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Author Topic: AM Broadcast Receiver Reconditioning  (Read 23094 times)
WB6DGN
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Posts: 618




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« on: August 09, 2013, 02:07:13 AM »

Hope this is the right place for this.  I am trying to recondition an old (late '30s to early '40s) AM broadcast console receiver.  Before I start on the chassis, I'd like to get an idea of the cost for refinishing the cabinet and reconing the electrostatic speaker.  Then, the rest should be fairly easy. (except, maybe, for 3 old style can type electrolytics)  Since in most old radios the electrostatic coil was also the input element for the power supply, I suppose that's the first thing that needs attention.

My question is; does anyone know of a reputable person/firm to recone the speaker and refinish the cabinet.  I have looked locally for antique furniture refinishers but the cabinet is light enough (its REAL wood) that I don't think shipping would be a major problem.  I'd rather work with someone who has an established reputation with this equipment than hit and miss with a local.

Any advice/suggestions are invited and welcome.  As you can probably tell, this is my first effort with this type of project.

Thanks,
Tom
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N4NYY
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« Reply #1 on: August 09, 2013, 05:06:07 AM »

There are a ton of speaker reconing companies. If you google them, you will find them.

The cabinet refinishing is what you make of it. Could involve stripping and refinishing. Or could involve repair, laminate, etc. I just do it one step at a time and buy materials as I need them. I tend to use wipe-on poly and avoid lacquer. Lacquer us great, but a pain in the ass to work with. In fact, if you insist on lacquer, I would do everything up to the clear coat, and maybe have a car auto body shop to it for you. 

Recapping is a good thing. But I would check each resistor. I have just started replacing all the resistor after experiencing that most tbe rigs from the 1960's or older, showed that the resistors were at tolerance edge, or way out. The ones that weren't, soon followed. The modern carbon film are cheap, more reliable, and superior to those old carbon comps.

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W8AAZ
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Posts: 379




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« Reply #2 on: August 09, 2013, 02:59:44 PM »

Electronic restoration of old ham rigs and broadcast sets is comparable, but not many hams are gonna maybe try to recone an old electodynamic speaker versus replace it, or do much woodworking or wood cabinet restoration.  I would refer you to a forum that would perhaps be more focused on this sort of project- http://antiqueradios.com/forums/index.php  where all those sorts of things are addressed and you may find answers doing a forum search without even having to post questions.  But if you expect to do more than one old broadcast set, it may pay to sign in. Expect to possibly replace all paper caps and electrolytics and at the very least test, if not replace, all resistors.  Most resistors in tube BC sets can be tested in-circuit, where they terminate in tube connections, as the tube elements present an open circuit when not operating. Except for filiments, of course.
« Last Edit: August 09, 2013, 03:03:39 PM by W8AAZ » Logged
KC4MOP
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Posts: 960




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« Reply #3 on: August 09, 2013, 03:57:49 PM »

Shipping the cabinet would be scary with today's clumsy shippers. Unless you crate it first. The speaker should not be too hard to find someone to re-cone.
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WB6BYU
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« Reply #4 on: August 09, 2013, 04:31:55 PM »

How authentic do you want the insides to be?

Last time I had a speaker go out in an old receiver like that we replaced it with a
permanent magnet type.  The other required change was to add a filter choke
for the HV power supply, since the electromagnet winding on the speaker served
that function as well.
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AC5UP
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« Reply #5 on: August 09, 2013, 05:02:32 PM »

What WB6BYU said.

Long ago and far away before Alnico magnets, Viagra, and Anthony Weiner the best way to build a durable magnet inside the voice coil was to wind a big 'ol solenoid around a soft iron slug and use that as a smoothing choke in the power supply. Back then large caliber electrolytics were also a future item, so to keep the hummms at bay an L-C combo tuned to 120 cycles was the hot ticket. Which means the avid restorer has two options: Keep the speaker as stock as possible including the original electomagnetic assembly with properly sized filter condensers - or - put in larger  condensers and maybe a smaller choke just to prove you aren't totally oblivious to vintage engineering practices.

