[Heath] Heath Digest, Vol 94, Issue 10
Al Skierkiewicz
markaren1 at att.net
Tue Oct 23 23:07:15 EDT 2018
Chris,
I forgot to add that I found the thunder quite by accident. After a quick
initial alignment to at least hear WGN AM (their tower is under 10 miles as
the crow flies) I was still looking over things with the radio on. I went
away for a few minutes and when I came back the gain was way down.
Suspecting a cold solder joint, I took my screwdriver, turned it around so
that I was holding the blade and then started tapping. When I accidently
hit the i.f. can, there was a lot of thunder and then the gain came back. I
then tapped on the other can and got more thunder and changing gain. That
began the long road to opening the can when I couldn't find solder issues.
That prompted an internet search and then a long road to figuring out what
to do. A good friend of mine, former work buddy, always recommended that
when restoring gear, I should make as few changes to the original as
possible. I had some silver paint and I thought I might use that, but then
closer inspection showed that some silver had actually migrated to the edges
of the mica and there were stains on the insulator base. My choice at that
point would be to wire in caps external. But my buddy Bob's voice kept
whispering in my head that I should only make a change internal to the can
so that the radio would remain as stock as possible.
Bob sent me this link as a possible JW Miller substitute for the cans...
https://www.surplussales.com/Inductors/Ind-SmAdjRF/Ind-SmAdjRF-1.html
I did not record the manufacture data on the coils but I did a search and
found the coil numbers in a data sheet. If anyone opens a i.f. can for this
radio, please post the manufacturer part number. I believe it is on the
insulated base.
Al
-----Original Message-----
From: Heath [mailto:heath-bounces at puck.nether.net] On Behalf Of
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Sent: Monday, October 22, 2018 11:00 AM
To: heath at puck.nether.net
Subject: Heath Digest, Vol 94, Issue 10
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Today's Topics:
1. Re: Heath Digest, Vol 94, Issue 9 (Al Skierkiewicz)
2. Re: Heath Digest, Vol 94, Issue 9 (ChrisIwata)
3. Mistake in my question to lists (John King)
----------------------------------------------------------------------
Message: 1
Date: Sun, 21 Oct 2018 11:55:15 -0500
From: "Al Skierkiewicz" <markaren1 at att.net>
To: <heath at puck.nether.net>
Subject: Re: [Heath] Heath Digest, Vol 94, Issue 9
Message-ID: <001d01d4695e$d75a5210$860ef630$@net>
Content-Type: text/plain; charset="us-ascii"
Chris, both of the i.f. cans in the AR3 are the same part number. To
calculate the capacitance, I simply measured the dimensions of the screened
silver areas, subtracting for the circular area and then pulled out the
reference books on calculating capacitance based on the thickness of the
mica sheet. I calculated the larger area to be 0.086238 in.sq. and the
smaller to be 0.0689 in.sq.
>From the Handbook C (pf)=.224((dielectric constant x area)/spacing
>between
plates) I chose 5.4 for the dielectric constant of mica and using a
calipers, I measured the thickness of the sheet at 0.001 in. So C=.224((5.4
x .08638)/.001)=104.3pf for the larger cap and substituting 0.0689 I
calculated 83pf for the smaller cap.
Al
-----Original Message-----
From: Heath [mailto:heath-bounces at puck.nether.net] On Behalf Of
heath-request at puck.nether.net
Sent: Sunday, October 21, 2018 11:00 AM
To: heath at puck.nether.net
Subject: Heath Digest, Vol 94, Issue 9
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To subscribe or unsubscribe via the World Wide Web, visit
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Today's Topics:
1. Re: Heath Digest, Vol 94, Issue 7 (ChrisIwata)
----------------------------------------------------------------------
Message: 1
Date: Sat, 20 Oct 2018 17:36:46 -0700
From: ChrisIwata <chrisiwata at aol.com>
To: heath at puck.nether.net
Subject: Re: [Heath] Heath Digest, Vol 94, Issue 7
Message-ID: <5BCBCA1E.60807 at aol.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Good result!
My AR-2 had the same problem with the IF cans.
Calculating the capacitance from the surface area and the width of the mica
wafer must have been hard: How did you do the measurements?
For those who don't have an inductance meter to measure the coils with the
internal cap disabled, the value for the caps is around 110pF. It will be
slightly different for primary vs secondary winding, and 1st vs 2nd IF can.
You might be able to pinpoint which cap(s) is bad by wiggling each IF can
solder lug successively. Do this with the radio ON and an insulated wand.
The mica wafer is physically attached to the solder lug. Anyway, that's
what worked for me. Thus, I didn't have to replace all 4 caps.
Chris, KL7DM
On 10/20/2018 1:31 PM, Al Skierkiewicz wrote:
> Guys,
> I have just finished restoring an AR-3. It was a labor of love as I
> my first ham receiver AR-3. I had purchased it used for $15 from
> George at the Radio TV Lab in Chicago. I saw this one at the hamfest
> in Oak Creek, Wisc for $25 and just wanted to get it going. My cap
> was not frozen but very stiff. I just shot some Lubriplate white
> grease into the ball bearings that make up the reduction. I waited
> for a day and just started moving the shaft until the grease got
distributed. Worked wonders.
> I had more problems with the fact that the kit wasn't fully correctly
> wired and that the silver mica caps in the i.f. transformers were all
noisy.
> (Thunder syndrome) If you tap on the cans and you hear tons of
> crackling and thunder, then you have the same problem. I removed the
> mica wafers and replaced the caps with dipped silver micas. I
> calculated the values from the area of the mica that was plated with
> silver. The fact that there were wiring errors meant that the radio
> had never been aligned. A RF signal generator is kind of necessary
> for alignment of this box. Although I got it working, I also bought a
> Q multiplier that wouldn't work at all. Turns out, that the i.f. was
> 50kHz low. Once I got everything correctly tuned, the Q mult worked
> great
as well.
