Date   

Re: 50 Watt Amp Final Transistors

ajparent1/KB1GMX
 

Frequency factor?   I've been working with power MOSfets for over
35 years never heard of that.  The heat is not related to frequency 
though if the amp is poorly done or being used above it design
bandwidth there may be more heat.

They work well to about 70mhz, and I've used them in bunches
at 50mhz.   Experience for me is it a robust (for is power capability)
and handy part.  

As to the new ones working better, than what?  Generally you have
worked out all the bugs and put in known good parts.  No other
explanation.

If you are referring to the other bargain parts likely the are not even
known parts.  I've not found a real IRF510 to behave much different
by manufacturer, at least those sold through quality vendors.

HInt: if any one gives me a power MOSFET not in an antistatic package
or wrapped in aluminum foil I will consider it dead unless and until
proven good.  ESD (carpet static) is very damaging to MOS devices
of all forms.  When you buy two and it comes in packaging very
different from the vendor package it had to be handled.  More often
than not that is when good parts become questionable.

There is  a market for companies that buy 30,000 and any left over get
sold off.  Those parts if handled properly are likely as good as new,
or maybe they are sold one at a time in poly bags without attention
to ESD.  Results and source for the very same part can be wildly different.

As to what makes IRF510 work well for RF is a set of characteristics that 
are well suited for the power and general use.  International Rectifier
Corp created the IRF510 about 30 years ago as a cheap high current
(up to 5.6A) switch to help put electronic controls in cars and
machines.  When they found out hams liked it for RF power as
it just worked, they were flabergasted.   Never their intent, but it
was good for them and what made it a good switch for motors and
coils were close to optimum for RF work in the 5-25W range.  It works
as a higher current part is bigger and suffers more capacitance, same
for higher voltage parts.

At RF be it some low frequency or the nosebleed microwaves you
design around the part.  What works is one that while imperfect is 
good enough that you can live with it.  There are no ideal parts except
in computer models.

The fancy RF devices are a collection of material more costly like gold,
special packages, and processes more complex so they can make a
transistor that can do 1000W (MRF6VP41KH, 370$).  A gem that
makes a MRI more reliable and uses fewer, to a 50KW DTV station.
 After all for that stuff that must run 24 by 365 and likely thousands
of dollars per hour for down time justify it.

The sand (processed silicon blanks) used for IRF510 is just as good
as used for the big device.

Allison
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Re: 50 Watt Amp Final Transistors

Shirley Dulcey KE1L
 

Another key difference between the IRF510 and the parts that are sold for RF use like the RD16HHF is that the characteristics of the IRF510 when used as an RF amplifier are not guaranteed. The manufacturer could completely redesign the part, and so long as the new version still meets or exceeds the specs they DO guarantee that would be considered an acceptable change, even though it might make your amplifier stop working. They could not do the same thing to the RF specs of a part that is being sold for use in RF amplifiers. The RF in the part number of the IRF510 does not come from radio frequency; it comes from the name of the original manufacturer of the transistor, International Rectifier.

It's very unlikely that such a radical change will happen to the IRF510. That part has been manufactured for nearly 40 years now and is made on an old process. They'll just keep using the old equipment to make them so long as people continue to buy.

Vishay bought Siliconix, the pioneer of power MOSFETs, in 1998. Vishay also bought the part of International Rectifier that made power MOSFETs in 2007 and merged in into their Siliconix division. The Vishay parts you can buy now are the lineal descendants of the original IRF510.

ON Semiconductor/Fairchild and STMicroelectronics both made IRF510s in the past. So did Rochester Electronics and New Jersey Semi-Conductor Products, specialists in end-of-life parts. All of those appear to be discontinued. The STMicro ones also seem to work well if you can get some from a source with reliable provenance. I've never run into an IRF510 from ON or Fairchild.

Inexpensive IRF510s are available from various sources in China; they can be found on Alibaba, Amazon, and eBay. Who is actually making those parts is unclear. One listing I looked at on Alibaba showed pictures of both Siliconix and STMicro parts; those could be first quality, factory rejects, or counterfeits. Other listings showed unmarked parts that probably come from Chinese factories, and their behavior may or may not have much resemblance to the Vishay transistors.