A well restored console won't hum (too much) if rebuilt to original spec, but be aware there is very little current reserve in the filter section for audio peaks. I think the bass is cleaner with some extra capacitance in the filters and although they're Lo-Fi, a console can be very pleasant to listen to for extended periods of time.
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KE3WD
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« Reply #6 on: August 10, 2013, 07:13:00 AM »

It all depends upon what you want for your end result. 

The electromagnetic speaker has its own sound, often desirable in certain equipments from old guitar amplifiers to certain old AM receiver sets. 

Changing it out to permanent magnet speaker will change that sound. 

Same as changing an Alnico magnet speaker out for a Ceramic magnet speaker, in which the audio will not sound as "smooth" for a variety of reasons to include changing the Efficiency curve of said speaker. 

So it all really depends on what you desire at that point, sometimes what you can afford or what you are willing to put into your restoration. 

That said, there are plenty of speaker reconers who can handle the old electromagnetic speakers, their pricing is not that bad, it is usually the shipping and waiting that deters folks from going that route from what I've observed.  Nothing wrong about saving the old electromagnetic speaker on shelf, though, while listening to the permanent magnet jobbie or using it to continue with restoration of other areas.  Keeping the original speaker around means that you will have it to ship to a reconer at a later date, or perhaps while continuing to work on the beast while the original is being reconed. 

If the radio is worth it, full restoration to original is worth it too, in my book.


73
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W9GB
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Posts: 3375




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« Reply #7 on: August 10, 2013, 07:58:33 AM »

Quote from: WB6DGN
My question is; does anyone know of a reputable person/firm to recone the speaker and refinish the cabinet.  I have looked locally for antique furniture refinishers but the cabinet is light enough (its REAL wood) that I don't think shipping would be a major problem.  I'd rather work with someone who has an established reputation with this equipment than hit and miss with a local.
Tom -

There is an entirely different hobby for Antique Radio Restoration and Repair.
Some of these individuals are radio amateurs, many are not -- but skilled or master craftsman in veneer refinishing, grill cloths, and custom fabrications.

Antique Radio Club of Illinois (ARCI) is an example, of a local/regional club.
Since many of the 1930s Radio Manufacturers were Chicago based, some members have DEEP knowledge for restoration of some manufacturers or models (their father, uncle, or grand-father may have designed it)
http://www.antique-radios.org/resourcelinks.htm

Restoration Resources
http://radioattic.com/resources.htm

IF you could tell us the Manufacturer and Model number, more specific assistance can be recommended.

Old Radio Doc -- Bob Eslinger, KR1U
http://www.oldradiodoc.com/index.php

Phil's Old Radios -- Philip I. Nelson
http://antiqueradio.org/restoration.htm

Radio Daze -- Antique Radio Parts & Service
http://www.radiodaze.com/

Philco Dealer Service Letter -- Cabinet Restoration, April 1951
Courtesy of retrieval & digitalization by Stan Watkins
http://www.stanwatkins.com/cabinet.htm

Chassis restoration
http://www.stanwatkins.com/chassis.htm
« Last Edit: August 10, 2013, 08:21:48 AM by W9GB » Logged
W9GB
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Posts: 3375




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« Reply #8 on: August 10, 2013, 11:33:56 AM »

John and Jean Goller - Leo, Indiana are well known for their Console Radio restorations.
http://johnjeanantiqueradio.com/

John and Jean Antique Radio
John Goller, K9UWA
Jean Goller, N9PXF
4836 Ranch Rd.
Leo, IN 46765
United States
Phone 1-260-220-9456

Kenneth Richmond of Richmond Designs
creates complete reproductions of classic 1930s radio cabinets
with authentic grill cloth reproductions (contracted specialty textile weavers)
Perfect for Smithsonian or Rick Dale's American Restoration (History Channel)
http://richmonddesignsinc.com/home

