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Author Topic: Stretchyman “40W TX” Failure Investigation and Remediation  (Read 3669 times)

Offline outhouse radio

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #45 on: July 03, 2021, 2040 UTC »
never have seen a video of one of these things actually performing while hooked to any equipment like a scope and meters etc ,
that's one reason why i never bought one of his things, i get a snicker every time someone airs with one of his things and you see the comment STRETCHY MOD on rocket chat  ;)
-
ps - i decided not to buy from him  or recommend one of his things to anyone long before this thread ever started ,
everyone has to make their own decisions ..

HAVE A NICE DAY

Offline Stretchyman

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #46 on: July 04, 2021, 1841 UTC »
You haven't watched YouTube then?

The newer designs are fine.

I'm trying my best and as suggested just ignore the the negative Twxt

You have a nice a nice day too!

Go away Charlie, we're all tired of you.

Str.
« Last Edit: July 04, 2021, 1847 UTC by Stretchyman »
'It's better to give than receive' so why RX when you can TX!

         15W and100W models available.

                   Buy one from me, NOW!


                                              ;)

Offline outhouse radio

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #47 on: July 05, 2021, 0232 UTC »
You haven't watched YouTube then?

The newer designs are fine.

 then do a video with them hooked to a scope etc and prove it . it's that simple .
because 13 minutes of you jabbering and waving your hands around doesn't prove a thing .
https://www.youtube.com/watch?v=Pf98INtkBeI
neither does 4 minutes..
https://www.youtube.com/watch?v=WS3opIkvGac
and neither does 3 minutes
https://www.youtube.com/watch?v=myWBTN394g4
-
come on now ,post a video with them working hooked to un-doctored equipment and show the masses how they actually work . because those video's don't do it and your word doesn't mean much .


if a picture is worth a thousands words , then just think what video proof is worth .  ;)

have a nice day


Offline KaySeeks

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #48 on: July 05, 2021, 1853 UTC »
I'm trying my best and as suggested just ignore the the negative Twxt

Go away Charlie, we're all tired of you.

We're not looking for you to be performing on-the-job training and you've shown yourself to be less than transparent. If you can't be trusted to get basic, important details right the first time, why should we trust you now?

I, for one, would like to see more details and inspection, not less. Your attitude leaves me with the impression that you are trying to prevent inquiry and hard questioning, and it's clear that I am not alone.

Reading back through some of these posts over the past 12-18 months just now, I can tell from your statements and answers that you might not be the right person to be making transmitters for anyone but yourself. I don't get a confident feeling that you know what you are doing.
« Last Edit: July 05, 2021, 1909 UTC by KaySeeks »
Just somebody with a radio, a computer and a pair of headphones...

Currently in Quebec.

Offline Charlie_Dont_Surf

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #49 on: July 06, 2021, 0625 UTC »
We're not looking for you to be performing on-the-job training

You hit a sore spot. You told the truth.
"such a TW*T". "Just ignore...." - Stretchyman


Every minute Charlie squats in the bush, his signal gets stronger...

Offline Charlie_Dont_Surf

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #50 on: July 06, 2021, 0645 UTC »
because those video's don't do it and your word doesn't mean much .

With talk like that you better watch out because the fanboy army is at this moment circling the wagons. They're coming for you.  :D
"such a TW*T". "Just ignore...." - Stretchyman


Every minute Charlie squats in the bush, his signal gets stronger...

Offline Stretchyman

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #51 on: July 06, 2021, 1341 UTC »
Let someone else do it then an put up with all the crap you lot spit out.

Fact is no one else will!

Good job I'm thick skinned.

I will leave you all alone.

Bye.

Str.
'It's better to give than receive' so why RX when you can TX!

         15W and100W models available.

                   Buy one from me, NOW!


                                              ;)

Offline radiogaga

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #52 on: July 06, 2021, 1557 UTC »
Dont let the door hit you on the way out................ ;D ;D ;D

rgg

Offline outhouse radio

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #53 on: July 07, 2021, 2105 UTC »
Let someone else do it then an put up with all the crap you lot spit out. <<<< TRUTH HURTS DON'T IT ...

