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Grundig radio cassette deck help

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zsm

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Grundig radio cassette deck help

PostFri Mar 02, 2012 8:03 am

Hi,

I got a Grundig car radio from German ebay. I think it came out of an old Mercedes. I can't read the model number anymore, I think it was 923G but that first number or letter is pretty faded. Here are all the images:

https://picasaweb.google.com/1011403374 ... directlink

Here is the front and the back:

Image

Image

It used some funky connectors for power and speakers it seems. I have googled a bit and only found wiring diagrams for newer Grundig car radios. I really don't want to mess-up +/- in particular. If anyone knows what years or models this came out of our other places to ask, I would really appreciate any help.

Thanks.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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zsm

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Re: Grundig radio cassette deck help

PostFri Mar 02, 2012 11:17 am

Alright my own little mystery car paid off today. It's a Weltklang WKC2535VD Stereo aka the "Brussels" stereo CR found in Golf I for example.

http://translate.google.com/translate?h ... t&resnum=6

And + goes to the vertical prong, negative to the one just to the side on the back of the radio chassis (search for pn 171 035 447).

http://forums.vwvortex.com/showthread.p ... rocco-1%29

It looks like I can just strip a little of the ends off the speaker wires and jam them in there, but if I want to be fancy, does any body know if this is what I am after?

http://www.audiospares.com/product.php? ... 137&page=1

Now to just figure-out what all the little buttons mean. U? Maybe that's FM cause of the U near the frequencies. The radio manuals on thesamba don't quite go far enough into '80, oh well, it will be fun.

http://www.thesamba.com/vw/archives/manuals/radios.php

Here's another neat page I stumbled on with all sorts of old car radios. Mine is almost at the very bottom. You know what rocks? The frequency indicator is made of a strip of LEDs! Oh yeah hi tech if not hi-fi.

http://www.oldtimerradio.com/auto.html
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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Re: Grundig radio cassette deck help

PostFri Mar 02, 2012 12:11 pm

The power connector is probably a Fastin-Faston connector, but I have no idea if that particular shape of F-F terminal housing is still available. If it is F-F, the terminals have the same dimensions as standard hardware store quick disconnect terminals.

I have a ton of obsolete F-F connectors in my Peugeot. In some cases I replace the entire housing on both sides with something currently available and in other cases I just put heatshrink tubing on each terminal and mate them individually.

The DIN 41529 speaker connector is neat. I have a low voltage lamp that uses that connection for power. I had read that it was most commonly used for speakers, but I've never actually seen another piece of equipment that uses it.
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zsm

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Re: Grundig radio cassette deck help

PostFri Mar 02, 2012 1:04 pm

Thanks Stu, DIN 41529 is exactly what I needed to know. And the quick release connectors are a great idea! Now I know what to do exactly. I still wonder what that extra prong is for below the +12V prong?
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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Isola

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Re: Grundig radio cassette deck help

PostSun Mar 04, 2012 7:24 am

Have you looked inside? I have a Grunding Weltklang 4002 from mid-70s and there is a schematic diagram folded and taped inside the top plate. That may come in handy if there's any more guesswork involved.

Yes, "U" is for FM. It stands for Ultrakurze Wellen (Ultra short waves), the German term for the FM band. "M" as Mittwellen is naturally for AM. U1 thru U3 are probably presets for FM stations. The mystery prong might be for driving an automatic antenna. At least there's such connection in the schematic of my Weltklang.

Sorry, can't help you with sourcing the connectors.
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zsm

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Re: Grundig radio cassette deck help

PostMon Mar 05, 2012 6:22 am

Thank you Isola, having the schematics under the cover would be great, I might, but I don't need them I think. Would be great if the radio ever broke. When my clothes washer broke down there were some diagrams like that under the front panel, that was great! Do you know how to use the presets? In the old radios I have used before you would pull the preset buttons out to set the preset. But I am afraid to tug on these so hard.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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Isola

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Re: Grundig radio cassette deck help

PostMon Mar 05, 2012 10:13 am

My Weltklang doesn't have presents, so I have no clear idea how they could work.

