Date   
Re: Taking apart ferrite transformers

Chuck Harris
 

A long time ago, I was involved in making a microwave oven
based surgical instrument sterilizer. We never got it
perfected, but metal in microwave ovens is a much overrated
concern. Some ovens even come with metal racks to divide
the oven's chamber for more effective utilization.

Back in the day poor loads could cause the magnetron's window
to arc over, eliminating the vacuum, but that was with glass
windows... not the fancy alumina ceramic windows used in a
modern oven grade magnetron... So, damage to the magnetron
from high VSWR is unlikely to the point of being impossible.

Try running your oven with nothing in the chamber, and notice
how it isn't damaged...

Even one turn of the coil in the transformer will have near
infinite impedance at 2.45GHz, so not much trouble there.

The ferrite will quickly heat to possibly dangerous temperatures,
that is where to be concerned. Depending on the potting, and
other configuration issues, explosion is likely.

For our sterilizer, we literally decimated the 60Hz that went
into the transformer, eliminating cycles to adjust the power,
giving a pretty fine adjustment. We had to make a minimum
on time to keep the maggy's filament happy... The modern
microwave oven is either on, or off. They adjust power by
adjusting the on/off ratio during a 10 second window. 20%
would be 2 seconds on, 8 off....

Don't imagine that the "power" settings will lower the power.

So, if I were going to try this, I would put the core on a
nice oven proof ceramic dish, and give it 1 second on high
power, and see what happens. Then 2 seconds, upping the
time until I saw the result I desired, or quit in defeat...

I take my ferrite cores apart by soaking them for 30 minutes
in a 130C oven. The core halves can then be twisted apart
by my heavy gloved hands.

-Chuck Harris

'Brian Clarke' brianclarke01@... [TekScopes] wrote:

I suggest that you look very carefully at the effect of having coiled copper in a microwave oven.



73 de Brian, VK2GCE

Re: Scope for my 3 Year old

ArtekManuals
 

Just instill the fear of death or his mothers wrath if he EVER pokes the
probes in the power outlet :-)

On 6/26/2017 7:33 AM, Joe joeshomeworkshop@... [TekScopes] wrote:

At that age any of the battery powered 200 series scopes would be a great
starter. They don't have a lot of bandwidth but are easy to use, have
small
controls that are not hard to operate by a youngster, are cute but
also are
far from being a toy.

Joe

On Sun, Jun 25, 2017 at 10:57 PM, edbreya@... [TekScopes] <
TekScopes@...> wrote:



Wow. That is both rare and great for someone to take scientific interest
at such an early age. I think you already have the basic scope you
need in
the 2215 - he can fool around with it and see plenty of stuff, and then
graduate to the 2465.

Ed






--
Dave
Manuals@...
www.ArtekManuals.com

Re: Scope for my 3 Year old

Steve Huston
 

On Sun, Jun 25, 2017 at 11:12 PM, Chris Juried cjuried@...
[TekScopes] <TekScopes@...> wrote:

I am looking for a scope for my 3 year old son who has shown great interest in electronics and my 2465 and 2215. I am setting him up with a small lab in his bedroom with a function generator and audio/visual peripherals. I want him to experiment with various waveforms and be able to correlate audibly and visually the waveforms he is experimenting with. We will work on the mathematics behind the waveforms as time progresses. In any case, I am looking for a basic, dual trace, 20 MHz or above. If it happens to have a DMM, Counter and/or any other mathematical calculations, on board, that would be of great benefit as well. Thought I would come to the group to see if anyone is letting go of a basic scope for a reasonable cost or for the price of shipping. Thank you all in advance.
You might want to look into the cheap digital units that can be
assembled too. My eldest two are also interested in electronics and
they've both built an Elenco AM/FM radio, so maybe some time with a
soldering iron putting together one of the DSO138 clones would be fun
and yield a working piece of equipment when finished.


