RC-MJ70 Line In DIN question

[EX_m71_Owner]

My Idea is to bypassing the phono amp.
In this case, you must open the radio, drill hole for 3.5mm jack,
find 8 pin connector, with a soldering gun making electrical connections.

Ah, now I see. With your first reply I did not understand because I thought my variation was just the same as yours. But what you added in the meantime about bypassing made clear that it is absolutely not the same. You see, I am not a specialist in reading schematics. My fault was, that I thought that the way of the signal from the DIN would be the same as the way from your new 3.5 jack. The reason for my mistake was that I just did not see the DIN plug anywhere in this schematics. I think I have found it now. I actually thought that it is the location shown below before, but I thought it was not this one,because there are 6 contacts and the DIN socket has only 5. Why is that? Am I right with the location of the DIN socket? See Pic:

 

[EX_m71_Owner]

I noticed that the aux input on my C-100F uses the same op amp, but it has a switch that allows you to toggle between line-in and phono on the same RCA jacks.

Instead of just using a 10k in series for line-in, they used a voltage divider setup with a 39K in series with a 6.8K to ground, which is probably a little better. When all positions for switch S102 are toward the op amps, it's in phono mode. When they are positioned away, it connects to the resistor divider networks for line-in mode. The part values are all slightly different but accomplish the same task.

If you don't want to add another jack, you could just convert the phono to be line-in instead Or add a switch and have both

Thank you Caution , even though I do real changes in the unit, they are only inside and can not be seen (without switch). And the times when I needed to really connect to a turntable for recording are long gone. The phono line is probably not used by many people generally .

 

[goodman]

Look carefully next picture.
On the top in purple color is DIN socket.
In blue color is DIN amplifier.
Signal from DIN socket go to DIN amp and go to recording head.
You dont need to do anything here.
In green is chinch for PHONO IN.
In red is PHONO amplifier.
Signal from PHONO chinch go to PHONO amp and conected to MODE SWITCH (3 yellow lines)
My idea is bypasiing Phono amp, and conect 3.5 mm jack to this 3 yellow lines
- this is the 8 pin conector - you need pin 6, 7, 8. (see my previous picture)
When MODE switch is on PHONO position,
signal from 3.5 mm jack go direct to FINAL JVC amplifier.




picture of din and phono plate.
In red is 8 pin connector - you need pin 6, 7, 8.

 

[EX_m71_Owner]

Thank you Goodman - and Caution
I should have had a closer look at Cautions 2 pictures (or the JW manual resp), but once I had seen the pictures made by Goodman (with the external jack) I only looked at this further. So I did not see the DIN socket of course because it was not on there.

Well , you both will probably think, if I really will do that change, that will turn out in a desaster and my M70 will , because I am obviousely not that what you would call an electronic specialist. But when I will be up to it I will have an electronic pro with me. I just wanted to understand as well and by that also learn something . And you helped me a lot - THANK YOU.

I will post, when I will do it. Before I will try to clean contacts of the unit, because I have a lot of problems especially with the SOurce switch. I have to "play" with it again and again everytime I change source until I can hear correct volume and both channels. When this is done I will do start with the modification.

 

[goodman]

Thanks for the kind words. I'm glad that I helped you.
I waiting for information and photos of the modification process.

PS:
I think, that you won't use phono and din connectors,
and won't make modification on phono board.
In this case, must disconnect 8 pin jack from phono board.
This is easy way to stop 12 v to phono amp (pin 5).
This is important step!!!

Connect 3.5 mm jack with resistors to this 8 pin connector. You need pin 6, 7, 8.
I agree with member caution about resistors. 10 kohm is min. value.
Adjust of sound level depends of type music, mp3 player volume, and this resistors.
You must test first with 33 k ohm, and low volume of MP3 player.
If sound level is low you can use 20 K ohms or 10 K ohms.

 

[goodman]

Is there any progress with this mod?

 

[Dancorp]

I just bought a JVC M70L that I am waiting to receive.
I would like to integrate a Bluetooth module... so a line-in is mandatory.
Any progress / tests to share ?

Does the DIN connector have a output line too ?
PB seems to mean PlayBack, like a kind of Line Out?.

 

[goodman]

Find a 8 pin jack.
Solder violet cable to ground (7).
Cut the cables for L (8) and R (6) channels at 4-5 cm before jack.
Solder 8a to 3 (L channel).
Solder 8b to 1 (L channel).
Solder 6a to 4 (R Channel).
Solder 6b to 2 (R Channel).

PHONO IN - work as before modification.
LINE IN - use 3.5 mm jack for line in, phono input is disconnected.
BT module line out must be connect to 3.5 mm line in jack.
You need power supply to BT module too.
This is on theory.
I don't have this box to made this mod.

 

[Dancorp]

Goddamn it! You made my day !
Thanks a lot for your study
I would try that when i will receive the box.

 

[Dancorp]

Where's Wally?
https://photos.app.goo.gl/wooGZBz1Zvyfakcu1

The easiest way would be to have the M70L service manual..
Someone to share it pls ?

 

[trippy1313]

I think it's in the download section. I use to have it till my PC crashed.

 

[caution]

CN571 is hard to get at. If you don't feel like disassembling to access it, you could follow the connector wires and solder to the other ends, on the main board.

You can barely see pin 1 at the bottom end, just like the way it's oriented in the schematic image in comment #28.

 

[Dancorp]

Thanks a lot Caution, i'll try to follow the connector.
fyi, i bought the service manual, but i can't upload it to the JVC section... why ?
https://drive.google.com/open?id=1RaGlZE9AILnmJ7qKRr50hz6hxG1ohzMT

 

[trippy1313]

Thanks a lot Caution, i'll try to follow the connector.
fyi, i bought the service manual, but i can't upload it to the JVC section... why ?
https://drive.google.com/open?id=1RaGlZE9AILnmJ7qKRr50hz6hxG1ohzMT

If it's one of SuperDuper's manuals from Analog-alley, might be a copyright thing or whatever it's called.

 

[caution]

Nah it's okay, it's not from his site.
You're right though, Dancorp. There's something wrong with the upload feature, there are 21 brands to select from for manuals and only 8 of them are selectable, the rest are ghosted out.

 

[Dancorp]

By following wires from connector, i located the 2 positions on the main board. (that's close to the source switch)
i just soldered my bluetooth board on them with 16K resistors.
That works fine !

https://photos.app.goo.gl/vQulYI3Jkht6ju2f1


Maybe it wiould not be recommanded to do that without cut the connection with the phono amp ?
(sorry for my english)

 

[caution]

Look carefully at the image in comment #28. Notice how he erased the connection between 6a/6b and 8a/8b? He shows you how to cut the connection to the phono amp and run the phono amp output (6a and 6b) to one side of a switch, and the line in jack you added to the other side of the switch. 8a and 8b are the common lines, going to the function switch. They should be on the common pins of the phono/line switch.

 

[Dancorp]

Dont worry, i understoud the image and connections to select the source using a DPDT switch.
By now, I tested the easiest way to connect my Bluetooth device.
I just want to know if the switch is mandatory or not.

 

[caution]

No. Without a switch, you could get noise/ground issues if something was plugged into both inputs simultaneously, but you'll probably never do that.

 

[goodman]

I glad that my instructions is helped to you.
Please show more pic and info about BT receiver and power supply.
This info maybe it's good for someone else boombox user.