[Hallicrafters] Re: Hallicrafters Digest, Vol 18, Issue 46

Sat Jul 30 12:50:58 EDT 2005

Whats XYL mean?

----- Original Message ----- 
From: <hallicrafters-request at mailman.qth.net>
To: <hallicrafters at mailman.qth.net>
Sent: Saturday, July 30, 2005 2:00 AM
Subject: Hallicrafters Digest, Vol 18, Issue 46

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> Today's Topics:
>
>   1. (no subject) (john)
>   2. Re: Repotting Transformers. (BOB D.)
>   3. Re: SX-42 BFO glitch (zuu6k at juno.com)
>   4. Re: SX28 power transformer (zuu6k at juno.com)
>   5. Re: Repotting Transformers. (Roger K8RI)
>   6. Re: High line voltage (Roger K8RI)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 29 Jul 2005 17:42:35 -0400
> From: john <johnmb at nc.rr.com>
> Subject: [Hallicrafters] (no subject)
> To: Hallicrafters at mailman.qth.net
> Message-ID: <6.2.1.2.2.20050729174139.0208ceb0 at pop-server.nc.rr.com>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> Re:
>
> >"SOAP BOX #2 ON! Regarding this "Bring it up slow on the"variac".
> >This is of no good as the rectifier cannot conduct till the cathode is
> >hot.then the almost full voltage is applied."
>
> Actually, in most cases, it's more like 65 volts...
>
> John K5MO
>
>
>
> -- 
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> ------------------------------
>
> Message: 2
> Date: Fri, 29 Jul 2005 18:07:37 -0400
> From: "BOB D." <k1vv at comcast.net>
> Subject: Re: [Hallicrafters] Repotting Transformers.
> To: "Roger K8RI" <hallicraftersgroup at rogerhalstead.com>,
> <Hallicrafters at mailman.qth.net>
> Message-ID: <003f01c59489$ee7a25a0$abe63c18 at BobDoherty>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> Maybe we are not getting all the details ...
>
> But what happened to the vacuum cleaner after it sucked up all the hot
> transformer varnish ....
>
> Don't think my XYL would be too happy about that ..
>
> Whitey K1VV
>
>
> ----- Original Message ----- 
> From: "Roger K8RI" <hallicraftersgroup at rogerhalstead.com>
> To: <Hallicrafters at mailman.qth.net>
> Sent: Friday, July 29, 2005 2:51 PM
> Subject: [Hallicrafters] Repotting Transformers.
>
>
>>I may have mentioned this before, but in case I didn't:
>> A friend of mine fashioned a metal canister with a fitting on the top 
>> that
>> would allow him to connect a vacuum cleaner.  He'd fill the container 
>> with
>> enough "hot" transformer varnish so he could completely imerse the
>> transformer without the thing running over.  The transformer, sans 
>> covers,
>> was then lowered into the varnish, the cover placed on the canister, the
>> vacuum cleaner hooked up and turned on.
>>
>> I don't think he'd run the vacuum cleaner for more than a minute, then
>> while the varnish was still hot he'd let the air back into the canister.
>> That would force the varnish into small internal places that would never
>> be reached by dipping alone.  It doesn't take a big vacuum system to do
>> this.
>>
>> Roger Halstead (K8RI and ARRL 40 year Life Member)
>> N833R - World's oldest Debonair CD-2
>> www.rogerhalstead.com
>> ______________________________________________________________
>> Hallicrafters mailing list
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>> List Administrator: Duane Fischer, W8DBF **for assistance**
>> dfischer at usol.com
>> ----
>> Hallicrafters Collectors International: http://www.w9wze.org
>>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 29 Jul 2005 15:09:25 -0700
> From: zuu6k at juno.com
> Subject: Re: [Hallicrafters] SX-42 BFO glitch
> To: roy.morgan at nist.gov
> Cc: hallicrafters at mailman.qth.net
> Message-ID: <20050729.151053.1160.3.zuu6k at juno.com>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Roy et al;
>
> I just went through this. IIRC the 7A4 is the BFO and the FM tuning meter
> amplifier. It receives an input from the discriminator and amplifies it
> to drive the meter over the FM tuning part of the scale. It does not do
> this at the same time. Since you would not use the BFO while listening to
> FM and visa-versa there is no conflict.
