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[SPAM] Re: [BITX20] IRF510 amplifier failures


K9HZ <bill@...>
 

In other words… let the chaos continue!

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

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email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Michael Hagen
Sent: Monday, January 29, 2018 2:02 PM
To: BITX20@groups.io
Subject: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

Why not let individuals make their decisions from the posts, and other's feed back.   That's how we learn?

Most contributors put a lot of effort in their responses trying to help with problems.

There is a very wide group here, which seems great to me.  But maybe its just too much for some?

I don't think anyone is on here that "just wants their BitX to work?"  They are having a good time learning and experimenting.

It is a lot reading nearly 3000 posts a month!  Wow.

73's

Mike, WA6ISP

 

On 1/29/2018 9:38 AM, K9HZ wrote:

This discussion highlights the best and worst parts of this forum.  There are many of us that are quite content to design away to meet a need… and we all have some great designs.  Lots of problems can be solved in more than one way.  We head off down the path of designing our circuits in the forum while others watch and say “what about me…I want one too… but which one?”.  I guess maybe the designers should all (and this has been done quite a bit here already) make YouTube videos of our circuits in operation so that the rest of the guys can choose what works for them (and that includes a look at the board size).  Otherwise it’s a little bit of “Hey, look what I’ve got” going on…  Of course I am guilty too.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

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email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Michael Hagen
Sent: Monday, January 29, 2018 1:23 PM
To: BITX20@groups.io
Subject: [SPAM] Re: [SPAM] Re: [SPAM] Re: [SPAM] Re: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

Yes, but I was talking Thermal was the only thing Raduino could do.  The thermal response would  be slow, so Radino could catch it.  I have made latching current sensors for small currents on HV supplies.   I used a comparitor with positive Feed Back.

Also an OptoIsolator in the high side sensing to get an isolated trigger.  Worked great.   I like the latching feature, doesn't oscillate, and you can light a Led.  A reset switch is not necessary, just turn off the device, clear the overcurrent, and re-power.

My Mega Pro RaduinoXP replacement has plenty of memory and extra ports to do Built in Test.  It is a little larger though.

It might be inconvenient in cabinets that have already been designed for Raduino.

I have it running my uBit.

73's

Mike

 

 

On 1/29/2018 9:05 AM, K9HZ wrote:

Hardware trip is gonna be way faster than the Raduino… but it still could work if a small safety margin is added. 

 

One thing we have not done that I think is imperative for the next Raduino replacement is a set of built in tools… like a 0-5V meter, frequency counter, LCR meter, etc…. like Hans did with his QCX.  It’s a nice touch for those who don’t have all the expensive equipment.  Hans is pretty cool about it and may share some of the algorithm structures to help get it off the ground where needed (even though his MCU is not an Arduino).

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Michael Hagen
Sent: Monday, January 29, 2018 12:44 PM
To: BITX20@groups.io
Subject: [SPAM] Re: [SPAM] Re: [SPAM] Re: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

QRT or Silent Key!   ha.. ha

Another reason for fast blowing fuses, and not Poly Fuses for reverse protection.

And you still may have to change the Mosfet.

For over current situation (not blowing the fuse with a diode for reverse polarity protection) a fast fuse still may not work?

A fast comparitor (over current detection) and high side P Fet as suggested by Bill is probably the best answer?

Thermal protection may be given over to the Raduino to do, if there are enough ports left? 

Or, besides thermistors, there are a lot of temperature sensors out there, Microchip makes some cheap ones.  Thirty cents or so.

73's

Mike, WA6ISP

 

On 1/29/2018 8:22 AM, Mvs Sarma wrote:

Nice Bill,

 I fear that Thermal shut down would be rather slow and doesn't hel\p. By that time the mosfet etc might gone QRT.

 Current sense and fasrt action only could save from damages like bad SWR etc.

Thanks

and rtegards

 sarma

 vu3zmv


Regards
MVS Sarma
 

 

On Mon, Jan 29, 2018 at 8:19 PM, K9HZ <bill@...> wrote:

After I sent this note, I figured someone would say “is there a board available” so even though I’m on vacation at our villa in the Caribbean I sat down with a piece of paper and started working on something.  So far I have designed a power FET switch to control voltage to the PA and a toggle trip mechanism.  I thought about the what conditions were desirable to trip the switch off and came up with 1. Over current, and 2. Over temperature.  I need to finish the designs to interface those parts and then bread board it.  I’ll design it so that you can implement either or both by just deleting or adding the interface parts, plus leave the trip line available so that you can design you own interface circuits (like high SWR trip too).

 

Sheesh I better retire soon… this is getting to be a full time job.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Leland Lannoye
Sent: Monday, January 29, 2018 10:12 AM
To: BITX20@groups.io
Subject: [SPAM] Re: [SPAM] Re: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

Is there a circuit or, better yet, a board available? It sounds like this could be current limiting as well.

 

 

 

Sent from my Verizon, Samsung Galaxy smartphone

 

-------- Original message --------

From: K9HZ <bill@...>

Date: 1/29/18 08:58 (GMT-05:00)

Subject: Re: [SPAM] Re: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

Now with this said… you could measure the current draw to the FET using a small Hall-effect device and use that to make a simple resettable trip circuit.  Very easy to do.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

 

email:  bill@...

 

 

I think you are missing the point.  Tim is somewhat correct in that limiting the current to the FETs at any point along the characteristic operational curve in any form causes non-linearity and distortion because of it.  It’s more akin to flat-topping although maybe not as sharp.  In any case, it’s not what you want to do.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Arv Evans
Sent: Monday, January 29, 2018 1:44 AM
To: BITX20@groups.io
Subject: [SPAM] Re: [BITX20] IRF510 amplifier failures

 

 

On Sun, Jan 28, 2018 at 9:59 PM, Tim Gorman <tgorman2@...> wrote:

It would seem to me that this type of operation is actually AM
modulation of final. When you limit the current flow in an FET that is
very similar to plate modulation in a vacuum tube. It certainly can't
be good for the linearity of the amplifier since the operational curve
would no longer be linear but, instead, flat-topped at some value.

Why not just fuse the power lead? It would tell you immediately that
you have a problem.

tim ab0wr

On Sat, 27 Jan 2018 12:13:49 -0800
"Arv Evans" <
arvid.evans@...> wrote:

> Hello
>
> Still thinking about IRF510 failures and ways to avoid making
> smoke.....
>
> It seems that there may be two ways to limit current in BITX RF PA
> stages that use the IRF510 device.  First would be to incorporate a
> current limiter in the positive voltage supply to the RF PA stage.
> Second might be to use current sensing in the RF PA supply line to
> cause a voltage drop in the MOSFET bias line(s). 
>
> In the first instance it should be possible to use another IRF510 or
> preferably a higher power, MOSFET as a control that limits voltage to
> the RF PA section if the current exceeds a preset value (usually this
> would be 2.0 to 3.0 amperes). 
>
> This circuit has not been built or tested by me (too cold in Idaho
> hamshack in winter). The MOSFET could be an IRF840, or similar.
> Option-B  potentially solves another problem, that of low level noise
> from powered RF PA stage during receive mode. 
>
> In the second instance we could get by with smaller control devices
> if we used current sensing in the RF PA power line to turn off bias
> to the IRF510 device(s). 
>
> This bias control circuit used by AC2CZ in his 50 watt IRF510 linear
> (
http://www.g0kla.com/scpa/SimpleCheapPA.php ).  You could probably
> do this using 2N3906 transistors.  I like the fact that it includes a
> warning light/LED.
>
> Arv  K7HKL
> _._


 

 



-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
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-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...



-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...