Poor receive levels

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JJ1ILX
 

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

Poor receive levels

Post by JJ1ILX »

Hi everyone,

I have my kit put together powered up and am starting to test things.

It currently transmits on all the bands at 3.8~4.1W at 12V with 81~83% efficiency. I can work on the toroids a bit later to see if I can improve that.

However there is very limited receive. A signal that is coming in 59+10db is only sometimes moving the S meter up to S4, but generally throughout 20 and 40M it just sits flat at S3 and I can only hear super strong stations.

I believe there are two possible causes:
1: T1 has a bad electrical connection
2: LT6231 is bad

Is there any simple test I can perform to determine if either is the potential cause, I especially would not like to desolder the IC chip if I can avoid it, so anything I can do to confirm that is the case if rewinding T1 does not solve the issue would be helpful.

Any other suggestions or potential diagnosis are also welcome.

David / JJ1ILX
dl6sez
 

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: Poor receive levels

Post by dl6sez »

Hello David,

if you see output power on a band there is no issue with T1.
If T1 is not correct, you should have blown your output bs170 output transistors on transmitting.

Have you changed "Att 2" in Menue? This should be left on "2" because it is needed to reset the AGC.
Is "AGC" Menue on?
Bad LT6231 or bad chinese copy/fake chip, or bad substitute chip would do a bad sideband supression, it does not really change sensitivity. I had this on mine, but receiver was good, only bad sideband suppression was my problem with LM833 instead of LT6231.
But beware of fake LT6231 from chinese supplier, i have 3 chips here which are obviously a fake.

Some of the Tayloe Mixer switches the
SN74CBT3253
in the circuit have had issues because they are bad chinese copies in the last months.
So if you didn't succeed with Menue changes, you could change/measure rx/tx switch Q1 2N2007,
and if it is okay, i would change SN74CBT3253.

73 de Chris DL6SEZ
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
JJ1ILX
 

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

Re: Poor receive levels

Post by JJ1ILX »

Hi Chris,

Thanks for the suggestions.

It looks like the issue is with LT6231. Actually the first mainboard I received from Up Tech Store on Aliexpress never booted up and they were great in helping me try to troubleshoot. In the end they sent me a new assembled main board. The were the ones to suggest the LT6231 initially.

I have tested the voltages on the first board they sent me and the top right to bottom left pin show 4.75V. The chip was also installed with all the other surface mount parts when the PCB was printed. Whereas the one they sent me it looks to have been soldered by hand, no solder bridges, but the voltage from the same pints is only 1.3V.

So this leads me to believe that might be the issue. I am going to attempt removing the low voltage chip and installing the chip from the initial board with the higher reading and will write an update on what happens.
storyofyouandme
 

Posts: 54
Joined: 03 Jan 2022, 15:30

Re: Poor receive levels

Post by storyofyouandme »

Finally, is your board 3253 fault or 6231 fault? Thank you.
73!
storyofyouandme
 

Posts: 54
Joined: 03 Jan 2022, 15:30

Re: Poor receive levels

Post by storyofyouandme »

I replied to the post a year ago and it is no longer valuable. Please delete my reply.
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