If you just need a few for repairs rather than thousands like Hans uses for making kits, I'd recommend sticking with Vishay parts from reputable distributors such as Digi-Key and Mouser. You can rely on those working, and at under $1 each they aren't going to break the bank.

On Sun, Mar 1, 2020 at 9:24 PM George Korper <georgekorper@...> wrote:
That part I get. Is frequency a factor? Is it just that higher frequency creates more heat?
The ones I bought from Digikey, why are they working better? Is it care in manufacturing, better materials
with less impurities? What in their construction makes these particular devices work better?

On Sun, Mar 1, 2020 at 9:12 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
There are plenty of parts that will do better for 5 to 30 times more.
THe common next up is the RD16HHF, about 5.50 each and rated
for 20W MAX and different pinout.  Something you would not
want to accidentally fry a pair of.

Or at the other extreme the MRFE101 device for a mere 45$ 
for two but to get the 100W it does need 0V power, its not usable
for more than a few watts at 12V..  Still not totally bullet proof.

The point being none are under a buck and few perform as well.
Generally none will be drop in without gross design and mechanical
changes.  IRF510 was one of those parts that does a lot fairly
well for a price that hard to beat.

At under a dollar each I always have a handful on hand, not
because they fail but because they are very useful for a lot
of things.


Allison
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Re: 50 Watt Amp Final Transistors

George Korper
 

Allison, I guess what I'm asking is can you find any clue on the Digikey data sheet that
is better than or different than the others? 

On Sun, Mar 1, 2020 at 9:24 PM George Korper via Groups.Io <georgekorper=gmail.com@groups.io> wrote:
That part I get. Is frequency a factor? Is it just that higher frequency creates more heat?
The ones I bought from Digikey, why are they working better? Is it care in manufacturing, better materials
with less impurities? What in their construction makes these particular devices work better?

On Sun, Mar 1, 2020 at 9:12 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
There are plenty of parts that will do better for 5 to 30 times more.
THe common next up is the RD16HHF, about 5.50 each and rated
for 20W MAX and different pinout.  Something you would not
want to accidentally fry a pair of.

Or at the other extreme the MRFE101 device for a mere 45$ 
for two but to get the 100W it does need 0V power, its not usable
for more than a few watts at 12V..  Still not totally bullet proof.

The point being none are under a buck and few perform as well.
Generally none will be drop in without gross design and mechanical
changes.  IRF510 was one of those parts that does a lot fairly
well for a price that hard to beat.

At under a dollar each I always have a handful on hand, not
because they fail but because they are very useful for a lot
of things.


Allison
-------------------------------
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Re: 50 Watt Amp Final Transistors

George Korper
 

That part I get. Is frequency a factor? Is it just that higher frequency creates more heat?
The ones I bought from Digikey, why are they working better? Is it care in manufacturing, better materials
with less impurities? What in their construction makes these particular devices work better?

On Sun, Mar 1, 2020 at 9:12 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
There are plenty of parts that will do better for 5 to 30 times more.
THe common next up is the RD16HHF, about 5.50 each and rated
for 20W MAX and different pinout.  Something you would not
want to accidentally fry a pair of.

Or at the other extreme the MRFE101 device for a mere 45$ 
for two but to get the 100W it does need 0V power, its not usable
for more than a few watts at 12V..  Still not totally bullet proof.

The point being none are under a buck and few perform as well.
Generally none will be drop in without gross design and mechanical
changes.  IRF510 was one of those parts that does a lot fairly
well for a price that hard to beat.

At under a dollar each I always have a handful on hand, not
because they fail but because they are very useful for a lot
of things.


Allison
-------------------------------
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Re: 50 Watt Amp Final Transistors

ajparent1/KB1GMX
 

There are plenty of parts that will do better for 5 to 30 times more.
THe common next up is the RD16HHF, about 5.50 each and rated
for 20W MAX and different pinout.  Something you would not
want to accidentally fry a pair of.

