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Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

I used another transmitter close to my v3 and blew q90.
Replaced q90 and all was good. Dave? kc2ipx

On Wed, May 13, 2020 at 9:18 AM Raj vu2zap <rajendrakumargg@...> wrote:
Also check Q90 EBC voltages. We have to eliminate a possible short of Q90 EB junction.

Raj

At 13/05/2020, you wrote:
>That you Ray, I will do that immediately.
>Jep




Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Also check Q90 EBC voltages. We have to eliminate a possible short of Q90 EB junction.

Raj

At 13/05/2020, you wrote:
That you Ray, I will do that immediately.
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

That you Ray, I will do that immediately.
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Just for info, now I completed the re-soldering of all the thru-hole joints of the ubitx board. But the problems remained unchanged.
So..., I must argue it is time to check individual transistors and diodes, starting from the front-end as suggested by Jonas.

As already briefly mentioned, here at my "marine" location some 50 km North of Rome I only have a digital multimeter instrument, and by now (due to pandemia lock-down) there is no chance to move to Rome and access an oscilloscope or whatsoever... Let's consider that an exercise for emergency conditions: Use more the brain instead of sofisticated instruments :-).
Cheers
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

This tells me the issue is with L1-4 T1 T2 or mixer diodes. check R100-103 for value and solder.

Raj

At 13/05/2020, you wrote:
Yes, it is exactly so.... so it is confirmed no RF reach the PA while I push the key in CW or speak on the microphone.
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Yes, it is exactly so.... so it is confirmed no RF reach the PA while I push the key in CW or speak on the microphone.
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Well.... yes, this might have happened. I had some other 100W trx on the same desk before, so I cannot exclude some RF entered the ubitx while I was transmitting using something else. I have only a dipole, but the antenna-switch was common to three transceivers.
How could I check if Q90 and the diode bridge are fried?
Bests
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Hi Dave,
no, it is not 6A.... it is just 0.6A which I think is the idling current on transmit (it is 0.12A on receive). When I press down the key or speak on the microphone it remains the same, which means no RF at all arrives to the PA input.
My ubitx V3 has been not modified at all, I only added an audio filter for CW and a CW keyer: these are separate boards not affecting at all the ubtix main board. Such add-ons have been working for long time before the present problem surfaced.
73
Jep
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

It's 0.6A which is correct with no modulation!

Raj

At 13/05/2020, you wrote:

6 amps is not normal on key down. Normal is something like 2+ amps.

What caused it to change? Did you modify the unit in any way from when it worked till when it didn't work.
Did you transmit locally on another radio with the ubitx on?

73
Dave
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Or even connected to a nearby antenna while transmitting on another radio?? It doesn't have to be turned on for Q90 and the 1st mixer diodes (D1 & D2) to be fried. I know this from experience... :-)?
The symptoms I had match yours (perhaps minus the 6Amps, but I don't?think I measured so cannot say for sure)

Regards,
Jonas - SM4VEY

Den ons 13 maj 2020 kl 13:15 skrev _Dave_ AD0B <davesters@...>:

6 amps is not normal on key down. Normal is something like 2+ amps.?

What caused it to change? Did you modify the unit in any way from when it worked till when it didn't work.
Did you transmit locally on another radio with the ubitx on?

73
Dave


_._,_._
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

6 amps is not normal on key down. Normal is something like 2+ amps.?

What caused it to change? Did you modify the unit in any way from when it worked till when it didn't work.
Did you transmit locally on another radio with the ubitx on?

73
Dave
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Jep,

I had 5 boards of V3 with bad solder of L1/2/3/4 also check L5/7

check continuity of toroidal coil on solder side.

These were the first uBitx with solder problems in cils.

