Date   

Re: 50 watt Amp IRF 510 Failure

geoff M0ORE
 

Firstly, it would be foolhardy to open a power device as some contain something nasty, Beryllium or something like that. Almost as bad for you as Coronavirus.

Secondly, a Spectrum Analyser looks at frequency versus  level, an oscilloscope looks at level versus time.


On 06/03/2020 15:39, Brad Thompson wrote:
Hello--

/speculation mode on/

If would be interesting to de-encapsulate some of the failed IRF 510s
and analyze what damage occurred to the die (or dice). To paraphrase
an old vaudeville routine, "Is there a doctor. er. failure analyst in the house?<g>.

Second, is it possible that transient parasitic oscillation occurs at some combination
of thermally-varying device characteristics? The oscillation frequency could be
somewhere in the VHF or lower UHF range and might occur quickly.  This
exploration would require a spectrum analyzer capable of capturing "snapshots"
of frequency versus time, and one or more sets of sacrificial IRF 510s.

/speculation mode off/

73--

Brad  AA1IP






Re: Fast shipping

George Korper
 

Well done Hans,
Shipping time was 7 weeks, now one week.
Forwarding cost was $60/ for two amps, now $0.
Now I can afford to buy more TOYS from you, and keep on irritating you.
All Best,
George
K3GK


Re: 50 watt Amp IRF 510 Failure

Brad Thompson
 

Hello--

/speculation mode on/

If would be interesting to de-encapsulate some of the failed IRF 510s
and analyze what damage occurred to the die (or dice). To paraphrase
an old vaudeville routine, "Is there a doctor. er. failure analyst in the house?<g>.

Second, is it possible that transient parasitic oscillation occurs at some combination
of thermally-varying device characteristics? The oscillation frequency could be
somewhere in the VHF or lower UHF range and might occur quickly.  This
exploration would require a spectrum analyzer capable of capturing "snapshots"
of frequency versus time, and one or more sets of sacrificial IRF 510s.

/speculation mode off/

73--

Brad  AA1IP


Re: Off-on switches

Greg Walters
 

Thanks Skip,

I got your email and have some on the way now. 
--
73,
Greg
KY4GW


Re: 50 watt Amp IRF 510 Failure

ajparent1/KB1GMX
 

Major comment for all amp builders regardless of design and designer.
IF the DC power applied is high for the power out HEAT will be an issue.
So measuring is required.  generally for the 50W amp if the efficiency is
less than 70% something is wrong.  For class C that is a minimum.
Reminder if at 70% that means for 50W out your putting in 72W in rounded
number the difference is heat, 22W worth.  IF the current is higher or the
power lower for a given input something is wrong.

Also the mosfets (Even RD parts) heat very fast internally and before the
heatsink rises 10C over ambient the device internally will have heated 
to a far greater extent.  So didn't seem to get warm has little meaning
as its too subjective.   I always use a contact thermocouple or IR gun
aimed at the device plastic when possible to measure.

AGAIN, just because your getting XX out does not mean the amp is 
performing as it should measurements are required to know that.


George,

With the above said something clearly is wrong with your build.

FIRST:  if the amp is works as it should the IRF510 is being asked to do
some work but not outside its design limits and should not heat greatly.
The nominal properly running performance at 20V should not stress the
devices unduly.

However if anything is not right it runs at moderate voltages and current
and heating is fast and failure will be sudden.

You have a TR switch part in wrong or the LPF  has a wrong part or 1 to many
turns on the transformers.

Its possible to do that and the near immediate lowering of power suggests
you have errors.

Quick calc of the efficiency 30W out for 50 in so efficiency is 60%, very very poor!
That means something is wrong.  Based on your number you lowered the
power out but the heat is still 20W!  At lower power the heating should be lower.
For 30W out I'd expect no more than 2.3A (18.8V) at 70% efficiency and maybe
less!

Is the output transformer wound correctly?

You might try lowering the power out of the QCX, try 3W (less DC in).

One thing to note, straight out of the instructions...  Assemble everything 
including mounting the IRF510s then solder them.  Why you want them in
good contact to the heatsink before soldering to insure the mosfets are
well mounted.


Andy,

That is not Georges problem.  Your problem is at 472khz you need more
ferrite (transformer inductance) and to get whatever power your getting
likely putting in more while getting less.  With poor efficiency heating
will be an issue.

Also using the RD part at MW is what some call bad juju.  The device gain
is very high and stability can be a big issue.  Also the bottom frequency by
design was 1.8mhz so all of the bypassing and the like is wrapped around
that as lowest frequency.