Or at the other extreme the MRFE101 device for a mere 45$ 
for two but to get the 100W it does need 0V power, its not usable
for more than a few watts at 12V..  Still not totally bullet proof.

The point being none are under a buck and few perform as well.
Generally none will be drop in without gross design and mechanical
changes.  IRF510 was one of those parts that does a lot fairly
well for a price that hard to beat.

At under a dollar each I always have a handful on hand, not
because they fail but because they are very useful for a lot
of things.


Allison
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Re: 50 Watt Amp Final Transistors

George Korper
 

Hans describes testing six to come up with one, What is the manufacturing difference that makes
the difference and is it consistent? I know it is cheap. Has any manufacturer come up with the same
specs in a better package? Or do similar transistors go for a lot more money? Just want to know to
learn more about these devices, I read the manual and understand Han's logic. Do the Yeasu's and Icom's 
make their own? QST could sure help out by doing a long article on this! 
Also do these Mosfet's do better on 40 than 20?

On Sun, Mar 1, 2020 at 7:04 PM Glen Leinweber <leinwebe@...> wrote:
My old National Semiconductor data book shows the IRF510 chip size....
98 thou x 87 thou
2.5mm x 2.2mm
The heat-generating area is a bit smaller than that.
Drain is bonded to the metal tab directly while the source
and the gate are attached with flying leads that conduct very little
heat away.
That chip is a tiny heater bonded to a far bigger slab of metal, which in
turn is molded to the IRF510's black epoxy.

That 3.5 C/W junction-to-tab heat spec is likely due to the small chip
size. The much larger contact area of metal tab -to- heatsink likely
means the tab runs just a bit hotter than the heatsink under it.

We used to rely on the black anodizing on the heat sink as an insulator.
Although the aluminum oxide is very thin, it is a remarkably tough insulator.
This was for 60W Class AB audio, where two transistors bore the heat load.

Not saying you should try this because I don't know the quality of that
heatsink extrusion - a little scratch can cause mayhem. As always,
follow Hans' excellent instructions.


Re: hot glue toroids

Steve in Okinawa
 

MARINE GOOP is the only adhesive/sealant I need. It's even self-leveling before it skins over. And something good actually happened in Japan recently! The DAISO 100-yen chain stores sell superglue in packs of 4, 1/4g tubes. Open one, forget to close it, and I'm out only 23 cents US. And they carry 3 types. Every boy's wish come true. JS6TMW


Re: 50 Watt Amp Final Transistors

Glen Leinweber
 

My old National Semiconductor data book shows the IRF510 chip size....
98 thou x 87 thou
2.5mm x 2.2mm
The heat-generating area is a bit smaller than that.
Drain is bonded to the metal tab directly while the source
and the gate are attached with flying leads that conduct very little
heat away.
That chip is a tiny heater bonded to a far bigger slab of metal, which in
turn is molded to the IRF510's black epoxy.

That 3.5 C/W junction-to-tab heat spec is likely due to the small chip
size. The much larger contact area of metal tab -to- heatsink likely
means the tab runs just a bit hotter than the heatsink under it.

We used to rely on the black anodizing on the heat sink as an insulator.
Although the aluminum oxide is very thin, it is a remarkably tough insulator.
This was for 60W Class AB audio, where two transistors bore the heat load.

Not saying you should try this because I don't know the quality of that
heatsink extrusion - a little scratch can cause mayhem. As always,
follow Hans' excellent instructions.


Re: DX Clusters and Spotting,,,

Andy Brilleaux <punkbiscuit@...>
 

Sounds to me like too many stations want their QSO's delivered to them on a plate.

They should sample the delights of tuning the bands themselves, instead of relying
upon everyone else to find it for them.

- Andy -


Re: hot glue toroids

ajparent1/KB1GMX
 

Arv,

I didn't forget.  It was in the class of:
  Caution this may be unsafe.
  Fire hazard, use caution, keep from fire and flames.
  Toxic materials , use in well ventilated area.
  Do not inhale fumes.

And my favorite:  
  "Kids do not do this at home, we are experts.".

