88855

Hello Jose,
One other item you didn't mention, would like to look at the power plug and
parts around it. It looks like the diode might be incorrect. I checked my
build
like yours and it was hard to see your diode. Lets check the installation
to be sure.
Chuck

Show quoted text

On Thu, Oct 14, 2021 at 2:35 PM EA4B <ea4bmg@...> wrote:

Thanks Gyula, HA3HZ, for your indications on how to lift the pins of the
IC's U6 and U7. I have done so, but the Softrock remains the same, the 5V
voltage keeps dropping and I can't find the cause. I have uploaded some
pictures where you can see PIN 8 of ICs U5 and U6 separated from the board.
I would like to recall that the replacement of the 78L05 was carried out
because I thought that the voltage dropped because it had been damaged, but
I was wrong, unfortunately I broke it and had to replace it with a 7805
instead.

Thank you Chuck Nolin, WA6LTV / 4, for your guidance. I also attach photos
of the Si570. This afternoon I checked that the oscillator works perfectly,
connecting the Softrock to the USB cable of the computer, starting the
CFGSR software and tuning the output frequencies of the Si570 with an hf
radio. The jumpers of J2 i'll correct at the future.

Thank you Ismo, OH2FTG, for your indication about the 7805. Before
mounting the 7805, I read its technical data sheet and also checked
-outside the Softrock- that its operation was correct.
I would like to recall that the receiver was working perfectly at the end
of the RX OpAmps part, but it all broke the moment I completed the TX
OpAmps part.
In the TX OpAmps stage, I have checked with a multimeter the value of the
resistors, they are all correct, but the values measured in R21 and R22 is
does not correspond to that of the real resistors.  The resistor on the
board R21 and R22 are 2.21K, but I measure 1.1K.
Also in the Dividers stage, the same thing happens, the resistors R13 and
R14 do not correspond to that of the real resistors. The resistors on the
board R13 and R14 are 10K, but I measure 5K.
The values of these resistors are divided by two in the circuit. Is this
correct, or is it the consequence of a fault in another part of the circuit?
I have uploaded new images of all these comments. There are here:
/g/softrock40/album?id=269060

Thank you very much for the help you are giving me.
73,
José María, EA4B

-- 
Thank you,
Chuck Nolin
WA6LTV/4

#88856

Sent email direct

-- 
Gyula HA3HZ

EA4B

#88857

Good Morning Group,

Finally I have been able to verify that the DIVIDER U5, IC 74AC74 gets hot when I connect the power.
Yesterday, I removed the integrated circuit IC U5 (74AC74) and the voltage returned to normal.
I have verified that the 7805's output voltage is the expected 5v as well as the RX OpAmps and TX OpAmps stage IC voltages are correct.
I checked IC5 again, soldered PIN 7 (ground) and PIN 14 (+ 5V) and again all voltage dropped as before.
The bottom line is that U5 (74AC74) is the cause of all the problems.

Thank you very much for your help.

73
Jose Maria, EA4B

P.D. Now I have a new problem because the 74AC74 costs only € 0.50 but the shipping cost is € 20 !!!

#88858

Good Morning Jose,

Please send your mailing address to me at kb9yig@... and I will mail a letter to you with a 74AC74 contained within at no cost to you.

Regards,
Tony, kb9yig

Show quoted text

On Oct 18, 2021, at 6:46 AM, EA4B <ea4bmg@...> wrote:

Good Morning Group,

Finally I have been able to verify that the DIVIDER U5, IC 74AC74 gets hot when I connect the power.
Yesterday, I removed the integrated circuit IC U5 (74AC74) and the voltage returned to normal.
I have verified that the 7805's output voltage is the expected 5v as well as the RX OpAmps and TX OpAmps stage IC voltages are correct.
I checked IC5 again, soldered PIN 7 (ground) and PIN 14 (+ 5V) and again all voltage dropped as before.
The bottom line is that U5 (74AC74) is the cause of all the problems.

Thank you very much for your help.

73
Jose Maria, EA4B

P.D. Now I have a new problem because the 74AC74 costs only € 0.50 but the shipping cost is € 20 !!!

EA4B

#88859

Good Morning Tony,

Thank you very much for your kindness.

Regards,

José María, EA4B

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Softrock rxtx ensemble TX Opamps Stage problems. Please help me.