Approx age from factory markings/approval markings trademarks etc (radio)

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Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 01 Jan 2018 23:52

Hello everybody.

Are there any people here who have knowledge of things like trade-marks, logos, factory markings, approval markings etc?

I have this item made by Telefunken which is related to fixed radio installations and was supposed to be part of the communications setup at one of the flak towers which were some of the last places to surrender. As with a lot of fixed (not mobile) installations, this device was basically a civilian device used by the military. It seems they often used normal civilian commercial items in these roles. However as with many stories like that, its hard to prove anything.

I wanted to start by ascertaining if its possible to find out the approx age of the item by some of the markings on various components.

There are conflicting reports that this item is either from the late 30s, fron right at the end of the war, or a post-war fake.

I attached 5 photos because its the max attachment number but i have about 20, so i will add them to replies.

Anybody know?

Thank you
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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby T. A. Gardner » 02 Jan 2018 04:49

DIN 41161 is the German equivalent of a "Mil Spec." It is a industry standard issued by the Deutsches Institut für Normung. It was the standard for paper insulated capacitors up to 1992 when it was superseded.

Image

So, there's no real way to tell when that component was manufactured.

The picture above it is of a vintage Rosenthal ceramic resistor. Again, no real means to tell for sure when it was made. Here are some examples:

Image

Image

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Waleed Y. Majeed » 02 Jan 2018 07:18

On the first picture you have what I suppose is markings on some bakelite. The "Cirkle+Pag" is probably the company, and beside this there's a "material prüfungs amt" stamp with "45-S". This indicates what type of bakelite it is - components used / water resistant / insulating or not etc. I think it was first used in 1924 and until 1945. I know there's a list online somewhere, just can't find it right now. Will have a better look later or find my own copy for you if no one else posts it in the meantime. So because of the company name I would say before or early war years. Later "Pag" would be substituted by a number code within the "wpa".

waleed

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 02 Jan 2018 09:52

Thank you for your replies.

So its looking like its likely to be a genuine pre 1945 item at least by the stamp on the bakelite case?

The vacuum tubes inside are made by Valvo (who supplied the German military pre 1945?) and Telefunken. I have photos of the batch codes on their bases, but i dont suppose they mean very much, as far as i know vacuum tube batch codes of the era are not very useful. I can post them if anybody is interested. One of the Valvo made tubes is marked Deutsche Reichsbahn but that could have easily been a replacement.

Here is another selection of some more trade marks. Im hoping somebody will recognize some more trade marks or approval numbers as at least confirming this device is pre-1945.

By the way the FRAKO component could be a post-war replacement. It looks like it has been disturbed after the device was manufactured. Its possible somebody in the 50s or 60s fitted it since original electrolytics did not have a very long shelf life.

I worked on a lot of pre 1945 comms and other electronic equipment and im surprised at the lack of birds. There is not one single bird logo anywhere in this device. Maybe its because its made for the civilian market by a commercial company, i dont know. Usually at least a few components in radios etc have a bird marking.

As a side note, if anybody happens to know of any photos
From the radio room of the zoo towers (probably the control tower) this device may be there. Or not.
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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Waleed Y. Majeed » 02 Jan 2018 14:30

Hello again! I knew something was incorrect in my first post and I apologize for those mistakes. Here are some corrections and additions on the "Materialprüfungsanstalt/amt - Berlin-Dahlem" markings + some links on other logos shown.
The 45 = Presswerk-AG, Essen (P A.G) and the S = Typ S - Phenolharz (Bakelit) mit Holzmehl all Füllstoff (phenol resin with wood flour/fine sawdust as filler). So the company code was incorporated into the MPA from the start. Testing was not compulsory, but it was mandatory for products that could be delivered to German Rail, Post and Army during the 1930s and onwards (1950s). I know many companies stopped using their own logos during the war years and only used the MPA but can not confirm this at the moment. Here are some useful links to manufacturers and bakelite types as promised earlier http://www.plugsocketmuseum.nl/MPADmarks.html
https://www.google.dk/url?sa=t&rct=j&q= ... CWLxaY8Ucc

