Grundig Stereo and Changer Info

[therealeasterbunny]

OK chaps, there now follows a transcript / excerpts from some quality emails (about 3-4 years ago) between me and a german chap who I got the 4871 off (he's THE dude when it comes to Grundig info / use and repair) ... His English (below) is a lot better than my German ...

I think Ive changed them all but if you see "clock screw driver" it means watchmakers (or small) screwdriver
--------------------------------------------------------------------------------------------------------------------------------------------

As follows, hope its some help to someone ... :

All the old cd changer compatible models (4870 RDS C, 4871, 5500 RDS C, 3880) have the same connectors:

- ISO block A (lowest block) for the power (8 pins, 2x4), for the black plug (normally with 5 cables)
- ISO block B (middle block) for the speakers (8 pins, 2x4), for the brown plug
- ISO block C (top block) for the cd changer adapter combined with line out (10 pins, 2x5), for the red plug of the MCD-A1
- a 3,5 mm stereo socket for the sound from the MCD-A1 into the radio

The models without cd changer control (4870 RDS A) have other connectors, 4 separated speaker connectors and so on.
Only the 3,5 mm stereo socket (for the discman) is the same.

The adapter MCD-A1 (black box / midle man uinit) is complete in itself, all cables are fixed connected,
except of the 5 m cable, of which I can make use of for an MCD 20. If the 5m cable is plugged in the adapter,
it makes "click", and to release it, a button on the plug must be pressed.

I have looked in the internet for the speedometer signal (for the speed controlled volume (SCV)) in the Vauxhall Carlton

(Opel Omega):

1986-1994: only with board computer, blue cable with red stripe behind the dashboard
1994-1998: blue cable with red stripe (ISO connector, chamber 3, pin 1) (whatever chamber 3 may mean)
1999-now:  blue cable with red stripe (ISO connector, pin 5) (Danger, damages car!!! see below!)

The connectors at the backside of the Grundig radio with cd changer control, at the right edge, looks like this:

1 3 5 7 9  (cd changer and line out) (red plug, nose beside pin 1)
2 4 6 8 10

1 3 5 7   (speakers) (brown plug, nose beside pin 1 and 2, middle high)
2 4 6 8

1 3 5 7  (black plug, power, not all pins used, not normized/standardized)
2 4 6 8  (nose beside pin 2)

All the plugs have a little nose, which makes click, if the plug is plugged in. To release the plug, push the plug tight into it's position, press the nose, then pull. If you pull first and then press the nose, nothing will happen. The nose is beside pin 1 or 2 or beside the middle of pin 1 and 2.

Attention: the picture above is from the radio, so look on the cable side of the plugs, not on the side where the pins come into the plug.

The grundig radio needs the speedometer-signal (blue-red cable of the Vauxhall Carlton) in pin 1 of the power plug (lowest plug, top row, left pin).

Near the nose of the black plug, but directly beside the nose is pin 2, above pin 2 is pin 1 for the speedometer signal. So, if you get the radio, first check if there is the blue cable with red stripe at this position (pin 1).

But if the blue cable with red stripe is at pin 5 (1999 to now), do not plug it in, the radio gives +12 volts at pin 5, and if the radio is switched on, then your car may be damaged. I will give you a 1 pin cable for the ISO connector, so that you can put it in the position for pin 1 and connect it with the blue-red cable, wherever it is. If it is at pin 5, cut it before installing the radio, and isolate the end of the cable (remember: +12 Volts at pin 5 if the radio is switched on). (Also a watchmakers screwdriver can be used to get the cable out of an ISO connector and put into another position, but it need a lot of trials to get an ISO contact out of the plastic connector. So cutting and reconnecting is much more easier.)

Then check, if the radio remembers the last station, if you switch the ignition off and on, and then put the radio so far into the dashboard that it makes "click". Else change power pin 4 and 7 against each other.

P.S.
(only for pedants and experts:)
Instructions: how to get out an ISO contact out of an ISO connector with the help of a watchmakers screwdriver
The ISO conact has a nose, which prevents it from slipping out of the plastic.
The nose is not at the cable side, the nose is at the contact side.
The nose is only on one side of the contact. Therefore look back at the cable side.
The cable is crimped. The metal ends of the crimp contacts touch each other in the middle and form a little slot.
At the ohter side, not the slot side, the through side of the crimp contact, is the nose.
But remember, it is not at the cable side of the plastic, it is at the contact side of the plastic.
There a little screw driver must be put in and press the nose tight into the middle of the crimp contact.

