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#ubitx-help #ubitx-help

hakan.sjostrom@...
 

Hi, I just finished my uBITX build. I was extremely careful with the wiring and double checked everything. The weather is extreme warm for the season here in Sweden. That's probably (;-) why I got a brain collapse and shifted the 8-pin contacts for the raduino resp. uBITX. I realised it after a short while. Everything looks ok, but I hear no signals, just birdies. Not a sound of even strong broadcast stations. Any hints?

Howard Fidel
 

Sounds like you forgot to connect the antenna?

On 6/3/2018 2:08 PM, hakan.sjostrom@... wrote:
Hi, I just finished my uBITX build. I was extremely careful with the wiring and double checked everything. The weather is extreme warm for the season here in Sweden. That's probably (;-) why I got a brain collapse and shifted the 8-pin contacts for the raduino resp. uBITX. I realised it after a short while. Everything looks ok, but I hear no signals, just birdies. Not a sound of even strong broadcast stations. Any hints?


hakan.sjostrom@...
 

No, (a LW antenna). I have tested the transmitter (works), but the receiver doesn't work

Howard Fidel
 

Since most of the circuits are bidirectional, and you can hear birdies, is still sounds like the antenna is not connecting to the receiver. Check relays K1 and K3 are not energized. Either one being pulled in will cause the problem. You could bypass the relays, and connect the antenna to the input of the low pass filter at C200 L1, as a quick test with a jumper wire.


On 6/3/2018 2:24 PM, hakan.sjostrom@... wrote:
No, (a LW antenna). I have tested the transmitter (works), but the receiver doesn't work


hakan.sjostrom@...
 

Thanks Howard for the hint. But the result is just the same. I am afraid I destroyed some component (the raduino?)

Howard Fidel
 

Sorry you are having this problem. If you shifted the Raduino1 connector, and the transmitter is really working, I don't see how that can cause your problem since all the signals must be working for the transmitter to work. It seems like you will need a signal source and a scope, although you could manage without the scope, to see where the problem is.
If you don't have those tools, you could check that all the stages that have RX voltage and make sure that the transistors in those stages have the appropriate DC voltages, i.e. Q10, Q11 etc.

Howard

On 6/3/2018 3:17 PM, hakan.sjostrom@... wrote:
Thanks Howard for the hint. But the result is just the same. I am afraid I destroyed some component (the raduino?)


hakan.sjostrom@...
 

Thanks Howard for all your help. By shifting the connectors my first thought was that the transistors should not be affected, but who knows.
Yes, I just have to go the hard way and measure as good as I can (don't have a scope). But if you can give some hints what the voltages for the transistors should be, it would be of much help. But you have been very helply so far, so I can't expect you to waste too much time on this.

Howard Fidel
 

OK. I will try to keep it simple. Lets take the example of Q10. It is not straight forward to calculate its operating point, because the bias voltage depends on the collector current, which is a function of the bias voltage. However, If you start R18, you should find about 12 volts on both sides of that resistor, since it is only 10 ohms. You should see a voltage drop of a few volts across R14, something between 4 and 10 volts would make sense. The two following transistors are emitter followers, so you should find 0.6 volts less on R15, and 1.2V less on R16 then you find at the collector of Q10.
Q30 is the same topology, so it should be similar. The other stages should be working since you have audio. You can also check with power off with your ohmmeter that you have continuity from the antenna input to the side of C204 that is not ground.  If you need more help. let me know.

Howard

On 6/3/2018 4:48 PM, hakan.sjostrom@... wrote:
Thanks Howard for all your help. By shifting the connectors my first thought was that the transistors should not be affected, but who knows.
Yes, I just have to go the hard way and measure as good as I can (don't have a scope). But if you can give some hints what the voltages for the transistors should be, it would be of much help. But you have been very helply so far, so I can't expect you to waste too much time on this.


Gary Anderson
 

Another set of eyes on this, and I concur with Howard.  I didn't see anything obvious that would have caused damage to the Radunio/Nano where TX works and RX is not working.
I would imagine that this shifting has happened to a few people already, easy to do.

Regards,
Gary

 

Would you switch off power and plug in the 8 pin like you did by mistake and take a photo
for us? That would help troubleshoot.

I am quite sure the connector can be plugged in only one way!

Raj

At 03/06/2018, you wrote:
Hi, I just finished my uBITX build. I was extremely careful with the wiring and double checked everything. The weather is extreme warm for the season here in Sweden. That's probably (;-) why I got a brain collapse and shifted the 8-pin contacts for the raduino resp. uBITX. I realised it after a short while. Everything looks ok, but I hear no signals, just birdies. Not a sound of even strong broadcast stations. Any hints?

hakan.sjostrom@...
 

