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Problem with Grundig radio Aux input


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Having a bit of a problem with the radio in my car, a Grundig MS201 which I believe is the factory fitted one.   I've been using the aux input to play music from an iPod since I had the car, which most of the time has worked perfectly.  Twice now though, the radio has decided when switched on that it no longer works and just displays the following:

 

qho1LF4.jpg

 

The first time this happened, it was "fixed" when I next disconnected the battery.  I don't particularly want to have to do that regularly just to fix the radio though, so I'm hoping there is a better fix!  

 

From the display shown in the photo, you can then change to the radio and it will play music.  It will not, however, let you change back to aux - the button does nothing.  

 

Some more information which might be useful:

  • I often use a USB charger through the cigarette lighter socket, and I think both times when the radio did this I had been using the charger when I last switched it off
  • The aux connector pinout is: 
  1. Pin 19: Left
  2. Pin 20: Right
  3. Pin 18: GND
  4. Pin 13 <-> Pin 15 bridged
  • A service manual for the radio, which contains the pinout on the rear connectors, can be found here

Thanks!

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First let's review how an external device can be connected and operated.

 

Connection

On MS 201 you can connect another CD player using the adapter Grundig CDP. Maximum input voltage can not exceed 2 Vrms.

Operation

Press repeatedly the button CD/TAPE briefly until "AUX" is displayed.

During traffic reports CD playback is interrupted. Traffic announcements can be interrupted by pressing briefly the button TP.

 

By the look of it, you don't have the CDP adapter. Is that right?

If yes, then somebody tried to 'emulate' it by bridging pins 13,15, thus shorting the CD-BUS input to ground. Unfortunately the microprocessor inside is not too happy with that arrangement. I see there is another unused input (CD-ON/OFF) that might need to play a role too as part of the emulation. It is possible that without proper input adaptation the microprocessor enters an uncertainty state and locks in. Another possibility is that local RDS (Radio Data System) signals cut the CD playback and again throw the microprocessor into a lock state. You may get out of it simply by pressing TP button. Or not.

 

HTH for now.

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Instead of spending a lot of time an effort trying to get someone's botched effort to get 2000's tech to work with 1980's, you can replace the headunit with something more up-to-date and more suited to the task, and do it in a fraction of the time. For example........

 

http://www.ebay.co.uk/itm/Car-Stereo-Headunit-In-Dash-Bluetooth-Radio-Player-MP3-USB-SD-AUX-FM-iPod-Non-CD-/171842452653?hash=item28029bbcad:g:JNIAAOSwjVVVkmSQ

 

Job done in less than 15 minutes. ;)

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First let's review how an external device can be connected and operated.

 

Connection

On MS 201 you can connect another CD player using the adapter Grundig CDP. Maximum input voltage can not exceed 2 Vrms.

Operation

Press repeatedly the button CD/TAPE briefly until "AUX" is displayed.

During traffic reports CD playback is interrupted. Traffic announcements can be interrupted by pressing briefly the button TP.

 

By the look of it, you don't have the CDP adapter. Is that right?

If yes, then somebody tried to 'emulate' it by bridging pins 13,15, thus shorting the CD-BUS input to ground. Unfortunately the microprocessor inside is not too happy with that arrangement. I see there is another unused input (CD-ON/OFF) that might need to play a role too as part of the emulation. It is possible that without proper input adaptation the microprocessor enters an uncertainty state and locks in. Another possibility is that local RDS (Radio Data System) signals cut the CD playback and again throw the microprocessor into a lock state. You may get out of it simply by pressing TP button. Or not.

 

HTH for now.

 

I don't have a special adapter, no.  After some googling, I bought one of these, having found someone here who made the same cable for their radio.  Although theirs is a different model, the pinout was the same as the one in the manual that I found for mine so I thought it was worth a try.  This was back in August, so it has worked fairly well for a cheap ebay fix.  I'll have a bit more of a play around with the buttons and see what happens.  It's a shame that it isn't possible to access the connectors easily when the radio is in place; pulling it out will probably make the problem go away as it will disconnect the power but I'll be no closer to understanding what's actually going on.

 

 

Instead of spending a lot of time an effort trying to get someone's botched effort to get 2000's tech to work with 1980's, you can replace the headunit with something more up-to-date and more suited to the task, and do it in a fraction of the time. For example........