So you need to revise the ferrites and transformers for 472khz, if done its
a very safe bet it will perform badly over 20mhz.  That's the trade to get 472.
Going for 2 decades in bandwidth is possible but you need a more complex
design with much more elaborate transformers.

Allison

-------------------------------
Please reply on list so we can share.
No direct email, it goes to bit bucket due address harvesting in groups.IO


Re: 50 watt Amp IRF 510 Failure

George Korper
 

😎


On Fri, Mar 6, 2020, 7:26 AM Hans Summers <hans.summers@...> wrote:
Hi George
 
Sorry about the caps lock. 

No problem mine gets stuck too sometimes. Particularly on Fridays. 
 
Is 4 watts too much drive?

No. It should be OK. 
 
Have you tried the Vishay IRF 510 ?

No. But the device is being used within specification. I have no reason to suspect that there should be any difference in behaviour between different IRF510s as long as they really are IRF510s not something else with an "IRF510" label printed on them. Vishays from Digikey ought to be the real McCoy. 

73 Hans G0UPL


Re: 50 watt Amp IRF 510 Failure

Hans Summers
 

Hi George
 
Sorry about the caps lock. 

No problem mine gets stuck too sometimes. Particularly on Fridays. 
 
Is 4 watts too much drive?

No. It should be OK. 
 
Have you tried the Vishay IRF 510 ?

No. But the device is being used within specification. I have no reason to suspect that there should be any difference in behaviour between different IRF510s as long as they really are IRF510s not something else with an "IRF510" label printed on them. Vishays from Digikey ought to be the real McCoy. 

73 Hans G0UPL


Re: 50 watt Amp IRF 510 Failure

Andy Brilleaux <punkbiscuit@...>
 

On Fri, Mar 6, 2020 at 12:36 PM, Hans Summers wrote:
then there could be some other issue such as wrong number of turns or connection of transformers etc. 
Hans raises a good point here.

I built an amp using an RD06HHF1 FET originally for 475Khz, and to the best of my knowledge I had done all
the right things regarding output transformers and RF chokes.

When I tested it on a dummy load everything was OK.

When I connected it to an antenna (on 475Khz) it did the same thing as Georges amp, stated drawing
ever increasing current.

The amp worked without issue on 160m - 6m.

I suspected that the output transformer probably needed more turns on it, but by then my interest in 475Khz
had waned so I was happy to have a 160m - 6m amp working properly and I didn't pursue it further.

SO HOW MIGHT THIS APPLY TO GEORGE ?

Well, maybe, a mistake in the transformer windings may have occurred when George built it (we all make mistakes).

Maybe to few turns somewhere, wrong winding connected ?

It's worth checking and eliminating such things, just in case.

73 de Andy


Re: Off-on switches

SkipF, NT1G <skip.flem@...>
 


Re: 50 watt Amp IRF 510 Failure

George Korper
 

OK Hans. 

It goes south at 10 wpm normal CW. 
Sorry about the caps lock. 
I'll see what happens with your IRF 510 when the new amps come in. 

I'm building an amp for 40 and with your supplied IRF510. Need to keep the supplied IRF510's for that. 

Then when I get my two new amps I'll swap out the finals and see if it is still doing the same thing.
It could be the transformers or LPF. 

Is 4 watts too much drive? Have you tried the Vishay IRF 510 ?


Re: 50 watt Amp IRF 510 Failure

Hans Summers
 

Hi George
 
QRP LAB DUMMY LOAD. 18.8 VOLTS. 2.66 AMPS. DECLINES STARTS IN 3 SECONDS KEY DOWN AND THEN IS RAPID.

Firstly, I think you may have an RF grounding or SWR problem, RF appears to be getting into your keyboard and causing the Shift key to be permanently operated, giving the effect as though the CAPSLOCK key had been pressed  :-D  :-D

Secondly... use of the QRP Labs dummy load beyond 20W is beyond the specification of its components; during testing of the amp during development, I did take it up beyond 80W but only briefly! 

Thirdly - your test goes beyond anything I have ever carried out here. I have not keyed for 3 seconds, or more than 3 seconds as your email implies. I've said several times here that it is rude to the IRF's to sit on the key; I only ever use my amp at full power in ordinary CW operations, during which the longest key-down it sees, is a dah, which at 12wpm lasts 0.3 seconds. The amp does use the IRF510s near their limits and it is prudent to be careful.

I have had over 500 QSOs without incident (other than the single power supply glitch I described and resolved). I believe the amplifier is reliable as long as it is treated right. If abused, no. 

If you're treating it right, AND it is blowing IRF510s then there could be some other issue such as wrong number of turns or connection of transformers etc. 

