[Hallicrafters] Piesoelectric effect case in point.
Carl
km1h at jeremy.mv.com
Sun Jan 2 18:22:00 EST 2011
----- Original Message -----
From: "Walt Cates" <cateswa at msn.com>
To: "Carl" <km1h at jeremy.mv.com>; "hallicrafters"
<hallicrafters at mailman.qth.net>
Sent: Sunday, January 02, 2011 5:24 PM
Subject: Re: [Hallicrafters] Piesoelectric effect case in point.
Carl,
I don't understand why you are so condescending. I did not base my statement
on one occurrence.
** It certainly sounded like it and Im not one to believe in many
coincidences.
It is based on thousands of repairs and 50 years as a R/D EE and ME. I
simply related an event that happened on the very day the discussion
appeared on the forum.
** And in those 50 years every ceramic cap has talked back to you?
My backround is similar and the occurrences were absolutely minimal until
recently which tells me it is an aging effect. Others may have a different
opinion.
Your quote "What does the piezo (correct spelling) effect have to do with
bypassing at
any frequency?
Its apples and oranges again plus this has split into 2 different
discussions....bypassing and audio coupling."
Well if you have a bypass or coupling capacitor that is exhibiting the
piezoelectric effect then you have a noise generator. It doesn't mater if it
is a bypass or a coupler. True coupling capacitors are generally working
into a higher Z and the effect is more pronounced.
** I see that you are obsessed with piezo, nothing else. May you live long
and prosper with Orange Duds.
Best Regards, Walt Cates, WD0GOF,
http://www.myhamshack.com/WD0GOF/<http://www.myhamshack.com/WD0GOF/>
Carl
KM1H
----- Original Message -----
From: Carl<mailto:km1h at jeremy.mv.com>
To: Peter Bertini<mailto:radioconnection at gmail.com> ;
rbethman<mailto:rbethman at comcast.net>
Cc: Walt Cates<mailto:cateswa at msn.com> ;
hallicrafters<mailto:hallicrafters at mailman.qth.net>
Sent: Sunday, January 02, 2011 1:10 PM
Subject: Re: [Hallicrafters] Piesoelectric effect case in point.
This is really grasping at straws.
What does the piezo (correct spelling) effect have to do with bypassing at
any frequency?
Its apples and oranges again plus this has split into 2 different
discussions....bypassing and audio coupling.
Carl
KM1H
----- Original Message -----
From: "Peter Bertini"
<radioconnection at gmail.com<mailto:radioconnection at gmail.com>>
To: "rbethman" <rbethman at comcast.net<mailto:rbethman at comcast.net>>
Cc: "Carl" <km1h at jeremy.mv.com<mailto:km1h at jeremy.mv.com>>; "Walt Cates"
<cateswa at msn.com<mailto:cateswa at msn.com>>;
"hallicrafters"
<hallicrafters at mailman.qth.net<mailto:hallicrafters at mailman.qth.net>>
Sent: Sunday, January 02, 2011 12:32 PM
Subject: Re: [Hallicrafters] Piesoelectric effect case in point.
Hello Bob and the group...
It flies because tube boat achor gear was made for frequencies above
54MHz.
Hallicrafters made tube transverters for 144MHz. It might be fun to take a
Twoer and replace the series resonant ceramic bypasses with mylars and see
if it still works.
The problem is tubes have gain well above the operating frequencies
covered
by the equipment. My comments were directed to taming VHF and UHF
parasitic
problems that can occur in RF and IF stages if the bypassing is
inadequate. You'll see many radios using low value spoiler resistors on
grid and plate leads to address that issue, or a few hundred ohm value
resistor on the screen, long with good bypassing practices to control
unwanted parasitics. This may be a non issue with 6SK7s, but for many of
the
more popular 7 pin minatures bypassing can be quite critical.
Pete
On Sun, Jan 2, 2011 at 11:58 AM, rbethman
<rbethman at comcast.net<mailto:rbethman at comcast.net>> wrote:
> This whole thread just doesn't fly for the Hallicrafters, Boatanchors,
> Heathkits, Nationals and the like.