Glass container, Styrofoam [polystyrene], MEK or toluene.
 Stuff the container with styrene ad then add enough solvent
 to collapse it.  Rinse and repeat for suitable gooeyness. Cover.

Allison
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DX Clusters and Spotting,,,

Joe WB9SBD
 

Greetings everyone,

As one that does not have a radio yet that can talk to a computer,
the use of Spotting systems is clunky and slow if used at all.

But today I bit the bullet, and tried two ways to find the guys in the North Carolina QSO Party,
It was their State QSO party today.

Now I am beginning to think it depends on what cluster you pull data from, as to what you will end up seeing.

My first thing I did was to make up a filter (explained how to by the awesome people here) for my DX Labs "Spot Collector" so it would ONLY show me North Carolina Stations.

Otherwise I would never even see the NC stations among the 100+ spots every minute.
It worked Great!

Then I did a similar filter thing in the N1MM+ Logger. Only show me NC stations.

Now neither are connected to the radio so I have to look and see what freq they are on and dial them in.

whatever. Like I said clunky, but wanted to help a qso party participant..

BUT there is something I noticed. And why the thought of what cluster you get the data from, may make a difference?

The number of stations displayed was easily double in Spot collector, that was what appearing in N1MM+
They were all still only NC stations, but all day there was easily double all the time.

Now I think a major part also is N1MM+ was connected to only one cluster,

where Spot collector, was connected to four clusters.

would this make that much difference?

I wonder, could N1MM+ get it's data from Spot Collector?

Joe WB9SBD


Re: hot glue toroids

Eric KE6US
 

I once (only once) poured a little MEK into a styrofoam cup. It didn't eat a hole in the bottom. It completely vaporized the bottom half of the cup and landed on the floor of the shop with a splash about as fast as if I had poured it directly from the can.

Eric KE6US

On 3/1/2020 12:23 PM, Arv Evans wrote:
Allison

Often forgotten is that polystyrene (white foam plastic cups and similar food containers)
dissolves very easily in several solvents, most notably gasoline.  When the solvent
evaporates the result is similar to Q-Dope that was popular back when we were young.

Arv
_._




On Sun, Mar 1, 2020 at 12:29 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Glues ad other...

Consider the real need.  If you are physically doing things that
need toroids anchored remember the LCD is GLASS.

Common RTV (room temperature vulcanizing) adhesives are
acetic base (acid) cured which is very bad for electronics.  There are
those designed with a different cure system (safe for food and fish)
that are OK.   Generally I don't use it as its messy!  Also impossible
to get off anything or doesn't stick at all!

Hot-melt glues, the general hobby types are ok for HF and a small
dab is more than enough.  I do use it but it too can be messy.

Cyanoacrylic, aka Superglue and Eastman 910, others, are very
good fast set glues but low strength.  I buy it as sold to hobby 
and model builders at the 1-3oz sizes under the brand name
Zap (they have several versions).

Goop and other clear adhesives are ok as well but messy and
use Toluene solvent.  Very strong!

Blutack, and similar,  ok but use only  a little.  I'd avoid it.

Epoxies, ok if not metal filled.  May represent extreme overkill!
Near impossible to remove with pout power tools!

Materials use for potting or encapsulating, avoid!  Most will impact
tuning of coils some and are often near impossible to remove.

If you think you may have to fix it, ever, then NONE OF THE ABOVE!

Allison
-------------------------------
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Re: hot glue toroids

Arv Evans <arvid.evans@...>
 

Allison

Often forgotten is that polystyrene (white foam plastic cups and similar food containers)
dissolves very easily in several solvents, most notably gasoline.  When the solvent
evaporates the result is similar to Q-Dope that was popular back when we were young.

Arv
_._




On Sun, Mar 1, 2020 at 12:29 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Glues ad other...

Consider the real need.  If you are physically doing things that
need toroids anchored remember the LCD is GLASS.

Common RTV (room temperature vulcanizing) adhesives are
acetic base (acid) cured which is very bad for electronics.  There are
those designed with a different cure system (safe for food and fish)
that are OK.   Generally I don't use it as its messy!  Also impossible
to get off anything or doesn't stick at all!