1. push the cable tight into the plastic so that the nose gets completely free
2. while pushing the cable tight into the plastic, press the end of the watchmakers screwdriver very very very tight against the nose of the crimp contact
3. pull the cable out
4. if it does not want, push the cable back, and do step 1 and step 2 at the same time again, then pull again
5. repair the nose of the crimp contact: it should have 1 to 2 mm distance.

The following Grundig car radios are compatible with the cd changer adapter MCD-A1:

Grundig WKC 3880 (not 3870)
Grundig WKC 4870 RDS C (with dark display, not RDS A with bright display)
Grundig WKC 4871 (there is only 1 Version existing: with dark display and cd changer control)
Grundig WKC 5500 RDS C (Porsche Design, with bright display, not 5500 RDS with dark display)

Attention: The display versions of the 4870 and of the 5500 are contrary, as you can read above.

This should help you if you want to look in ebay.de or in the UK.

The 4870/4871/5500(Porsche-Design) are technical identical, except of the design:

The 4870 has the best designed left-right-button,

The 4871 has the best plastic (you do not see fingerprints on the plastic, it is always looking like a new one),

The 5500 (Porsche Design) looks also good but I do not like it, the keys are very small, the letters of the keys are not

illuminated, only a small point in each key is illuminated. The volume/bass/treble-buttons are made of thin plastic, I like the rubber ones of the 4870 and 4871 much more.

The 3880 is a newer model, with changeable display colours (by pulling the volume button, between green-yellow-orange-red),
but it a easier model.  It has a mechanical drive (but also with music search function, I think), it has not Dolby C, only Dolby B, and I think it has no connection for the speedometer for the speed controlled volume. But because it is a newer model it is often in a better condition than the other ones. And it seems to have button contacts made of metal, so the keys are reliable. I did not have the 3880, but it seems to be rather identical with the WKC 6500, but this one has a direct Mini-ISO-connection for the new CD-Changers MCD30/36/40 (cable with the blue Mini-ISO-plug).

Technical about the connectors:

The versions without changer control have DIN connectors (with 4 separated speaker connectors), the versions with changer
control have ISO connectors (for 1 black and 1 brown plug, each with two rows and 4 columns). But I think Vauxhall has ISO
connectors.

The ISO connector is only half normized. Sometimes it is needed to exchange the permanent plus with the ignition plus. If the
radio wants the code or starts at 87,5 Mhz every time you switch the ignition off and on, the radio does not remember the
station you heared before. Then you have to switch the permanent plus with the ignition plus in the ISO connector.

Attention: nearly all 4870/4871/5500, which you can get within eBay, need to be repaired / serviced in some form, even if the seller does not mention it (tape bands, radio FM board soldering etc).

Regarding the cd changer: I have the MCD 20 (three of them at the moment, but not in one car, flap with magnet catch), the
track changing time seems to be about 1.5 seconds, so it seems to be a little bit faster as the MCD10. I have not tested long
CD-Rs. But the error correction is very good, as good as the MCD 30, I have tested it with an scratched cd which I got over
eBay (thousands of scratches, seemed to have been in a child room before).


The Grundig WKC 4870 RDS C (with dark display) is compatible with CD-Changers.
The Grundig WKC 4870 RDS A (with bright display) is not compatible with CD-changers, only with Discmans...

Other technical data:

The adapter MCD A1 has a socket (13 pin female).

So for the cd changer Grundig MCD 10 you need the MCD A1 and a 13 pin cable with one plug (male) and one coupling (female
plug). You can test the MCD10 directly in the MCD A1, without any cable, but then it is not long enough to reach the boot of
the car. So I hope your blue/grey cable has a plug and a coupling.

The cable with two plugs (male) is for the Grundig MCD 20 (this has a socket, no plug). The cable has a sticker at each end
"to cd changer" and "to Adapter", but it makes no difference, which end is plugged in where, all the pins are connected 1 to
1.

[melinx]

I have not seen such a comprehensive, detailed and useful piece of information anywhere else on the internet !
This is definitely going into my Grundig file, many thanks.

