Good morning. I'm servicing my JVC RC M70 boombox and came across an issue where the siders are not working. When I turned them upside down the contacts that run along the slider fell out so they have become disconnected from the plastic slider that runs along the rails. Does anyone know where i can source these sliders? if not, I will have to attempt to repair them.
JVC RC M70 Base and Treble Sliders/Fader Switches
- Thread starter Droptopfiveo
- Start date
BoomboxLover48
Boomus Fidelis
Contact Superduper
If he has time and availability, he can service them for you and will work like new.
Since you are a new member, I don't know how you can PM him.
Try www.analogalley.com
If he has time and availability, he can service them for you and will work like new.
Since you are a new member, I don't know how you can PM him.
Try www.analogalley.com
Last edited by a moderator:
AE_Stereo
Member (SA)
I have a question related to the Bass/Treble controls. In the case with fallen contacts of the sliders, does the deck remain at Maximum Bass and Treble levels?
Or in other words, can we live without the Bass & Treble controls working, if I am only interested in maximum Bass & Treble levels always?
Or in other words, can we live without the Bass & Treble controls working, if I am only interested in maximum Bass & Treble levels always?
BoomboxLover48
Boomus Fidelis
Reminds me a Sharp GF-535 (Japanese version of GF-9000) I have to work on.
It has no response to bass or treble.
I think when the wiper falls off, it shorts the circuit and goes to the maximum for bass and treble.
Normally it's like 50K resistor but it varies. More resistance wiper includes in the circuit, lesser treble/bass.
The circuit restricts like that to control bass and treble.
Hope I make some sense.
It has no response to bass or treble.
I think when the wiper falls off, it shorts the circuit and goes to the maximum for bass and treble.
Normally it's like 50K resistor but it varies. More resistance wiper includes in the circuit, lesser treble/bass.
The circuit restricts like that to control bass and treble.
Hope I make some sense.
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Going by memory here so don't quote or rely on this, but on the M70, I believe losing a feeler on the treble slider will kill the channel. Losing the bass feeler and the channel continues to play but the signal passes through without adjustment of the signal. Losing a volume slider feeler will obviously kill the channel.
As for the RC-838, the volume control rarely ever has any issues, those are build differently than the other Alps sliders and far superior quality. The other Alps branded sliders such as bass/treble/balance/record-level sliders are all prone to failure. The record ones rarely ever have issues except noise and intermittence issues common on all older equipment. But losing a feeler on any of the other sliders pretty much kills the channel in stereo mode. What confuses folks is that the channel returns when you put the system in any of the mixing modes (biphonic, wide, etc). The thing is that the affected channel on those modes are really just playing the audio from the working channel ported back with some delay, so it's really only playing the program from a single channel.
In my experience with my JVC RC M 70 there was no base or treble. I believe this would be the case for all of the boomboxes with slider type adjustments. The sliders make contact with a solid bar and sliding it back and forth changes the tone (bass/treble). When the contacts fall off there are no adjustment to increase the base or treble.
This is an incorrect generalization and does not occur with ALL, it depends entirely upon the boombox and the circuit design. On some, the audio signal travels across the feelers. When the feelers falls off, the signal no longer has a path to the amplifier.
Transistorized
Member (SA)
With my JVC M70's, whichever channel dropped out with bass or treble issues caused that respective channel to demontrate a centered selection. Neither reduced or full. Just neutral. I am sure this could vary depending how the slider fails
BoomboxLover48
Boomus Fidelis
That’s exactly what I am getting on my Sharp GF-535.
Wes125
Member (SA)
that seems to be a common problem nowadays..i had the same issue with a 1981 panasonic box..the tone didn't work on the left side..i thought it was a circuit board prob but someone on here told me to check the slider control..thanks for that info. it now works as it should
I have a Victor m70 in a box under the bed waiting for cleanup/deoxit and some superglue. I was preparing by watching a m70 restoration video by a Japanese guy on YouTube, about 2 hours long where he also needs to solve the same problem from memory - completely disassembled the slider to put back the loose feelers; I remember watching this and going - this looks full on, hope I don't need to do this.
It is doable but high risk. If someone has already solved this problem for you or has more experience, why not ask them.
By the way, I have also found an old m90 restoration website in Japan - they actually disassemble every pot completely to wipe clean the tracks; so complete strip down; not just deoxit via the the openings; again it sounds full on and risky, but that's how you can check if the pots have dust and any loose feelers (m90 pots can get scratched by those)
It is doable but high risk. If someone has already solved this problem for you or has more experience, why not ask them.
By the way, I have also found an old m90 restoration website in Japan - they actually disassemble every pot completely to wipe clean the tracks; so complete strip down; not just deoxit via the the openings; again it sounds full on and risky, but that's how you can check if the pots have dust and any loose feelers (m90 pots can get scratched by those)
Wes125
Member (SA)
it's not the same with all boomboxes. nor is it with general hi-fi..without the controls the tone or base can be set to high. or no tone/base at all..it can be the same with the volume control aswell..I don't know the technical side of why it's like this but I've had enough stereos over the years to experience this issue..I have some spare slider controls what came out of an aiwa AF 5050 music centre..I would have thought the Japanese would have used these same slider controls in a wide range of hi-fi equipment over the years