zener diode question

[Ian Field]

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:0599c63a-bc72-457f-85ee-71b25a7fe71c@r4g2000vbf.googlegroups.com...

On Apr 16, 2:12 am, jurb6...@gmail.com wrote:
My question is why use shunt regulation in the first place.

Also true about the "pass" transistor, any transistor of suitable ratings
will work and most likely help solve any thermal problems. It doesn't
even matter if it is NPN or PNP. Works both ways.

The only reason to use shunt regulation is if you expect spikes which
should be clamped. This can happen in an automotive application for
example by just having loose or dirty battery cables, or any electrical
fittings between the alternator (generator) and the load. This porblem is
compunded these days by the fact that a modern fuel injected car with
multiple coils (a coil pack)pulls a hell of alot of current to just run.
Have any idea what a heated O2 sensor pulls ? what's more a car might
have three or four of them. That is on top of an injector for every
cylider maybe more.

The thing is I am am having a hard time imagining another situation where
such a regulation scheme would be appropriate. If it's automotive then it
is, but that has not been revealed.

Yes this is related to my post of several months ago. I employed
Arfa's suggestion of using two of my 6.8V 10 watt zeners in series to
make a 13.6 V diode. And from my previous discussion this was then
put in series with the rectified 24VAC, (39VDC) to drop the voltage to
the input of my 12V regulator to a safer level. These two diodes were
mounted with insulators and silicone grease on a large old black
aluminum heat sink that I pulled out of a 1960's Delco automobile
radio. With the diodes in the circuit the voltage to the input of the
regulator was 19VDC, and under full load it was 16.5VDC, which is just
about where I wanted it to be. The only problem is that the diodes as
well as the heat sink were getting extremely hot when the regulator
was fully loaded, (1.0Amp).

Something there doesn't ring true - at full load, your load is forcing down
the voltage and easing below the zener's conduction voltage.

The zeners should run cooler when you draw full load!

 

[Michael A. Terrell]

Ian Field wrote:

klem kedidelhopper wrote:

Yes this is related to my post of several months ago. I employed
Arfa's suggestion of using two of my 6.8V 10 watt zeners in series to
make a 13.6 V diode. And from my previous discussion this was then
put in series with the rectified 24VAC, (39VDC) to drop the voltage to
the input of my 12V regulator to a safer level. These two diodes were
mounted with insulators and silicone grease on a large old black
aluminum heat sink that I pulled out of a 1960's Delco automobile
radio. With the diodes in the circuit the voltage to the input of the
regulator was 19VDC, and under full load it was 16.5VDC, which is just
about where I wanted it to be. The only problem is that the diodes as
well as the heat sink were getting extremely hot when the regulator
was fully loaded, (1.0 Amp).

Something there doesn't ring true - at full load, your load is forcing down
the voltage and easing below the zener's conduction voltage.

The zeners should run cooler when you draw full load!

Read what you replied to. The Zeners are in series, not shunt so you
have it backwards. The current & heat go up with increased loading.

 

[Jamie]

klem kedidelhopper wrote:

On Apr 16, 2:12 am, jurb6...@gmail.com wrote:

My question is why use shunt regulation in the first place.

Also true about the "pass" transistor, any transistor of suitable ratings will work and most likely help solve any thermal problems. It doesn't even matter if it is NPN or PNP. Works both ways.

The only reason to use shunt regulation is if you expect spikes which should be clamped. This can happen in an automotive application for example by just having loose or dirty battery cables, or any electrical fittings between the alternator (generator) and the load. This porblem is compunded these days by the fact that a modern fuel injected car with multiple coils (a coil pack)pulls a hell of alot of current to just run. Have any idea what a heated O2 sensor pulls ? what's more a car might have three or four of them. That is on top of an injector for every cylider maybe more.

The thing is I am am having a hard time imagining another situation where such a regulation scheme would be appropriate. If it's automotive then it is, but that has not been revealed.


