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Technical Topics => The RF Workbench => Topic started by: Antennae on September 22, 2019, 1532 UTC

Title: Stretchyman 40w GaN TX is sick
Post by: Antennae on September 22, 2019, 1532 UTC
I have a Stretchyman 40W transmitter I use for communications on the ham AM band. Got good reports BTW.

So I hooked up my 24V powersupply into the  TX and it made a couple pop noises and then it quit working.  The PS is an AC to 24V DC converter.

I think I may have had the transmitter "on" and my PS was "on" when I plugged the PS into the TX. 

It made a pop noise in the past, so I've been plugging them together with them off.  Then I first turn on the PS, and then I turn on the TX.  But I didn't do that this time and now it doesn't work.  I checked the fuse and its good. 

Any ideas whats wrong? Maybe I can replace something? 
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Kage on September 23, 2019, 1943 UTC
Damn I was hoping this post would be about how sick, as in awesome his transmitters are. He seems to be quite the tech guru and knows a hell of a lot more than me on class D and E hands on work. Sure he will chime in :) Really no idea why I am replying, just thought the title of the post was about how cool his little rigs are and I probably drank a few too many beers or something.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on September 23, 2019, 2039 UTC
Yeah I thought the same!

Why not ask me...

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on September 25, 2019, 0533 UTC
I still await a reply and have PM'd you 'ANTENNAE'

I'm still somewhat perplexed at your post and lack of response......

When inquiring about any issues with a product purchased I would have thought getting in touch with seller/designer would have been the first thing to do?

PLEASE reply to my PM.

Regards

Stretchy.


p.s. BTW when turning on ANY supply it wont be regulated and pump-out A.C.

There's lots of things to try and maybe its just a burnt connector.....
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on September 25, 2019, 1618 UTC
Hold your horses dude!  Here's my response why I posted this here:  It was to see if anybody else had this problem.  And if a solution was given on this post it would help other viewers out in the future in case theirs popped.  Its already probably going to help people out because now they know how to plug in their power supply (and what can happen if they don't do it properly).  I'm grateful and fortunate that Stretchy is here to help.   
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Pigmeat on September 26, 2019, 0824 UTC
Did you check the fuse in the power supply? You can give both the trusty smell test while they're shut off. If one smells like ozone and the other doesn't you know where your problem is before you go poking around.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on September 26, 2019, 1511 UTC
Hey Pigparts, they both kind of smell electronicsy.  The supply as a problem is a good point. But I tested with a battery and still no avail. 
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on September 26, 2019, 1911 UTC
I posted it for sale in the For Sale forum.  Shipping included.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 03, 2019, 0018 UTC
FWIW, I removed the old MOSFET and it failed the test with a multimeter.  So I ordered a new one and installed that today. It worked but it made a big pop noise.  I turned it on and off and it stopped working again after the 3rd time. 
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 03, 2019, 0528 UTC
TBH I'm not happy as one, you have refused my offer of (free) help and two, messing about when I have already offered advice as to where to start.

You have surely assumed (somewhat incorrectly) you would be charged some astronomical fee to fix the unit when I have in the past never charged a cent and even paid the return postage.

For any future purchasers of any of my products, just send it back, you wont be charged.

Str.

Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 03, 2019, 1750 UTC
Its not all "unicorns and fairy-free," it costs money to ship it there and time/work to pack it up to send it on an international journey as well as the time without a transmitter.

Messing about was fun.   

I think one of the integrated circuits  broke and that blew out my transistor. 

Does anybody else have problems with their stretchyman transmitters? 

Title: Re: Stretchyman 40w GaN TX is sick
Post by: JimIO on October 03, 2019, 2038 UTC
I worked for years troubleshooting SMPS's. You have to replace all of the bad components before you power it up. Sending it back to the guy who designed and built it is a no brainer.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: redhat on October 03, 2019, 2126 UTC
These modern transmitters have a lot in common with switching supplies...both operate in switch mode (class D or E) and the waveforms feeding the power devices have to be right or the smoke comes out.  I too spent a few years working on SMPS's exclusively and the first thing you did before bringing up the mains was testing the drive waveforms.  If they don't look right, your mosfets won't last long.

