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Grundig radio cassette deck help

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Isola

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  • Location: Finland

Re: Grundig radio cassette deck help

PostTue Mar 06, 2012 12:49 pm

If the voltage on the power antenna prong varies with constant supply voltage, we have exactly two alternatives that make sense: either it's not the power antenna connector, or you have an oxidized fuse. I'll place my bet on the latter. Replace the fuse and clean the holder, they're almost certainly ruined by oxidation. It's quite common problem with elecrical devices that have been out of use for some years.

The same applies to the FM tuning. Looking at schematic, I'm sure the large dial should work on FM frequencies, too. The switch bank needs a good cleaning. The FM/AM selector (interlocked switches M and U) also selects the input for the led scale driver. If that switch is stuck open or oxidized, it will leave the led driver input floating. The pull-down resistor then, well, pulls the signal down, and only the leftmost led shines. This applies to both AM and FM.

Ok, so your Volvo was actually ready for that text message based service. That was new to me, even though the larger Volvos are very common here. I still think that this service is not the TP, but TMC. Yes, just that what I told I've never heard implemented in car radios, but GPS devices only. And now Wikipedia is telling me that it has been in use in Finland since.... 1998! Until 2006, it was a free service, but apparently receivers were scarce. Since then it has been a commercial service, and according to Wikipedia, the GPS device manufacturers have contracts with the operator. I'm not 100% sure if its use is tied to map updates so that it is effectively a subscription-based service, or how it is funded. My business sense strongly supports the map update scheme, but I have to check that.

The TP service is less fancy. Actually it is exactly the modern version of this cool Verkehrsrundfunk. (Please don't question my logic: in 70s German car radio it's something between cool and awesome, but in today's German car radio it's "less fancy".) Anyway, I can hear it put to work quite often. When enabled, if any TP-aware station starts delivering a TP bulletin, that station is tuned in. After the bulletin, the previous station (or CD or whatever) is resumed. The only drawback is that the service is nationwide, and temporarily non-operational ferry services on small village roads 600 km away are not that important for me. But definitely much better this way than with no bulletins at all.
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zsm

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Re: Grundig radio cassette deck help

PostTue Mar 06, 2012 4:58 pm

Thanks again! I have cleaned corrosion from things like car battery terminals and cables with metal brushes, but likely that is not the ay to do it with this radio. What do you recommend? Cotton swab? Cotton swab with rubbing alcohol?

Shoot yesterday I did some googling and I stumbled on a PDF explaining how some Volvo radios worked from Volvo trucks. But I deleted it and can't see it in the history anymore, sorry. There was a radio in there a bit like mine, only single CD instead of 3 CD. It explained some the TP feature, it was like you said scan the FM, but if you were listening to the radio then you heard silence. In mine (a C70) I had the center speaker, but if I had not I could have had the (very expensive at the time, so I would not have) GPS that popped-up there. You are probably right and I am confusing that the GPS would indicate that traffic or accident instead of the radio. My memory is not the best.
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

PostWed Mar 07, 2012 6:02 am

Cleaning corroded electronics is balancing between removing the deposits and doing more harm. I'd recommend isopropanol and dry cloth or a cotton swab for starters. A toothbrush (with said isopropanol) is also effective. They sell also little spray cans labeled Contact cleaner or something like that. These are usually not much more than isopropanol, but they are pretty convenient as you can aim the spray inside switch enclosures etc. There are also same stuff with lubricants, which is basically good for moving parts.

Avoid sanding the contacts as long as you can. Rubbing with extremely fine-grain sand paper (P1000+) is obviously effective, but it will destroy the very thin protective plating on terminals. If the part is really badly corroded it is appropriate to ask whether there's any plating left to save, but still I'd avoid sanding as long as anything else produces visible results.
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zsm

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Re: Grundig radio cassette deck help

PostThu Mar 08, 2012 7:47 am

I ran out of time to investigate yesterday, sorry. Most likely will not have time again until Friday evening. The fuse contacts looked good though, but I now know what fuse to buy and will replace it. I did not get the cover off yet, but as soon as I know more I'll respond. With your valuable advice, I'm sure it will go well though, 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

PostSat Mar 10, 2012 9:39 pm

Well I could not really figure to out. It really was not corroded at all and all the switches tested fine. I thought there might have been a loose solder joint in two spots, but close examination and testing with the multimeter showed that was not the case. Also some poking and prodding with the probes I was able to figure-out basically how the LEDs work, but nothing could get the U and M to work showing the lights what frequency was tuned. Another interesting thing was that there was the S/K switch there, there was no effect though in either position though the traces did go somewhere. The U button though is molded in such a way that it does not reach that S/K switch. There was a prominent resistor in one place also that I did not expect from the wiring diagram, but I'm not going to touch it. It's magic as far as I'm concerned.

In the end I just put the radio back together again and installed it tonight. It works great. I have the M tuned to my favorite and use the U1-3 to tune FM. Where I mounted it just above the glove box area you can't really see it too well anyway so it's not a big deal. Oh I also replaced the fuse just in case. Anyway, thank you for all your help Isola, results are fine, though I'm just too stupid to figure out those little nits regarding the freq display in M and U without using a preset it seems.
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

PostSat Mar 17, 2012 6:22 am

You're welcome. Maybe a radio is after all to be listened to and not watched, so one can do without the freq display. If it starts bugging you, it should be fairly easy to get the display working.
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