[R-390] RE: R-390 Digest, Vol 14, Issue 37
Jacobs, Gordon
G_Jacobs at wfec.com
Mon Jun 27 11:17:57 EDT 2005
Does anyone have a clamp that fits the Oldham coupler that I can buy. TNX
Gordon KA5ZTI g_jacobs at wfec.com
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Today's Topics:
1. Re capping an IF Deck (Dennis L. Wade)
2. Re: Re capping an IF Deck (Joe Foley)
3. Re: Re capping an IF Deck (Flowertime01 at wmconnect.com)
4. Re: Re IF Deck Product Detector Add On
(Flowertime01 at wmconnect.com)
5. Re: Re capping an IF Deck (Dennis L. Wade)
6. Re: Re IF Deck Product Detector Add On (Kenneth Arthur Crips)
----------------------------------------------------------------------
Message: 1
Date: Sun, 26 Jun 2005 15:52:06 -0700
From: "Dennis L. Wade" <dwade at pacbell.net>
Subject: [R-390] Re capping an IF Deck
To: r-390 at mailman.qth.net
Message-ID: <42BF3196.1030109 at pacbell.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Good Afternoon,
I spent some quality time with my Motorola '390A yesterday and this
afternoon. I actually got the cleaned and recapped RF deck back in the
frame and everything is synced up nicely now. Some may remember my last
post as being PTO woes...I'll be posting a follow up to that saga just
as soon as I finish eating my crow. :/ I did learn some good lessons
though.
In the meantime however, I have now pulled the IF deck in preparation
for recapping. This is an EAC unit, the only non-MOTO module in my rig.
This one was factory(?) mod-ed to use a product detector module
mounted behind the function switch. A new connector was added to feed
the new module.
I mention this because it appears that at least some of the recapping
may have been done for me. I find no "brown beauties" in this deck at
all. In (some of) their place have been installed "Westcap" units,
however I can't tell if they are still paper units or not. They do
appear to be in good physical shape. These are in places such as C-531,
C-549 and C-533. My inclination is not to replace these.
Other caps are Aerovox units that are probably wax paper jobs. These
live in places such as: C-528, C-529 and C-521 among others. Some of
these seem to be in good physical condition, but some have deformed from
their original round shape to oval in some cases. Which if any of these
should I replace? My general feeling is that knowing my (lack of)
experience I don't want to go into places in this crowded deck I don't
need to be.
The only symptom I think I have, at the moment in this radio, is low
AGC voltage.
AGC cap. The replacement unit I have has rather short leads. What
is
the best physical arrangement for putting this guy in. Lift one lead
from the old cap and put it across the old? Advice would be appreciated.
Thanks all in advance for your collective wisdom.
Dennis
--
--------
Dennis L. Wade
KG6ZI
Carmichael, CA
------------------------------
Message: 2
Date: Sun, 26 Jun 2005 18:29:26 -0700 (PDT)
From: Joe Foley <redmenaced at yahoo.com>
Subject: Re: [R-390] Re capping an IF Deck
To: r-390 at mailman.qth.net
Message-ID: <20050627012926.91920.qmail at web30415.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
>
> In the meantime however, I have now pulled the IF
> deck in preparation
> for recapping. This is an EAC unit, the only
> non-MOTO module in my rig.
> This one was factory(?) mod-ed to use a product
> detector module
> mounted behind the function switch. A new connector
> was added to feed
> the new module.
++++++++
If this is a '67 EAC the chances of it needing any
caps replaced are slim. Unless it has seen abuse or
damage of some sort.
The only cap that should be replaced without
consideration on the IF deck of a '67 EAC is the one
that protects the mechanical filters.
Joe
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------------------------------
Message: 3
Date: Sun, 26 Jun 2005 21:29:55 EDT
From: Flowertime01 at wmconnect.com
Subject: Re: [R-390] Re capping an IF Deck
To: r-390 at mailman.qth.net
Message-ID: <8a.29ab32ae.2ff0b093 at wmconnect.com>
Content-Type: text/plain; charset="US-ASCII"
Dennis,
There are variations of four choices for the ACG cap.
1. Do nothing or similar more nothing.
2. The slow 2uf AGC cap can be replaced in the can like rebuilding power
filter caps.
Not more or less messy than power filter caps.
3. Add a new cap under the deck. Leave or remove the above deck can. C551
4. Install a socket in the deck hole and mount the cap in a crystal oven can
and plug that into the new socket. An 8 pin octal socket will mount nicely
and the
other C548 cap will also fit in the oven can.
Along with these rebuilds it is suggested that C548 be increased from .1 uf
to 1. uf.
Pushing C548 up into the new can fits nice. After recapping the IF deck,
there
is much more space under the deck. Those brown tubes were "big" in their own
way.
It is C553 that keeps the 1st IF B+ out of the crystal filters. Inspect this
cap to see
if it looks like a 600 volt rated cap. You may want to replace this cap if it
even looks
like less that a stellar quality item in your deck. Some time now for peace
of mind over the next 50 years is a small price and some quality time with
your
receiver.
