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 Post subject: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 4:41 pm 
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Location: Mt. Prospect, IL USA
I was checking out the serial numbers on my Zenith sets. I have a '51 H500 with serial number L 11540, and a 7-M-918 with serial number M305559. This would tell me that the 7-M-918 was still being produced in 1951. Actually, it started as the 7-H-918 FM-only set in '49. Would the "M" in lieu of the "H" indicate the set was made post '49? I also have a 12H092 console with a date from 1950 ink-stamped on the inside of the chassis.

It's curious to see that Zenith made sets for years without re-designating them each model year. There was an AM-only set (K510???)that looks like the 9-H-918 FM-only set. Were they ever sold concurrently?


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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 5:47 pm 
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Things get confusing for Zenith sets after WWII.
I would not doubt certain models remained in production more than a year or two.

I too have wondered about the use of an "M" rather than "H" on the 7-M-918.
Originally H designated FM reception and M designated an Automotive radio.

-Steve

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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 6:14 pm 
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To add more confusion, in 1957 Zenith ran out of letters to indicate the year, so they started over with "A" in 1958.

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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 6:38 pm 
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From Nostalgia Air, it seems the last Zenith auto radio listed is for the 1949 Nash. Maybe when my 7M918 was produced, Zenith auto radio production had ceased. GM had their own Delco, Ford got Philco, several independent carmakers went belly-up, maybe that market dried up and Zenith began to concentrate more on television... My uncle worked in the Zenith auto radio engineering department until 1939, when apparently Zenith changed their method of automatic tuning, and he got laid off... then bought a Philco... :lol:


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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 7:23 pm 
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Here's the letter to year codes for Zenith TV, it may parallel some radio/phono, I dunno:

Attachment:
zenyrs.jpg
zenyrs.jpg [ 88.68 KiB | Viewed 277 times ]

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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 7:36 pm 
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Tim Tress wrote:
To add more confusion, in 1957 Zenith ran out of letters to indicate the year, so they started over with "A" in 1958.


And in 1970, 1985 and 1999

-Steve

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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Mon 08, 2018 8:13 pm 
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Chuck,
I believe the M-chassis type code was an errant code. I have taken quite a bit of data on these sets and will try to verify and post the particulars this evening.

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Concentrating on collecting pre-WWII Zenith radio models for the EXPORT market


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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Tue 09, 2018 2:36 am 
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Location: Kansas City
Herewith is my serial/production data on the 7H918 and 7M918.
COLUMNS:
1. Model#
2. Ser #
3. Logging date by M Blankinship

4. Earliiest possible Production date: Year/Week
5. SPKR RETMA Inverted code Year (1st digit) week (2nd/3rd digit)/MFR code (4th-6th digit)
6. I.F. RETMA Inverted code Year (1st digit) week (2nd/3rd digit)/MFR code (4th-6th digit).
Example: 938.343
1949, 38th week. 343=Zenith manufactured assembly