It looks like the owner's manual is available online at manuals-in-pdf.com. The site requires a (free) registration, but I generally don't like sites that want all your personal information just for being allowed to download something remotely interesting. Anyway, you can try your luck, but wouldn't that be too easy? Reverse engineering old German technological creations is just irresistible.

The schematic diagram seems to be easily available: Google gave immediately at least three valid results. The schematic indicates that the buttons U1, U2 and U3 are indeed presets. They are implemented as trimmer potentiometers, but the schematic does not reveal if there is any mechanical connection between the push-buttons and the trimmers. Maybe pulling them out and then turning the tuning dial does the trick, but just maybe. Give it a try, but gently.

More findings on the schematic: The unit has an automatic frequency control function, so it should keep the frequency stable once tuned in. And... did you notice something missing? Yes, there's no needle. Instead, there are 16 leds to indicate the tuned frequency. 16 leds in 1978! (Date guesstimate based on the assumed date marking on the schematic.) Plus apparently two green leds for power and tape indicators. Somehow I think this is an interesting intermediate step between the old variable-capacitor tuned receivers and the modern synthesizer tuners.

The schematic also shows an output for a power antenna. It's probably the mystery prong next to the positive supply pin. It's actually nothing more than an a connection to the main power line after the fuse and the main switch. You can use it to supply max. 1 amp to power up whatever you want when the radio is turned on.

What I find really interesting for me is that the schematic shows various parts associated with a function called Verkehrsrundfunk and its operating mode Durchsagebereit. These translate loosely to Traffic radio and Announcement stand-by. It really looks like there has been a system for transmitting traffic information over broadcast radio years before the RDS. Do we have any German readers that could tell us more about that?

I regret the pronounced atomictoasterism in this post - it looks like I'm sliding toward electronics as soon as I can find a pretext.
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Re: Grundig radio cassette deck help

PostMon Mar 05, 2012 2:17 pm

Isola, what? This was a great comment, no apologies needed! I saw now the schematic thanks to you. I can see the speakers are to be 4 Ohm impedance for example. I was now intrigued as well by the verkehrsfunk. I see some things going back all the way to '73!

http://www.thesamba.com/vw/archives/man ... /12_13.jpg
http://www.radiomuseum.org/r/grundig_ve ... ecode.html
http://www.kofferradios.de/ar/bp/bp792.html

In mine I bet I lack the traffic radio decoder board. See my U button is double wide where there is U and SK in the schematic. Man that would have been neat to look at. It had some ICs and seemed to be wired to the stereo decoder and LED control IC! Would it speak? Maybe only beep and light a LED? Maybe the idea was to then tune to some news station?

Anyway I had a Volvo with neat radio about ten years ago. It was disappointing to read what was available in Europe like TP (for traffic program). You could press it and then it would scan for a station broadcasting traffic info, then decode the message on the LCD. Also if you had the built in GPS it would highlight where the accident was between two exits or whatever. Also there was an announcement feature, like if there was some emergency the radio would tune to a station doing the announcement. Also you could scan by categories like rock or country, or say you wanted to pause the CD anytime there was a News broadcast on the station you had been tuned to earlier, it could do that. And of course we were not supporting even the song names in US or the tune to a stronger station repeating the same content!

The 1 amp power is nice to know about as well, thanks again.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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zsm

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Re: Grundig radio cassette deck help

PostMon Mar 05, 2012 11:41 pm

I tried it out, U1-3 are all knobs, you twist them to tune FM! When then you press one it remembers what it had been tuned to earlier. The big knob on the right tunes AM.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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Isola

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Re: Grundig radio cassette deck help

PostTue Mar 06, 2012 3:28 am

Ok, I actually suspected the presets could work that way. I'm only wondering if it's too easy to accidentally twist the preset dial knob sligtly when pressing it, but maybe they're not that sensitive and the AFC function takes care of the rest. Looking at the schematic, the large tuning dial should tune AM and FM equally. FM tuning should be engaged when the U button is depressed and none of the presets is selected. By the way, the triangle or down arrow key should switch between mono and stereo, although you probably noticed that in the schematic already.

I have to spend the afternoon digging more info about the Verkehrsrundfunk. It sounds really interesting. Probably it listens to another station and upon detection of a certain set of tones (like selective call on CB radio), it activates the Durchsage, effectively overriding the present programme with another. The SK button, if present, enables this functionality.

