Jump to content



Photo

M70 line in tapped on PCB, but question.....


  • This topic is locked This topic is locked
12 replies to this topic

#1 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 17 March 2015 - 08:42 PM

So I have the line in pads tapped on the pcb in my M70. The bluetooth module is working.


Apparently the RCA jacks are a 'switched' type where you have to have a physical rca plug pushed into the jack for the input to work.

Sort of like how headphone jacks work where the normal speaker signal is sent through them until a headphone is plugged in, then the sound is routed to your headphones and turns off to the speakers.

How can I bypass having to plug something into the jack?

This seems stupid easy but I'm going mental over this....

#2 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 17 March 2015 - 08:51 PM

Nevermind, I'm smart!

Thanks anyway!

#3 Superduper

Superduper
  • Boomus Fidelis
  • 6,869 posts
  • LocationSomewhere over the rainbow, USA

Posted 17 March 2015 - 09:03 PM

It just means you tapped the wrong pin.  You need to tap the location AFTER the switch.



#4 -GZ-

-GZ-
  • Members (SA)
  • 2,235 posts
  • LocationBoom Central

Posted 17 March 2015 - 09:13 PM

It just means you tapped the wrong pin.  You need to tap the location AFTER the switch.


Duh, Joe. Everyone knows that.

#5 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 17 March 2015 - 10:09 PM

When a rca plug is not in the jack, the common (-) and positive (+) pads touch in the back of the jack.


Why?

The way I see it, there is no other way to tap the jacks on the M70.

#6 trippy1313

trippy1313
  • Members (SA)
  • 1,968 posts
  • LocationSeattle-Tacoma, WA

Posted 17 March 2015 - 10:13 PM

Duh, Joe. Everyone knows that.


Haha. I was gonna ask him to explain what he did to bypass it. Oops.

#7 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 17 March 2015 - 10:22 PM

Lol u guys

#8 Superduper

Superduper
  • Boomus Fidelis
  • 6,869 posts
  • LocationSomewhere over the rainbow, USA

Posted 17 March 2015 - 11:09 PM

OK here is something for you to try:

 

Attached File  jvc_rc-m70_line-in_tap_location.jpg   54.74K   12 downloads

 

The design of shorting the (+) to ground when no rca jack is inserted is a good design because it prevents noise from entering the audio signal path when that circuit is not being used.  Low level signals are very prone to interference.  The cap and resistor isolates the circuitry on both sides.  Try tapping into the circuit at the other side of R721/R821.  Check it and report back.  A small amount of the signal will get shunted to ground but enough should pass to work.

 

 



#9 Lasonic TRC-920

Lasonic TRC-920
  • Moderators
  • 14,080 posts
  • LocationNaples, Italy

Posted 17 March 2015 - 11:54 PM

Glad you got this working Joe,

 

Is the system functioning as you hoped?



#10 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 18 March 2015 - 07:54 AM



OK here is something for you to try:

 

attachicon.gifjvc_rc-m70_line-in_tap_location.jpg

 

The design of shorting the (+) to ground when no rca jack is inserted is a good design because it prevents noise from entering the audio signal path when that circuit is not being used.  Low level signals are very prone to interference.  The cap and resistor isolates the circuitry on both sides.  Try tapping into the circuit at the other side of R721/R821.  Check it and report back.  A small amount of the signal will get shunted to ground but enough should pass to work.

 

I might try that later. For now I just bend the (-) tab away from the (+) tab at the back of the RCA jacks. I put the info in my M70 BT mod thread. I saw that there was a cap and resistor in the circuit just after the RCA jacks so I didn't want to feed signal into the system after those. Its all good right now:

 

 

Attached File  IMG_3938.JPG   76.15K   11 downloads

Attached File  IMG_3939.JPG   71.68K   6 downloads



#11 Dancorp

Dancorp
  • Members (SA)
  • 103 posts
  • LocationMarseille, France

Posted 03 May 2017 - 05:19 PM

Thanks of the tip !

I can't find your BT mod topic, is it still available ?

(I'm looking for a way to power my BT board (6v>12v))



#12 -GZ-

-GZ-
  • Members (SA)
  • 2,235 posts
  • LocationBoom Central

Posted 03 May 2017 - 09:01 PM

Duh, Joe. Everyone knows that.


Haha. I was gonna ask him to explain what he did to bypass it. Oops.
Ha. I WAS kidding....two years ago.

#13 blu_fuz

blu_fuz
  • Moderators
  • 10,503 posts
  • LocationWI

Posted 04 May 2017 - 10:55 AM

Thanks of the tip !

I can't find your BT mod topic, is it still available ?

(I'm looking for a way to power my BT board (6v>12v))

 

 

https://boomboxery.c...oth-module-mod/