[FIXED] JVC M70 - Right Speaker Whispering (Unable to cutoff)

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Dancorp

Dancorp

Member (SA)
Hi everyone,

In advance sorry for the english, i'm just a poor frenchy :)
I restore my first boombox thanks to this amazing board.
Oxeded lever buttons, power switch, source switch... most of issues have been solved.
I still got one: i'm unable to turn off right speaker, it still whispering.
I'm also unable to fine increase the volume at start. it jump with a loud sound.
Lever have been cleared many times with a french elec. contact cleaner.
It sound like a ground problem, (when a touch the lever, i got like small impulsion in the speaker) I have already check solders without success

A video of the problem :
https://www.youtube.com/watch?v=ifhhY5pOpPg


Thanks in advance for your help

Dan

EDIT : Fixed ! https://boomboxery.com/forum/index.php/topic/26480-jvc-m70-right-speaker-whispering-unable-to-cutoff/#entry349597
 
baddboybill

baddboybill

Boomus Fidelis
Dancorp said:
Thanks a lot for your help, I will try to disassemble it.
Click to expand...
Your best bet is to message Superduper. (Norm) as he restores the slider controls. ;-) not sure if hes to busy but it dont hurt to ask
 
Dancorp

Dancorp

Member (SA)
Before PM Superdumper, i have a question.
Is that possible to swith a volume slider with one used for the recording level ?
 
Superduper

Superduper

Moderator
Staff member
Dancorp said:
Is that possible to swith a volume slider with one used for the recording level ?
Click to expand...
No, not compatible. Record level pot is 50k ohm "A" curve and no center tap. Volume pot is 550k ohm, "B" curve with center tap.
 
Superduper

Superduper

Moderator
Staff member
500 vs 550 should be ok. BUT..... The pins are in wrong position, the taper is different & the shaft is not the same so you won’t be able fit the original knobs.
 
Dancorp

Dancorp

Member (SA)
i have to disassemble my M70 to get sliders sizes, pins localisation, the shaft... to check if i would be able to fit 3th party sliders on my boombox.
Of course that will be not easy to find the same shape or to fit it, but originals pots are not available anymore. this solution must be study.
 
caution

caution

Member (SA)
When I was looking for M70 sliders, I did find some that had the B curve and a center tap, but either had different dimensions or pin locations, so even in the best situation, you will have to glue the pot into position and jumper the pins, and maybe also add a riser so it still sits at the right height.

As far as I know, no other boxes used the M70's sliders, unlike the M90 pot, which Toshiba and Panasonic (and maybe others) used on many models.
 
Dancorp

Dancorp

Member (SA)
Thanks a lot for your comments guys. Finding a well sized pot with all features looks close to be impossible.
I can expand search results by removing features...
Can someone explain the purpose of the midpoint ?Is this feature mandatory or can i fit a legacy pot with jumpers?
Is the B curve mandatory too ? if i found a A curve pot, will the lever still friendly usable ?
Thanks in advance

Dan
 
caution

caution

Member (SA)
Nope. 50K.
38454971841_be74525b16_o.jpg

37568455175_cd9b81ef71_o.jpg
 
Dancorp

Dancorp

Member (SA)
You're right, I do not remember where I read 500K.
It is easier to find 50K potentiometer, it's cool.
But I have to find some who have the loudness tap.

Size : 45mm x 8mm with a 15mm shaft.
 
caution

caution

Member (SA)
Good luck finding one, nobody else has. You'd be better off finding a parts unit and scavenging from it.
 
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