> Al
> WB9UVJ
>
>
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Message: 2
Date: Sun, 21 Oct 2018 13:12:39 -0700
From: ChrisIwata <chrisiwata at aol.com>
To: heath at puck.nether.net
Subject: Re: [Heath] Heath Digest, Vol 94, Issue 9
Message-ID: <5BCCDDB7.5030804 at aol.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Wow, you came in pretty close. I'm guessing, the hardest part for accuracy
was to measure the thickness of the wafer.
The IF cans on the AR-2 have different part numbers (52-4 & 52-5), but they
are pretty much the same.
Chris, KL7DM
On 10/21/2018 9:55 AM, Al Skierkiewicz wrote:
> Chris, both of the i.f. cans in the AR3 are the same part number. To
> calculate the capacitance, I simply measured the dimensions of the
> screened silver areas, subtracting for the circular area and then
> pulled out the reference books on calculating capacitance based on the
> thickness of the mica sheet. I calculated the larger area to be
> 0.086238 in.sq. and the smaller to be 0.0689 in.sq.
> From the Handbook C (pf)=.224((dielectric constant x area)/spacing
> between
> plates) I chose 5.4 for the dielectric constant of mica and using a
> calipers, I measured the thickness of the sheet at 0.001 in. So
> C=.224((5.4 x .08638)/.001)=104.3pf for the larger cap and
> substituting 0.0689 I calculated 83pf for the smaller cap.
> Al
>
>
>
> -----Original Message-----
> From: Heath [mailto:heath-bounces at puck.nether.net] On Behalf Of
> heath-request at puck.nether.net
> Sent: Sunday, October 21, 2018 11:00 AM To:heath at puck.nether.net
> Subject: Heath Digest, Vol 94, Issue 9
>
> Send Heath mailing list submissions to
> heath at puck.nether.net
>
> To subscribe or unsubscribe via the World Wide Web, visit
> https://puck.nether.net/mailman/listinfo/heath
> or, via email, send a message with subject or body 'help' to
> heath-request at puck.nether.net
>
> You can reach the person managing the list at
> heath-owner at puck.nether.net
>
> When replying, please edit your Subject line so it is more specific
> than
> "Re: Contents of Heath digest..."
>
>
> Today's Topics:
>
> 1. Re: Heath Digest, Vol 94, Issue 7 (ChrisIwata)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 20 Oct 2018 17:36:46 -0700
> From: ChrisIwata<chrisiwata at aol.com>
> To:heath at puck.nether.net
> Subject: Re: [Heath] Heath Digest, Vol 94, Issue 7
> Message-ID:<5BCBCA1E.60807 at aol.com>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
>
> Good result!
>
> My AR-2 had the same problem with the IF cans.
>
> Calculating the capacitance from the surface area and the width of the
> mica wafer must have been hard: How did you do the measurements?
>
> For those who don't have an inductance meter to measure the coils with
> the internal cap disabled, the value for the caps is around 110pF.
> It will be slightly different for primary vs secondary winding, and 1st vs
2nd IF can.
>
> You might be able to pinpoint which cap(s) is bad by wiggling each IF
> can solder lug successively. Do this with the radio ON and an insulated
wand.
> The mica wafer is physically attached to the solder lug. Anyway,
> that's what worked for me. Thus, I didn't have to replace all 4 caps.
>
> Chris, KL7DM
>
> On 10/20/2018 1:31 PM, Al Skierkiewicz wrote:
>> Guys,
>> I have just finished restoring an AR-3. It was a labor of love as I
>> my first ham receiver AR-3. I had purchased it used for $15 from
>> George at the Radio TV Lab in Chicago. I saw this one at the hamfest
>> in Oak Creek, Wisc for $25 and just wanted to get it going. My cap
>> was not frozen but very stiff. I just shot some Lubriplate white
>> grease into the ball bearings that make up the reduction. I waited
>> for a day and just started moving the shaft until the grease got
> distributed. Worked wonders.
>> I had more problems with the fact that the kit wasn't fully correctly
>> wired and that the silver mica caps in the i.f. transformers were all
> noisy.
>> (Thunder syndrome) If you tap on the cans and you hear tons of
>> crackling and thunder, then you have the same problem. I removed the
>> mica wafers and replaced the caps with dipped silver micas. I
>> calculated the values from the area of the mica that was plated with
>> silver. The fact that there were wiring errors meant that the radio
>> had never been aligned. A RF signal generator is kind of necessary
>> for alignment of this box. Although I got it working, I also bought
>> a Q multiplier that wouldn't work at all. Turns out, that the i.f.
>> was 50kHz low. Once I got everything correctly tuned, the Q mult
>> worked great
> as well.
>> Al
>> WB9UVJ
>>
>>
> ---
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Message: 3
Date: Mon, 22 Oct 2018 00:28:22 +0000 (UTC)
From: John King <k5pgw at yahoo.com>
To: Heath List <heathkit at mailman.qth.net>, "heath at listserv.qth"
<heath at listserv.qth>, Heathkit List <heath at puck.nether.net>
Subject: [Heath] Mistake in my question to lists
Message-ID: <138526752.1035555.1540168102231 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"
I apologize for saying Apache. The BFO question has to do with my Mohawk.
Thanks to Brian for catching my error.
I was very tired from working on the Mohawk all day. I guess I am too old
for that lengthy attempt to concentrate.
The receiver is a MOHAWK. 73, John, L5PGW
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