I understand the frustration, but you need the have the tools and know-how to work on these things.  Its not like the tube days when you could swap a tube or two and see what happens.  More often than not in solid state, you're greeted with pops, bangs, and puffs of smoke.

+-RH
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Josh on October 03, 2019, 2135 UTC
Tried to see what voltage the ps is sending to the fet yet?
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 04, 2019, 0125 UTC
I see. Thats why Stretchy had me check it with an oscilloscope.  It has a sinusoidal wave where there should be a square wave. 
Thanks for your input, I'm done with it for now. I'll use it as a decoration, kind of like a star wars model with battle damage. 
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 04, 2019, 1105 UTC
"Its not all "unicorns and fairy-free," it costs money to ship it there and time/work to pack it up to send it on an international journey as well as the time without a transmitter".

So for the $30 it will cost to send it back, you can't be bothered?  + time without a TX, er.... it doesn't work!

I cant see the logic there, at all.

You can't test a FET with a multimeter (def not this one as it's got two devices in one package) I could go on, but wont....

I've tried my best, I'm not going to force you to send it back.

Good luck.

Stretchy.

Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 04, 2019, 1646 UTC
Dude, I ain't lyin' or tryin' to slander you, Stretchypants.   ::) 

I'm a member of a shortwave pirate forum and I've got my own conspiracy theories about you and your extraordinary repair policy, so there.   ;)

Here's a nice video of the method I used to test the mosfet with my multimeter:
https://www.youtube.com/watch?v=tL7bQuJaXKA

Title: Re: Stretchyman 40w GaN TX is sick
Post by: JimIO on October 04, 2019, 1752 UTC


 ...and I've got my own conspiracy theories about you and your extraordinary repair policy, so there.   ;)

Here's a nice video of the method I used to test the mosfet with my multimeter:
https://www.youtube.com/watch?v=tL7bQuJaXKA


Gotta love (not) the stand w trump and epoch times ads you get when you click that link.    8)

~
Title: Re: Stretchyman 40w GaN TX is sick
Post by: redhat on October 04, 2019, 1818 UTC


 ...and I've got my own conspiracy theories about you and your extraordinary repair policy, so there.   ;)

Here's a nice video of the method I used to test the mosfet with my multimeter:
https://www.youtube.com/watch?v=tL7bQuJaXKA


Gotta love (not) the stand w trump and epoch times ads you get when you click that link.    8)

~

Serves you right for not running adblock
Title: Re: Stretchyman 40w GaN TX is sick
Post by: JimIO on October 04, 2019, 1951 UTC
"Serves you right for not running adblock"

For now I'll just wait a bit then click skip ad.

I need to figure out why in firefox after 67 the override colors does not work first.

~


'

Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 05, 2019, 0836 UTC
As already stated the internal structure of the GaN FET is not standard and is CASCODE and contains 2 devices. It can't be tested using the method stated. The fault has nothing to do with the FET anyway.

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 05, 2019, 1600 UTC
Well, for posterity's sake, my old one didn't pass the test and my new replacement did pass the test.  And you mentioned there are 2 devices in the FET, that would make sense because I heard multiple pops...before it stopped.  R.I.P.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 05, 2019, 1908 UTC
Please if anyone has any problems with any of my products please send it back immediately.

I can assure you it will be a swift turnaround and at minimal cost.

Please don't mess around and waste your time (and mine) as has happened here.

Stretchy.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: JimIO on October 06, 2019, 0258 UTC
 ..that would make sense because I heard multiple pops...before it stopped.  R.I.P.

