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I need a V3 or V4 uBitx board.

 

I debated on whether I would admit to being this stupid to the group, but while fitting the click fix board to my perfectly working uBitx all mounted in a custom enclosure, I vaporized a trace on the bottom of my board. Obviously I did something wrong, although I don't know what. I reversed the mods to the PCB and replaced the vaporized trace with a piece of wire and fired it up. I have no RX or TX however the Raduino is working and outputting the correct clock signals on the three pins. It does switch to TX when pressing the PTT, and believe it or not, the whole audio section seems to work fine. I can touch parts in the audio section and hear a loud 60 cycle hum out of the speaker. I can hear a slight hiss in the speaker that does not change when removing the antenna. So this brings me to the part where I ask if it would be worth trying to trouble shoot this board, (any idea where to start?) or just replace it. Does anybody have just a Ubitx PCB they would sell me (cheap) as my raduino works fine. This radio worked good, I should have left it alone:-( Picture of burnt trace below.

Joel
N6ALT

 

I forgot to mention that the board smoked when I pushed the PTT, it was working sort of until I did that.

Joel
N6ALT

RICHARD
 

If you decide not to fix it I will buy it from you.

73 Dick

 

Sent from Mail for Windows 10

 


From: BITX20@groups.io <BITX20@groups.io> on behalf of Joel Caulkins <caulktel@...>
Sent: Saturday, June 23, 2018 10:55:48 AM
To: BITX20@groups.io
Subject: [BITX20] I need a V3 or V4 uBitx board.
 
I debated on whether I would admit to being this stupid to the group, but while fitting the click fix board to my perfectly working uBitx all mounted in a custom enclosure, I vaporized a trace on the bottom of my board. Obviously I did something wrong, although I don't know what. I reversed the mods to the PCB and replaced the vaporized trace with a piece of wire and fired it up. I have no RX or TX however the Raduino is working and outputting the correct clock signals on the three pins. It does switch to TX when pressing the PTT, and believe it or not, the whole audio section seems to work fine. I can touch parts in the audio section and hear a loud 60 cycle hum out of the speaker. I can hear a slight hiss in the speaker that does not change when removing the antenna. So this brings me to the part where I ask if it would be worth trying to trouble shoot this board, (any idea where to start?) or just replace it. Does anybody have just a Ubitx PCB they would sell me (cheap) as my raduino works fine. This radio worked good, I should have left it alone:-( Picture of burnt trace below.

Joel
N6ALT

Jerry Gaffke
 

Easy enough to foul up like that, I've done worse.
More than once.

Well worth an hour or two of trying to chase this down.
I'd expect it to be repairable.

The trace you burned is the TX +12v rail.
My best guess is it somehow got wired up to ground during your mods.
Look hard for other burn spots where the TX rail might have been damaged.
And look hard at wherever it had been shorted, may be some damage there too.

Verify that your RX rail is 12v during receive and TX is 12v during transmit.
Sounds like that is probably the case.

Exactly what list of mods were you trying to follow?
Exactly what was the mis-wire?

Where do you hear 60hz hum when probing around the audio during RX?
Do you get noise when touching T7 pins 3 and 5?

Did you restore C50 and C63?
Perhaps C63 got cracked when working with it, perhaps receive audio is 
not making it through C63.  Perhaps try replacing C63 with some other cap of 0.1 to 1 uF.
Maybe the traces got ripped up a bit around C63 when it was removed?

You can continue  touching stuff back through the receiver all the way to the antenna,
should hear increasing noise as you continue further back. 
Just touch it with 3 feet or so of wire connected to nothing, that's enough of an antenna
to pick up household QRM and inject it into the circuitry.
The further back you go, the more amplification it gets before arriving at your speaker.
When you get to a spot where touching stuff no longer makes an audible difference,
you have gone past the fault in the receiver.