 

http://www.ebay.co.uk/itm/Car-Stereo-Headunit-In-Dash-Bluetooth-Radio-Player-MP3-USB-SD-AUX-FM-iPod-Non-CD-/171842452653?hash=item28029bbcad:g:JNIAAOSwjVVVkmSQ

 

Job done in less than 15 minutes. ;)

 

Yeah, I could try to find a replacement stereo that fits in the dash, but as the one that's there does actually have an aux output I didn't see any reason to replace it at the time.  I'm also a bit sceptical as to the quality of the unit you linked, I can't imagine you get much for £15.  Do you own one of these? 

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Yeah, I could try to find a replacement stereo that fits in the dash, but as the one that's there does actually have an aux output I didn't see any reason to replace it at the time.  I'm also a bit sceptical as to the quality of the unit you linked, I can't imagine you get much for £15.  Do you own one of these? 

 

The headunit I've got cost me £40, but I was looking for something a bit more specific (3 pairs of outputs), and I still use CDs from time to time. The unit listed doesn't have a CD-drive, I assumed that wasn't a problem as yours is a tape-player.

 

In terms of quality: are you talking build or sound? To be fair, if your talking sound, you need to replace the speakers first.....they're probably nigh-on 20 years old, about 8watt and made of paper......I'd be surprised if the cones are still intact.

 

For £15, you're getting an amplifier a couple of codecs (MP3, WMA etc) and a card-reader (saves cables hanging out the front ;) ) There are more expensive ones out there, but more money doesn't mean better quality. (in either build or sound)

 

Looks like the headunit has been out once or twice in it's lifetime - check nothing has been crushed as it was put back in.

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The headunit I've got cost me £40, but I was looking for something a bit more specific (3 pairs of outputs), and I still use CDs from time to time. The unit listed doesn't have a CD-drive, I assumed that wasn't a problem as yours is a tape-player.

 

In terms of quality: are you talking build or sound? To be fair, if your talking sound, you need to replace the speakers first.....they're probably nigh-on 20 years old, about 8watt and made of paper......I'd be surprised if the cones are still intact.

 

For £15, you're getting an amplifier a couple of codecs (MP3, WMA etc) and a card-reader (saves cables hanging out the front ;) ) There are more expensive ones out there, but more money doesn't mean better quality. (in either build or sound)

 

Looks like the headunit has been out once or twice in it's lifetime - check nothing has been crushed as it was put back in.

 

Oh yeah, I know that the speakers in the car are "poor" haha,  I would like to replace them at some point I think!  In this case I was thinking mainly in terms of build quality, a car is quite a harsh environment for equipment to operate in which is why I'm a bit wary of something cheaper failing.  

 

I've had the headunit out a couple of times (though the dash was already scuffed up like that before I did anything), and I was quite careful not to trap wires when I put it back so I don't think it's that.  

 

You're right in that I don't use tapes, or CD's in the car, just an iPod and occasionally the radio, so perhaps it is time to upgrade the car's soundsystem...

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If memory serves, the front speakers are 14cm ones. No idea on the rears as I had a Fun truck, so I ended up cutting holes in the rear panels and installing some bigger ones back there. ;) ;)

 

If you pop over to the ICE section on here, there are some exceptionally knowledgable people with regards to upgrading "the old stuff", and would be able to point you in the right sort of direction for upgradeing, even on a budget. :) :)

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No luck playing with the radio, it seems to have completely forgotten that it even has an aux setting.  :/

 

If memory serves, the front speakers are 14cm ones. No idea on the rears as I had a Fun truck, so I ended up cutting holes in the rear panels and installing some bigger ones back there. ;) ;)

 

If you pop over to the ICE section on here, there are some exceptionally knowledgable people with regards to upgrading "the old stuff", and would be able to point you in the right sort of direction for upgradeing, even on a budget. :) :)

 

Thanks for the info! No rear speakers on my car :( it does have wiring as far as the side pillars for these I believe though, so there is the potential for some if I could find a suitable fitting position.  From brief reading, it seems that the front speakers are super easy to replace, sorely tempted to upgrade things now!

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Thanks for the info! No rear speakers on my car :( it does have wiring as far as the side pillars for these I believe though, so there is the potential for some if I could find a suitable fitting position.  From brief reading, it seems that the front speakers are super easy to replace, sorely tempted to upgrade things now!

 

"Super easy" is a good description......pop the cover (no need to remove door-card, speakers are actually attached to it), remove 4 screws, unplug old one, plug in new one (adjust bucket connectors as needed), put the 4 screws back, pop the cover back on.

