M70 Line In Problem

[Ken]

This will sound confusing, but I hope someone else has run into this before and can shed some light on my problem.

My M70 will not play in "line in" mode. When I put the function switch to that position - silence. Yet, when I put the same switch in "din" mode, AND turn my I-pod way down, AND depress "pause" & "play" - I get music.

Any ideas why I have to basically use the tape monitor function to hear my i-pod? I'm pretty sure that the din function - "line in" if you will - should be working. The function switch may be the culprit (I think) but I would like to avoid looking at that if I don't have to. The actual function switch seems to be really buried under the main circuit board.

Anyone seen this one before? It's driving me crazy.

Thanks in advance, & I'm going out for breakfast. I think I need to step back from this on for a few minutes...

 

[monchito]

kenpat unless the switch needs some cleaning which means taking the back off and trying to put some deoxit on that switch and work it to see if that would at least correct those small problems,,, its really better to do that first before just for incase thats all thats neded,, i have had other boxes that would do simular behavior and it was mostly the main funtion switch either dirty or pitted badly inside,basicly when the switch is like that it needs to be replaced but the good mayority of boxes with a good deoxit treatment is all that its needed......

 

[mellymelsr]

with Monchito. I have had 6 M70's and cleaning the function switch with de-oxit has taken care of the problem on all of them. Accessing the swith is very easy. Remove the chassis and you can spray it from the front side. You will want to toggle the switch up and down to give it a good cleaning and hopefully that will do the trick. The chassis can be removed in about 10 minutes....

 

[bolzn]

I had the same problem and it worked after i did what is described in the 2 posts before.
Im always very feared when something doesnt work, but these old devices are so resistant.

 

[Ken]

Well, cleaning the function switch didn't help a bit. Everything still works great, except for line in.

Methinks this one will stay on the shelf for a little while. I've got continuity all the way from the line in through the switch (S502,) but I don't have an o-scope to check actual signal from there on out. Oh well, future project, I guess (unless someone has any ideas.) It's not like it's my daily player and I do have a backlog of repairs and maintanence to get to...

 

[Superduper]

Check the line-muting transistor X306 (& X406? for the other channel?). This transistor mutes the line-in signal if the transistor is forward biased. Check the base voltage when function switch is set to line-in to make sure it is not forward biased. Obviously, you should make sure the transistor is not shorted as a matter of good practice, although it is doubtful that both left/right channel muting amps both failed at the same time.

Also, you say that you have continuity from line-in to the function switch S502. How did you check for continuity? With a voltmeter? Because the line-in jacks are capacitor coupled so with a DMM, you wouldn't normally read normal continuity since the capacitor blocks DC.

 

[Ken]

Looking at the schematic, I see your right as rain. I must have confused it with my current project as the M-70 has been buttoned back up for a week now. My bad.

THAT project is waiting for parts. I guess it's time to close it up and open the M-70. I don't like to leave multiple projects open at the same time. It takes up too much room and my memory obviously can't handle it.

Thank you very much.

 

[Ken]

"Houston, we have a problem..."

I just noticed that I'm using a schematic that has LINE IN PLUGS on it. It would help if I were using one that had DIN PLUG CONNECTIONS on it! I think now that I have the right schematic (for an RC M70L) I may be able to make some headway.


Oh, and if anybody ever thinks they might need a european model schematic, just let me know...

 

[chevyman-uy]

I have the same problems in the line in, plug in my cell with a din cable and not sound , press repeatedly rec / play and achievement have sound only in the right channel ,whithout bass y try to cleanned the swicht have if that solves the problem,
the line is in operation without being in the rec function? that is correct?

Any help ,thanks!

 

[chevyman-uy]

clear the rec/play swicht solve the problems ,now get sound ,but only if rec+play are press is nornal on a euro(m70-L) version? ,I'm using a mini jack / din one with 3 connections, will try to test one whit 5 as soon as possible,be if that is the solution.

 

[mmcodomino]

clear the rec/play swicht solve the problems ,now get sound ,but only if rec+play are press is nornal on a euro(m70-L) version? ,I'm using a mini jack / din one with 3 connections, will try to test one whit 5 as soon as possible,be if that is the solution.

Yup, the L-Version only plays when rec and play are pressed .
It is a little weird and I have not seen something like that before but it is true.
Put the switch on "DIN", then press rec and play and you're going. The VUs show the line-level.
It sadly is no AUX as used in a VZ2000 for example where the DIN works as a line-in plug.
Time to get a J or JW M70 OR play some mixtapes through it!

 

[Ken]

clear the rec/play swicht solve the problems ,now get sound ,but only if rec+play are press is nornal on a euro(m70-L) version? ,I'm using a mini jack / din one with 3 connections, will try to test one whit 5 as soon as possible,be if that is the solution.

Yup, the L-Version only plays when rec and play are pressed .
It is a little weird and I have not seen something like that before but it is true.
Put the switch on "DIN", then press rec and play and you're going. The VUs show the line-level.
It sadly is no AUX as used in a VZ2000 for example where the DIN works as a line-in plug.
Time to get a J or JW M70 OR play some mixtapes through it!

Are you sure, Max?

That would explain my problem also. You have to be kidding, though. I can't believe that JVC would make the din function on a box that big dependent on depressing the play/record button. :annoyed:

Oh, well. A phono/line level converter solves the problem, I guess.

 

[chevyman-uy]

Thanks mmcodomino ,for explain the correct funtion , as kenpat said, I probe with a phono / line adapter and works, not as loud as the line, but is cheap to find a "USA model
somme pics of the of work later today

 

[hollyrockets]

So, will this solution fix one channel being stronger than the other one? In other modes they are equal.

 

[chevyman-uy]

try using another cable, I change it and fix the difference in volume.
I hope it helps

 

[hollyrockets]

try using another cable, I change it and fix the difference in volume.
I hope it helps

You know, usually I would overlook the obvious, but this time I tested the cable by plugging it into the other M70 and it worked OK. Thanks for the suggestion, though.