Philco Radios - Ron Ramirez
http://philcoradio.com/index.htm
« Last Edit: August 10, 2013, 11:44:41 AM by W9GB » Logged
N4NYY
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Posts: 5224




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« Reply #9 on: August 10, 2013, 06:49:23 PM »

I would re-cone if you are selling the radio or are a purist. The value will be greater. If you do not give a shit and and just want it to function for you personal use, then a permanent magnet speaker is fine. The only disadvantage is that some have huge magnets and could be a space fitting problem for the chassis.
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W9GB
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Posts: 3375




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« Reply #10 on: August 10, 2013, 08:30:06 PM »

Quote from: WB6DGN
... except, maybe, for 3 old style can type electrolytic capacitors.
Tom -

Replacement of the Electrolytic Can Capacitors is quite easy, with MANY approaches.

The Radio Begineer (Restorer)
http://antiqueradio.org/begin.htm

Hayseed Hamfest can build to your specification using new production can parts.
http://hayseedhamfest.com/capacitors.html

Strategies to Repair or Replace Old Electrolytic Capacitors
http://www.nmr.mgh.harvard.edu/~reese/electrolytics/
Tim Reese, MGH NMR Center
Charlestown Navy Yard
13th Street, Bldg 149 (2301)
Boston MA 02129

Good luck with it.

w9gb
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WB6DGN
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Posts: 618




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« Reply #11 on: August 10, 2013, 09:16:05 PM »

WOW!  Thanks for all the good advice and the references.  Enough references to keep me busy for a long time.

Yeah!  I am sort of a purist; not a collector (at least yet) but I have been often called a "perfectionist" (NOT as a complement).  The PM speaker won't do, though I know it would work OK.  And, I'd still have to hide the old speaker somewhere in back or try to find a filter choke to replace it.  Besides, the first radios I worked on as a kid all had electrostatic speakers so the nostalgia value would be diminished a lot with the PM speaker.  There's room in the bottom easily for a 15" speaker but the one supplied is only an 8" so I wouldn't think reconing it would be too expensive.

The radio is a Silvertone, Sears, I think, but the sticker with a model number is long gone though I can see where it used to be; the glue is still there!  The dial looks sorta like a Gilfillan or, at least, similar; a big round dial with frequencies on top and a logging scale at the bottom and same amber color as the Gilfillan used to be.  Its about five or six inches in diameter.  Knobs are intact for three of the five controls and the dial works though there's lots of slack in it.  It also has the "magic eye" tuning aid at the top of the dial though I can't tell if it works until I replace the PS capacitors.  Tubes are octal, "G" type as opposed to the smaller GT types common later.  I wish it were old enough to use the original 4, 5, and 7 pin types, though.  I'd sure like to find one of those but I know that would complicate finding replacements if needed!
Anyhow, I'm excited about getting started on this and I'll be looking at some of the neat sites recommended for more ideas and information.  Thanks again to everyone who responded and if anyone else has some suggestions, PLEASE let me know; email if you prefer.
Thanks to all,
Tom

Forgot to mention:  I also found a Motorola VHF base station, not too much newer than that receiver.  Uses the loktal tubes and a killer (hopefully NOT literally) power supply.  Perhaps that would be a bit more appropriate for eHam.  I'll post a further description when I get started on it but the receiver comes first!
Tom
« Last Edit: August 10, 2013, 09:25:34 PM by WB6DGN » Logged
AC5UP
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Posts: 4546




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« Reply #12 on: August 11, 2013, 01:36:07 AM »

The radio is a Silvertone, Sears, I think, but the sticker with a model number is long gone though I can see where it used to be; the glue is still there!