--

Steve Huston - W2SRH - Unix Sysadmin, PICSciE/CSES & Astrophysical Sci
Princeton University | ICBM Address: 40.346344 -74.652242
345 Lewis Library |"On my ship, the Rocinante, wheeling through
Princeton, NJ 08544 | the galaxies; headed for the heart of Cygnus,
(267) 793-0852 | headlong into mystery." -Rush, 'Cygnus X-1'

Re: Scope for my 3 Year old

Trevor
 

The Tektronix/Sony 305 might be suitable, with dual trace, built in DVM and battery operation. However, it's only 5MHz, and the DVM does not display CRT screen related functions, like some more modern scopes that give a numeric value to a cursor. Perhaps a Tek/Sony 335 and a separate cheap hand held DVM is a better choice.

see:
http://w140.com/tekwiki/wiki/305
http://w140.com/tekwiki/wiki/335

Re: Scope for my 3 Year old

Joe
 

At that age any of the battery powered 200 series scopes would be a great
starter. They don't have a lot of bandwidth but are easy to use, have small
controls that are not hard to operate by a youngster, are cute but also are
far from being a toy.

Joe

On Sun, Jun 25, 2017 at 10:57 PM, edbreya@... [TekScopes] <
TekScopes@...> wrote:



Wow. That is both rare and great for someone to take scientific interest
at such an early age. I think you already have the basic scope you need in
the 2215 - he can fool around with it and see plenty of stuff, and then
graduate to the 2465.

Ed




Re: Super Cold Spray Substitute

bc
 

I think they did put R134A on the "do not discharge to air" list (it's
illegal to vent R134A ACs when servicing them) but the small amounts
used in the "canned air" and "cold blast" are probably OK.  R134A is a
strong GHG, but does not deplete the O3 layer.
I'd just put the warning out that the car AC R134A cans are cheap,
these cans don't appear to have valves unlike regular spray cans.  I
wish I could transfer 134a into my empty butane cans which do have
valves on them.
Incidentally you can use butane as cold spray too, except you have to
watch out for sparks: your cold area could get mighty toasty instead
(at least if it does get toasty, the mercaptan smell will quickly go
away.)
On Sun, 2017-06-25 at 01:12 -0400, Chuck Harris cfharris@...
[TekScopes] wrote:
 



  


    
      
      
      Canned air, and freeze spray, as currently available

are just R134A.



Any R134A with oil in it will be mostly oil, little

refrigerant.



-Chuck Harris



David @DWH [TekScopes] wrote:

Freon will work just fine however it sometimes includes compressor
oil so I would

test it on a sheet of paper first.
 
On 19 Jun 2017 16:16:50 +0000, you wrote:
 
I just ran out of Super Cold Spray and I need to troubleshoot a
heat related

issue on a 2465B A1 board.  Can I just use some R-134A Freon?
 


    
     

    
    






  
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Re: Taking apart ferrite transformers

 

Hello,

I cook them in boiling water for at least 15 minutes, pins on the bottom of
the pan avoids uneven heat to the core.
Once cooked whip them out and pull core by hand and glove while still hot.

Keep the water ready in case you need another dip.

Scratching the bulging glue off the edges of the core before boiling will
help.

Not a quick method but avoids breaking the core most of the time.
I'll have to try the oven.

Paul



Le lundi 26 juin 2017, 'John Snyder' Kochcal@... [TekScopes] <
TekScopes@...> a écrit :
Ed

I have taken a part a few transformers and I found heat was the key,
similar
to the 100-150 Celsius mentioned but I liked Fahrenheit and used about
275-300, that worked well for me. The heat gun was generally too hot too
quick and I found it did not penetrate well. I got a used toaster oven
with
a little pan and placed a thermocouple in it, and set the thermostat to
get
the Fahrenheit I was looking for. Once heated through and through (about
20
min) most of the time I would work on it for a few seconds and then place
it
back in the oven to reheat and work some more. A heat gun can kick it over
the edge but can also easily melt the form.

Some come apart nicely, some are impossible, some you can get the core but
melt the bobbin, you can never tell what's in a transformer until you give
it a try.

And it depends what you are after.

Of course there is no real economy to the process but that's not always
the
point.