>
> 73, Ed K6UUZ
>
>> 8) It's not clear to me, but the tube used (a 7A4) is supposed to be
>> both
>> the BFO and the S-meter Amplifier. (A cute trick!)  Shorting out the
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 29 Jul 2005 14:56:43 -0700
> From: zuu6k at juno.com
> Subject: Re: [Hallicrafters] SX28 power transformer
> To: k0ewu at juno.com
> Cc: Hallicrafters at mailman.qth.net
> Message-ID: <20050729.151053.1160.2.zuu6k at juno.com>
> Content-Type: text/plain; charset=us-ascii
>
> Back in 1955 we had a severe flood in Yuba City, CA. I got water 3 inches
> from the ceiling in my house. I worked for Sears as a TV repairman. We
> removed the power transformers from the then tube-type submerged TV's and
> after removing the covers submerged them in hot paraffin >212 degrees F.
> We left them there until the bubbling stopped (all the moisture
> evaporated). After dripping dry and cooling off, we reassembled them. If
> the customer had not turned it on to try it, we saved a lot of them.
>
> 73, Ed K6UUZ
>
>
> On Fri, 29 Jul 2005 14:28:06 -0500 k0ewu at juno.com writes:
>> SOAP BOX #2 ON!
>>         Regarding this "Bring it up slow on the"variac".
>> This is of no good as the rectifier cannot conduct till the cathode
>> is
>> hot.
>> then the almost full voltage is applied.
>> If you really want to do this, put a solid stat rectifier in place
>> of the
>> tube,
>> monitor the dc plate voltage and the tx input current.if all goes
>> well
>> the input current will increase as the input voltage increases and
>> should
>> drop down as the caps reform.The dc out will follow the input, but
>> if
>> the dc suddenly drops quite a bit
>> and no longer increases as the input does--there is a low
>> resistance
>> short some where.
>>
>> BUT do not do this if the rig has been stored in a damp or high
>> humidity
>> location
>> for some months.     next
>>
>>  AN easy way to warm the trans former is to apply  dc current of
>> about
>> 700 ma to the ac input, short the rectifier socket plate to plate
>> to
>> protect from surges as the dc is applied or removed.
>> The transformer should warm up from the current in the primary in a
>> short
>> time , let it cook this way for 6 to 8 hours, remove the short on
>> the hv
>> winding (at the tube socket)
>> after the dc is removed
>> then use the forming excersize as above.
>> I have used this method for years to dry out motors, transformers
>> and
>> other ac devices after total immersion in flood waters and other
>> fresh
>> water dunking.
>>
>> cAN OTHERS ADD TO THIS?  comments?
>>
>> JACK----------K0EWU at juno.com
>> ______________________________________________________________
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>> dfischer at usol.com
>> ----
>> Hallicrafters Collectors International: http://www.w9wze.org
>>
>>
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 29 Jul 2005 23:25:11 -0400
> From: "Roger K8RI" <hallicraftersgroup at rogerhalstead.com>
> Subject: Re: [Hallicrafters] Repotting Transformers.
> To: "Bill Gerhold" <k2wh at optonline.net>,
> <Hallicrafters at mailman.qth.net>
> Message-ID: <001c01c594b6$55559d00$6500a8c0 at roger2>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
>
>
>
>> We do this all the time at my work place only on transformers up to 1000
>> kva.  Your friend is doing it in the wrong order.  First the vacuum, then
>> the varnish, and then the pressure.
>
> With limited resources and home made equipment it's far easier to do it 
> his
> way.
> The hot varnish has a very low viscosity so the air bubles still get out
> which is the main reason for heating it.
>
>>
>> Its called VPI or Vacuum Pressure Impregnation.  After the vacuum stage,
>> the
>> varnish is pumped into the tank and the work is allowed to soak and
>> absorb.
>
> I agree, this is the proper order if you have the equipment.
> With a good roughing pump you can maintain 10^-1 Torr and a half hour at
> that will get rid of almost any air that would be a problem as long as 
> it's
> not trapped in old varnish.  We had the equipment to go to 10^-6, but not
> for transformer potting. That was float zone refining as well as some
> electron beam heaters.  It takes quite an electron beam to melt a 7 or 8"
> diameter chunk of of Silocon.  The mass spectrometer would make 10^-7, but
> it used liquid Nitrogen cold traps  in addition to Ion pumps after the
> difussion pumps made 10^-5 or 6.
>
> We used to use a two part silicone to pot some very high voltage
> transformers.    They were dipped under vacuum and we just let the
> atmospheric pressure force it into the windings. It was a relatively slow
> cure at room temp, or about an hour at 250F "as I recall".