73 Hans G0UPL


Re: 50 watt Amp IRF 510 Failure

George Korper
 

Nothing has time to get too hot. I am running the QCX on  12 V 7812 as suggested but it still is 4 watts out.
Is overdriving a possibility?


Re: 50 watt Amp IRF 510 Failure

geoff M0ORE
 

Are the transistors getting hot?  Are they the same temperature as the heatsink? Is the dummy load getting hot?

On 06/03/2020 12:07, George Korper wrote:
QRP LAB DUMMY LOAD. 18.8 VOLTS. 2.66 AMPS. DECLINES STARTS IN 3 SECONDS KEY DOWN AND THEN IS RAPID.


Off-on switches

Greg Walters
 

Howdy all,

I'm building my second clock kit (with GPS) and mounting it in a custom box. I need to mount the buttons remotely so I don't have to open the box any time I want to make an adjustment. 

I'm looking for buttons that have the positive "click" or detent that I can panel mount. I'm referring to the push-button switches in both the clocks and QCS kits. They don't have to look like those switches, just have a positive click or detent like them. 

If anyone knows what I'm trying to ask for, please help. Google isn't helping me, probably because I'm not asking the right question. 
--
73,
Greg
KY4GW


Re: QCX 40 NO POWER OUTPUT #40m #qcx40 #problem

Greg Walters
 

Dave,

I tried to switch it with practice mode on and off. No difference.

I think the issue is way before the output areas. My voltages are off all over the board, as noted above. I can't even trust the on board test equipment because it gives me false readings. 

I don't have any fancy equipment to troubleshoot this better. I don't have a lot of time either. 

I'm half tempted to sell this broken thing to someone who has the time and tools to troubleshoot and fix it. I'll gladly buy and build another one as I love building these radios. This was the first one I built and has been running the longest. I think I have built 3 maybe 4 others since then. 

If anyone would be interested in buying my broken QCX 40, I'd sell it cheap, you pay shipping. Maybe $20? It is mounted in a custom box, but I'd pull it out of that so I could put the new 40 in there. The switches are all mounted both on and off board. The key input, and audio jack are mounted off board. The RF out is also off board. And the display is off board. I've attached a photo for anyone interested. 


--
73,
Greg
KY4GW


Re: 50 watt Amp IRF 510 Failure

George Korper
 

THIS IS THE SECOND SET. YOUR TECHNIQUE WAS AMAZING. ALL REPLACED IN TEN MINUTES.
BUT UNFORTUNATELY EXACTLY SAME RESULT.


Re: 50 watt Amp IRF 510 Failure

George Korper
 

QRP LAB DUMMY LOAD. 18.8 VOLTS. 2.66 AMPS. DECLINES STARTS IN 3 SECONDS KEY DOWN AND THEN IS RAPID.


Re: Fast shipping

Hans Summers
 

Hi Daniel

Thanks, yes, it is going very well... around 60-70% of customers are choosing the FedEx option, and are consistently reporting the 3-4 days shipment time stated by FedEx/TNT. 

73 Hans G0UPL

On Fri, Mar 6, 2020 at 2:02 PM danielu@... danielu@... <danielu@...> wrote:
My parcel was shipped on March 2 and arrived  me on March 6 with FedEx Express. Incredibly fast.
Daniel Ungureanu
73
Y08SAK


Fast shipping

danielu@upcnet.ro danielu@upcnet.ro
 

My parcel was shipped on March 2 and arrived  me on March 6 with FedEx Express. Incredibly fast.
Daniel Ungureanu
73
Y08SAK


Re: U4B-2 balloon

William Bradley
 

Thanks Hans, am thinking an idea for my ARC.

Will
Mi0wwb 


On 6 Mar 2020, at 10:06, Hans Summers <hans.summers@...> wrote:

Hi Will 


This is the 2nd test flight for the QRP Labs U4B balloon tracker. It is not yet commercially available.

The balloons are from China via AliExpress, they cost around US$15 for a 10-pack.

73 Hans G0UPL 

On Fri, Mar 6, 2020, 12:58 William Bradley via Groups.Io <w.r.bradley=btinternet.com@groups.io> wrote:
Sounds a really fun and educational project.   What retail supplier do you use to purchase the balloon and radio kits from?

Will de Mi0wwb 


On 6 Mar 2020, at 09:43, Patrick, ON4CDJ <on4cdj@...> wrote:

The U4B-2 is still going strong, and above the Ukrainian-Russian border as of now.
Received with very modest 20m endfed wire a few meters above ground and lots of RF noise :-/

73, Patrick ON4CDJ
<Schermafdruk van 2020-03-06 10-37-41.png>