Luckily these days, there is an endless supply of cores going to the
recycling/dumps that you can practice on and I found just looking at the
various constructions interesting.

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, June 25, 2017 8:41 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Taking apart ferrite transformers

Thanks all, for ideas on transformer knock-down. I think I'll try cooking
some with a heat gun first. I have one of those old 1500W "paint stripper"
heat guns that looks like a big hair dryer, but actually runs very hot
(would burn hair instantly). If it looks like it will be hard to control
and
damage the bobbins, I'll have to try an oven with temperature control, or
acetone soaking (with lots of patience). I have a fine-point hot air
blaster
that I use for stripping SMD parts from boards, but it may have problems
cooking what it's supposed to without melting or burning the plastic
parts.
It's so hot that although it's fine for most SMD parts, anything with a
plastic base or frame tends to fry way before the solder melts. I could
also
try my flow solder machine, but only on transformers where only the outer
legs of the core are glued, and nothing else - I can picture maybe dipping
them into the solder a little at a time, and flipping them. Too much on
one
side may crack the core, like ruining a good steak on the BBQ.

Ed





------------------------------------
Posted by: edbreya@...
------------------------------------


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

Yahoo Groups Links






------------------------------------
Posted by: "John Snyder" <kochcal@...>
------------------------------------


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

Yahoo Groups Links



Re: Taking apart ferrite transformers

ykochcal
 

Ed

I have taken a part a few transformers and I found heat was the key, similar
to the 100-150 Celsius mentioned but I liked Fahrenheit and used about
275-300, that worked well for me. The heat gun was generally too hot too
quick and I found it did not penetrate well. I got a used toaster oven with
a little pan and placed a thermocouple in it, and set the thermostat to get
the Fahrenheit I was looking for. Once heated through and through (about 20
min) most of the time I would work on it for a few seconds and then place it
back in the oven to reheat and work some more. A heat gun can kick it over
the edge but can also easily melt the form.

Some come apart nicely, some are impossible, some you can get the core but
melt the bobbin, you can never tell what's in a transformer until you give
it a try.

And it depends what you are after.

Of course there is no real economy to the process but that's not always the
point.

Luckily these days, there is an endless supply of cores going to the
recycling/dumps that you can practice on and I found just looking at the
various constructions interesting.

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, June 25, 2017 8:41 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: Taking apart ferrite transformers

Thanks all, for ideas on transformer knock-down. I think I'll try cooking
some with a heat gun first. I have one of those old 1500W "paint stripper"
heat guns that looks like a big hair dryer, but actually runs very hot
(would burn hair instantly). If it looks like it will be hard to control and
damage the bobbins, I'll have to try an oven with temperature control, or
acetone soaking (with lots of patience). I have a fine-point hot air blaster
that I use for stripping SMD parts from boards, but it may have problems
cooking what it's supposed to without melting or burning the plastic parts.
It's so hot that although it's fine for most SMD parts, anything with a
plastic base or frame tends to fry way before the solder melts. I could also
try my flow solder machine, but only on transformers where only the outer
legs of the core are glued, and nothing else - I can picture maybe dipping
them into the solder a little at a time, and flipping them. Too much on one
side may crack the core, like ruining a good steak on the BBQ.

Ed





------------------------------------
Posted by: edbreya@...
------------------------------------


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

Yahoo Groups Links

Re: Taking apart ferrite transformers

Ed Breya
 

Yes, there are solvents that can undo epoxy resins. One that I recall from long ago is dimtheyl formamide (I think). I think I told this story before here a while back, but here's a short redo: Way back about forty years ago, my boss had this epoxy-potted lawnmower ignition module that had crapped out, and he wanted to un-pot it to see what was in there and maybe fix it. He brought it to work, and called a friend in the chemistry lab to see what might do it. A couple of days later, we received a bottle of DMF, or whatever it was. All I can recall was the approximate name, and that it smelled kind of like dead animal, and that it did indeed work, but slowly - it softened and swelled the potting so that it could be chunked out to expose the guts.

