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 Post subject: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Sun 15, 2021 7:58 pm 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
Hi, I'm Daniele from Livorno, Italy. I'm a modest collector of portable transistor radios produced from 50's to 70's. In particular I like Zenith radios very much and have some of them, including a few of the popular Royal 500 models. Recently I found at a flea market a hand-wired Zenith Royal 500. It has lost the typical layout label inside the battery cover, but it has quite a low serial number of 10950 and from circuit inspection (and the date code of 549 on the tuning capacitor) I guess it is a 7XT40 chassis, with black Sylvania transistors, circuit version #1.
The unusual (to me) - may be negligible - thing that captured my curiosity is a big capital "S" which appears ink-stamped on the tuning capacitor (please have a look at the attached image). What could have been its meaning, if it had any?
Many thanks for your feedbacks.
Best regards
Daniele


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3.jpg
3.jpg [ 347.02 KiB | Viewed 2231 times ]
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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Sun 15, 2021 10:43 pm 
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Location: Panama City, FL 32401
Probably means Sylvania, for the transistors. If not I have no idea. That's certainly a rare find, and a very low serial number. The "549" would be 49th week of 1955. Supposedly they started making them in November of '55. Very nice. "Molto bene!" :D

The date on the audio transformer is 50th week of '55!


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Sun 15, 2021 11:13 pm 
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Location: Mountains of Mourne. Ireland.
EIA code 273 denotes R/C Radio Condensor Company.
Condensor is the old-fashioned word for capacitor.

The letter S may be a quality control (or batch) stamp of theirs or a Zenith production line stamp.

The EIA Source Code is a numeric symbol that was assigned and registered by the Electronic Industries Association (EIA) that could be stamped or marked on any or all products to identify the production source or the vendor assuming product responsibility.

Greg.


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Sun 15, 2021 11:34 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 7087
Location: Indianapolis, IN
Hello Daniele,

Could you provide a picture of the front of your radio ?

Am wondering if perhaps the tuning range of that cap may be different for export as I've never seen that "S" stamp before.

Recently refurbished one of these (S/N 12183) and am trying to piece together a second, so haven't posted the project yet here at ARF. Also saved many pictures found on-line of the chassis, but none have that ink-stamp.

John


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Mon 16, 2021 6:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: SoCal, 91387
I have a 7XT40, with socketed Transistors. There is no rubber stamp on the tuner.


Attachments:
Zenith Royal 500 inside.jpg
Zenith Royal 500 inside.jpg [ 530.85 KiB | Viewed 2163 times ]
Zenith Royal 500 label.jpg
Zenith Royal 500 label.jpg [ 480.29 KiB | Viewed 2163 times ]

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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Mon 16, 2021 9:09 am 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
xrhonda91 wrote:
Hello Daniele,

Could you provide a picture of the front of your radio ?

Am wondering if perhaps the tuning range of that cap may be different for export as I've never seen that "S" stamp before.

Recently refurbished one of these (S/N 12183) and am trying to piece together a second, so haven't posted the project yet here at ARF. Also saved many pictures found on-line of the chassis, but none have that ink-stamp.

John


Hello John,

I attach here below a close photograph of the front panel. It looks the same as other Royal 500's that I have.
The audio volume scale has vanished thus I'm planning to replace the entire metal plate with another in much better conditions.

Best regards
Daniele


Attachments:
11.jpg
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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Mon 16, 2021 1:38 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 7087
Location: Indianapolis, IN
Hello Daniele,

Yes, the tuning range is the same---maybe someone else will be able to solve this mystery. Wonder if Zenith stamped that "S" when a radio was returned for factory servicing back then ???

Good luck !

John


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Mon 16, 2021 2:53 pm 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
xrhonda91 wrote:
Hello Daniele,

Yes, the tuning range is the same---maybe someone else will be able to solve this mystery. Wonder if Zenith stamped that "S" when a radio was returned for factory servicing back then ???

Good luck !

John


Hello John, I have also imagined that some past owner decided to mark the radio that way for some reasons, though I never found nothing similar before. Sometimes I found owner's names or initials roughly scratched (sigh!) on the back cover of the case or hand-written notes on the layout label inside the battery door. Well, it will probably remain a little mistery.
Kind regards
Daniele


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 17, 2021 8:11 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 779
Location: Kansas City
I've looked at hundreds of Royal 500s and have never seen that outlined "S" stamp before.

Usually on the earlier 500s, a black date stamp (production or test date?) was placed there.

I do see a 550 date code on the transformer, built by Zenith (343).

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***SERIAL NUMBERS: ZENITH & INTEROCEAN models 200-699 needed for project--PM me-THANKS***


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 17, 2021 8:19 pm 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
Martin Blankinship wrote:
I've looked at hundreds of Royal 500s and have never seen that outlined "S" stamp before.

Usually on the earlier 500s, a black date stamp (production or test date?) was placed there.

I do see a 550 date code on the transformer, built by Zenith (343).


May be hand-written or stamped by some past owner for unknown reasons.
Regards
Daniele


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Wed 18, 2021 9:35 am 
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Joined: Aug Wed 18, 2021 9:34 am
Posts: 1
Six germanium PNP transistors. I'm not sure about the Zenith transistors, but if they were Mullard they would be one OC-44, two OC-45, one OC-71 and two OC-72. I could draw the circuit diagram from memory. I started my interest in electronics working in radios exactly like that.