And some additional logo info I found - Ela prüffeld stamp: https://www.nonstopsystems.com/radio/pd ... bungen.pdf

“Siemens & Halske” logo history (if correct it is a pre 1925 version :? ): https://www.famouslogos.net/siemens-logo/

NSF: Nürnberger Schaubenfabrik und facondreherei/fassondreherei until 1940 / Nürnberger Schrau­benfabrik und Elektrowerk GmbH part of AEG from 1941 https://www.radiomuseum.org/dsp_herstel ... ny_id=1423

Like the NSF the Rosenthal logo history is also interesting due to aryanization, but I'll leave that for you to decide :wink:
But I will add this stating the logo dates 1934-1956 and not post 1957 http://www.retroselect.com/Rosenthal/Rosenthal.htm
And once again sorry about the previous mistakes although I still think many of the parts you shown are pre war and war period items, possibly also later.

waleed

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 02 Jan 2018 18:26

Thanks for your help.

Why couldnt they just write a year somewhere inside? Grr.

The device also has a serial number, but i am not sure if its possible to date Telefunken serial numbers. There does not seem to be much information about this.

From its build quality and generally how its made, i get the impression it was made in times of low resources. For example, there are several examples of using two components instead of one (eg 2x 0.5M instead of a single 1.0M). It also has the “wrong” vaccuum tube, however has clearly been built from the start to use that “wrong” tube. So its almost like they alteady made the frames with one number stamped into them, however when they actually assembled it, they didnt have those tubes so they used ones they had.

all that suggests the “bad year/s” of the war? When resources were running out. But im not sure.

I wish there was a book of telefunken serial numbers! But looks like there never was one.

The fact that ELA means PA amplifier also makes a lot of sense.

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Waleed Y. Majeed » 02 Jan 2018 21:44

"chopshop" I've got one more possibility you might want to check. I don't know enough to know what to look or ask for but you do ;)
https://www.radiomuseum.org

Cheers and happy new year
waleed

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby T. A. Gardner » 02 Jan 2018 22:01

The new photos of components appear to all be capacitors. The printed data is the specification for the component. Its rating in farad (well, microfarad), temperature range, voltage, polarity (the + sign) and in some cases a part number. These were probably made for decades the same way. There isn't much new in capacitor design in the 40's to 70's.

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 02 Jan 2018 23:45

T. A. Gardner wrote:The new photos of components appear to all be capacitors. The printed data is the specification for the component. Its rating in farad (well, microfarad), temperature range, voltage, polarity (the + sign) and in some cases a part number. These were probably made for decades the same way. There isn't much new in capacitor design in the 40's to 70's.


Hi. Thanks for that information. My hope in posting photos of the caps is that their part/production batch numbers somehow encode their production date.

For example (irrelevant to here but just as an example) some other electronic component manufacturers had the week and year counting from some other year. So as an example if you know that specific company counts years from 1926, and you see 1213xxxx as a production code, it would mean that the item was manufactured in the 12th week of the 13th year counting from 1926, so that would mean spring 1939. Some other digits may also encode where it was made if the manufacturer had various facilities.

Most manufacturers just stamped a year somewhere.

The reason i posted photos of mostly caps is because they usually have a short lifespan so manufacturers mostly applied this kind of technique to caps.

By the way radiomuseum only has info that this model appeared in 1938. But some things which were first made in 1938 were still being made in the 60s.

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby T. A. Gardner » 03 Jan 2018 00:26

The only caps that don't age well are ones with oil filling. The rest are only going to wear out in use. The small oil ones tend to start growing "hair" (dust clinging to them) as they age. They also get an oily look.

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 03 Jan 2018 17:01

T. A. Gardner wrote:The only caps that don't age well are ones with oil filling. The rest are only going to wear out in use. The small oil ones tend to start growing "hair" (dust clinging to them) as they age. They also get an oily look.


Hi. Unfortunately capacitors are pretty much the most problematic components. I work with antique electronic devices all the time and capacitors are always replaced.

The only exceptions are ceramic caps. They dont usually degrade. However pretty much every other type has its own problems.