>
>> Then the air is pumped in under pressure forcing the varnish into the
>> windings and crevices.  The work piece is then taken to a large oven and
>> baked for a few days.  It makes the windings, and the core a one piece
>> unit
>
> He used to do that in his first wire's oven.
>
>> with no movement of the windings at all and very quiet laminations.
>>
>
> As to those who asked, the vapor pressure of the varnish is high enough 
> that
> none of it gets into the vacuum cleaner<:-))  However, vacuum cleaners
> depend on the air flow through them to cool the motor.  You don't want to
> let them run very long that way.
>
> 73
>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
>
>> K2WH
>> Electrical Engineer in Power Generation,
>> Transformer Design Engineer and all around
>> Ham Radio Operator.
>>
>>
>> -----Original Message-----
>> From: hallicrafters-bounces at mailman.qth.net
>> [mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Roger K8RI
>> Sent: Friday, July 29, 2005 2:51 PM
>> To: Hallicrafters at mailman.qth.net
>> Subject: [Hallicrafters] Repotting Transformers.
>>
>> I may have mentioned this before, but in case I didn't:
>> A friend of mine fashioned a metal canister with a fitting on the top 
>> that
>> would allow him to connect a vacuum cleaner.  He'd fill the container 
>> with
>> enough "hot" transformer varnish so he could completely imerse the
>> transformer without the thing running over.  The transformer, sans 
>> covers,
>> was then lowered into the varnish, the cover placed on the canister, the
>> vacuum cleaner hooked up and turned on.
>>
>> I don't think he'd run the vacuum cleaner for more than a minute, then
>> while
>>
>> the varnish was still hot he'd let the air back into the canister. That
>> would force the varnish into small internal places that would never be
>> reached by dipping alone.  It doesn't take a big vacuum system to do 
>> this.
>>
>> Roger Halstead (K8RI and ARRL 40 year Life Member)
>> N833R - World's oldest Debonair CD-2
>> www.rogerhalstead.com
>>
>> ______________________________________________________________
>> Hallicrafters mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
>> Help: http://mailman.qth.net/mmfaq.html
>> Post: mailto:Hallicrafters at mailman.qth.net
>> ----
>> List Administrator: Duane Fischer, W8DBF **for assistance**
>> dfischer at usol.com
>> ----
>> Hallicrafters Collectors International: http://www.w9wze.org
>>
>>
>>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Sat, 30 Jul 2005 02:02:48 -0400
> From: "Roger K8RI" <hallicraftersgroup at rogerhalstead.com>
> Subject: Re: [Hallicrafters] High line voltage
> To: <hallicrafters at mailman.qth.net>, "john" <johnmb at nc.rr.com>
> Message-ID: <005101c594cc$7640bac0$6500a8c0 at roger2>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
>
>
>
>> Regardless of the specification for the radio, running high filament
>> voltage is without question, one of primary ways to prematurely kill a
>> tube. The other is forcing the tube to run hotter.
>>
>> There's no rocket science and no debate...running high filament voltage
>> WILL reduce your tube lifetime.
>>
>> Do I care on a 6AU6...probably not, but I sure do on my 3-500Zs and 
>> 572Bs.
>
> "It seems" as if I remember reading that you don't want low voltage either
> when it comes to power tubes.  If the filaments are straight tungsten, 
> they
> are very forgiving, but thorated and indirectly heated coated cathodes are
> not.  OTOH, you can sometimes bring weak tubes back to life with a couple 
> of
> minutes of raising the filamanet about 10%.  If they are already weak 
> there
> isn't much to lose and everything to gain.
>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
>
>>
>> John K5MO
>>
>>
>>
>> -- 
>> No virus found in this outgoing message.
>> Checked by AVG Anti-Virus.
>> Version: 7.0.338 / Virus Database: 267.9.7/60 - Release Date: 7/28/2005
>>
>> ______________________________________________________________
>> Hallicrafters mailing list
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>> Help: http://mailman.qth.net/mmfaq.html
>> Post: mailto:Hallicrafters at mailman.qth.net
>> ----
>> List Administrator: Duane Fischer, W8DBF **for assistance**
>> dfischer at usol.com
>> ----
>> Hallicrafters Collectors International: http://www.w9wze.org
>>
>
>
>
> ------------------------------
>
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>
> End of Hallicrafters Digest, Vol 18, Issue 46
> *********************************************
> 