Target 401k


Last edited by Halvorsons on Aug Thu 19, 2021 9:08 am, edited 1 time in total.

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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Wed 18, 2021 3:22 pm 
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Joined: Oct Mon 02, 2017 8:53 am
Posts: 1594
Location: Panama City, FL 32401
Possibly a "QC" stamp of some kind. I've never seen that either.


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 Post subject: General question: restore/repair or keep it "as is"?
PostPosted: Aug Thu 19, 2021 8:44 am 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
A general question while I'm approacing some polishing/restoration work on the Royal 500 radio you can see in the attached image (it has quite a low S/N of 10950). Clearly it could benefit from replacement of the front cover (at least the upper metal plate). Or it could be left as is, to avoid "renewing" it too much. What's the correct balance, in your view, when it comes to transistor radio restoration? Thanks
Best regards
Daniele


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IMG_20210819_094600.jpg
IMG_20210819_094600.jpg [ 427.69 KiB | Viewed 1949 times ]
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 Post subject: Zenith Royal 500 front metal plate
PostPosted: Aug Thu 19, 2021 9:07 am 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
Hi all,
it happens I have a spare metal plate (the one with the volume and tuning scales) coming from a broken front panel of a black Royal 500. Anyway by comparing it with another black Royal 500 that I'm going to take care of, it appears the spare thing looks far less "goldish" than the original one.
When did the "silveer" version appear, during production history of Royal 500? Thanks
Best regards
Daniele


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IMG_20210819_095518.jpg
IMG_20210819_095518.jpg [ 399.16 KiB | Viewed 1946 times ]
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 Post subject: Re: General question: restore/repair or keep it "as is"?
PostPosted: Aug Thu 19, 2021 12:47 pm 
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Posts: 521
Location: New Hampshire
Hey Daniele,

I think your radio could use polishing and cleaning but since yours is a lower S/N I personally wouldn't replace anything on the exterior. I would look just fine if it were cleaned up.


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Thu 19, 2021 11:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 39253
Location: SoCal, 91387
An interesting dilemma to be sure. Don't worry about "correctness" so much. Determine what looks better to you, and roll with that. Personally, the existing bezel matches the color of the grill, which I think is more noticeable than the numbers for the VC.

If you can later obtain a grill that matches the color of the loose upper bezel, then you might consider replacing both.

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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 24, 2021 12:53 am 
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Joined: Nov Sun 29, 2020 5:59 pm
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Location: Northeast Illinois 60188
I just picked up a Zenith Royal 780 at a swap meet yesterday and stamped on the tuning capacitor is this giant letter "E".
This radio is of a similar vintage to your 500. I can only surmise that the letter is a factory mark of some kind.


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Zenith Tuning Cap.jpg
Zenith Tuning Cap.jpg [ 493.88 KiB | Viewed 1651 times ]
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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 24, 2021 4:48 am 
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Joined: Feb Fri 01, 2019 11:35 pm
Posts: 704
Location: Riverside Ca. 92504
I compared my 500 A s/n 24683 with my 500B s/n 206247 and the Bs front plate seems more silvery. I have a second 500 A and will add that in too as it is s/n 97392 and a later 500A I will take a couple of pics tomorrow in better light to confirm this. I have soft lighting in my room and I can tell better in the natural light. I finally found a replacement transistor for the output transistor that is bad. It will not be a matched pair but should play. Discovered the bad transistor after a full recap . Tom


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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 24, 2021 11:27 am 
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Joined: Sep Fri 14, 2018 11:18 pm
Posts: 64
Location: Livorno, Italy
jimtech wrote:
I just picked up a Zenith Royal 780 at a swap meet yesterday and stamped on the tuning capacitor is this giant letter "E".
This radio is of a similar vintage to your 500. I can only surmise that the letter is a factory mark of some kind.

Really interesting. At least I can now suppose the "S" on my 500 was stamped at factory (not by a past owner at home). Thanks a lot for this information.

Here another one like yours:


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Immagine.png
Immagine.png [ 866.61 KiB | Viewed 1620 times ]
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 Post subject: Re: Zenith Royal 500 probably 7XT40 #1
PostPosted: Aug Tue 24, 2021 4:54 pm 
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Joined: Feb Fri 01, 2019 11:35 pm
Posts: 704
Location: Riverside Ca. 92504
Here is the pics of the Zenith Royal 500As verses the Zenith Royal 500B. The Royal B seems to be a little more silvery than the A. I have a translucent royal 500A and the scrip is different that a regular royal 500A. The Zenith Royal As are red/maroon and the Zenith Royal B is black. Tom


Attachments:
File comment: Three 500s front. The blak one is a 500 B for comparison
IMG_1855.JPG
IMG_1855.JPG [ 777.15 KiB | Viewed 1608 times ]
File comment: The back of the 500s
IMG_1860.JPG
IMG_1860.JPG [ 724.32 KiB | Viewed 1608 times ]
File comment: grill comparison
IMG_1859.JPG
IMG_1859.JPG [ 826.11 KiB | Viewed 1608 times ]
File comment: top plate comparison
IMG_1857.JPG
IMG_1857.JPG [ 739.96 KiB | Viewed 1608 times ]
File comment: translucent script
IMG_1864.JPG
IMG_1864.JPG [ 617.03 KiB | Viewed 1608 times ]
File comment: translucent 500A next to a regular 500A
IMG_1866.JPG
IMG_1866.JPG [ 610.89 KiB | Viewed 1608 times ]
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