JVC m-70 help

[majestic]

The patient.......JVC M-70..

The problem....As sold the left channel did not play but if, as the seller stated "if the wire is wiggled then it plays but when the cover is put back on it wont stay"...

Well upon initial inspection, Aside from three missing screw... .....I found that the right channel did not play...

Off comes the back housing and I start by checking the connections to the speakers.... ..There hooked up...Damn thought it would be an easy one.....Ok. Some trial and error. The control were scratchy as heck , so much that if you breathed the volume was lost.

I removed the 4 pin connector and moved the right channel over to the left channel and the right speaker played fine.
Reinstalled all the connectors to the correct place. Next I tried to remove the large board that contains the main speaker connectors and I could not figure it out....I moved on.....

Next I figured I would check the VU meters and the respond to volume controls on both channels......I plugged in my head phones and both channels play fine........ ...Ahh I at least know the sliders and board up to that point was fine....I moved on.....

Now, for some reason there were two slim pieces of wood squeezed between the headphone jack and black surrounding cover..... ...Ahhh We have here some homebrew engineering ...

Ok. Now after I removed the two pieces of wood the channel is not so touchy.....It's smooth as you increase the volume....But I still do not have any right channel operation. If I wiggle the jack its causes static but still no right channel...

Any ideas. what is the magic to remove the PCB so that I can look directly at the headphone jack...

All help will be greatly appreciated...... ...

My fixer upper is here and everything is there with the exception of the screws that I hope someone can help me with.....
And everyone was right....This thing is built like a tank indeed...

C'mon you know you like a challenge.......

 

[majestic]

...No takers.....maybe after the first morning cup of java...

I'm off to work and wont be back on the box till later tonight.

 

[floyd]

i know the m70's are notorious for bad volume sliders ,they tend to wear out with use , you could try some deoxit spray in the slider controls for starters ,if that doesnt help check the amp ic chips and look for bad or cold solider joints throughout the pc boards ,also spray the function switch as well.

 

[Superduper]

The M70 is one of the more trickier boxes to free from the case. It's not hard, rather it has screws secured at some rather obscure locations. Check your PM. I've sent you something that should help you.

 

[majestic]

The M70 is one of the more trickier boxes to free from the case. It's not hard, rather it has screws secured at some rather obscure locations. Check your PM. I've sent you something that should help you.

Got it....Thanks

 

[majestic]

Thanks Guys for the help....

After I removed the chassis I found that I could not get a clear look at the headphone jack I reinstalled the chassis and continued with the wiggle test.

I found that from all the wiggling that It indeed had developed cracks on the solder points on the headphone jack. At first they were not noticeable, but the cracks got wider from the wiggling. When I bridged the circuit with my screw driver the right channel came alive....YES.!!! I soldered the right and left channel as I noticed fine cracks on the left channel starting as well....

So basically all the joint's from the PCB to the headphone jacks received new tinning and now both channels play without scratches or cut out's..........Floyd your suggestion on the cold solder was spot on............ .........

Super the pics are clearer than found and will help me identify the correct reassembly when I get a chance to clean it.....Thanks

Now to clean it.......

What the best cleaner for the PCB in terms of foreign liquid causing the dreaded white powder to form.....?????? I noticed this thing had coke and other nasties in it.........