If there's loss of noise at or immediately beyond a mixer (other side of the filter that's in front of the mixer)
then check the si5351 clock going into the mixer.  You can check the si5351 clocks by monitoring them in some
other shortwave receiver.   With stock firmware, Clk0 is around 11.9965 mhz, Clk1 is at 32.995mhz (LSB) or 56.995 (USB),
and Clk2 is at the 44.995mhz+OperatingFreq.  So if you are tuned to 7mhz, then clk2 should be within a few khz of 44.995+7=51.995mhz

Jerry, KE7ER


On Sat, Jun 23, 2018 at 10:55 am, Joel Caulkins wrote:
I debated on whether I would admit to being this stupid to the group, but while fitting the click fix board to my perfectly working uBitx all mounted in a custom enclosure, I vaporized a trace on the bottom of my board. Obviously I did something wrong, although I don't know what. I reversed the mods to the PCB and replaced the vaporized trace with a piece of wire and fired it up. I have no RX or TX however the Raduino is working and outputting the correct clock signals on the three pins. It does switch to TX when pressing the PTT, and believe it or not, the whole audio section seems to work fine. I can touch parts in the audio section and hear a loud 60 cycle hum out of the speaker. I can hear a slight hiss in the speaker that does not change when removing the antenna. So this brings me to the part where I ask if it would be worth trying to trouble shoot this board, (any idea where to start?) or just replace it. Does anybody have just a Ubitx PCB they would sell me (cheap) as my raduino works fine. This radio worked good, I should have left it alone:-( Picture of burnt trace below.

Joel

Don, ND6T
 

No worries, Joel! Although I am sorry that it happened. The trace appears at first glance to be the TX trace. If it were cut in the wrong place and jumpered to the +12 volt bus then you were probably transmitting. Look at the PA finals. Best to check resistances in several places in the TX areas. No, it can be repaired. Just a bit of an adventure.
I advocate using a current limited supply to avoid that. I dial the maximum current down to just over what I would expect to be normal before applying power. In this case a 0.2 amp current fold-back would be appropriate. By observing the voltage with your finger on the switch you can usually avoid most unpleasantries. Drop me a line on my regular email if you want. 73,
Don

Michael Maiorana
 

Joel,
The first thing I would do is find the trace you burnt on the schematic. Then I would look at the steps that you took to install the mod and see if/how they are related.

Let us know what you find. 

Mike M.  Ku4qo 

On Sat, Jun 23, 2018, 1:55 PM Joel Caulkins <caulktel@...> wrote:
I debated on whether I would admit to being this stupid to the group, but while fitting the click fix board to my perfectly working uBitx all mounted in a custom enclosure, I vaporized a trace on the bottom of my board. Obviously I did something wrong, although I don't know what. I reversed the mods to the PCB and replaced the vaporized trace with a piece of wire and fired it up. I have no RX or TX however the Raduino is working and outputting the correct clock signals on the three pins. It does switch to TX when pressing the PTT, and believe it or not, the whole audio section seems to work fine. I can touch parts in the audio section and hear a loud 60 cycle hum out of the speaker. I can hear a slight hiss in the speaker that does not change when removing the antenna. So this brings me to the part where I ask if it would be worth trying to trouble shoot this board, (any idea where to start?) or just replace it. Does anybody have just a Ubitx PCB they would sell me (cheap) as my raduino works fine. This radio worked good, I should have left it alone:-( Picture of burnt trace below.

Joel
N6ALT

Don, ND6T
 

Joel,
Since it did not go poof until you activated the PTT, then it might have been an incomplete cut of the TX trace. With both TX and RX voltages active then both sets of IF amps will be active (truly bidirectional) and will likely form a full-on oscillation! Check Q12, Q21, Q32, and Q40 as a start. Like Mike says, look for discoloration. Sniff the areas. -Don

 

Thanks for all the great replies, I'm really embarrassed to admit I did this. Jerry, you are right about what caused this. It didn't work at all when I tried it the first time, after looking at everything I thought I had the wire going to C50 on the click board on the wrong pad, so I swapped them, (big mistake), now at least I had bad receive, then I pushed the PTT, that's when the magic smoke got let out. I checked the raduino outputs with my frequency counter and the outputs were all what they should be for the frequency I was on.

C50 and C63 are replaced with new caps and are fine. I will check the other things you mentioned as well. Thanks for the offers to buy my board, but that doesn't really help me with my problem. I will try to repair before I think about selling it. Thanks again for all your help. I will post on this thread and let you all know how things turn out. Picture of top side of PCB below.

Joel
N6ALT

 

Oh, one more thing Jerry, The mods I had done was the cutting of the traces per the instructions on Don ND6T's site. I bridged them back to factory and checked with a MM to make sure the path was back. There is no visible damage to the top side of the PCB as looked at with my USB Microscope, (a good one).

Joel
N6ALT

Jerry Gaffke
 

Possible, I don't really know what would happen if both sides of a bidi amp were turned on.
But his burnt trace probably saw amps, and not obvious to me how the bidi amps could pull that kind of current.
DC paths from TX to ground are hundreds of ohms, AC out has a series 50 ohm resistor.