Yes this is related to my post of several months ago. I employed
Arfa's suggestion of using two of my 6.8V 10 watt zeners in series to
make a 13.6 V diode. And from my previous discussion this was then
put in series with the rectified 24VAC, (39VDC) to drop the voltage to
the input of my 12V regulator to a safer level. These two diodes were
mounted with insulators and silicone grease on a large old black
aluminum heat sink that I pulled out of a 1960's Delco automobile
radio. With the diodes in the circuit the voltage to the input of the
regulator was 19VDC, and under full load it was 16.5VDC, which is just
about where I wanted it to be. The only problem is that the diodes as
well as the heat sink were getting extremely hot when the regulator
was fully loaded, (1.0Amp). In the interest of survivability
assessment for my test I ran the unit overnight. So I added more
aluminum and beefed up the contact of the heat sink to the mounting
surface. Now the heat sink runs cooler however the diodes are still
too hot to hold a finger on at full load. This surprises me. If I had
good contact with the heat sink shouldn't IT be warmer than the
semiconductor mounted to it? The thought now occurs to me that since I
had to use plastic insulators from the junk box between the diodes and
the heat sink they may not be providing suitable thermal conductivity,
and this could also be a problem. I tried to buy a couple of suitable
insulating diode mounting kits for DO-4 devices that would provide
good thermal contact with the heat sink but I couldn't find a source
for them. My distributor couldn't find any and NTE doesn't seem to
sell them separately. I remember in my previous post that you had
suggested a transistor arrangement last time Jamie, but you're correct
in that I didn't fully understand what you were referring to at the
time. Now that Phil has provided the schematic it seems quite clear.
Thanks Phil. I could certainly try that arrangement too but after
putting this all down on paper, (so to speak), now I guess I'm
wondering. What if thermal conductivity between my diodes and my now
massive heat sink is my problem? My junk box mounting hardware
certainly could be suspect. Perhaps I should try to obtain the correct
insulators and then reassess this heat issue. Does anyone have a
source for them? The diodes are 1N2970B stud mount. Thanks, Lenny

http://www.datasheetcatalog.org/datasheet2/a/0a1whup4cfhdaygr9zxyqtaki7yy.pdf
My god.

Jamie

 

[Jamie]

Ian Field wrote:

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
message news:SG1bt.540231$J13.57137@newsfe08.iad...

Arfa Daily wrote:



"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:85e12e55-6f89-418e-9292-89a68c5a75ad@hc4g2000pbb.googlegroups.com...


I need to come up with a zener diode that will handle 1.0 amp
of current at 12V. I currently am using two 6.8V 10 watt stud
mount zeners in series mounted with insulators on a large
heatsink but it's pushing it. When the current spikes to 1.0 amp the
diodes get pretty hot.
Since I have a bag of these diodes Would it be a problem to
employ four of them in a series/parallel arrangement to attain
13.60V at 20watts? I realize that the exact voltage that each
diode "clips" at might be a bit different but would that really
matter? It would be a simple job to simply add one diode in parallel
with each one presently there. Thanks, Lenny


This is to do with the question from a couple of months back, where I
suggested using a couple of series zeners to drop a fixed amount in
your power supply, yes ?

I'm not a fan of putting zeners in parallel to up the power rating,
as it's almost impossible to guarantee that they will both have
exactly the same knee voltage, resulting in the current not dividing
equally between them, if at all. At 1 amp, you are not actually
exceeding the 10 watt rating of the zeners, as long as your heatsink
is managing to keep the junction temperatures below the quoted maximum.

I think I would be more inclined to either change to a larger
heatsink, or a matt black one if it's plain ally, or paint the
existing one black, or add a fan, or whatever combination of any of
those. As you have 13.6v across the zeners, you could just 'steal' a
bit of that to run a small 12v fan. Just connect directly across the
zeners, "+" terminal to the upstream side and "-" to the downstream.
That would be my preferred solution.

