Isolated, regulated, toroidal step down transformer AC power supply design. - Page 6

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Anyone who is genuinely mystified by my belligerence, either:

a) Didn't read or understand the thread and the chronology of its
development.

b) Doesn't understand the basic rules and principles of equality, or
understands them but does not apply them in newsgroups and believes that
different criteria  or rules should be applied.

In which case, it would be helpful if you explained the basis on which you
discriminate
between my belligerence and Phils (or anyone else's.)

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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**Nope. That ain't it. I've been here since the start. I asked you what the
application was. I also asked you what Voltages you had measured on the
regulator inputs. So far, no answers.

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**Here's how it works in the real world:

* You ask a seemingly reasonable question (from your, very un-knowledgable
viewpoint).
* You are asked to supply more information, so WE (the knowledgable) can
decide if you request is reasonable or not.
* After we are supplied the information (which includes Voltage
measurements), then a better solution can be supplied.

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**I'm not discriminating between yours and anyone else's belligerence. I am
simply stating fact: You are acting belligerently. And, in several annoying
ways:

* You persist in top posting. Think of it in terms of a normal convesation.
One person makes a comment and the other person responds, AFTER the original
comment. Top posting reverses that convention. A convention which us humans
have dealt with for many thousands of years. Top posters seem unable to
understnad this uttery basic fact of life.
* Despite repeated requests, you STILL refuse to supply basic information
about the device. You tell us what speakers you use, what capacitors you
use, you even tell us about your family life, yet you STILL refuse to supply
the fundamental information required for us to give you a sensible answer.
* Despite repeated suggestions that we have superior solutions, you continue
to return to your own, quite insane one.
* Depsite repeated advice that your regulators are unlikely to be faulty,
you persist in insisting that they MUST be faulty, when it is more likely
that something else, far more prosaic is obviously wrong (that the
regulators simply do not have enough input Voltage).



--
Trevor Wilson
www.rageaudio.com.au



--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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Give up Trevor. Even if he coughed up the info, he wouldnt understand
the suggested fix. Although its hilarious that he cant measure ripple
current but wants to build a 1% AC regulator.

and its more pig-headed than belligerent behaviour - one can be
belligerent and right, which he is not.

I recommend a 2kVA true-sinusoidal UPS to fix the problem. but use
monster cables to connect the 9Vac, and ensure the mains plug is gold
plated. Hopefully whilst mark is earning the money to pay for this
stuff, he will stop posting (top or bottom)

some people should not be allowed soldering irons. or keyboards.

Cheers
Terry

Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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**Exellent point.

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**Oh yeah. One of my mates wanted to install silver wire in his amplifier,
CD player or something. I asked if he could solder and he assured me that he
could. After the stuff stopped working, I told him to bring it down. YIKES!
He was using acid flux paste to solder with. The corrosion was extensive.
God knows what kind of iron he had. I gave him one of my old temperature
controlled things and a roll of Multicore solder and an hour's worth of
instruction. I haven't seen any of his gear back on the bench, so I guess
all is now OK.


--
Trevor Wilson
www.rageaudio.com.au



--

Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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We had the same issue when I was working for a major whitegoods manufacturer
in the late 80's. The 7805's were getting pop-rivetted to the board through the
heatsink, then we'd be getting failures. Can't remember the failure rate though.
The 7805 tab transferred the shock of the pop-rivetting action to the the 7805
die
and fractured it. Same solution, no further problem.


Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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the
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though.
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die
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yep. good old AN1040 strikes again. I had to explain to the C.M. that
its basically a lump of glass soldered to a copper tab, and smacking it
hard with a hammer was a bad idea.

I had an even funnier one with the same UPS - doing a forensic analysis
on a failed unit, the flyback battery charger had died. I desoldered the
FET & heatsink, and when I lifted it out of the PCB, the FET spun
freely. The CM had used a nylok nut, and the nylon had melted, dribbling
out the back of the nut, which then worked itself loose. oops. So I
spec'd the same captive-spring-washer nuts we used, which were really
cute - they had a spring washer that looked like a belleville with 4
radial cuts, and the center of the nut was crimped around this, so the
spring washer could spin. lovely, and cheap.