In mid 1990s, the Radio Data System replaced this. I've always thought that RDS in used in the US, too, but isn't it that widespread? Maybe I'm biased to think so because my Harman/Kardon home hifi set that so proudly says "Designed in the USA" implements the RDS functionality flawlessly. (Interestingly, much better than my past Becker car radio, even though Becker was an European part of the Harman group). Most modern car radios implement the RDS very well, nearly as you described. The other side of the story is that radio stations don't follow the rules: Especially the local stations are notorious for replacing their station name (the Programme Service field) by a scrolling advertisement, which is explicitly banned in the RDS specification. The Programme Type is also often misused, so it's of little value. But what usually works (except for that damn Becker) is the follow-the-station functionality. And what really works, and is actually useful, is the traffic announcement functionality.

The Traffic Message Channel function that can deliver info about accident locations etc. is an even newer scheme, although it's techically based on RDS and shares the RDS message channel. I've never heard of a radio that can output these messages, but the decoded data can be fed to a GPS navigator which can then both show the location to be avoided, and naturally compute a new route. Sounds pretty clever and as far as I know, it really works. Here in the middle of nowhere it's of little value but having spent some hours in a true German Stau, hoping not to miss the ship, I can see its potential usefulness.
Last edited by Isola on Tue Mar 06, 2012 8:06 am, edited 1 time in total.
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Re: Grundig radio cassette deck help

PostTue Mar 06, 2012 4:16 am

Here goes: A Federal Highway Administration study on pre-GPS era navigation systems, from 1981. It introduces briefly the existing or planned systems, and one of them is ARI (Automotive Road Information), which seems to be just this. The story goes:

"ARI (Automotive Road Information) Traffic System(ll) for VHF/FM
Transmitters was developed by Blaupunkt in the early 1970's, for use in West
Germany. This system transmits traffic information over the State owned FM
broadcast system. This system differs from the DAIR and CACS in that it is a
regional informational system. The ARI transmissions occur on specified
broadcast stations w h i c h interrupt normal programming. The motorist may
manually tune his car FM radio to the proper frequency or he can install a
scanner that automatically tunes his radio when a traffic broadcast occurs. It
is interesting to note that functionally equivalent systems are in development
or in use in several of the European countries and in Japan as well. The
primary reason for this is the state ownership or the significant degree of
state control of the broadcast systems. This would appear to imply that a major
institutional impediment toward adoption of this type of system in the United
States is the private ownership structure of the broadcast system."

Apparently I'm too young to realize these have been in operation before the RDS radios. Even though the technological solutions are more or less viable and have been decent alternatives in 1960s to 1970s, they now look so out-of-place from todays point of view. But the use of magnets arranged in binary patterns in road surface, together with overhead transmitters along streets sounds wonderful. Not to even talk about entering your route to the navigator via punch cards. Anybody else having an urge to listen to Kraftwerk's Autobahn?
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zsm

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Re: Grundig radio cassette deck help

PostTue Mar 06, 2012 8:36 am

Well now we know, man that's all so German tech of the sort when I was kid, cool! So I too did think that the large knob would tune AM and FM. But something must be wrong. When I twist it for AM I can hear that it tunes different frequencies, but only the left most LED is lit. In FM twisting the knob does not seem to change the tuned frequency. Maybe it thinks it is in SK mode and tuned to whatever frequency was used for that when U is depressed and U1-3 are not. Looks like I will open the cover and probe and jumper some to see what is up, yes I'm excited. Also the resistance of the radio must vary as the voltage out of the antenna control varies. It will be hard to use that for anything other than a motorized antenna. Thanks again for all the info.

Whoops forgot before. When I had that Volvo I lived in CA from 2000-2002. Back then and in that region very few stations even broadcast any radio text, and when they did, it was simply the station call sign. In Poland it was very well done. A typical use was for a station to alternate between time of day, call sign, and song name. I never was able to use the TP feature to try it out. I'm hazy but I do think the manual had an image of the radio with something like this on the screen:

Accident on A100
westbound between
E4 and E5.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS
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