Arfa


It is a lot easier to find and mount power transistor on a heat sink
than it is finding high power zeners. You can create a high current
zener this way.


I was thinking of suggesting something involving power transistors, but
there seems to be a growing opinion that the OP isn't using a big enough
HS, if space is an issue - maybe drill & tap for the zener studs in a
surplus CPU cooler.

Along the power transistor route, the TL431 programmable zener is a good
place to start - most of the manufacturers that source this part have
published application examples of adding an external booster transistor.

He's clamping the supply to keep it just under detonation level.

I guess he isn't to concern about saving energy, the greenies would be
all over him if they found out!

At least he can keep himself warm in the winter!

Jamie

 

[Trevor Wilson]

On 4/17/2013 7:02 AM, Ian Field wrote:

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:0599c63a-bc72-457f-85ee-71b25a7fe71c@r4g2000vbf.googlegroups.com...
On Apr 16, 2:12 am, jurb6...@gmail.com wrote:
My question is why use shunt regulation in the first place.

Also true about the "pass" transistor, any transistor of suitable
ratings will work and most likely help solve any thermal problems. It
doesn't even matter if it is NPN or PNP. Works both ways.

The only reason to use shunt regulation is if you expect spikes which
should be clamped. This can happen in an automotive application for
example by just having loose or dirty battery cables, or any
electrical fittings between the alternator (generator) and the load.
This porblem is compunded these days by the fact that a modern fuel
injected car with multiple coils (a coil pack)pulls a hell of alot of
current to just run. Have any idea what a heated O2 sensor pulls ?
what's more a car might have three or four of them. That is on top of
an injector for every cylider maybe more.

The thing is I am am having a hard time imagining another situation
where such a regulation scheme would be appropriate. If it's
automotive then it is, but that has not been revealed.

Yes this is related to my post of several months ago. I employed
Arfa's suggestion of using two of my 6.8V 10 watt zeners in series to
make a 13.6 V diode. And from my previous discussion this was then
put in series with the rectified 24VAC, (39VDC) to drop the voltage to
the input of my 12V regulator to a safer level. These two diodes were
mounted with insulators and silicone grease on a large old black
aluminum heat sink that I pulled out of a 1960's Delco automobile
radio. With the diodes in the circuit the voltage to the input of the
regulator was 19VDC, and under full load it was 16.5VDC, which is just
about where I wanted it to be. The only problem is that the diodes as
well as the heat sink were getting extremely hot when the regulator
was fully loaded, (1.0Amp).

Something there doesn't ring true - at full load, your load is forcing
down the voltage and easing below the zener's conduction voltage.

The zeners should run cooler when you draw full load!

**The zeners are in SERIES with the load.

--
Trevor Wilson www.rageaudio.com.au

 

[Michael A. Terrell]

Jamie wrote:

He's clamping the supply to keep it just under detonation level.

No, he isn't, Maynard.

 

[Arfa Daily]

<snip>

He's clamping the supply to keep it just under detonation level.

He is not doing any clamping with his zener arrangement. It is a simple
constant voltage series dropper ...

Arfa

I guess he isn't to concern about saving energy, the greenies would be
all over him if they found out!

At least he can keep himself warm in the winter!

Jamie

 

[Arfa Daily]

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:20jbt.6020$8L4.1433@fx29.fr7...

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:0599c63a-bc72-457f-85ee-71b25a7fe71c@r4g2000vbf.googlegroups.com...
On Apr 16, 2:12 am, jurb6...@gmail.com wrote:
My question is why use shunt regulation in the first place.

Also true about the "pass" transistor, any transistor of suitable
ratings will work and most likely help solve any thermal problems. It
doesn't even matter if it is NPN or PNP. Works both ways.