Fact is no one else will!

Good job I'm thick skinned. <<< YOU SPELLED ARROGANT A&&HOLE WRONG ....

I will leave you all alone. <<< WE CAN ALL HOPE ...

Bye. <<< PLEASE LET IT BE TRUE ...


Str.

i knew he wouldn't post video proof ..

no offense intended to anyone running one of his things ...
like i said earlier , we all make are own decisions ...
have a great day/night
 
« Last Edit: July 07, 2021, 2114 UTC by outhouse radio »

Offline redhat

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #54 on: July 08, 2021, 1542 UTC »
I guess I should have read this document Sooner.

Some thoughts;

I have lost a handful of SiC devices over the last few years while building my transmitter, and usually they failed because of my assumptions in design leading to a few deficiencies.  One thing I did find during my research is that most of the failures occurred during drive loss events.  This seems to be evident in the transient nature of the waveforms you observed.  Most DDS devices produce a DC output when not programmed, and this is specified in the Analog Devices datasheet for the AD9850.  I think Stretchy was using a 9800 series DDS in his devices, mainly for cost reasons.  Until the program is loaded into the DDS, it will latch the output of the PA on, causing an overcurrent failure of the transistor.  My solution was to add a drive loss protection circuit, and I have not lost another device since.

The later versions of his transmitters I noted the elimination of the modulation transmitter, and instead feeding the PA directly from the modulator.  This may well have solved the problem, as the modulator has overcurrent sensing and protection built in.

+-RH
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WinRadio Excalibur, Airspy HF+, Kenwood KDC-U356 for mobile listening.
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Offline Charlie_Dont_Surf

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Re: Stretchyman “40W TX” Failure Investigation and Remediation
« Reply #55 on: July 08, 2021, 2151 UTC »

Until the program is loaded into the DDS, it will latch the output of the PA on, causing an overcurrent failure of the transistor.


In this doc (https://app.box.com/v/3ysyx-444reop) in Figure 17 on page 18,
I show the behavior of the gate (which means that it is coming straight from the DDS through the FET driver). It goes through some sort of power-on behavior which causes the gate to pulse and since the drain voltage is already applied, the transistor turns on, etc. Unfortunately, the gate (and thus the DDS) behavior was not at all consistent - each time you turned it on, it looked slightly different (different pulse length, different number of pulses, etc.), which lead me to believe that it is not the result of some sort of UVLO or POR, which I would think would be the same each time you turned it on.

My solution was to add a drive loss protection circuit, and I have not lost another device since.

What you describe is the elegant and preferred solution, IMO. The caveman solution in this case (in addition to protection passives all over the place) was to change the power supply sequencing so that the DDS supply goes on first to let the DDS and the gate go through its (unpredictable) turn on sequence then - after some period of time where it is safe - apply the drain voltage while it is on but still idle. Obviously if you wait too long to apply the drain voltage, the gate will already have a squarewave drive applied and you risk problems not unlike the problem you are trying to solve.

I did not do this in the end because I thought that the modifications would be a bit advanced for some and I was trying to keep things on the simple side.

The later versions of his transmitters I noted the elimination of the modulation transmitter, and instead feeding the PA directly from the modulator.  This may well have solved the problem, as the modulator has overcurrent sensing and protection built in.

My understanding is that his 100W TX uses a PWM.

I have a PWM circuit in the works that is meant for a wide-variety of mid and low-power transmitters, and I suppose could be an add-on to replace the Class-D amp and modulation transformer in a Stretchy 40W TX. It generates its own internal and external DC voltages and has a simple power sequencer (TI LM3880) to apply those voltages in an ordered manner, creating a safe and predictable turn-on and turn-off sequence for the whole TX. The revision 2 PC board is back from the fab house but I am focused on other things at the moment and haven't populated it yet.
« Last Edit: July 09, 2021, 0429 UTC by Charlie_Dont_Surf »
"such a TW*T". "Just ignore...." - Stretchyman


Every minute Charlie squats in the bush, his signal gets stronger...