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peter_77
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Flickering display on TX
« on: 08. June 2021, 09:55:35 »

Just finished a 0.6 mcHF. Everything works fine and as expected. Only one little thing....
If i push the TUNE button or press the PTT the underscore and the the blue freq. step button start to flicker wildly.
Luckily i have a second RF board and put the UI onto the second RF and here everything is fine. No flickering on TX. I also changed the LCD and here is the same behaviour.
I my guess is it must have something to do with the RF board. Detailed behaviour:
  • At initial power on and the very first push on TX display does NOT flicker. All the following TX show flickering
  • While TX is on pushing another button, no matter which one, stops the flickering

Did anybody have an idea what can cause this weired behaviour ?
 flicker.zip
« Last Edit: 08. June 2021, 10:17:18 by peter_77 »
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SP9BSL
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Re:Flickering display on TX
« Reply #1 on: 08. June 2021, 10:51:47 »

Hi Peter,
never saw this before. Looks like you have interaction with frequency multiplier buttons (below the freq knob). I use daily newest firmware and this never happened to me. Look for short circuit or floating pin in STM.
« Last Edit: 08. June 2021, 10:52:25 by SP9BSL » Logged

73 Slawek
peter_77
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Re:Flickering display on TX
« Reply #2 on: 08. June 2021, 12:45:43 »

Hi Slawek !

Thanks for your reply. I guess i can exclude the UI and the STM cause as i said i have a second RF 0.6 board and putting the UI onto that one never showed this error.
So i guess there is something wrong on the RF itself. The only difference is that the RF which causes the flickering on TX hat the RX/TX relay modification while the other one has not.
I'll also have a second I40 UI here and will check that on the suspicious RF board if it behaves different.
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Re:Flickering display on TX
« Reply #3 on: 08. June 2021, 14:14:51 »

I think the issue is on the I2C-bus there (SI570, temp-sensor)...

vy 73
Andreas
« Last Edit: 08. June 2021, 14:15:19 by DF8OE » Logged

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peter_77
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Re:Flickering display on TX
« Reply #4 on: 09. June 2021, 12:21:28 »

Hi Andreas !

Jepp, i guess you are probably right. At first boot an error message said it could not detect the SI and thermal sensor and continued booting but surprisingly the waterfall was active.
A following powercycle did not show the error anymore and could'nt be reproduced too. So my first guess was just a "hickup" at initial boot but maybe there is some more. 
So whats the recommendation ?
Just to follow the i2c line on both pcb's and check for faulty soldering ?
Interesting too: When i remove the shielding between UI and RF it stays stable, no flickering on TX. Maybe mechanical tensions cause this by a bad soldering ?!
So most likely a faulty soldering at the connector between both pcbs. Need to findout where the i2c is located... 
« Last Edit: 09. June 2021, 12:23:53 by peter_77 » Logged
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Re:Flickering display on TX
« Reply #5 on: 09. June 2021, 12:34:41 »

Hi Peter,

all you suggested is pointing to the right track. I cannot 100% diagnost via the distance but I think a soldering problem is highly supposed 

You will fix it - I am sure.

Good luck - vy 73
Andreas
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peter_77
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Re:Flickering display on TX
« Reply #6 on: 13. June 2021, 11:06:45 »

So, after crosschecking all solderings on the UI PCB i am pretty sure the suspect is wild and vagabonding RF.
As i said above: Luckily i have another RF 0.6 board and the main difference is one has the TX relay modification and the other one uses pin diodes.
I placed the UI onto the pin diode RF board and all is fine...no flickering.
Also when i use a breakout test PCB which keeps both PCBs apart at distance for measuring and maintenance and i use the relay modified RF PCB no flickering at all and all ist stable.
When i put the relay RF back to back with the UI as normal i have the flickering. No matter if there is the shielding plate in between or not.

After that i asked myself if the relay modification described on the I40 website is correct ?
There you can see pins 2 and 3 of the Omron relay is placed over the D3 pads.
2 and 3 are the closing contact. (Relay is the 5V non U version !)
So that means in RX condition the TX PA Out contact via C78 is contacted through via C81. (D3 pad closed)
On TX when the relay gets 5V the pin 2 and 3 contacts over D3 are open, which means the output via C81 is disconnected from TX PA Out.
That sounds weired to me.
I would have expected that in TX condition (relay active) the contacts via D3 should be closed.
So is this probably an error in the TX relay modification diagram from the I40 website ?
« Last Edit: 13. June 2021, 11:11:52 by peter_77 » Logged
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Re:Flickering display on TX
« Reply #7 on: 14. June 2021, 04:57:55 »

No, there is no error.

In RX the antenna path is connected to RX and in TX the connection is open. TX is alwas connected and never interrupted.

vy 73
Andreas
« Last Edit: 14. June 2021, 04:58:06 by DF8OE » Logged

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Re:Flickering display on TX
« Reply #8 on: 18. June 2021, 13:37:30 »

I modified the relais modification a bit so that it comes closer to what the pin diodes do. (see bottom) C78 now was pulled to ground at TX what D4 does.
But...unfortunately no difference. The step prompt flickering rate is much lower but definitely not gone. 
One guess is that i have not installed R54 and C79 at port "ANT_RX_ON". So that one is kinda "free" in the air and probably gets some RF unter TX conditions. So far not testet this with placing a 100nF towards ground there.
Maybe i give this a last try otherwise i make Digi Key happy and order 2 pin diodes to finally get rid of this annoying issue.
 RelMod.jpg
« Last Edit: 18. June 2021, 13:40:35 by peter_77 »
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Re:Flickering display on TX
« Reply #9 on: 18. June 2021, 13:58:15 »

Hi Peter,

I am definitely sure the relay mod is not the issue. Maybe it has influence - but that's all. You do have a problem with RF radiation at another place that you have not located yet. Dropping the relay mod does not remove the problem - only one sympthom (maybe there are others at signal purity e.g.)

vy 73
Andreas
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peter_77
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Re:Flickering display on TX
« Reply #10 on: 19. June 2021, 10:10:35 »

But giving the fact that the same UI runs without any issue on another RF board with pin diode RX/TX excludes the UI board itself as a suspect i assume.
The other way round that RF board with a I40 UI board is also fine. Its a bit weired i admit.
I crosschecked also the step buttons and their 100nF to ground, all fine.
Anyway...i'll wait for the pin diodes and will report what happened after the conversion. 
« Last Edit: 19. June 2021, 10:11:53 by peter_77 » Logged
DF8OE
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Re:Flickering display on TX
« Reply #11 on: 20. June 2021, 07:14:23 »

Hi Peter,

again: you are following the wrong track. There is no logic that supports the idea of switching has an influence on LCD and hundreds os mcHF using relay mod are working properly.

Please remind what switching does:
In TX it is ideally "not present". Signal path from PA to antenna jack is ALWAYS active.
In RX it switches preamp input to antenna.

Your flickering is only in TX. If switching is ideally not present there the relay solution is a much better approach than the PIN diode approach. PIN diodes do behave as normal diodes when you go down with working frequency. So you are crippling your TX signal.

You do have RF at places where RF should not be. Maybe you can compensate this by leading some RF via PIN diodes to GND. But I think if you replace the switching the issue will persist. You will see 

vy 73
Andreas
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