The only reason to use shunt regulation is if you expect spikes which
should be clamped. This can happen in an automotive application for
example by just having loose or dirty battery cables, or any electrical
fittings between the alternator (generator) and the load. This porblem
is compunded these days by the fact that a modern fuel injected car with
multiple coils (a coil pack)pulls a hell of alot of current to just run.
Have any idea what a heated O2 sensor pulls ? what's more a car might
have three or four of them. That is on top of an injector for every
cylider maybe more.

The thing is I am am having a hard time imagining another situation
where such a regulation scheme would be appropriate. If it's automotive
then it is, but that has not been revealed.

Yes this is related to my post of several months ago. I employed
Arfa's suggestion of using two of my 6.8V 10 watt zeners in series to
make a 13.6 V diode. And from my previous discussion this was then
put in series with the rectified 24VAC, (39VDC) to drop the voltage to
the input of my 12V regulator to a safer level. These two diodes were
mounted with insulators and silicone grease on a large old black
aluminum heat sink that I pulled out of a 1960's Delco automobile
radio. With the diodes in the circuit the voltage to the input of the
regulator was 19VDC, and under full load it was 16.5VDC, which is just
about where I wanted it to be. The only problem is that the diodes as
well as the heat sink were getting extremely hot when the regulator
was fully loaded, (1.0Amp).

Something there doesn't ring true - at full load, your load is forcing
down the voltage and easing below the zener's conduction voltage.

The zeners should run cooler when you draw full load!

No, they are in series with the load to act as a constant voltage dropper,
so they pass the full load current. The drop across them is slightly higher
when they are passing a high current.

Arfa

 

[Phil Allison]

"Arfa Daily"

"Phil Allison"
"Arfa Daily"

The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the stud
end and the heatsink, and a plastic top hat washer on the other side of
the heatsink, with the hole being large enough to accommodate the narrow
part of the insulator. I have mounted stud diodes like this many times,
and never had a problem.


** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them
into a threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you
wish to get anything like the maker's power ratings.

Fuck head.



Many extremely high power computer linear power supplies that I worked on
some years ago, would disagree with you.

** No they wouldn't.

You fucking, pig ignorant moron.

" Ye canne change the laws of ffysiks... "


.... Phil

 

[mike]

On 4/16/2013 9:23 PM, jurb6006@gmail.com wrote:


You want 12 volts just dig up an old AT type PC power supply. Now
there's something I am sure you have laying around.

That can be made to work, but it's rarely the slam-dunk that you imply.

Think about how the regulation works. You'll figger it out.

 

"No, they are in series with the load to act as a constant voltage dropper,
so they pass the full load current. The drop across them is slightly higher

when they are passing a high current.

Arfa "

Well excuse me, I am not familiar with the original thread so I didn't know that.

Now getting back to Lenny, there are so many better ways to do this it ain't funny. You know if you just take a regular old OPAMP to control a regulator transistor and put inductance at the output it is so easy to coax it into oscillation it ain't funny. That would be my actual solution. Shit, you can do it almost without math because you can design it to let it pick it's own frquency. What do you care the frequency ? Figure anything the devioes are comfortable with and be done with it. Hell, just eliminating the input filtering would allow you to make a quasi switcher out of it, with a little bit of refinement you're done. Maybe I'll draw something up.

When you are as old as Lenny (and me) you have large inductors laying around so you do not need superfast switching MOSFETS, this shit can be done with a 2N3055.

Another thing is that this whole thing is wrong. There is too much head voltage and not enough balls (current) behind it. We are only talking one ampere here ? You want 12 volts just dig up an old AT type PC power supply. Now there's something I am sure you have laying around.

If you are dropping from 24 to 19 rectified, it must be one el cheapo transformer. Maybe get one out of a car battery charger. I know we like to hang on to our pipe dreams sometimes but you know that heat dissipated costs money.

Anyway, I should draw something up but that is a pain in the (_|_) these days becasue I have to go to another PC to scan it AFTER I draw it on paper. I can't do it on a PC, though I have only tried with regular graphics programs. I know there are some available for designing electronics and some are even free, but I have thusfar been too stupid to figure out how to use them effectively.