Troubleshooting tip: Turn the PS off just before you hear the first pop.    8)

~
Title: Re: Stretchyman 40w GaN TX is sick
Post by: OgreVorbis on October 06, 2019, 0927 UTC
I'll bet the problem is that one of the NCPs is fried.

My newer transmitter uses those NCPs and I fried a lot of them during the testing process. Yes, it is best to apply the low level voltage first and then the HT after.

But Stretchy knows what he's doing and probably has good symmetry and square waves.

I fried so many of those NCPs when I was designing mine. Just a tiny bit off in symmetry or a slightly rounded wave will make those things bake themselves really fast.

I doubt there is a problem with Stretchy's transmitter as he's been doing this a long time. I just don't like those NCPs very much, they're not any better than the 614s and they can't dissipate heat, so if there is a small problem, you're screwed. Maybe it's better in the long run though because it won't allow you to be sloppy. Even in optimum conditions, you can't apply more than 15V to them.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 06, 2019, 1603 UTC
In my design I drive a GaN FET with 8V, I fact it's fine with just 6V. The NCP drivers are perfect and barely get warm.

Please can everyone stop guessing what's wrong with this Tx. I suspect because A.C. has been applied momentarily, everything had fried. I know the op has stated there's only 5V arriving at the RF PCB and there should be 12V.

The op has decided to refuse my offer to fix it for free, let's leave it there shall we.

I'd rather not spend anymore time with this thread.

The End.

Hopefully....

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: ChrisSmolinski on October 06, 2019, 1615 UTC
You're free to ignore this thread, Stretchy, as the original poster, and others, are free to continue it. We can always learn something  :)

In my design I drive a GaN FET with 8V, I fact it's fine with just 6V. The NCP drivers are perfect and barely get warm.

Please can everyone stop guessing what's wrong with this Tx. I suspect because A.C. has been applied momentarily, everything had fried. I know the op has stated there's only 5V arriving at the RF PCB and there should be 12V.

The op has decided to refuse my offer to fix it for free, let's leave it there shall we.

I'd rather not spend anymore time with this thread.

The End.

Hopefully....

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 06, 2019, 1859 UTC
Not the end then....?

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 06, 2019, 1948 UTC
Its not over 'cause the OP's in da house, woot woot!

To prevent AC with my 24V AC to DC power supply, if I were to have a second go at it, I would wire in 2 x 12v lightbulbs so they make a 24v load to the power supply.
So my sequence would go like this:

Turn on PS and make sure my 24 volts worth of lights are powered on
Make sure xmtr is off
Then plug PS into transmitter
Then turn on xmtr and start calling CQ

That way I figure the PS would be producing DC before it goes into the transmitter. 
Title: Re: Stretchyman 40w GaN TX is sick
Post by: JimIO on October 06, 2019, 2106 UTC
Wut  ;D kind of PS is it that you would need to do that?

Antenna: usually a random wire with tuner

Is that wut ;D you use to TX?

~
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Antennae on October 07, 2019, 0315 UTC
I have a cheap-o PS I got from amazon. Its really stable and has its own variable fan. Says it can do up to 15A.

https://www.amazon.com/gp/product/B01CS5G8J6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I've got an inverted L that is about a 1/4 wave on upper 80m where the AM guys are.  There's a ground rod at the feedpoint and thats where I put the tuner. 

Title: Re: Stretchyman 40w GaN TX is sick
Post by: Kage on October 07, 2019, 0354 UTC
And this is why I don't sell my old homemade transmitters to people. I've been asked before but always feared something like this would happen and I don't even build on a professional level like stretchy does. Oh those multiple pops... sure someone wasn't making microwaved popcorn in the other room? I could use some reading this thread.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: OgreVorbis on October 07, 2019, 1041 UTC
I have a cheap-o PS I got from amazon. Its really stable and has its own variable fan. Says it can do up to 15A.

