JVC M70JW Restore

[DJACKSO9]

Hello! I am new to the vintage boombox scene and yesterday I picked up this JVC M70JW off of Marketplace for a pretty good price. I took it apart and cleaned it a bit, and now I have a few questions. I want to make it look as close to the original as possible. Attached are photos for reference. Thanks!

1. Were the slide and buttons on the top originally red or was this something someone did after? I googled pictures and did not see any other ones that have red buttons.
2. What is the best thing to use to clean this grime off the top without taking off the silver paint?
3. The speaker on the right pops when I slide the slider and the speaker on the left will not change volume when the slider is moved. I have read up a little and saw that these are known to have slider issues. Is that most likely what the issue is and what's the best way to troubleshoot that?

 

[riker1068]

This will help. You'll learn a bit more as you read. Good luck... https://www.boomboxery.com/forum/search/32055/?q=M70&o=date

 

[Transistorized]

That red paint is certainly something that someone did as none came that way. You want to avoid a solvent. Maybe 70 ISO and a q-tip but nothing like nail polish remover, etc.

Also, you are correct. The Alps sliders are well known for failing over the years. Usually it's the Bass/Treble that fail on a single channel but, all of them can fail at any time. The tiny fingers were placed onto a plastic nylon sliding block inside the control. The plastic block had tiny nipples that the sliding contact feelers slid down onto during manufacture. Then they melted the plastic stub over the base of the contact to hold the feelers in place. Over time, the plastic becomes brittle and also is subject to shrinking. This causes the melted stub to crack and fail at which point the contact feeler disconnects and falls off causing the failure. Unfortunately, they can become damaged/broken if the control is operated too much after the failure. Sometimes, they simply fall out or come up missing. The only way to know is to disassemble and check them.

I have provided a photo to show what these look like inside for reference. You can see where I have used a tiny amount of clear epoxy at the base to hold the "fingers" onto the block. Those oval looking white circles in the middle are the two stubs that were melted to hold the finger in place and are what eventually fails. The photo makes everything look much larger than it really is. Once glued, it should last the rest of the radios life....or mine. Sometimes the conductive carbon coating can crack on the back of the potentiometer where the rivets are located causing a loss of a channel output. In these cases, a conductive paint can be used to restore the connection. This can be checked with a muti-meter.

I am not an expert with this type of stuff. I get lucky sometimes though. TBH, this repair was way outside my wheelhouse, but nonetheless was a successful repair.

 

[BoomboxLover48]

Our Tech Guru Superduper can very professionally repair those sliders and make it sound like brand new.
Please PM him for his availability.