SERIAL LIST:
---1------------2------------3---------------4---------------5---------------------6------------------
7H918 M218761 2/25/2018
7H918 M218824 3/8/2014
7H918 M219030 1/3/2015
7H918 M219068 5/3/2014
7H918 M219156 11/12/2012
7H918 M219385 1/21/2014
7H918 M219620 1/3/2015
7H918 M220502 12/15/2011
7H918 M221579 11/24/2013
7H918 M221842 4/19/2015
7H918 M222169 9/4/2017
7H918 M223500 9/4/2017
7H918 M224553 9/28/2010
7H918 M224607 9/4/2017
7H918 M224615 9/4/2017
7H918 M224965 9/4/2017
7H918 M225601 11/6/2013
7H918 M225708 6/17/2018
7H918 M226231 9/12/2017
7H918 M226463 11/6/2013
7H918 M226697 1/21/2014
7H918 M227123 1/3/2015
7H918 M227132 10/1/2009
7H918 M227175 9/4/2017
7H918 M228047 10/1/2009
*
7H918 M242849 10/1/2009
7H918 M242947 10/1/2009
7H918 M242960 11/6/2013
7H918 M244160 11/6/2013
7H918 M244706 9/4/2017
7H918 M245200 7/14/2010
7H918 M245451 9/4/2017
7H918 M245627 1/3/2015
7H918 M246895 10/1/2009
7H918 M247130 11/16/2013
7H918 M247158 9/4/2017
7H918 M253555 1/21/2014
7H918 M253571 9/10/2017
7H918 M253693 1/19/2014
7H918 M253838 1/21/2014
7H918 M254020 10/17/2010
7H918 M254477 12/21/2011
7H918 M254496 10/1/2009
7H918 M255925 11/6/2013
7H918 M256051 9/4/2017
7H918 M256224 11/6/2013
7H918 M256850 2/6/2018
7H918 M257302 10/1/2009
7H918 M257444 7/13/2018
7H918 M257655 7/27/2014
7H918 M257724 9/4/2017
7H918 M257841 10/1/2009
7H918 M258567 3/28/2010
7H918 M258707 1/21/2014
7H918 M259487 10/10/2017
7H918 M259922 12/15/2011
7H918 M260228 9/4/2017
7H918 M260590 9/4/2017
7H918 M260928 12/21/2011
7H918 M261454 9/30/2017
7H918 M261928 11/6/2013
7H918 M262239 11/24/2013
7H918W M262539 7/27/2014
7H918 M262616 2/20/2014
7H918 M2XX018 9/10/2017
*
7H918 M300275 10/1/2009
7M918 M300331
7M918 M300620 12/15/2011
7M918 M301460 12/28/2013
7M918 M301883 9/4/2017
7H918 M302093 10/1/2009
7M918 M302680 12/2/2010 Earliest MFR Date: 1949/38 RETMA OUPUT XFMR: 938.306
7M918 M303051 3/28/2010
7M918 M303143 9/4/2017
7M918 M303708 1/3/2014
7M918 M303749 9/4/2017 Spkr RETMA#:938.306
7H918 M304950 10/1/2009
7M918 M305096 11/6/2013
7H918 M305265 10/1/2009
7H918 M305790 10/1/2009
7M918 M307772 3/28/2010
7M918 M308465 6/2/2018
7M918 M309218 7/14/2010
7M918 M311791 9/4/2017
7M918 M312204 1/19/2014
7M918 M31251X 9/4/2017
7M918 M313363 1/19/2014
*
7H918 M494330 10/1/2009 Earliest MFR Date: 1949/40 SPKR RETMA # 94X.343
7H918 M494814 11/24/2013
7H918 M495411 12/2/2010
7H918 M495887 8/22/2010
7H918 M497026 4/19/2015
7H918 M497655 10/1/2009
7H918 M497981 12/15/2011
7H918 M497982

So, I conclude that it is apparent that the 7M model alternates the 7H models in serial number sequence in a couple of areas production end, specifically the third group. If you examine the list, one should note four separate groupings, or production 'runs' of serial numbers with large gaps separating each from the other groups. I have highlighted the gaps with asterisks. The highest serial numbers on this list were probably assembled in mid to late 1949, based on a number of other models (7H920, 7H921, G516, etc.) where I gathered RETMA and M-prefixed serial number data. My estimate of total production on these is 47,500 units.

It is difficult to retrieve the RETMA codes for this model, since nearly all the examples I have seen have the radio back cover installed. I don't know if the 7M was truly a typo, but I have not found any documentation in Zenith/McDonald papers or service manuals regarding this 7M variation.

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Martin
Concentrating on collecting pre-WWII Zenith radio models for the EXPORT market


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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Oct Tue 09, 2018 9:22 pm 
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Looking at the car radios in the first few of the Sams AR manuals, it looks like Zenith bailed out of the OEM market around 1950. The Colonial/Sylvania sets made for Ford around 1951-52 bear a striking resemblance to the earlier Zenith designs, including the unique IF transformers; apparently, Zenith sold the tooling to them, with the Ford contract.

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Tim KA3JRT


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 Post subject: Re: Zenith model numbering overlap postwar
PostPosted: Dec Wed 05, 2018 4:28 pm 
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I have an old Zenith FM radio 7M918 that has not been operated in years that I will send someone if they want to pay the postage.
John McIlvoy 214-293 1049
Can Pickup in Houston or Dallas


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