Ed

Re: Scope for my 3 Year old

Ed Breya
 

Wow. That is both rare and great for someone to take scientific interest at such an early age. I think you already have the basic scope you need in the 2215 - he can fool around with it and see plenty of stuff, and then graduate to the 2465.

Ed

Re: Taking apart ferrite transformers

Merchison Burke
 

Master Bond has a technical department at "https://www.masterbond.com/contact". They may be able to answer questions about dissolving or softening cured epoxy.


On 2017-Jun-25 9:08 PM, @DaveM [TekScopes] wrote:

On another thought, I Googled foe methods to disassemble glued ferrite cores. Many comments led to the same conclusion... judiciously applied heat and knife pressure. There was one post that I saw that recommended to Contact a company in NJ called Masterbond. They sell a product that removes potting compound type epoxies. It works wonderfully without damage to the board or components. I visited that web site, but didn't find any mention of solvents to dissolved cured epoxy. You might try them and see what they can offer.

Cheers,
Dave M

---
This email has been checked for viruses by AVG.
http://www.avg.com

Re: Taking apart ferrite transformers

Ed Breya
 

Thanks all, for ideas on transformer knock-down. I think I'll try cooking some with a heat gun first. I have one of those old 1500W "paint stripper" heat guns that looks like a big hair dryer, but actually runs very hot (would burn hair instantly). If it looks like it will be hard to control and damage the bobbins, I'll have to try an oven with temperature control, or acetone soaking (with lots of patience). I have a fine-point hot air blaster that I use for stripping SMD parts from boards, but it may have problems cooking what it's supposed to without melting or burning the plastic parts. It's so hot that although it's fine for most SMD parts, anything with a plastic base or frame tends to fry way before the solder melts. I could also try my flow solder machine, but only on transformers where only the outer legs of the core are glued, and nothing else - I can picture maybe dipping them into the solder a little at a time, and flipping them. Too much on one side may crack the core, like ruining a good steak on the BBQ.

Ed

Scope for my 3 Year old

Chris J
 

Hi all,
I am looking for a scope for my 3 year old son who has shown great interest in electronics and my 2465 and 2215. I am setting him up with a small lab in his bedroom with a function generator and audio/visual peripherals. I want him to experiment with various waveforms and be able to correlate audibly and visually the waveforms he is experimenting with. We will work on the mathematics behind the waveforms as time progresses. In any case, I am looking for a basic, dual trace, 20 MHz or above. If it happens to have a DMM, Counter and/or any other mathematical calculations, on board, that would be of great benefit as well. Thought I would come to the group to see if anyone is letting go of a basic scope for a reasonable cost or for the price of shipping. Thank you all in advance.
 Sincerely,   
  Chris Juried  
Audio Engineering Society (AES) Member 
InfoComm-Recognized AV Technologist
http://www.JuriedEngineering.com (Juried Engineering, LLC.)
http://www.TubeEquipment.com (Tube Equipment Corporation)
http://www.HistoryOfRecording.com (History of Recording)
http://www.linkedin.com/in/chrisjuried (LinkedIn)Email: CJuried@... 
Voice: (954) 478-4355


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Re: Regarding linear power supplies

Ed Breya
 

The 723 is a classic, and still very useful. It uses a buried Zener reference, so is capable of pretty low noise compared to most newer, easier to use three-terminal ones with bandgap references. I prefer it to almost anything else for positive supplies up to 100 mA, for low noise analog and digital circuits. It does take more parts to implement small regulators, so it depends on the application.

Ed

Re: Regarding linear power supplies

 

Hi Ancel,
It is finally approaching End of Life. I say "finally" because it has been going strong since 1970 when I first used it. As Brian pointed its long life was probably due in part to its rich set of capabilities some of which you cannot get in a "more modern" regulator.