[therealeasterbunny]

no probs (and thanks for the comments on behalf of my deutsch friend)

I will also publish very shortly (hopefully tonight) the WKC4871 user guide (this also has indepth info) (and given that the 4871 is technically the same as the 4870 you can also use the info to poke around the 4870  ).

Its more juicy than a jaffa... and coming soon to a forum near you

Cheers!

[melinx]

I will very much look forward to seeing the 4871 info: This sort of information is like finding a diamond amongst gravel and is what I always thought the internet should be about.
Incidentally my Diplomat was fitted with the 4870 RDS V and it developed some very odd problems.
In an attempt to get over this with a replacement, I bought a 4870 RDS C from Germany,
I find the dark display quite attractive at night but almost invisible in daylight !!
The RDS C also (as your German friend says) had problems !! and so I 'bit the bullet'
and purchased the service manual (again from German ebay)
Both you and your friend may be interested in my post in "How to" in I.C.E if you are not already aware of it !! I'm still thinking 'no, they couldn't have'

[therealeasterbunny]

How weird is that?

The doc is now ready! It was going to be a PDF but my PDF writer does not seem to like the GIF scans ...

http://www.therealeasterbunny.pwp.blueyonder.co.uk/carltons/grundig/grundig_4871_4870_v100.doc

[HMK]

Many, many thanks to Easterbunny & Melinx for this Grundig info. I know that Melinx has posted before about spare parts for the 4870 (the radio pre-set buttons, I think it was).

Had never come across the 4870 until I got one in a Carlton I bought last year & now I'm a great fan.

The big question IS.............Have you got a circuit diagram for the 4870, & if so, will you be able to post it up?

I'm an 'old time' electronics, radio & tv engineer (qualifications now well out of date including my 'distinction' grade in power amplification & fm reception). All the same, I shouldn't mind getting hold of a duff 4870 as a 'freebie' to have a mess about with - try & suss out this fm de-modulator fault that people go on about.....if I ever get time!!

Someone said the other day (it was one of you two chaps, but can't remember who without checking) that they had found that the aerial socket was found to be not connected to the board.......just a thought - it wasn't some sort of capacitive 'isolated' connection & had been made in that way? As you said though, it worked a lot better once you had 'hard wired' the connection.

I could check the one in my car, but it works so well that I'm leaving it well alone at the moment.

[melinx]

Another 'real jewel' from therealeasterbunny, I printed it out and gloated over it !!
Are we expected to master operating this highly complex set and drive ? what were they trying to do ! give us an inferiority complex or kill us !!
On a more serious note : -
The 4870 RDS C has a jack socket on the back and although it can be heard to be operating the disc changer there is no sound !! I had assumed that was because the sound input on that model was the jack socket but maybe it has worse problems than those I have already fixed ?
Incidentally, the 4870 RDS V display seems to work quite happily in the RDS C set and vice versa.
In answer to HMK I have the circuit diagrams for the RDS C there are quite a number of them in this complex set, they are large 'fold out' type and I'm afraid it is quite beyond my ability to post them on this site.
The aerial connection (or lack of one) has no sign of a missing component or even provision for one and there is no extension of the copper track which could provide a 'loose' capacitive coupling.
A pointer to the belief that it is intended for direct connection to the aerial as shown in the circuit diagram is the fact that the coupling capacitors in that area are a few picofarad high voltage types, there would be no need for high voltage types if a 'loose' proximity coupling was intended and there is also a gas discharge spark gap across the aerial input.
An old radio amateur axiom : - NEVER try to judge a receivers performance using an 'off air' signal.
Be aware that the operation of this set is based on a dedicated microprocessor and if any faults  are traced to any of the numerous chips, most of them were special to Grundig and are no longer available.