It boils down to your basic OPAMP to be used as a comparator, that is easy. however what you have to do is to provide a positive AC feedback path from before the output inductor. You ALWAYS use an emitter resistor and reading across that with a scope you set the frequency for the best efficiency. Actually with a large inductor and a cheap transistor that will be a rather low frequency. With a more expensive transistor and a cheaper inductor it will be a higher frequency.

You could even chop it unfiltered at the 60 or 120 Hz rate. (that's 50 or 100 for Phil because them people are 16 % slower down there). If you can design it you can even do it without an output inductor.

There are too many easier ways to do this which make this current design undesirable, along with the extremely shitty efficiency.

Damn, you could do it using a regular SCR and Zener diodes and then let the current regulatior that comes after just act as an active filter. Old Sears/Warwick TVs did that. (so did others, at least hitachi that I know of)

Does anyone remember those ? The only difference here is that there is a power transformer.

 

[Wild_Bill]

Years ago I found the easiest method for me to create schematics was using a
Paint (bmp) drawing program.

There may be some sources for component symbols now, but I ended up making
my own symbols, which is time consuming but it goes more quickly after
drawing about a dozen symbols.

The bmp files saved as monochrome aren't excessively large like they tend to
be in color. Angled lines tend to be a bit rough, but creating a diode, for
example, is easily done with the drawing board zoomed-in to 200-400%.

I never found the Paint program to be of much use for anything else, but
black/white schematics are very easy to interpret.

--
Cheers,
WB
..............


<jurb6006@gmail.com> wrote in message
news:358479f8-98e5-451b-9e11-bfce300a94ee@googlegroups.com...

Anyway, I should draw something up but that is a pain in the (_|_) these
days becasue I have to go to another PC to scan it AFTER I draw it on paper.
I can't do it on a PC, though I have only tried with regular graphics
programs. I know there are some available for designing electronics and some
are even free, but I have thusfar been too stupid to figure out how to use
them effectively.

It boils down to your basic OPAMP to be used as a comparator, that is easy.
however what you have to do is to provide a positive AC feedback path from
before the output inductor. You ALWAYS use an emitter resistor and reading
across that with a scope you set the frequency for the best efficiency.
Actually with a large inductor and a cheap transistor that will be a rather
low frequency. With a more expensive transistor and a cheaper inductor it
will be a higher frequency.

You could even chop it unfiltered at the 60 or 120 Hz rate. (that's 50 or
100 for Phil because them people are 16 % slower down there). If you can
design it you can even do it without an output inductor.

There are too many easier ways to do this which make this current design
undesirable, along with the extremely shitty efficiency.

Damn, you could do it using a regular SCR and Zener diodes and then let the
current regulatior that comes after just act as an active filter. Old
Sears/Warwick TVs did that. (so did others, at least hitachi that I know of)

Does anyone remember those ? The only difference here is that there is a
power transformer.

 

[Arfa Daily]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:at6e9mFo62mU1@mid.individual.net...

"Arfa Daily"
"Phil Allison"
"Arfa Daily"

The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the
stud end and the heatsink, and a plastic top hat washer on the other
side of the heatsink, with the hole being large enough to accommodate
the narrow part of the insulator. I have mounted stud diodes like this
many times, and never had a problem.


** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them
into a threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you
wish to get anything like the maker's power ratings.

Fuck head.



Many extremely high power computer linear power supplies that I worked on
some years ago, would disagree with you.

** No they wouldn't.

You fucking, pig ignorant moron.

" Ye canne change the laws of ffysiks... "


... Phil

Aw, Philip. And there was me thinking that the vet had finally gotten your
meds just about right ... !

Never mind. We all know that it is actually you who is the fucking pig
ignorant moron, not just for what an offensive twat you are, but also
because despite knowing everything there could ever be to know, you have
actually, apparently, learnt nothing in your half arsed life. Sad ...