 

If memory serves, the wiring for the rear speakers plugs into a connector just in front of the front door, behind a panel. If you give Uma a shout, he could well have the right cables for the job. (I suspect there's actually a spare Felicia or two in his shed ;) ) I don't know where the "factory fit" position for the rears is, or it they were round or oval speakers.......if the parcel-shelf is up to it, that's a good place to put some serious noise-makers of your own choice ;) ;)

(Oh and the boot is a good place for a sub-woofer too)

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areed

In terms of keeping the car original, your car has a distinctive quality. The German radio you have is very reliable compared to present headunits. And less flashy as well. Of course you could go on the same overbeaten path and join the club of those who stabbed the parcell shelf and carry a box in the boot. In my opinion a Skoda Felicia is very far from being a Hi-Fi audio environment and a dance club. It is a mean of transportation and for the short time you spend in it, listening your favourite music at decent volume is more than enough. Moreover, you don't want to drive without having an audio feedback from the traffic. It is as dangerous as crosswalking the road with headphones on. Just my 2 cents.

 

PS

I know it is very easy to fall for today's marketing but I am sure you will not add value to your car buying a new headunit which, if you think more, you don't need. I know the inside of 'modern' headunits and they don't compare to the quality reliability of an original car system. People pay big money today for original headunits and untouched parcell shelves. I wonder why...

Edited by RicardoM
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"Super easy" is a good description......pop the cover (no need to remove door-card, speakers are actually attached to it), remove 4 screws, unplug old one, plug in new one (adjust bucket connectors as needed), put the 4 screws back, pop the cover back on.

 

If memory serves, the wiring for the rear speakers plugs into a connector just in front of the front door, behind a panel. If you give Uma a shout, he could well have the right cables for the job. (I suspect there's actually a spare Felicia or two in his shed ;) ) I don't know where the "factory fit" position for the rears is, or it they were round or oval speakers.......if the parcel-shelf is up to it, that's a good place to put some serious noise-makers of your own choice ;) ;)

(Oh and the boot is a good place for a sub-woofer too)

 

Parcel shelf is a no-go as I remove it fairly often for transporting things, and the boot is full of my car jack and stands unfortunately! I've seen an estate Felicia with rear oval speakers in a breakers yard, but the place where they were fitted doesn't really exist in my hatchback.

 

 

areed

In terms of keeping the car original, your car has a distinctive quality. The German radio you have is very reliable compared to present headunits. And less flashy as well. Of course you could go on the same overbeaten path and join the club of those who stabbed the parcell shelf and carry a box in the boot. In my opinion a Skoda Felicia is very far from being a Hi-Fi audio environment and a dance club. It is a mean of transportation and for the short time you spend in it, listening your favourite music at decent volume is more than enough. Moreover, you don't want to drive without having an audio feedback from the traffic. It is as dangerous as crosswalking the road with headphones on. Just my 2 cents.

 

PS

I know it is very easy to fall for today's marketing but I am sure you will not add value to your car buying a new headunit which, if you think more, you don't need. I know the inside of 'modern' headunits and they don't compare to the quality reliability of an original car system. People pay big money today for original headunits and untouched parcell shelves. I wonder why...

 

Don't worry, I'm definitely not looking to install some crazy window-shaking hi-fi setup!  I like being able to hear the car itself so that I can keep an ear out for unexpected noises haha.  Almost all of the driving I do is long journeys though, so it is very nice to have some music on while I travel.  I would rather keep the original head unit if I can figure out how to get the aux working again, I do have a few ideas to try before I give up on that though.  Changing the front speakers to improve the sound quality is very tempting, but may not be worth the money

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Very reasonable thinking, Andy. I will look in the mean time more in depth at the guts of MS201 to see what is going on with those extra inputs. MS201 had been used by default with a proprietary CD changer unit connected to those inputs (CD-BUS, CD ON-OFF, A+, etc.) In its absence those inputs have to be connected in such way the microprocessor doesn't 'search' for the CD changer and happily allows using the amplifier with an auxiliary source of signal. I hope this make sense.

 

By the way, the information I gave you about MS201 comes from the user guide (in Czech).

Tell me, when you press repeatedly the button CD/TAPE, does "AUX" come on to display?

Does the bridge between pins 13-15 look like a jumper from factory? Or is it just a wire that flaps in the breeze and could make random contact?

 

GycNFVW.jpg

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I've looked over schematics in more depth and all is clear now.

CD-BUS is not a bidirectional data bus as I tought initially but a data input used to get status data from the CD changer. Connecting CD-BUS to ground is enough to tell the u-processor "there is no CD changer installed, accept auxiliary signal source".

CD-ON/OFF is an output used to turn on the CD changer.

