Loss of RX on all bands

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SP9TKW
 

Posts: 57
Joined: 03 Jan 2022, 21:11
Location: Krakow

Loss of RX on all bands

Post by SP9TKW »

Hi All,

Could I trouble you for some guidance and advice on fixing loss of RX on all bands on my *Rxxxx* kit.

I build it first as LO Band configuration and it worked ok with exception of efficiency issue. Made number of QSO around Europe.

I decided to convert into CLASSIC Band configuration hoping to improve efficiency. I got 80, 40, 20 and 15 bands done and efficiency was 70-75% without any tuning. This was already improvement by at least 5%.

After another attempt of tuning and assembling TRX in the case (4 outside walls) RX has gone. I can hear very gentle humming when volume is high and I can TX using internal microphone.

I haven't got osciloscope I'm affraid so any basic and simple tests are called for.

Thank you.
73 Marek
DL2MAN
 

Posts: 706
Joined: 30 Dec 2021, 19:18
Contact:

Re: Loss of RX on all bands

Post by DL2MAN »

In most cases, loss of RX is something simple like:
- Bad / Cold Solder Joint on one of the Coils or SMA Connector
- Bad/Non Existent connection between RF Board and Mainboard
- Bad SMA/BNC Adapter
- Bad Cable
When it comes to troubleshooting the RX Portion, an RF Generator and Oscilloscope is very handy.....
I use a the cheap (50$) TinySA as signal Generator and my Rigol 200MHz Digital Oscilloscope.

The RX Path is basically:
- Filter Board (through Relay of active Band Module)
- Inter-PCB Connector Pin RF
- Mainboard RX/TX Switch Q1
- Mixer 3253 (U6) -> also check PLL Chip 5351 (U3) if Clock signals are present
- OpAmp U9
- From there I and Q (already at Audio Frequencies) go directly into AtMega

To troubleshoot RX Path, put the (tr)uSDX into Practice mode (so you don´t accidently blow up your signal generator), insert a Signal into the SMA Connector of RF Board, high enough to make it visible with oscilloscope and follow down the RX Path and see where it stops. This is, where your problem is.
When it´s not on the RF Board, you can remove it and inject RF into Pin "RF" of Mainboard Inter PCB Connector and follow from there. Each Board can be checked individually, however: On Mainboard it requires it to be switched on, so be careful, not to short anything with the probes, and "release the smoke in those multileg fuses" as I´ve read somewhere on facebook :lol:

73 Manuel; DL2MAN
SP9TKW
 

Posts: 57
Joined: 03 Jan 2022, 21:11
Location: Krakow

Re: Loss of RX on all bands

Post by SP9TKW »

Thanks Manuel,

I will follow your instructions. Will ask around, maybe I can borrow oscilloscope for a weekend.

73 Marek
andergrin
 

Posts: 7
Joined: 07 Feb 2022, 13:50

Re: Loss of RX on all bands

Post by andergrin »

Hello. I have a similar problem. After a couple of days of testing and having perfect reception, I turn on the radio another day and can pick up any signals, only noise. I disconnect RF board and tested Si5351 with an oscilloscope, and CLK0 and CLK1 is present.
Can it be that SN74CBT3253 (U6) is broken? Should it be any signal on pin 9 of U6, when it is no any input signal?
Last edited by andergrin on 01 Jul 2022, 10:41, edited 1 time in total.
DD5MA
 

Posts: 14
Joined: 11 Mar 2022, 21:20

Re: Loss of RX on all bands

Post by DD5MA »

Same with me. In teh beginning all was fine and I did some menue-tests. All of a sudden the RX is gone. The S-Meter shows S0 (S-zero) and only at max. Volume I can hear crazy sounds from the speaker? More ideas for solutions. 73 Frank DD5MA
Supply was from *Rxxxx*.
andergrin
 

Posts: 7
Joined: 07 Feb 2022, 13:50

Re: Loss of RX on all bands

Post by andergrin »

andergrin wrote: 28 May 2022, 16:04 Hello. I have a similar problem. After a couple of days of testing and having perfect reception, I turn on the radio another day and can pick up any signals, only noise. I disconnect RF board and tested Si5351 with an oscilloscope, and CLK0 and CLK1 is present.
Can it be that SN74CBT3253 (U6) is broken? Should it be any signal on pin 9 of U6, when it is no any input signal?
After about a month, I turn the radio on, and get excellent receiving on all bands. I do nothing to the radio at this period of time, and it's just works again.
DD5MA
 

Posts: 14
Joined: 11 Mar 2022, 21:20

Re: Loss of RX on all bands

Post by DD5MA »

DD5MA wrote: 28 May 2022, 16:43 Same with me. In teh beginning all was fine and I did some menue-tests. All of a sudden the RX is gone. The S-Meter shows S0 (S-zero) and only at max. Volume I can hear crazy sounds from the speaker? More ideas for solutions. 73 Frank DD5MA
Supply was from *Rxxxx*.
*Rxxxx* gives good service and installed a new board. Works perfect now and the Output Power and efficiencs is better than my second China-Import. (Both were ready to use assembled units).
ik3otw
 

Posts: 5
Joined: 20 Jul 2022, 18:01

Re: Loss of RX on all bands

Post by ik3otw »

Hello,
I also have a similar problem. After about a month of not bad reception, now only background noise.
If I inject a very strong signal into the antenna, it is barely perceived.
I have verified that the RF signal arrives, without appreciable attenuation, up to (U6).
Probably this IC (U6) failed?
If any of you here, who have complained about this anomaly, had managed to solve the problem I would be very grateful to please understand how.
73 Bob iK3OTW
JJ1ILX
 

Posts: 9
Joined: 05 Apr 2022, 22:27

Re: Loss of RX on all bands

Post by JJ1ILX »

I had this problem with one of my boards and went along the RF path as Manuel suggested and found the problem to be the inter-PCB connector. The rf pins on each board had continuity on both sides, but when they were connected together there was no continuity between the two boards. I think because I spent a lot of time on tuning removing and inserting pins it stripped out the internal pin a bit and had a poor conection. I added a bit of solder to the male pin and problem was solved, much easier than removing the header.
Dirkus
 

Posts: 20
Joined: 07 May 2023, 12:14
Location: Elizabeth City, NC, USA

Re: Loss of RX on all bands

Post by Dirkus »

DL2MAN wrote: 19 May 2022, 10:26
- Mixer 3253 (U6) -> also check PLL Chip 5351 (U3) if Clock signals are present…

73 Manuel; DL2MAN
I imagine the clock signals should look like square waves here. I’ve only got a “DSOShell” pocket oscilloscope, and I think the top end on that is 1MHz. I don’t see anything at U3 pins 9 and 10. What should I be seeing, and what can I do about it? I take it I’ll be doing some very fine soldering to replace U3?
-=-=-=-=-=-=-=-=-=-=-=-
DE KO4PCX
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