Arfa

 

[Arfa Daily]

"mike" <ham789@netzero.net> wrote in message
news:kkl9ij$ncf$1@dont-email.me...

On 4/16/2013 9:23 PM, jurb6006@gmail.com wrote:


You want 12 volts just dig up an old AT type PC power supply. Now there's
something I am sure you have laying around.

That can be made to work, but it's rarely the slam-dunk that you imply.
Think about how the regulation works. You'll figger it out.

It is, however, a technique quite often used in commercial equipment. Whilst
I would agree that it is not the most elegant, it does not have to be "made"
to work - it just does. I'm not quite sure I follow what you think the
problem is with the regulation. A zener diode produces a more or less
constant voltage drop across its (reverse biased) junction. Yes, I would
agree that the drop does vary a little with the current flowing, but the
drop is substantially constant, certainly enough so, if you are not going to
draw a huge range of currents through it, and definitely not a problem if
the 'dropper' is going to be followed by a 'real' regulator, as it was going
to be in Klem's application, if you remember from - or even read - his
original thread from a couple of months back.

He was looking for a simple solution because he did not fully understand
some of the more elegant and complicated ones that were being put to him. As
he had some high power zeners of an appropriate voltage to hand, the
solution that I offered him fitted the bill in that it was simple, he
understood it, and above all, it worked, and apparently has been doing so
for a couple of months now.

So, if you want a simple 'dropper' that is largely current independant, then
I think the term "slam dunk" fits this technique remarkably well !

Arfa

 

"That can be made to work, but it's rarely the slam-dunk that you imply.
Think about how the regulation works. You'll figger it out. "

It would only be a slam dunk if the 12 volt line was the one being sensed by the regulation loop. Actually it would not be hard to modify it to make it so, but that would require taking it apart. I can think of no way to tie it in with the lower source to make it follow. The only other way would be for the error amp to cause a load on the sensed line, which is as bad as what we have now. I big mess. Inside the PS though, simple cutting a foil and adding the right resistor would do it.

But is it that critical ? a passive regulator runing like that is probably not all tha ttight anyway. Remember I missed the original thread so I don't even know the purpose of this thing. All I know is it need about an amp. It certainly isn't for car stereos, what is it ?

 

"Years ago I found the easiest method for me to create schematics was using a
Paint (bmp) drawing program. "

I never figured out how to copy and paste in that damn thing. Same with Paintshop Pro. I didn't even try with Adobe, screw it.

 

[mike]

On 4/17/2013 1:25 AM, Arfa Daily wrote:

"mike" <ham789@netzero.net> wrote in message
news:kkl9ij$ncf$1@dont-email.me...
On 4/16/2013 9:23 PM, jurb6006@gmail.com wrote:


You want 12 volts just dig up an old AT type PC power supply. Now
there's something I am sure you have laying around.

That can be made to work, but it's rarely the slam-dunk that you imply.
Think about how the regulation works. You'll figger it out.


It is, however, a technique quite often used in commercial equipment.
Whilst I would agree that it is not the most elegant, it does not have
to be "made" to work - it just does. I'm not quite sure I follow what
you think the problem is with the regulation. A zener diode produces a
more or less constant voltage drop across its (reverse biased) junction.
Yes, I would agree that the drop does vary a little with the current
flowing, but the drop is substantially constant, certainly enough so, if
you are not going to draw a huge range of currents through it, and
definitely not a problem if the 'dropper' is going to be followed by a
'real' regulator, as it was going to be in Klem's application, if you
remember from - or even read - his original thread from a couple of
months back.

He was looking for a simple solution because he did not fully understand
some of the more elegant and complicated ones that were being put to
him. As he had some high power zeners of an appropriate voltage to hand,
the solution that I offered him fitted the bill in that it was simple,
he understood it, and above all, it worked, and apparently has been
doing so for a couple of months now.