Hot-melt glues, the general hobby types are ok for HF and a small
dab is more than enough.  I do use it but it too can be messy.

Cyanoacrylic, aka Superglue and Eastman 910, others, are very
good fast set glues but low strength.  I buy it as sold to hobby 
and model builders at the 1-3oz sizes under the brand name
Zap (they have several versions).

Goop and other clear adhesives are ok as well but messy and
use Toluene solvent.  Very strong!

Blutack, and similar,  ok but use only  a little.  I'd avoid it.

Epoxies, ok if not metal filled.  May represent extreme overkill!
Near impossible to remove with pout power tools!

Materials use for potting or encapsulating, avoid!  Most will impact
tuning of coils some and are often near impossible to remove.

If you think you may have to fix it, ever, then NONE OF THE ABOVE!

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


Re: hot glue toroids

ajparent1/KB1GMX
 

Glues ad other...

Consider the real need.  If you are physically doing things that
need toroids anchored remember the LCD is GLASS.

Common RTV (room temperature vulcanizing) adhesives are
acetic base (acid) cured which is very bad for electronics.  There are
those designed with a different cure system (safe for food and fish)
that are OK.   Generally I don't use it as its messy!  Also impossible
to get off anything or doesn't stick at all!

Hot-melt glues, the general hobby types are ok for HF and a small
dab is more than enough.  I do use it but it too can be messy.

Cyanoacrylic, aka Superglue and Eastman 910, others, are very
good fast set glues but low strength.  I buy it as sold to hobby 
and model builders at the 1-3oz sizes under the brand name
Zap (they have several versions).

Goop and other clear adhesives are ok as well but messy and
use Toluene solvent.  Very strong!

Blutack, and similar,  ok but use only  a little.  I'd avoid it.

Epoxies, ok if not metal filled.  May represent extreme overkill!
Near impossible to remove with pout power tools!

Materials use for potting or encapsulating, avoid!  Most will impact
tuning of coils some and are often near impossible to remove.

If you think you may have to fix it, ever, then NONE OF THE ABOVE!

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 Final Transistors

ajparent1/KB1GMX
 

Geoff,

Be very careful with heatsink compound (silicone based) as mixed with
soldering the result is very poor.

Also the arctic silver types are conductive so again caution.

For power devices I have a .45kg of Thermaloy 251G for that.
It only needs a very little amount!

Allison
-------------------------------
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Re: hot glue toroids

Curt wb8yyy
 

John

Indeed, I forgot the matter of winding sensitivity to power output, in spite of dozens of builds. Great idea to use hot glue to hold turns in place. While there is better stuff for higher frequencies, hot glue is fine for HF. Thanks for pleasant correction.

Curt


Re: 50 Watt Amp Final Transistors

Hans Summers
 

Hi Geoff

I don't believe there is any substantial benefit to the use of heatsink compound in either the 10W Linear or the 50W QCX Amp. 

The thermal resistance of the IRF510 silicon junction to the metal tab is already 3.5C/W. I believe the heat compound just doesn't make enough difference to be important. It isn't harmful, just not necessary. I never use it on any of mine. By all means add some, if is harmless... but I wouldn't bother to buy any heatsink compound if you don't have any. 

In a larger MOSFET device with a much lower internal thermal resistance, then yes it would be very important to improve the tab-to-heatsink thermal resistance by say, a half a C/W because that would be a huge proportion of the total. But in small systems like an IRF510 I don't think it's important.

I have no idea about tightening torque for the bolts, I have no tools for measuring such things nor mechanical engineering expertise to know what are appropriate recommendations. I don't think I'm strong enough to break the thread of the heatsink supplied. What I do sometimes, being right-handed, is tighten bolts using a screwdriver held in my left hand. That way I know what when it comes time to loosen them, I can use my right arm for the task... so I'll always have more power available for un-screwing than was used for the assembly. 