[melinx]

Further to my earlier post :- I recently purchased from German ebay, a Grundig 4871 RDS.
It turned out to have more faults than stated !! as therealeasterbunny's German friend says
"caveat emptor"
This set also has a 3.5 mm stereo socket on the back, the same as the 4870 RDS C, my original RDS V does not; consequently neither the 4871 or the 4870 RDS C variant produces any sound from the 10 disc CD system although the disc selection etc can be heard to operate correctly.
This is the modification that works if anyone has the same problem :- there are 2 screened leads going to the top ( 10 pin ) socket in the head unit cage; cut them and connect them to a 3.5 mm straight stereo jack plug.
Drill or file a hole in the cage immediately behind the jack socket in the head unit big enough to take the plug.
You will find the CD system now works perfectly.
When cutting the leads, I left enough cable on the cage socket and soldered on an in line 3.5 mm socket which allows me to swap between variants easily.
Another problem on the 4871 was that the display bulbs were burnt out !! I decided to replace these with high intensity green LED's in an attempt to improve the daylight visibility of the dark display fitted to both the 4870 c and 4871 variants.
I used 3 mm LED's ( the 5 mm will be much too big ) in the removeable display unit the 3 bulbs are in series and can be replaced by the LED's by slightly enlarging the hole in the PCB.
the PCB track must be cut and a 390 ohm resistor soldered across.
The results are a slight improvement in visibility but not as much as you may think because LED's give an intense beam rather than the diffuse light from the filament bulbs.
The whole display now lights up green which looks novel at night !! I suppose I will get used to it !!
Incidentally, the removeable display unit from the 4871 will not fit the other variants

[chrismec]

Think you lost me completely in the second paragraph
Dont do lecy's at all

[Murph]

Damn good posts though.

This is what TC is all about!

[chrismec]

Damn good posts though.

This is what TC is all about!

I'll agree with that

[dj67blue]

anyone know where i can get a new face off panel for a 4870 RDS V as my one has got serious problems?
Had to put another radio CD in as cannot stand driving without music

[HMK]

What's wrong with the one you've got?

If it's the LCD display that's going black then you'll find that most of them are like that - it's a 4870 weakness

I managed to get a nearly good one from a forum member on here to replace mine that had gone nearly all black. Once they start going, it's only a matter of time before the black creeps across the display. I wouldn't worry too much about it. Just get rid of any security code while you can still read the display & then carry on using it 'blind'

If it's the buttons, then you'll find that most of them go like that - they need cleaning internally with 'iso-propyle alcohol' to get them working again.

If it's the lighting, then it could be one of the soldered in internal lamps. They're wired in series (like christmas tree lights) so if one goes, then they ALL go out. They're a special bulb of about 4.5 volts NOT 12 volts as you might have thought. Again, don't worry about it, they're not worth trying to get repaired unless you can do the work yourself.

I love the 4870, but then, I can do the repairs needed to mine myself (so far)

[Elwood]

Lots of information here, but is there a fix for the dreadful fading problem?

[HMK]

What on earth do you mean by "the dreadful fading problem"?

Fading of the black plastic to grey in the hot sun light?? LOL

Fading of the LCD display when it goes black???

Fading of the sound?

More info required

[dj67blue]

Buttons are knackered and cant get it to work properly

[melinx]

If you reckon it's just the buttons, have a look at my post in Grundy 4870 rds.
If you fail to get a replacement and you feel you can tackle it, new nipples should fix it( if the nipples are still available )

[melinx]

Since my post below, I have checked with CPC and the nipples are no longer available.
The only place (apart from Bulgaria and similar places) offering these is a company called Domberg in Ireland who price them at 5 Euro !! Not bad for a piece of rubber 4mm diameter ?
It doesn't need many of these replacing to make a hole in your pocket.
With the integrated circuit chips in these head units also being unavailable, it is getting close to the 'just forget it' point.
I've bought two head units so far, both had faults and are only kept for spares.

[Elwood]

What on earth do you mean by "the dreadful fading problem"?

Fading of the black plastic to grey in the hot sun light?? LOL

Fading of the LCD display when it goes black???

Fading of the sound?

More info required

Fading in and out of the sound when in radio mode. Apparently a common fault with the 4870. If you don't have this problem, then you're lucky.

[dj67blue]

stripped the face plate and got it going again but now after @5 mins after initial power up (AKA plugging it up at the back) it goes into a mode where the unit tells you about itself but does not do anything else.....HELP!!

[dj67blue]

Feel like thowing the bl**dy thing in the bucket And trying to get another unit to power the disc changer

[jonnybear]

Yea the fadin you talk of, is the volume going loud then quiet, i used to have that problem but it went away for long time but me thinks its because i dont have the speed signal wire in the back of the cluster (in fact i know it aint in lol) i think its picking up signals from the dash itself could be totally rong but, i shall find out and let you know.