So, if you want a simple 'dropper' that is largely current independant,
then I think the term "slam dunk" fits this technique remarkably well !

Arfa
I can only recommend that you read the first sentence that you quoted.

My input has nothing to do with the dropper. It's about trying to get 12V
out of a AT PC supply without thinking about what you're doing.

 

[klem kedidelhopper]

On Apr 17, 4:13 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

"Phil Allison" <phi...@tpg.com.au> wrote in message

news:at6e9mFo62mU1@mid.individual.net...











"Arfa Daily"
"Phil Allison"
"Arfa Daily"

The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the
stud end and the heatsink, and a plastic top hat washer on the other
side of the heatsink, with the hole being large enough to accommodate
the narrow part of the insulator. I have mounted stud diodes like this
many times, and never had a problem.

** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them
into a threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you
wish to get anything like the maker's power ratings.

Fuck head.

Many extremely high power computer linear power supplies that I worked on
some years ago, would disagree with you.

** No they wouldn't.

  You fucking, pig ignorant moron.

  " Ye canne change the laws of ffysiks...  "

...   Phil

Aw, Philip. And there was me thinking that the vet had finally gotten your
meds just about right ... !

Never mind. We all know that it is actually you who is the fucking pig
ignorant moron, not just for what an offensive twat you are, but also
because despite knowing everything there could ever be to know, you have
actually, apparently, learnt nothing in your half arsed life. Sad ...


Arfa

While I would have to agree with Phil's earlier statement that it
would be ideal to simply screw the diodes into threaded holes on the
heat sink, they are electrically in series, so that is not possible.
The heat sink is also mounted through the extra aluminum I've
subsequently added directly to the chassis, which of course is
building ground. So that would be another disaster. I liked the fan
idea, however sadly there is no room for it, not even a small CPU
cooler type. And while I would admit that this is not a "green" power
supply, once this heat issue is resolved it should be a reliable one.
In the interim I did take another look at my mounting arrangement
though and it appears that I may have used two plastic washers on the
one side of the diodes where I should have used mica. What sort of
brain fart spurned that idea I'll probably never know, but that might
be my problem. I may be attempting to transmit heat through plastic.
Duh? Anyway, If so it's apparently working, to some degree, but
obviously not enough degrees. I'll check this out tomorrow and update
this thread. Thank you for the link to the mounting kits Arfa, and to
everyone else for your input. Lenny

 

[Phil Allison]

"Arfa Fuckwit TROLL Daily"

The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the stud
end and the heatsink, and a plastic top hat washer on the other side of
the heatsink, with the hole being large enough to accommodate the narrow
part of the insulator. I have mounted stud diodes like this many times,
and never had a problem.

** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them into a
threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you wish
to get anything like the maker's power ratings.

You colossally STUPID, BULLSHITTING pommy fuck head.





.... Phil

 

[Arfa Daily]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:at7ik6F16gtU1@mid.individual.net...

"Arfa Fuckwit TROLL Daily"


The correct way to mount them is exactly the same as you would a TO3
transistor. That is with a mica washer between the flat face of the stud
end and the heatsink, and a plastic top hat washer on the other side of
the heatsink, with the hole being large enough to accommodate the narrow
part of the insulator. I have mounted stud diodes like this many times,
and never had a problem.


** A TO3 device has a large surface area.

A DO4 stud device has almost none unless you include the thread.

So it is blindingly obvious that for best heatsinking, you screw them into
a
threaded hole.

The heatsink may then need to be insulated from other metal work.

This is how all high power stud diodes zeners must be mounted, if you wish
to get anything like the maker's power ratings.

You colossally STUPID, BULLSHITTING pommy fuck head.





... Phil

Oh dear, he's off and running again. Go on Philip, scoot on back to the vet
and tell him that you're hearing the voices and seeing the pretty lights
again. Perhaps he will be able to up the level of your horse tranquillizer
pills for a few days until you're suitably subdued ...

Arfa