MTCD - Swap Radio Module TDA7786 for TEF6686

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bicer79

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Jun 7, 2016
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typos1

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Apr 3, 2007
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No idea, cant see why not, but this thread and indeed this forum is specifically about MTCD/E units, you need to be aware of that and you didnt seem to be.
 
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jtrouter

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Mar 14, 2017
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Hey guys, not going to ask about switching the chip:) I have always had loder simple cars. My main driver is a 95 Jeep wrangler and i know that has a plain old basic antenna. I have a MTCE that i bought to put in a handy me down 2004 Lexus ES330 that was gifted to me when my mom died. Do you know or how would i be able to tell if it has a dual diversity antenna ? And if i understand is if it does have one of these type of antennas i will need to make sure it has power to it while the radio is running? Thanks you for reading and will be looking for replies.
 

typos1

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Look and see if it has 2 antenna leads, power is needed if it has a phantom power supply to the antenna, not if its diversity.
 

jojidlo

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Jun 8, 2020
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Hi all.

After a long time I would like to add my experience with replacing those two tuners. Unfortunately in my case, it didn't work. I replaced original 7786 by 6686, but radio was not able to find any radio stations. To be more precisely, car radio didn't do anything in radio mode. Looks like, that it was not able to communicate with new tuner 6686. So I decided to replace tuner back to original and after that, everything worked again.

So I don't recommend this replacing.
 
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jtrouter

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Mar 14, 2017
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Look and see if it has 2 antenna leads, power is needed if it has a phantom power supply to the antenna, not if its diversity.
You mean 2 as is the center wire and ground lead as in coax cable or 2 pairs of wires as in 4 conductors? I am not sure as I have not removed the old one yet but I want to be sure I am ready for anything before I remove the old head unit.
 

typos1

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Apr 3, 2007
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No I mean 2 as in 2 antenna leads - diversity means 2 antenna leads (pretty certain theres no such thing as "dual diversity" as that would mean 4 antenna leads !).

Phantom power is different to diversity it just means a power supply is fed through the antenna lead, no way of telling by looking at it.
 
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amnesia106

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Feb 27, 2021
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Hi guys, I roll up the thread. I have a Android head unit called TS-4G and drive an Opel insignia. I replace the original radio with the Android one, but the radio signal is worst. Dump sound, no signal, no AF. I put a amplifier between the radio and my two car antennas, connected over fakra connectors. The amplifier is powered up with 12v (phantom) with amp I have very low signal, without nothing, so I decided to put my Orginal Radio back in. Now i look why is the signal so bad. I opened the Android head unit and check the reciever. There is a 7786AF-6 build in. Now is the question, replace it with a 6686 or not... ?! Or, how can i improve the signal strength.
6D47AFF2-E4C6-4064-88AC-4735B908E497.jpeg
 
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marchnz

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Nov 26, 2012
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Hi guys, I roll up the thread. I have a Android head unit called TS-4G and drive an Opel insignia. I replace the original radio with the Android one, but the radio signal is worst. Dump sound, no signal, no AF. I put a amplifier between the radio and my two car antennas, connected over fakra connectors. The amplifier is powered up with 12v (phantom) with amp I have very low signal, without nothing, so I decided to put my Orginal Radio back in. Now i look why is the signal so bad. I opened the Android head unit and check the reciever. There is a 7786AF-6 build in. Now is the question, replace it with a 6686 or not... ?! Or, how can i improve the signal strength.View attachment 5234991

Is it an MTCD? The radio module might be similar or use same tuner, but this thread discusses MTCD/E head units.
 

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    Update 27/07 - did not improve the radio enough to recommend this modification/change.

    Apparently the TEF6686 module has better performance than the TDA7786 - e.g. 7786 poor sensitivity, selectivity, multipath issues etc. My JY TDA7768 is terrible, even with an RF amp, so to find out if the TEF is any better, thought I would try and investigated swapping tuner modules. Reviewing the GS board I have as a spare part against my JY, I identified the modules are pin-for-pin compatible.

    Sucessfully swapped the Radio module from a donor GS board containing a TEF6686 Module into my JY board originally containing a TDA7786. The GS board was quite difficult to unsolder the module, perhaps due to leadfree solder, fortunately the JY board was easy, the desolder wick readily desoldering the module.

    As for results, I have bench tested and RDS, tuning, audio etc is OK, I am yet to test in the vehicle. Will update this thread with results.

    See attached images. Note that the JY case had additional mounts that over time might short out against the non-ground PCB tracks, resulting in complete failure of the unit!

    Welcoming any questions.
    2
    Hi all.

    After a long time I would like to add my experience with replacing those two tuners. Unfortunately in my case, it didn't work. I replaced original 7786 by 6686, but radio was not able to find any radio stations. To be more precisely, car radio didn't do anything in radio mode. Looks like, that it was not able to communicate with new tuner 6686. So I decided to replace tuner back to original and after that, everything worked again.

    So I don't recommend this replacing.
    2
    Schematic for TEF6686 TDQ230V86&TDQ230V186 from aliexpress.

    http://dox.bg/files/dw?a=d233a435d4

    I hope it is cross compatible with TDA7786.
    Appropriate match up is needed I guess.
    It would be great if someone who is familiar with electronics could confirm that and give the pin match up schematic.

    PIN description (google translation from chineese...)
    (1) Antenna ANT, no external device, antenna seat and TUNER 1PIN, with 0.25mm line width signal line, the safety distance of 0.25mm to GND shielding. Signal line from the bottom BOTTOM layer, go to high frequency The first foot. (TOP layer interference and more.) Otherwise, EMC S1 (anti-jamming capability) problems, practical sensitivity is poor.
    (2) tuner RF_GND and GND and TUNER CASE between a piece of ground GND, EMC effect is good.
    (3) tuner TUNER, the best power supply regulator IC 5V.
    (4) TUNER L / R output de-emphasis circuit de_emphasis, improve signal to noise ratio S / N.
    (5) 3PIN 6PIN: NC and INTB are connected to the MCU I / O port to reset and interrupt the read status data. Easy to switch directly TDA7703 TDA7706M TDA7786.
    (6) (I) SDA (II) SCL PIN on the need to series 101 ~ 102 resistor, for MCU and TEF668X IC in the data transmission, if the MCU (3.3V and 5V) and TEF668X IC directly connected to the data transmission and reception due to Isolation resistance, data transmission error! SET external requirements to take two 472 pull-up resistor, pull-up resistor connected to 5V.
    2
    Are they MTCD/E head units ?
    1
    Next week this module come to me , so in the next weekend I have time to swap.

    https://www.aliexpress.com/store/pr...32809641460.html?spm=2114.12010612.0.0.y1ZYeS

    That's great, don't forget these are not pin-pin identical and will have to figure out swapping pins. Search for the manufacturer PDF and check against the mtcd schematic. I'll upload the module PDF later today.