Yes the connector can only be plugged in one way, but the mistake I did was that I shifted the two connectors (for the uBITX board resp. the raduino board)

 

When I inserted the Raduino one pin to the left the raduino was toast!
The damage depends how many pins did you shift left or right.. one of
the pins has 12v and that would fry the Si chip or the nano.

Raj

At 04/06/2018, you wrote:
Yes the connector can only be plugged in one way, but the mistake I did was that I shifted the two connectors (for the uBITX board resp. the raduino board)

hakan.sjostrom@...
 

Raj, I did not shift the pins - I put the Raduino connector on the ubitx board and vice versa!
And more: the CW part works with RF out. (Have not tested the SSB part yet.)
And when I connect the antenna the noice level increases. But I hear no signals what so ever, just birdies and background noise.
Håkan

 

Hakan,

Got it! the only severe damage could have been cause by PIN 3 +5v and 4 Gnd.. now this would have
connected to volume ground and center variable pin. If the volume as at minimum as it would be
when you switch on then the volume control would be damaged.

5V would have gone through the volume ctrl to PTT line which would have sustained the voltage.
This would have happened if the center pin of volume control went op.

Raj

At 04/06/2018, you wrote:
Raj, I did not shift the pins - I put the Raduino connector on the ubitx board and vice versa!
And more: the CW part works with RF out. (Have not tested the SSB part yet.)
And when I connect the antenna the noice level increases. But I hear no signals what so ever, just birdies and background noise.
Håkan

 

I think OTOH that this problem is not due to your accidental interchange.

CW is generated by the first mixer stage so it is something in the 2nd stage or
later. Check BFO frequency and IF stage (2nd) for any bad solder and specially
check the T3-T7. Shake them gently and see if any change.

Raj

At 04/062018, you wrote:
Raj, I did not shift the pins - I put the Raduino connector on the ubitx board and vice versa!
And more: the CW part works with RF out. (Have not tested the SSB part yet.)
And when I connect the antenna the noice level increases. But I hear no signals what so ever, just birdies and background noise.
Håkan

hakan.sjostrom@...
 

Thanks Raj, I will look on that! But now a little more info: I looked up a very strong broadcast station at 13.580 on my little transistor radio (with a small telescopic antenna) and I could hear on it my ubitx! But very weak..
Could it be an idea to order some 2N3904 and start replacing?
Håkan

 

That is good news, I would look at one of the trifilar interstage transformer being shorted.
I mentioned the numbers earlier.

If the transformers are fine then a dry solder in the RX chain or filter would be the culprit.
A DC voltage check on RX BiDi amps would confirm they are OK or not.
A general check to know if a 3904 is blown (very unlikely) is voltage across Base and emitter.
It should be around 0.6-0.7v.
If you get no voltage then check if that stage is getting Rx 12v. Also unlikely in this case.

I will bet on the trifilars as for now!

Raj

At 04/06/2018, you wrote:
Thanks Raj, I will look on that! But now a little more info: I looked up a very strong broadcast station at 13.580 on my little transistor radio (with a small telescopic antenna) and I could hear on it my ubitx! But very weak..
Could it be an idea to order some 2N3904 and start replacing?
Håkan

hakan.sjostrom@...
 

To check if the trifilars are shorted I have to unsolder them, so I wait a little with that.
But I measured the 3904:s. All of them had zero volts between base and emitter.
I also measured the voltage between each leg and earth. The highest voltage was around 0.005 volt. Looks strange to me..
And I must tell it was 30 years since I was an active ham, I am 70 now so I'm a little rusty on the electronic skills  ;-)
Håkan

Howard Fidel
 

What range did you use on your meter? The ones in the transmit chain are working so when in transmit, you should have 0.6V there.

Howard

On 6/4/2018 12:03 PM, hakan.sjostrom@... wrote:
To check if the trifilars are shorted I have to unsolder them, so I wait a little with that.
But I measured the 3904:s. All of them had zero volts between base and emitter.
I also measured the voltage between each leg and earth. The highest voltage was around 0.005 volt. Looks strange to me..
And I must tell it was 30 years since I was an active ham, I am 70 now so I'm a little rusty on the electronic skills  ;-)
Håkan


hakan.sjostrom@...
 

I feel a little stupid (again). I just realised that there are a lot more transistors  than I first thought. At my time there were no such small transistors. Yes, I measured only the RX ones. I guess I will have some problems getting back on the air again..