73 Hans G0UPL 


On Sun, Mar 1, 2020, 21:04 geoff M0ORE via Groups.Io <m0ore=tiscali.co.uk@groups.io> wrote:

Hans,

What are your thoughts on the use of a very thin smear of heatsink compound to assist in the heat transfer. I usually polish both surfaces prior to mounting and use a tiny amount of compound to help get better thermal contact. I confess I haven't read the assembly instructions for the 50 Watt amp but do you suggest a tightening torque for the bolts. The instructions for the 10 Watt Linear amp just says to tighten them but not too tight in case you strip the threads.

It would of course be difficult to supply a tiny amount of compound with the kit, I have a 10ml syringe that I purchased many, many years ago and still have 9ml left!

Geoff

On 01/03/2020 17:14, Hans Summers wrote:
HI George 

Yeah a large number of IRF510s and other MOSFET types perished during my R&D work... some quietly, some very loudly like a gun.

They get hot fast because they are dissipating a LOT of power as heat! So say the thermal resistance from IRF510 to heatsink is 3.5C/Watt and you're dissipating 20W per device, then the temperature rise will be 70C (on top of the current heatsink temperature). Being a relatively small device, their heat capacity is relatively small and so the temperature rise is quite rapid. 

Do NOT sit on the key! Use the amp as for normal CW type of duty cycle and everything will be fine. Normal CW is something around 50% duty cycle on average. 

You want to tune up your antenna? So you want to sit on the key while you make your adjustments? No! You shouldn't be doing that at full power anyway! Tune up at much lower power. 

During all my development I operated sensibly. In an hour of back to back QSOing consisting of some average QSOs and a few rag chews, with a digital thermometer sensor squeezed into the heatsink fins, the heatsink temperature was around 40-45C. Say 20C over ambient. 

In my opinion understanding the equipment you use and its limitations, then treating it always with the respect and kindness it deserves, is key to its long life. 

My 50W amp prototype has been used for around 700 QSOs in the last 9 months. At a guess, that's around 100 hours of operation. In all that time I had one failure of a pair of IRF510s at switch on. Not due to over heat stress. Just a power glitch. I later modified the QCX firnware and added the resistor mod described here http://qrp-labs.com/qcx/qcxmods/ptt.html and flipped the power switch back and forth until I got bored, and couldn't make the glitch destroy anything again. 

So it's quite a robust amp as long as it is used respectfully. 

If you do burn some IRF510s then think of it as fantastic education and the cost of the new ones is the very low price of the education! 

73 Hans G0UPL 


On Sun, Mar 1, 2020, 19:45 George Korper <georgekorper@...> wrote:
THANK YOU HANS,
The paragraph in the 50 PA on heat and is excellent. 
I was waiting for the right  Finals from Digikey, so I tried two different sets
IRF 510's  from Amazon. I can't believe how fast they heat up. What I don't understand
is why. What is wrong inside them? I am saying thank you because, it gave me a small taste of what
your experimenting is like. Buddy, you've got persistence. 

On Sun, Mar 1, 2020 at 11:37 AM George Korper <georgekorper@...> wrote:
THANK YOU ALLISON.  I tried your technique and you know what? 
You saved me from a great deal of grief! Again, I will just say, THANK YOU ALLISON!!!



On Sat, Feb 29, 2020 at 6:27 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
No, none as adding lead length via sockets is a bad thing.

With popper care board damage should  not happen.

Hint if you destroy them,  disassemble, cut the leads at
the package,  (they are dead!) and extract the leads one
at a time with a sufficiently hot iron and tweezer.

Clear the holes by heating the solder and using inertia
(sudden stop while molten) should clear the hole.

Do not drill or use pins or try to poke the tip of the iron in.
That often does more damage.

Allison
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Re: 50 Watt Amp Final Transistors

geoff M0ORE
 

Hans,

What are your thoughts on the use of a very thin smear of heatsink compound to assist in the heat transfer. I usually polish both surfaces prior to mounting and use a tiny amount of compound to help get better thermal contact. I confess I haven't read the assembly instructions for the 50 Watt amp but do you suggest a tightening torque for the bolts. The instructions for the 10 Watt Linear amp just says to tighten them but not too tight in case you strip the threads.