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Sunday, June 25, 2017 5:07 PM
To: TekScopes@...
Subject: [TekScopes] Re: Regarding linear power supplies

Isn't the 723 kinda obsolete?
------------------------------------
Posted by: AncelB <mosaicmerc@...>
------------------------------------

Re: Taking apart ferrite transformers

Brad Thompson <brad.thompson@...>
 

On 6/25/2017 9:08 PM, @DaveM [TekScopes] wrote:
I have an old Wahl Thermal Spot http://www.ebay.com/itm/Wahl-Thermal-Spot-Tester-/272690160714?epid=1603930498&hash=item3f7d99a44a:g:9nUAAOSwFe5X0Ybf that I've used successfully to disassemble ferrite cores. It's a small version of a heat gun, with a small nozzle that can be directed at a single component, rather than half of your workshop. I see a few on Ebay at the moment. One has a buy-it-now price of $40, but allows you to make an offer. $40 seems a bit pricey for this item,
<snip>

Hello--

Take a look at the Darice Embossing Multi-Purpose Heat Tool, 320 Watt
by Darice ($ 12 98 on Amazon) and likely comparably priced in Wal-Mart, Michael's, JoAnn's or other stores with craft departments. There are similar tools
available under different brand names.

This is a small AC-powered hot-air source that's about the size of a CueCat (*)
bar-code scanner, or a cruller (**). (Apologies for the obscure references<g>).

73--

Brad AA1IP


(*) https://en.wikipedia.org/wiki/CueCat

(**) https://en.wikipedia.org/wiki/Cruller

Re: Taking apart ferrite transformers

Brian Clarke <brianclarke01@...>
 

I suggest that you look very carefully at the effect of having coiled copper in a microwave oven.



73 de Brian, VK2GCE



From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, 26 June 2017 10:20 AM
To: TekScopes@...
Subject: Re: [TekScopes] Taking apart ferrite transformers





I have heard of placing the transformer in a microwave oven which heats the core enough to soften the adhesive.
I don't know the details so use caution when trying!!!



Posted by: "Erik Hultine" <erik@... <mailto:erik@...> >

Re: Taking apart ferrite transformers

 

I have an old Wahl Thermal Spot http://www.ebay.com/itm/Wahl-Thermal-Spot-Tester-/272690160714?epid=1603930498&hash=item3f7d99a44a:g:9nUAAOSwFe5X0Ybf that I've used successfully to disassemble ferrite cores. It's a small version of a heat gun, with a small nozzle that can be directed at a single component, rather than half of your workshop. I see a few on Ebay at the moment. One has a buy-it-now price of $40, but allows you to make an offer. $40 seems a bit pricey for this item, but the others are much higher, with no make-an-offer option. I use mine to direct the heat nozzle at the epoxy joint while applying pressure with a box cutter blade (razor knife). Takes a few minutes per unit, but rarely do I break the core. The joint comes apart easily with heat and knife pressure.


On another thought, I Googled foe methods to disassemble glued ferrite cores. Many comments led to the same conclusion... judiciously applied heat and knife pressure. There was one post that I saw that recommended to Contact a company in NJ called Masterbond. They sell a product that removes potting compound type epoxies. It works wonderfully without damage to the board or components. I visited that web site, but didn't find any mention of solvents to dissolved cured epoxy. You might try them and see what they can offer.


Cheers,
Dave M

---In TekScopes@..., <edbreya@...> wrote :

After more thinking and optimizing the power system for my 576 tube test fixture, I'm probably going to need the option of custom winding the converter transformer. I've got lots of various ferrite flyback transformers pulled from all kinds of SMPSs, and would like to pick some candidates for stripping down and rebuilding. These are all commercially made types, that are varnished/glued together, etc, and I need a quick and simple way to undo a bunch of them en mass, and preserve the cores and bobbins. I know this kind of thing has come up before on the Tek HV transformers, but just wondering what's presently considered the best for this situation with varnish, polyurethane, epoxy, etc. The two methods I think will be heat or solvents (or both).

I was picturing soaking them in a jar of acetone, but I vaguely recall the last time I did this (long ago) it was a very slow process.

Any suggestions?

Ed




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Re: Taking apart ferrite transformers

Erik Hultine
 

I have heard of placing the transformer in a microwave oven which heats the core enough to soften the adhesive.
I don't know the details so use caution when trying!!!

Re: Regarding linear power supplies

mosaicmerc
 

Isn't the 723 kinda obsolete?