HFU HF Underground
Technical Topics => The RF Workbench => Topic started 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?
-
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.
-
Yeah I thought the same!
Why not ask me...
Str.
-
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.....
-
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.
-
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.
-
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.
-
I posted it for sale in the For Sale forum. Shipping included.
-
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.
-
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.
-
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?
-
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.
-
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
-
Tried to see what voltage the ps is sending to the fet yet?
-
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.
-
"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.
-
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
-
...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)
~
-
...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
-
"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.
~
'
-
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.
-
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.
-
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.
-
..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)
~
-
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.
-
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.
-
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.
-
Not the end then....?
Str.
-
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.
-
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?
~
-
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.
-
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.
-
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.
-
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
-
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 :)
-
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.
-
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.
-
MEANWELL are fine and dirt cheap. I use a 48V 10A one on my 100W design. Coming soon.....
Str.
-
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.
-
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?