If the next comment is something along the lines of " I wish I could find a schematic but I don't have the model number... " go here:  http://makearadio.com/beitmans/

You can download the Beitman books by published year and you'll find within each book the make & models listed alphabetically. If you think the radio is around 1947 or so, look at the Silvertone section in the 1946 / 1947 / 1948 books. Then pay attention to the tube lineup and other telltales for a similar chassis. Look closely and you'll see a link below the Beitman indexes for Rider manuals: ( http://hertzmail.com/Riders-vols/ ) which is the same as the source schematics found at Nostalgia Air ( http://www.nostalgiaair.org/Resources/ ) but in the original book form. Sometimes seeing the book in sequence makes it easier to find a match for something similar to what you have.

BTW: A few years ago I tracked down an AM / FM mystery chassis based on two telltales: The FM dial scale was marked by FCC channels 200 to 300 (not frequency) and the push-pull audio PA had the tubes lined up as 6V6 - 5Y3 - 6V6. Almost always you'll see the 6V6's next to each other, but on this one.......... Turns out the chassis came from a Farnsworth AM / FM / Phono console and is something of a rare bird.
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KE3WD
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Posts: 5688




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« Reply #13 on: August 11, 2013, 07:21:45 AM »

About the reconing of electromagnetic speakers: 

I have sent these kind of speakers to various reconers with great results in the past, but in just about every case the target was restoration of older guitar amplifiers or organ tone cabinets from an era gone by.  Musicians are pretty picky about doing anything and everything possible to realize the original sound of these devices as opposed to replacing with more modern parts.  There are good reasons why substituting a choke coil and a PM speaker can sound a lot different from that originally installed electromagnetic jobbie. 

First thing to make sure of is that the electromagnetic coil is still in good operating condition, sometimes can be as simple as an ohmmeter check, in other cases one should do whatever it takes to put the coil under real voltage operating conditions and ascertain that there is no internal insulation breakdown or internal shorting in there.  Most all reconing shops I've dealt with do not get into the rewinding of those coils, accepting and reconing only those speakers in which the coil is found to be in good health. 

Once over that slight hurdle, one should always contact whatever reconing service they are interested in using beforehand and make certain that the shop can tell you that they can do the particular size and type of speaker you have.  IME it is a lot easier to find shops that have access to 12" and 15" replacement cones with spider and voicecoil, although the 8" speaker, once very popular, is indeed still a good candidate for reconing as well. 

Also find out the voicecoil impedance, some of the electromagnetic speakers went as far as using the 16 ohm voice coil, others could be as low as the oft-stated "3-4 ohms". 

And - if a certain reconer you have contacted tells you that they are not geared up to do your particular speaker size and type, but they do recone electromagnetic speakers, the gift of gab can go long way towards getting them to recommend another outfit that they may know where the job can be done. 

Here's one outfit that is like that: 

http://www.tonewheelgeneral.com/index.php?load=/recone.html



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W9GB
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Posts: 3375




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« Reply #14 on: August 11, 2013, 10:19:58 AM »

Tom -

Radio Attic Archives -- Photos to ID your 1920s to 1950s radios
http://www.radioatticarchives.com/index.htm

1935 Sears Store -- Silvertone radio department
http://www.sfhobbies.com/sfhobbies/radio/SearsStore/index.jsp

Silvertone models
http://www.radioatticarchives.com/archive.htm?page=s4#Silvtn

Silvertone 1942 (1936)
1936 was the first year for eye tubes, in Sears Silvertone models.
http://www.radioatticarchives.com/radio.htm?radio=11151

SF Hobbies is a good web site on Silvertone models
http://sfhobbies.com/

Speakers used in Silvertone radios
http://sfhobbies.com/sfhobbies/radio/speakers/index.jsp

==
The Internet forum that you desire, Antique Radio Forum
http://antiqueradios.com/forums/viewforum.php?f=1&sid=ba212a46042dc8845653c22c061fddb0

A Silvertone 1732 restoration recently featured.
« Last Edit: August 11, 2013, 10:39:20 AM by W9GB » Logged
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