Cheers
Terry

Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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the
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though.
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7805 die
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In my last job we used those sort of nuts (with integrated washer)  in
conjunction with
self broaching threads that were pressed into pcbs. The nut and thread held
down a plastic housing, and that wasn't going anywhere. It's a nice idea.


Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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save up your pocket money and get one of these: (or similar)

http://2mix.co.uk/shop2mix/product_info.php?products_id55%5&osCsid37%705bebbccbcd8acedef38e66a4e5cc

Bye.
   Jasen

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Thanks. I am currently trialing my existing UPS for just that purpose.

I need to collect a few weeks data.

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http://2mix.co.uk/shop2mix/product_info.php?products_id55%5&osCsid37%705bebbccbcd8acedef38e66a4e5cc
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Re: Isolated, regulated, toroidal step down transformer AC power supply design.




Mark, several of the people who are answering you here are capable of eating
the vast majority of electronics repairers for breakfast when it comes to
design. All of the people of relevance on this group are capable of
designing half wave rectified voltage doubling designs in their sleep. Why
the big secrecy with respect to your application? You really are going on
like a wanker............



Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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15

A common 7815 regulator will put out a stable 15v for input voltages between
17.5v and 30v. That's plenty of headroom for any overvoltage situation on
the mains side.




Re: Isolated, regulated, toroidal step down transformer AC power supply design.


It certainly would be reassuring to know that I have more head room than I
remember.

Show me your spec please. I remember reading something less (much less), but
I haven't got it in front of me.

I am sure that you can appreciate that since I am replacing a wall-wart
power supply with a toroidal step down transformer, the cost of an
additional IC regulator is rather trivial when compared to the cost of the
rest of the project.

It may turn out that the particular IC's that I have in place don't regulate
to a 30 VDC input, either by design or circumstance.

The application certainly occasionally behaves erratically (on/off clipping
of output) and I know that this behaviour coincides with over voltage supply
problems. I monitor the domestic supply using software which queries and
records data from an UPS. So there is no doubt about the cause. 100%
correlation.

If the cost of certainty (solving the problem by putting in a bigger, better
IC regulator) is about 10 bucks (and, apparently, putting up with a few
arse-clowns because I was foolish enough to ask for help @
'aus.electronics') then I can go the extra distance, I guess.

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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Maybe if you bothered looking at the datasheets for the devices you are
using.
Usual first step before using a device is read the datasheet or manual.

For a 7815
http://www.fairchildsemi.com/pf/LM/LM7815.html
http://www.national.com/ds/LM/LM340.pdf

input range is 17.5V to 30V DC.
Need minimum of 17.5 to get regulated 15V output.

Using a simple AC circuit + bridge rectifier or diodes + linear reg is a lot
cheaper and simpler than mucking around with AC regulation.

May not be the most energy efficient circuit but is simple and easy to fault
find.
Also a less noise than any switchmode or boost/buck  converter circuit.

Alex



Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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but

You haven't tried Googling 7815 datasheet?

I think you also need to revise basic power supply design, in particular,
the manner in which regulators work, and the recommended filtering
configuration on the input and output of the regulator.

As others have pointed out, it may well be that your AC power supply isn't
supplying adequate voltage to prevent one or both of the regulators dropping
out under load.

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No, I don't appreciate that perspective, because it isn't the most obvious
answer to what you've explained. The fact that you believe a regulator
requires an input voltage within some percentage, either postive or
negative, of the output voltage underpins where your thinking has gone
wrong.

You're also convinced the issue is overvoltage, whereas looking at the whole
system, it looks more like the AC transformer isn't putting out enough
voltage. It could well be that another plug pack with a higer output voltage
and suitable current rating would solve the problem, or it could be that the
plugpack you have is a dud.

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clipping
supply

Possibly, but there's a much more obvious answer that does a better job of
explaining your problem.