Various foil types (paper, wax, tar, plastic etc) become leaky with age. Not physically but electrically. They turn into resistors. This is what kills the vast majority of antique equipment. They leak a positive dc voltage which makes the next stage draw heavy current and overload everything, burns things out.

Electrolytics have the shortest service life which is why their production codes often have an encoded date. Even “modern” electrolytics often fail after about 10 years. The no1 cause of death for even modern products. Electrolytics degrade even if they are not used. So if you find some new-old-stock caps they will likely be bad. Electrolytic caps failing is why you often see DKE38s with the VY2 vacuum tube burnt out. In the old days people used to re-form them but its not really done anymore.

And finally oil filled caps, they are the most dangerous because the oil inside them can be a VERY nasty chemical.

So this is why we NEVER EVER just plug our grandfathers old radio into the wall after finding it in the basement (or antique shop or whatever).

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Waleed Y. Majeed » 03 Jan 2018 18:21

Thanks for the info. Have two old german field telephones but never looked inside. Would there be anything to be worried about if used. Have no batteries and only tried to generate a current by turning handle... evil torture instruments! :)
But what if I connect a battery - dangerous?

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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 04 Jan 2018 12:32

Waleed Y. Majeed wrote:Thanks for the info. Have two old german field telephones but never looked inside. Would there be anything to be worried about if used. Have no batteries and only tried to generate a current by turning handle... evil torture instruments! :)
But what if I connect a battery - dangerous?

waleed


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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Vintage-electronics-chopshop » 04 Jan 2018 22:46

So i might have found a lead, im not sure.

This picture here of a Siemens dual capacitor, this is a big can capacitor thats not only soldered before other components are fitted, but also screwed to the frame. I think its safe to consider it being fitted on manufacturing and not a late addition since replacing it without disturbing other parts would be impractical. the thing highlighted in yellow kinda looks like a production code. 24Y7

Using this source here:
http://www.matilo.eu/wp-content/uploads ... des-EN.pdf

Remembering that their factory listing is unfortunately incomplete, 24 could easily be one of the missing codes. It certainly follows the syntax of existing codes for the 39-45 era, 2 digit numbers.

The 3rd digit is Y, which if that thing is a date code, would make it either 1943 or 1968.

I think its safe to say 1968 is completely impossible since by then they they already had solid state diodes, even transistors existed, styling changed a lot and the remaining vacuum tube tech was mostly all-glass 9 and 7 pin, so there is no way anybody would make this device in the late 60s.

The last digit is 7 which would make aug.

So if that thing IS a date code, it would make this device manufactured in aug 1943.

What do people think of that?

By the way, how was the war going in aug 43? Would you think that a device which was made different from its original design in order to save resources because the war was going bad and everything sucked be consistent with that date? Or did that happen later, and in aug 43 times were still good for Germany?

(Sorry my knowledge of history is very poor. I just fix things. Im one of those people who can read a tech manual cover-to-cover but get bored after page 2 of a book with a story).
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Re: Approx age from factory markings/approval markings trademarks etc (radio)

Postby Funksammler » 05 Jan 2018 10:51

Recycled or NOS wartime components can often be found in immediate postwar equipment. The electronics industry was well and truly destroyed at the end of the war so it was a matter of mend and make do... Some of the components appear to be postwar dated however, the NSF capacitor 1948 and the Frako elco 1954 and the blue plastic wrapped capacitor is definitely post war, so unless these appear to be replacements I would say that your piece of equipment is postwar from the mid 1950's. It is perhaps better to post an overall picture as the type of wiring and other components may give further clues. The absence of Wa.A eagle stamps is to be expected, as Flak towers would have been equipped via the Luftwaffe procurement system, so BAL stamps would have been more logical on wartime equipment. This procurement system would also have resulted in an Ln number and the usual wartime coding of the tag plate, absence of which would be another strong indication of a postwar piece of civil defence equipment.

What I find strange is that the bakelite compound code appears to be stamped into aluminium, very unusual or are my eyes deceiving me...?

regards,

Funksammler


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