Date   

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
-------------------------------
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

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
-------------------------------
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

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
-------------------------------
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

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


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
-------------------------------
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

Hans Summers
 

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
-------------------------------
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
 

Amazon as a source is generally ok.

But the actual supplier is often a Ebay site and may be suspect.
One would think at the typically low prices for the IRF510 forgeries 
would be not worth it, but apparently it is real issue.  

Also VIshay and other have SIRF510 which is the same device
but the pin out is different, the drain and source reverse and the tab 
is source (grounded).  If put in a IRF510 spot they will immediately
heat up, maybe explode.  Reason there is a parasitic diode in
MOSFETS becaus eof the silicon and will look like a diode across
the power supply is subjected to wrong polarity. This kind of odd
pin out of parts is not  uncommon but unless clued it it will be
a unpleasant surprise..

They could also be off spec parts (formerly known as floor sweepings)
or that lot of parts has a very low Vgth (gate threshold voltage)
requiring a lower bias setting.   

I'd add this time of year ESD (carpet sparks) will kill most mosFETs.
That would show in a tester as unaccaprtable gate leakage or
outright dead.  In a circuit as an immediate fail on power up.

You did zero the setting first and reset for that pair?

Most if not all MOSfets are not drop in and require setting
the bias for the given devices in use.   THat applies to the
expensive RF Power LD-MOSFETS (the 200$ plus devices)
as well.

Also do not under any circumstances try to operate without
heat sinks mounted.

Allison
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Re: 50 Watt Amp Final Transistors

George Korper
 

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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