A+ is an output to feed +12V to CD changer.

The Grundig CDP adapter is doing exactly what your DIY auxiliary input jack does, except it looks better and has a plug that fits the back ISO socket and shorts pins 13-15.

 

In conclusion, the setup is correct (I know, you'll say 'duh... that thing worked, I know that'). But I had to check. If you get AUX displayed, all it's fine.

 

Now, about the CHECK message. I see the following possibilities:

  1. the bridge between pins 13-15 doesn't make good contact and the uprocessor asks to check the CD changer
  2. the wires that supply power and ground to MS201 don't make good contact
  3. a voltage spike in the vicinity of MS201 throws the uprocessor into a locked state (maybe asking for unlock code?) that needs a reset

Do you have the unlocking code or was it bypassed by previous owner?

Edited by RicardoM
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I have one off them radios in the shed doing nothing I orso have a 401 model and you could mount some rear spekers in the rear doors near the seats I am breaking a felicia if you fancy a road trip you can have some spare door cards the front speakers are 13cm and rear wires are in kick panels

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Very reasonable thinking, Andy. I will look in the mean time more in depth at the guts of MS201 to see what is going on with those extra inputs. MS201 had been used by default with a proprietary CD changer unit connected to those inputs (CD-BUS, CD ON-OFF, A+, etc.) In its absence those inputs have to be connected in such way the microprocessor doesn't 'search' for the CD changer and happily allows using the amplifier with an auxiliary source of signal. I hope this make sense.

 

By the way, the information I gave you about MS201 comes from the user guide (in Czech).

Tell me, when you press repeatedly the button CD/TAPE, does "AUX" come on to display?

Does the bridge between pins 13-15 look like a jumper from factory? Or is it just a wire that flaps in the breeze and could make random contact?

 

I've got the English user guide, so this page looks familiar.  Pressing the CD/TAPE button does nothing unless you press and hold, which gives you the EXPERT settings menu.  I bought the 8-pin connector, the wire jumper is a loop from one pin to the other on the back of the plug, which is insulated so shouldn't be able to short to anything else.

 

I've looked over schematics in more depth and all is clear now.

CD-BUS is not a bidirectional data bus as I tought initially but a data input used to get status data from the CD changer. Connecting CD-BUS to ground is enough to tell the u-processor "there is no CD changer installed, accept auxiliary signal source".

CD-ON/OFF is an output used to turn on the CD changer.

A+ is an output to feed +12V to CD changer.

The Grundig CDP adapter is doing exactly what your DIY auxiliary input jack does, except it looks better and has a plug that fits the back ISO socket and shorts pins 13-15.

 

In conclusion, the setup is correct (I know, you'll say 'duh... that thing worked, I know that'). But I had to check. If you get AUX displayed, all it's fine.

 

Now, about the CHECK message. I see the following possibilities:

  1. the bridge between pins 13-15 doesn't make good contact and the uprocessor asks to check the CD changer
  2. the wires that supply power and ground to MS201 don't make good contact
  3. a voltage spike in the vicinity of MS201 throws the uprocessor into a locked state (maybe asking for unlock code?) that needs a reset

Do you have the unlocking code or was it bypassed by previous owner?

 

Thanks for doing all this research!  I think I have the unlock code, but from checking the EXPERT settings the code protection is deactivated.  The connector is a proper 8-pin ISO one so I think that the connections are solid, though I will check this with a multimeter when I pull out the radio.  I suspect it is something like your #3 possibility, in that the radio has been upset by variations in the supply voltage and has decided to ignore the Aux input.

 

I am going to try and replicate this with the radio pulled out this weekend, and see if I can get it to accept the Aux connection again by unplugging and re-plugging the connector.  

 

 

On the other hand, if the tape-player still works, one of these should do the job......

 

http://www.ebay.co.uk/itm/NEW-CAR-AUDIO-TAPE-CASSETTE-ADAPTER-IPHONE-IPOD-MP3-CD-RADIO-NANO-3-5mm-JACK-AUX-/141870222350

 

Yep, one of those would work.  I used an FM transmitter with my iPod yesterday to play music over the radio, which kind of worked but was less than ideal.

 

 

I have one off them radios in the shed doing nothing I orso have a 401 model and you could mount some rear spekers in the rear doors near the seats I am breaking a felicia if you fancy a road trip you can have some spare door cards the front speakers are 13cm and rear wires are in kick panels

 

Spare door cards would definitely be a good idea if I went ahead with fitting rear speakers, thanks for the offer!  I see you're in Bedfordshire which isn't too far from me, I'll have a think about it :) 

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I've got the English user guide, so this page looks familiar.