It would of course be difficult to supply a tiny amount of compound with the kit, I have a 10ml syringe that I purchased many, many years ago and still have 9ml left!

Geoff

On 01/03/2020 17:14, Hans Summers wrote:
HI George 

Yeah a large number of IRF510s and other MOSFET types perished during my R&D work... some quietly, some very loudly like a gun.

They get hot fast because they are dissipating a LOT of power as heat! So say the thermal resistance from IRF510 to heatsink is 3.5C/Watt and you're dissipating 20W per device, then the temperature rise will be 70C (on top of the current heatsink temperature). Being a relatively small device, their heat capacity is relatively small and so the temperature rise is quite rapid. 

Do NOT sit on the key! Use the amp as for normal CW type of duty cycle and everything will be fine. Normal CW is something around 50% duty cycle on average. 

You want to tune up your antenna? So you want to sit on the key while you make your adjustments? No! You shouldn't be doing that at full power anyway! Tune up at much lower power. 

During all my development I operated sensibly. In an hour of back to back QSOing consisting of some average QSOs and a few rag chews, with a digital thermometer sensor squeezed into the heatsink fins, the heatsink temperature was around 40-45C. Say 20C over ambient. 

In my opinion understanding the equipment you use and its limitations, then treating it always with the respect and kindness it deserves, is key to its long life. 

My 50W amp prototype has been used for around 700 QSOs in the last 9 months. At a guess, that's around 100 hours of operation. In all that time I had one failure of a pair of IRF510s at switch on. Not due to over heat stress. Just a power glitch. I later modified the QCX firnware and added the resistor mod described here http://qrp-labs.com/qcx/qcxmods/ptt.html and flipped the power switch back and forth until I got bored, and couldn't make the glitch destroy anything again. 

So it's quite a robust amp as long as it is used respectfully. 

If you do burn some IRF510s then think of it as fantastic education and the cost of the new ones is the very low price of the education! 

73 Hans G0UPL 


On Sun, Mar 1, 2020, 19:45 George Korper <georgekorper@...> wrote:
THANK YOU HANS,
The paragraph in the 50 PA on heat and is excellent. 
I was waiting for the right  Finals from Digikey, so I tried two different sets
IRF 510's  from Amazon. I can't believe how fast they heat up. What I don't understand
is why. What is wrong inside them? I am saying thank you because, it gave me a small taste of what
your experimenting is like. Buddy, you've got persistence. 

On Sun, Mar 1, 2020 at 11:37 AM George Korper <georgekorper@...> wrote:
THANK YOU ALLISON.  I tried your technique and you know what? 
You saved me from a great deal of grief! Again, I will just say, THANK YOU ALLISON!!!



On Sat, Feb 29, 2020 at 6:27 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
No, none as adding lead length via sockets is a bad thing.

With popper care board damage should  not happen.

Hint if you destroy them,  disassemble, cut the leads at
the package,  (they are dead!) and extract the leads one
at a time with a sufficiently hot iron and tweezer.

Clear the holes by heating the solder and using inertia
(sudden stop while molten) should clear the hole.

Do not drill or use pins or try to poke the tip of the iron in.
That often does more damage.

Allison
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Re: BPF 80m

Martin DK3UW
 

thanks for all the feedback.

Hajo and I had other things to work on, thats why we did not come back. I am on the road again next week but then I will come back to our findings hopefully.

73's
Martin
DK3UW


Re: LED question

ajparent1/KB1GMX
 

OK which led the read or green?

The green is seeing a very low current (around 2ma at 20V) so
it will not be bright at 12-14V.   Usually green leds are to me are
not normally very bright.    Cheap trick is the blue leds even at
very low currents tend to be very bright, they would work there.

The other red led unless the wrong series resistor has been put in
(R16 should be 470 ohms)  or you are putting more than 6V into
the Keying port (X2 PTT)  any red led should work there.

If the red let is too bright make R16 a larger value say 1K to start.

If you fried the led (red) how much keying Voltage was put on
the PTT pin?  [DO NOT EXCEED 12V).]


Allison
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