Raj

At 13/05/2020, you wrote:
Hi Ray,
I just re-soldered the D1-D2 bridge and its two trifilar toroids, and also L1..L4 that follow it, but the "simptoms", i.e. reduced RX sensitivity and no power on TX, remained unchanged.
So the signal is probably "trapped" somewhere else in the path. Will have so continue searching....
Stay tuned, cheers
Jep, IZ0WIT
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Hi Ray,
I just re-soldered the D1-D2 bridge and its?two trifilar toroids, and also L1..L4 that follow it, but the "simptoms", i.e. reduced RX sensitivity and no power on TX, remained unchanged.?
So the signal is probably?"trapped" somewhere else in the path. Will have so continue searching....
Stay tuned, cheers
Jep, IZ0WIT
Re: #raduino #v5 #raduino #v5

 

Hi, I copied the pinout from Jim Sheldon¡¯s post except the 22 Ohm resistor on pin8 ( I don¡¯t have 22 ohm at the moment). Plug the nano with debug sketch , touch function is working & all beeps are presents , but on R1.5.0 , no touch still , but it¡¯s fine with me , ubitx is working anyway, alignment & calibration next , again BIG thank you for the folks here in bitx20 group.?

darwin EI3IHB?
Re: #raduino #v5 #raduino #v5

 

Hi ,really appreciated this big help especially from Reed and the folks here in bitx20 group .?

?
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Hi Ray,
it seems we had a very similar problem then... I will try doing this check just now !
Will let you know, thank you so much
Jep, IZ0WIT?
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Yes, on Rx itself I have slighty over 100 mA, it becomes about 600 mA on key down or PTT-ON on SSB.?
If I speak on the microphone the drain current does not increase, but I could listen at my voice on a separate receiver in the nearby.
So the signal is lost somewhere from the mixer to the PA.? In CW I could list at the signal, but total current remains at 0.6A.
The suggestion to hunt for possible cold joints sounds right. I will do it.
Thanks
Jep, IZ0WIT
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Jep,

Check soldering on trifilar toroids. Had this issue on a board.

Check soldering on mixer diodes. Use the tip of a small screwdriver of similar and press down on the SMD diodes leads
and see if that makes a difference. It will look soldered but not!
One of my low sensitivity and low output boards had this problem.

Raj

At 13/05/2020, you wrote:
Hi,
I checked the BNC and also the two-pin plug on the motherboard, and the very short RG174 coax to the BNC: all seems OK.
As a matter of fact, when I listen at the ubitx TX signal on a separate receiver, I could hear the signal increases on keying, but the RF-out level from the PA is negligeable.
Could be a fault of the mixer stage? That could explain the twin problem on RX .AND. TX ?
Is 0.6A total current on TX key-down normal or it should be higher?
Thank you fot he kind help, 73
Jep, IZ0WIT
Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Jep ,
I used to measure 150 to 200mA on Rx itself.?
I came across a situation where few pins of exciter were dry. I put my funer bowand try shaking components. Where ever i had doubt, i soldered. Like this i had to solder around 10 to 12 , may be crystals, may be bi and trifilar trafos. Etc.?
Finally the set responded well and is now stable.?

Hope it helps

On Wed, 13 May 2020, 12:19 pm Jep, <giuseppe.cavarretta@...> wrote:
Hi,
I checked the BNC and also the two-pin plug on the motherboard, and the very short RG174 coax to the BNC: all seems OK.
As a matter of fact, when I listen at the ubitx TX signal on a separate receiver, I could hear the signal increases on keying, but the RF-out level from the PA is negligeable.?
Could be a fault of the mixer stage?? That could explain the twin problem on RX? .AND.? TX ?
Is 0.6A total current on TX key-down normal or it should be higher?
Thank you fot he kind help, 73
Jep, IZ0WIT

Re: Poor RX sensitivity, no RF out - #v3 #ubitx #ubitx-help

 

Hi Dave,
I tapped that relay with the scriwdriver handle, but nothing happens. RX low sensitivity is real, I could hear strong signals on 40m at evening, but I have to keep the vol. control near its maximum; anyway this is not an audio amp. problem as the sidetone level on keying is high.
73
Jep, IZ0WIT
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