Please share it.

 

I am going to try and replicate this with the radio pulled out this weekend, and see if I can get it to accept the Aux connection again by unplugging and re-plugging the connector. 

Excellent idea. See if you can 'upset' the unit by plugging / unplugging an electrical load around it. A voltage / current spike might be too much for the radio. Most important, you need to make the display show AUX. What happens if you remove the bridge?

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Please share it.

 

Sure!  I'll scan it when I next have time at work :)

 

Excellent idea. See if you can 'upset' the unit by plugging / unplugging an electrical load around it. A voltage / current spike might be too much for the radio. Most important, you need to make the display show AUX. What happens if you remove the bridge?

 

That's the plan.  Unfortunately I can't try just removing the bridge, due to the design of the cage around the radio and the 8-pin connector.  The radio needs to be out of the cage for me to unplug the aux adapter.  If I can recreate the symptoms once I have pulled the radio, I will definitely try this though.

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On the fuse box there's a plug a green one right hand side on top 3 wires red yellow brown that's the power to the radio unplug that and try if your in really good need off this being fixed I can give the spare unit I have

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Some news:  I managed to recreate the issue today!  I tried a variety of things, turning the radio on and off with and without the USB charger/lights etc., all with no luck.  What finally did trip the radio up was the following:

 

Drive for ~8 miles with the radio and USB charger in use, so that everything is warmed up.  Turn off the engine with the charger and radio still on, then turn off the radio and unplug the charger.  On turning the the radio back on, it displays the CHECK message and the Aux input no longer works.  

 

Fortunately, just unplugging/replugging the aux connector on the back of the radio fixes the problem.  As the connector cannot be removed with the radio in the dash, I will fit a small switch in series with the jumper on the back of the connector.  This should let me reset the aux connection if it freaks out again, without having to pull the radio, disconnect the battery or remove fuses.

 

On the fuse box there's a plug a green one right hand side on top 3 wires red yellow brown that's the power to the radio unplug that and try if your in really good need off this being fixed I can give the spare unit I have

 

Ah that's useful to know, thanks! Thanks also for the offer, I don't think that this radio is actually broken though, so I will stick with it for now.

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Drive for ~8 miles with the radio and USB charger in use, so that everything is warmed up.  Turn off the engine with the charger and radio still on, then turn off the radio and unplug the charger.  On turning the the radio back on, it displays the CHECK message and the Aux input no longer works..

Hats off for your determination in finding the root of the problem.

New finding: AUX message is displayed only when a CD changer / CD player is present. Otherwise the unit doesn't react to CD/TAPE button. So you're good with that.

Now let me ask you this: if you do the same maneuvers to replicate the fault but with everything cold, will the unit display the CHECK message too?

 

All I'm thinking now is that being an old radio, some electrolytic capacitors dried and have a lower capacity and a higher ESR (Equivalent Series Resistance). I'm talking about some filtering capacitors for main voltage and 5V reference voltage. Heat worsens things and voltage / current spikes could trigger a CHECK (error) message.

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Hats off for your determination in finding the root of the problem.

New finding: AUX message is displayed only when a CD changer / CD player is present. Otherwise the unit doesn't react to CD/TAPE button. So you're good with that.

Now let me ask you this: if you do the same maneuvers to replicate the fault but with everything cold, will the unit display the CHECK message too?

 

All I'm thinking now is that being an old radio, some electrolytic capacitors dried and have a lower capacity and a higher ESR (Equivalent Series Resistance). I'm talking about some filtering capacitors for main voltage and 5V reference voltage. Heat worsens things and voltage / current spikes could trigger a CHECK (error) message.

 

I tried the same procedure ~2 miles into the journey, when I stopped for petrol, and it didn't fall over.  The engine was about up to temperature at that point though, so no I haven't tried that exact procedure with everything stone cold.  Simply turning the radio off with the charger plugged in (and the engine off) didn't make the error appear either.

 

What you say about it being an old radio sounds reasonable.  I've fitted a small switch behind it now, in the pin 13-15 jumper, so that if the error appears I can "reset" the aux connection easily which is good enough for me.  Cheaper and easier than swapping out the whole head unit, too. :)

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  • 4 weeks later...

Please don't forget about it.

 

I'm hoping to get it scanned tomorrow :)  

 

I have a quick unrelated question:  Where would you place axle stands when jacking up the rear of the car?  On the front I use the wishbone mounts, but the rear suspension fittings are different and I don't think it would work in the same way.

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