I don't understand why so many people buy those unbranded Chinese power supplies. I've seen many of those malfunction.
I could understand if the price was significantly cheaper, but IT IS NOT.

You can get a good quality meanwell of that power level for $30
$19 vs $30 bucks isn't a big deal.

https://www.trcelectronics.com/View/Mean-Well/LRS-350-24.shtml (https://www.trcelectronics.com/View/Mean-Well/LRS-350-24.shtml)

Once you get into the higher wattages, then it makes sense. For those higher powers, eltek flatpacks, and Chinese Velikas are good.
https://www.aliexpress.com/item/32835899833.html (https://www.aliexpress.com/item/32835899833.html)

Sorry to get off topic. I'm done.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: redhat on October 07, 2019, 2334 UTC
I have a cheap-o PS I got from amazon. Its really stable and has its own variable fan. Says it can do up to 15A.

I don't understand why so many people buy those unbranded Chinese power supplies. I've seen many of those malfunction.
I could understand if the price was significantly cheaper, but IT IS NOT.

You can get a good quality meanwell of that power level for $30
$19 vs $30 bucks isn't a big deal.

https://www.trcelectronics.com/View/Mean-Well/LRS-350-24.shtml (https://www.trcelectronics.com/View/Mean-Well/LRS-350-24.shtml)

Once you get into the higher wattages, then it makes sense. For those higher powers, eltek flatpacks, and Chinese Velikas are good.
https://www.aliexpress.com/item/32835899833.html (https://www.aliexpress.com/item/32835899833.html)

Sorry to get off topic. I'm done.

Agreed.  Mean Well is as bottom of the barrel as I'll go.

+-RH
Title: Re: Stretchyman 40w GaN TX is sick
Post by: ChrisSmolinski on October 08, 2019, 0934 UTC
Hamfests are great sources for cheap but good power supplies. I have seen Vicor switchers for reasonable prices.  I have a Lambda 5V linear supply (9A rating I think) I use to power my netSDR and KiwiSDR. Sure the efficiency is not great and it runs a little warm, but it has a clean output. It runs around 48C but is rated to over 70C.   I keep meaning to put a little muffin fan on it to move some air around but all the fans in my collection are 12V  :)
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Pigmeat on October 08, 2019, 1935 UTC
Yep, hamfest power supplies are cheap. If they blow you've got pre-milled box with plenty of spare parts. I've never paid over ten bucks for one.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Josh on October 10, 2019, 1819 UTC
Some of those surplus open frame supplies are amazing, had a 10 amp 12v job that you couldn't measure a dip in v or a when you slapped a car headlight across the output.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Stretchyman on October 10, 2019, 1823 UTC
MEANWELL are fine and dirt cheap. I use a 48V 10A one on my 100W design. Coming soon.....

Str.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: KaySeeks on October 23, 2019, 2025 UTC
These modern transmitters have a lot in common with switching supplies...both operate in switch mode (class D or E) and the waveforms feeding the power devices have to be right or the smoke comes out.  I too spent a few years working on SMPS's exclusively and the first thing you did before bringing up the mains was testing the drive waveforms.  If they don't look right, your mosfets won't last long...
Its not like the tube days when you could swap a tube or two and see what happens.  More often than not in solid state, you're greeted with pops, bangs, and puffs of smoke.

I'm in violent agreement with the above.
Title: Re: Stretchyman 40w GaN TX is sick
Post by: Charlie_Dont_Surf on June 27, 2020, 2100 UTC

So I hooked up my 24V powersupply into the  TX and it made a couple pop noises and then it quit working.  The PS is an AC to 24V DC converter.

I think I may have had the transmitter "on" and my PS was "on" when I plugged the PS into the TX. 

It made a pop noise in the past, so I've been plugging them together with them off.  Then I first turn on the PS, and then I turn on the TX.  But I didn't do that this time and now it doesn't work.  I checked the fuse and its good. 




I see that this problem has been catching on. Maybe it is caused by a virus?