CR-4024/CR-4123: The Definitive Thread
 

Hi all,

I'm making this thread because I have a CR-4024 FM/MW/LW stereo/tape deck in the top mount position in my centre console, and, whilst I absolutely love it, there is almost no information for it online.

The goal here is for this to become a treasure trove of information on this particular stereo - usage instructions, history, where they can be found, repair information; everything is welcome.

I have included the CR-4123 as I believe this is the US-market equivalent of the CR-4024; functionally equivalent, but with a different faceplate for the LHD centre console and (likely) different tuning frequencies (citation needed). If there are other part numbers that can be considered identical or very similar, please drop me a personal message and I'll edit the relevant numbers into this post.

The only thing I will encourage people to do if they are contributing information, is to keep each individual point to a separate post. For example, instructions for setting the clock, and instructions for saving a station to memory should each be given their own post, thus making it easier to refer back to and reference in other threads.

Whilst questions and issues regarding these particular units are welcome, please can they be posted in a separate thread, and reserve this one for solutions and knowledge.

Cheers in advance,
Adam

Is There A Security Code?
 

No, there is no security code on this unit, so no need to worry when removing it for repairs, or when disconnecting the battery to carry out other work on the vehicle.

How To Set The Clock:
 

Taken from the Brickboard instructions for the CR-4123, and combined with my experience:

NOTE: A pointy object such as a pen, toothpick, paperclip, etcetera will be required to press the clock button.

1) Upon first power-on, the clock function will be disabled. Enable the clock function by pressing the 'CLOCK' button - the time should be showing (mine defaults to 23:00).
2) Press the 'MEM' button. The display should return to showing the currently tuned frequency - the ME segment, on the right, should be flashing.
3) Press the 'CLOCK' button again. The current hour should be showing.
4) Adjust the hour by rotating the tuning knob: clockwise to increment, and anticlockwise to decrement.
5) Confirm the hours setting by pressing the 'CLOCK' button - the minutes should now show.
6) Repeat step 4 above to set the minutes, and again confirm by pressing the 'CLOCK' button - the display should now show the newly-set time, and the colon separator should now be flashing.

The clock will now show by default, and the tuning frequency will only be displayed when the user selects a saved station or interacts with the tuning knob (tune-up, tune-down, or push-to-search).

The user can toggle the primary display between tuning frequency, and the clock by pressing the 'CLOCK' button. Note, however, that once the time is set, time is kept up-to-date in the background, even if the clock is not set to be the primary display (i.e. the clock function is not disabled like it was when first powered on).

How To Save A Station:
 

The process for saving a station is simple:

1) Tune to the desired frequency.
2) Press the 'MEM' button - the ME segment on the right should now be flashing.
3) Press one of the numbered buttons (1 thru 5) to allocate the current tuning frequency to that save slot.

These can be overwritten at any time following the steps above.

There are defaults at first power-on which appear to be spaced equidistantly across the frequency.

I have yet to test whether the saving of, for example, MW stations, affects previously saved LW stations, etc. This could be the functionality of the 'LO' and 'MO' buttons? I will edit this post and update it in due course once I have tested this.

Photograph Of Unit:
 

Attached is a crisp photograph of the front of the unit (albeit, not installed in the vehicle as I still have some tests to run on it).

Alternative Link: https://drive.google.com/file/d/12Ws...ew?usp=sharing

Unit Pinout:
 

The following gives a pinout of the 9-pin connector, along with a photo of the rear of the unit showing the DIN connector(s), aerial connector, grounding screw, and 9-pin connector.

For pins 1 & 5 of the 9-pin connector, I am unsure of their intended functionality, since the large square connector which connects the stereo harness to the car harness is not fully populated in my case, and all audio signals are passed through the DIN connector to the factory external amplifier.

The powered antenna output (pin 7, red wire) is labelled "not used" since my vehicle does not have a powered antenna, although the wire on the car side of my harness is still present.

In my case, grounding is achieved via a screw and washer clamping an eye-ring crimped onto a wire to the unit's chassis (which is electrically grounded). As a result, the ground pin of the 9-pin connector (pin 6, black wire) is left unpopulated.

For anyone interested, I created the pinout diagram using a free, online program called EasyEDA (not a sponsor). This software is usually used for PCB design, but the schematic editor allows for neat production of pinout diagrams too.

Alternative Links:
https://drive.google.com/file/d/1kiF...ew?usp=sharing
https://drive.google.com/file/d/1eXp...ew?usp=sharing

Removing The Top Plate:
 

The unit has two plates that can be easily removed for maintenance and inspection. The top plate gives access to the cassette holder and the reverse side of some PCBs, and is held in by two metal retaining clips located towards the front of the unit and by two cross-head screws located on the back of the unit.

To remove the top plate:

1) Remove the screws circled in the attached image.
2) Pull the top plate straight upwards, away from the unit from the back to approximately a 45° angle.
3) Pull the plate backward (from the unit's perspective to release the retaining clips located at the front of the unit. One of the clips is partially trapped by one of the tabs on the front plate, thus some wiggling may be required to release it fully. Work gently but firmly to avoid damaging the front face plate.

Alternative link: https://drive.google.com/file/d/14HC...ew?usp=sharing

Removing The Bottom Plate:
 

The unit has two plates that can be easily removed for maintenance and inspection. The bottom plate allows access to the back side of the main control board, including the main control Integrated Circuit (IC), and is held in by two metal retaining clips located towards the front of the unit, two cross-head screws located on the back of the unit and one smaller screw located on the left-hand side of the unit (when viewing right-way-up from the front).

To remove the bottom plate:

1) Remove the screws circled in the attached images.
2) Pull the bottom plate straight upwards, away from the unit from the back to approximately a 45° angle.
3) Pull the plate backward (from the unit's perspective to release the retaining clips located at the front of the unit.

Alternative Links: https://drive.google.com/file/d/1HF5...ew?usp=sharing
https://drive.google.com/file/d/1Bob...ew?usp=sharing

Another Equivalent Unit, CR-4021:
 

I have just found an eBay listing for a CR-4021 which appears to be the same unit, but with mounting for the 740/760 of the time period (the listing was for an '85 model). I would have edited post #1, but I am unable to do so now, hence this additional update.

Update - Station Memory:
 

Another update post that I intended as a simple edit to the original. This time, in response to my uncertainty on post #4 regarding saving stations into memory.

The unit appears to automatically handle allocating separate memory for each frequency band: FM, MW, LW. It also retains the last-selected station for each band as well.

This means that you can store 5 FM stations, 5 MW stations, and 5 LW stations independently. These are then accessed by pressing the relevant saved station button, whilst on the corresponding frequency band, as selected by the plastic ring behind the tuning dial.

Additionally, if you were previously listening to station 5 on MW, and then switched to FM and selected station 3, the unit would immediately switch back to playing station 5 when the frequency band was returned to the MW position. Hopefully, that makes sense.