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better

Perhaps if you had stated from the start that your plugpack-powered preamp
(I'm guessing) is exhibiting distortion and that you suspect a power supply
issue, you might have gotten more rigorous and methodical advice. The next
question would have been what are the regulators, what voltage is appearing
at the input of each regulator, and are they getting hot.

That said, *nobody* deserves the kind of response and language that a
certain person has used in this thread.

Also, if you are asking for help and advice, it's polite to observe accepted
etiquette - that inlcudes refraining from top-posting particularly if asked
not to.





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the
IC's
of
on



Re: Isolated, regulated, toroidal step down transformer AC power supply design.


Three things:

1) "7815" gives about 4 million hits on Goggle.

2) I asked for the help a little over 48 hours ago, and since that time I
have had to suffer about 30 attacks, but NO HELP what-so-ever.

3) I have a family and one particular dependant who is bed ridden.

What did you expect from me?

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Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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    I haven't been paying close attention to this thread, but no item of
audio (or any other mains-powered) equipment which is working properly
is going to be affected by tiny mains voltage variations. If that's
happening, then it's faulty and it should be looked at and repaired by
someone who understands electronics.
    All this talk about toroidal transformers, voltage regulators and
acoustically transparent capacitors seems irrelevant, or did I miss
something by not reading everything?
    BTW: 'wall wart' is another Americanism creeping into the Australian
vernacular. I suppose one day we'll have 117V 60Hz mains and beoome the
51st or 52nd or whatever it is state of the USA.



Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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A Google on 7815 datasheet gets you the answer - very first result.
Secondly, it isn't really about the specific attributes of the 7815 - as
soon as you've had anything to do with power supplies, you get familiar with
some very basic rules, one of which is that you need 2-3v extra at the input
of a regulator for it to work - that applies to 7805s, 7812s etc.

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That's because you didn't provide sufficient information from the start, and
I don't mean to be rude, but what you initially suggested was absurd - it
was. Really. It might have made sense to you given your background, but to
anyone with experience in almost any field of electronics, regulated power
supplies are such common and basic things that we pretty much all understand
how they work, the issues that arise and how to deal with them.

What you said initially was the equivalent of saying: "How can I synthesise
better fuel?" Then you say "I've purchased lots of really expensive fuel
filters, which are black by the way - that hasn't helped, so I clealry need
to re-sythesise my existing fuel to make it more consistent".

Everyone laughs at you. Particulalry when we discover how much those fuel
filters cost.

Finally you say: "My engine is running badly, I think it's a fuel problem".

And if you were really being straight-up with us, you'd also say "Actually,
I built the engine, it's running badly, does anyone want to buy some really
good fuel filters?"

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I'm honestly sorry to hear that one of your family is ill, and I'm also
sorry that you've had to endure such unpleasant language and abuse, but it's
Usenet, a base level of mocking and general derision comes with the
protocol.

If you really want help, rather than seeking confirmation of your various
theories, just tell us what the actualy device is, who designed and built
it, what the voltage is at the input of the regulators is and what caps you
have on each side of the regulator.

Oh, and maybe refrain from top-posting - it really does annoy people.





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than
less),
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particular,
isn't
obvious
and
of
preamp
next
within
x%)
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situation



Re: Isolated, regulated, toroidal step down transformer AC power supply design.



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 7815s are good to 35V, do you want something worse?

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How did you observe this?  What do you mean by "clipping"?
A regulated DC power 'rail' is supposed to be a flat line on the scope
all the time...

Bye.
   Jasen

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


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So you aren't the mark who attemped to mock Phil over some misunderstandibng
of your voltage doubler?  

you must be an imposter then.

Fuck off.

--

Bye.
   Jasen

Re: Isolated, regulated, toroidal step down transformer AC power supply design.


pffffft...  The CLAIM to the possession of a SPECIFIC piece of knowledge (or
the lack of it) does not equate to expertise (or the lack of it).

Shoddy post, Jasen.


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