There are ranges of paranoid for your IF deck.
Real severe leaves you unwilling to even apply power to your receiver.
Not real common but known to occur.
Less sever cases accept nothing less than a real full rebuild with nothing
less
than orange drops. Some will not even accept a self build and require the
work be performed by a real "professional restorer."
Having a radio is supposed to bring you joy and not anxiety and misery.
Lesser degrees of paranoid will let you install almost any current good brand
of cap in the deck to get the brown tubes out and keep the receiver
receiving.
Real caviler owners will run the receivers until the smoke escapees and then
only replace the minimum carbon needed to return the receiver to operation.
As with all preventive maintenance the objective is to put in the minimum up
front work to avoid even more work later. So changing caps is good.
Only the brown and black tube caps in the R390/A are known to be more likely
bad than good today given there age. Also for ever bad cap found some will
post
here that there old caps are still hanging in and working good.
As you do not have the brown tubes, your deck either never had them or has
been
rebuilt. A look at the solder will likely provide some clue as to
originality. Some fried
wire at the terminals is a clue someone got there with a solder iron after
the wire had aged many years.
You will likely be OK with what is in the deck. Do inspect the cap to the
filters,
C553, you may want a good 600 volt cap in there. Something you have some
confidence in. An orange drop is good. A Radio Shack part not so good.
Other than that you just need to reach a comfort level you can be happy with.
There are reasons to change lots of the caps. Some value changes have been
offered over the years to improve the frequency response mostly in the audio
deck.
Changing C553 to a break down voltage of 600VDC to protect the mechanical
filters.
Changing C548 .1 AGC to 1. For less AGC pumping are a few.
Caps like resistors have their own popcorn noise. Parts have been hunted down
and
changed out just to get a better receiver noise floor.
As you have no brown tubes in your deck, you have no known issue driving you
to make any changes. Now you get to make choices based on satisfaction and
enjoyment.
Enjoy
Roger KC6TRU
------------------------------
Message: 4
Date: Sun, 26 Jun 2005 21:32:42 EDT
From: Flowertime01 at wmconnect.com
Subject: Re: [R-390] Re IF Deck Product Detector Add On
To: r-390 at mailman.qth.net
Message-ID: <9e.28e2deb0.2ff0b13a at wmconnect.com>
Content-Type: text/plain; charset="US-ASCII"
Dennis,
Do you have any pictures of the product detector as
installed in your receiver?
I am exploring product detectors in general and looking
specifically at what has been done to R390's.
Thanks
Roger KC6TRU
------------------------------
Message: 5
Date: Sun, 26 Jun 2005 19:31:48 -0700
From: "Dennis L. Wade" <dwade at pacbell.net>
Subject: Re: [R-390] Re capping an IF Deck
To: Joe Foley <redmenaced at yahoo.com>
Cc: r-390 at mailman.qth.net
Message-ID: <42BF6514.3050907 at pacbell.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Yep, you're right Joe. Its an EAC deck from '67. Funny how I never
checked that detail before.
So, the AGC cap may be the only one I do (well, and C553). Wonder if I
can just float that AGC cap in there, with leads appropriately insulated
of course......
Dennis
Joe Foley wrote:
>> In the meantime however, I have now pulled the IF
>>deck in preparation
>>for recapping. This is an EAC unit, the only
>>non-MOTO module in my rig.
>> This one was factory(?) mod-ed to use a product
>>detector module
>>mounted behind the function switch. A new connector
>>was added to feed
>>the new module.
>
> ++++++++
> If this is a '67 EAC the chances of it needing any
> caps replaced are slim. Unless it has seen abuse or
> damage of some sort.
>
> The only cap that should be replaced without
> consideration on the IF deck of a '67 EAC is the one
> that protects the mechanical filters.
>
> Joe
>
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--
--------
Dennis L. Wade
KG6ZI
Carmichael, CA
------------------------------
Message: 6
Date: Mon, 27 Jun 2005 00:07:00 -0600
From: "Kenneth Arthur Crips" <CRIPS01 at MSN.COM>
Subject: Re: [R-390] Re IF Deck Product Detector Add On
To: <r-390 at mailman.qth.net>
Message-ID: <BAY107-DAV1110273C56549979402BF0BFEE0 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"
There have been discussions on this list for years about adding a product
detector to an R390A. My feeling is why bother with it. The R390 series
are all fine radios but for whatever reason they didn't build them with
product detectors. As you know I have the Eldico Electronics SBA-1 SSB
adapter this unit vastly improves the side band performance of My 1967 EAC
R390A, it adds a notch filter and a good 2 watt audio amp. If you want to
improve the side band performance of the R390 get one of the many side band
adapters that where made instead of modifying the receiver. For SSB
reception There are so many good receivers and transceivers out there with
product detectors as part of their original design I can't see adding one to
the R390A.
Ken
Kenneth A. Crips Radio Station W7ITC
Cheyenne, Wyoming with The Chew Crew
Beezie, Chic', and Cowboy three
outrageous Irish Terriers.
------------------------------
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