On Sat, Jun 23, 2018 at 11:52 am, Don, ND6T wrote:
Joel,
Since it did not go poof until you activated the PTT, then it might have been an incomplete cut of the TX trace. With both TX and RX voltages active then both sets of IF amps will be active (truly bidirectional) and will likely form a full-on oscillation! Check Q12, Q21, Q32, and Q40 as a start. Like Mike says, look for discoloration. Sniff the areas. -Don

Don, ND6T
 

No, looks like TX to one of the many ground connections on the kit board. Quite solid, thus the smoked trace. There is something else going on, too. Probably minor. -Don

Jerry Gaffke
 

A good reminder to install a 0.5 Amp fuse or polyswitch plus a series diode (1n4007 perhaps)
from power supply into the main 12v power rail of the uBitx or Bitx40 board.
Would likely have avoided all the trouble here. 
The main board does not care about the forward voltage across the diode.
Fusing most of the rig at only 0.5 Amps means far less damage will occur before that fuse blows.

I keep have a separate fuse of 3 Amps from power supply into the PA-PWR rail.
Don't bother with a diode there, since if reverse polarity does occur the IRF510 intrinsic diodes
will conduct and blow the 3 Amp fuse.   When running from a battery, would prefer not to have
a diode drop into the IRF510 drains, as it reduces available power out.

Jerry


On Sat, Jun 23, 2018 at 02:23 pm, Don, ND6T wrote:
No, looks like TX to one of the many ground connections on the kit board. Quite solid, thus the smoked trace. There is something else going on, too. Probably minor. -Don

 

Well after testing some voltages on the board, the RX rail is present everywhere it's supposed to be but the TX rail is missing everywhere. I'm thinking I may have toasted K1 but still checking.

Joel
N6ALT

 

Yay! K1 was indeed bad, I now have a working receiver and transmitter, however the output power is only 500mw compared to the 12 watts before. Do we think the IRF510's are shot? What would be the best way to check them or should I just replace them, I have plenty in stock.

Joel
N6ALT

 

Hi all,

 I want to thank you all who held my hand through this, I am now back up and running. The low power was because I had my power supply in current limiting mode, I now have full power out and worked a field day station a 1000 miles away. I will install a fuse in the primary radio path now that I've learned a important lesson. Some people just need to learn the hard way:-)

Joel
N6ALT

M Garza <mgarza896@...>
 

Congratulations and good work!

Marco - KG5PRT

On Sat, Jun 23, 2018 at 7:12 PM Joel Caulkins <caulktel@...> wrote:
Hi all,

 I want to thank you all who held my hand through this, I am now back up and running. The low power was because I had my power supply in current limiting mode, I now have full power out and worked a field day station a 1000 miles away. I will install a fuse in the primary radio path now that I've learned a important lesson. Some people just need to learn the hard way:-)

Joel
N6ALT

Jerry Gaffke
 

Cool!
It does pay to just dive in and try.  Sometimes.

I am curious though, what was wrong with the receiver?
Perhaps trouble around C50?

Jerry


On Sat, Jun 23, 2018 at 05:12 pm, Joel Caulkins wrote:
I want to thank you all who held my hand through this, I am now back up and running. The low power was because I had my power supply in current limiting mode, I now have full power out and worked a field day station a 1000 miles away. I will install a fuse in the primary radio path now that I've learned a important lesson. Some people just need to learn the hard way:-)

 

The receiver would not work until I changed the relay. I was wondering about that myself, why would the absence of TX voltage cause the receiver not to work unless a RX voltage was missing also. I checked all that I saw on the schematic and they were all there. Don’t know.

Joel
N6ALT

 

Joel,

If the TX track is burnt there it is likely that a plated through hole (PTH) has also burnt.
Check along the burnt line from top to bottom connections.

Check the RX/TX supply voltages everywhere.. you could have welded the relay contacts !!

Raj

At 24/06/2018, you wrote:
Oh, one more thing Jerry, The mods I had done was the cutting of the traces per the instructions on Don ND6T's site. I bridged them back to factory and checked with a MM to make sure the path was back. There is no visible damage to the top side of the PCB as looked at with my USB Microscope, (a good one).

Joel
N6ALT

 

Check the PTH as I mentioned..

At 24/06/2018, you wrote:
Well after testing some voltages on the board, the RX rail is present everywhere it's supposed to be but the TX rail is missing everywhere. I'm thinking I may have toasted K1 but still checking.

Joel
N6ALT