>
> The entirety of the "Kemet" document referenced, has to do with
> MICROWAVE applications!
>
> READ the tables. Do you find ANYTHING below 100 MHz?
>
> So how would "our" bypassing and blocking in equipment apply since at
> the highest, we only get to 54MHz?
>
> Walt - you've got apples and oranges.
>
> Bob - N0DGN
>
> On 1/2/2011 11:10 AM, Carl wrote:
> > Walt, That is a bit of a stretch to attempt to prove a point you only
> tried
> > to make yesterday.
> >
> > I would suspect that putting that cap on a TC-6A or other high end cap
> > tester at rated voltage you will discover the actual reason for the
> failure.
> > My bet would be on a internal fracture which are far from an unknown
> failure
> > mode.
> >
> > Nobody is questioning the piezo effect in ceramic caps, it is how and
> when
> > they manifest themselves that is surrounded by hype that ripples down
> > and
> > starts a great panic among the unwashed hordes.
> >
> > If you really want to do a service then take that radio, hook it to a
> scope
> > and HP Distortion Analyzer and run tests with various construction new
> > production capacitors. Run it at audio levels that are within the
range
> of
> > the radio.
> >
> > Carl
> > KM1H
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Walt Cates"<cateswa at msn.com<mailto:cateswa at msn.com>>
> > To:
"hallicrafters"<hallicrafters at mailman.qth.net<mailto:hallicrafters at mailman.qth.net>>
> > Sent: Saturday, January 01, 2011 10:09 PM
> > Subject: [Hallicrafters] Piesoelectric effect case in point.
> >
> >
> >> As luck would have it, today I have a SR-150 in the lab that suffers
> from
> >> "microphonics". It was easy enough to localize the area by lightly
> tapping
> >> the chassis with a plastic tuning wand. I turned the rig over and
> started
> >> tapping components. Sure enough it was C64 a .01uf ceramic disk. This
> >> capacitor couples the audio output from the product detector to the
> first
> >> audio amp. When replaced with a modern poly cap the microphonic
> condition
> >> was eliminated.
> >>
> >> What I have noted over the years is that ceramic disk capacitors used
> >> as
> >> coupling capacitors seem to be more vulnerable to this condition.
This
> is,
> >> as the Kemet report states because of the high difference of
potential
> >> across the dielectric and termination into a high impedance. In this
> case
> >> with the SR-150 one side is 250v the other side is zero volts.
However
> the
> >> low side sees a relatively high impedance of 500k. When there is
> >> receive
> >> signal present with a strong audio the pieso effect ( that is its
> >> susceptibility to vibration ) is dampened. When you remove the signal
> and
> >> there is no audio present the pieso effect into the high Z of the AF
> GAIN
> >> pot (500k) supports the effect and the microphonics gets much more
> >> pronounced.
> >>
> >> Best Regards, Walt Cates, WD0GOF,
> >>
http://www.myhamshack.com/WD0GOF/<http://www.myhamshack.com/WD0GOF/<http://www.myhamshack.com/WD0GOF/%3Chttp://www.myhamshack.com/WD0GOF/>>
> >>
> >> I pity the self made man, he is definitely working at a disadvantage.
I
> >> cherish the help from God, family and mentors.
> >> ______________________________________________________________
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> --
> +------------------------------------------------------------------+
> | AM Amateur Radio Operator NØDGN |
> +------------------------------------------------------------------+
> |
http://home.comcast.net/~rbethman/<http://home.comcast.net/~rbethman/>
|
> +------------------------------------------------------------------+
> | Bob Bethman \\\|///<> " The absence of a danger |
> | \\ ~ ~ // signal does *NOT* mean |
> | rbethman at comcast.net<mailto:rbethman at comcast.net> (/ @ @ /)
that everything is OK " |
> +----------------------o00o---°(_)°---o00o-------------------------+
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