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JVC M90 Switch help


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#1 jimslim

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Posted 09 July 2017 - 10:21 PM

Hello everyone, new to Boomboxery. I have a JVC rc-m90jw that I bought new when I was a young man. I used it until the tape deck no longer worked and then put it in a closet until now. I loved the sound that this machine can produce and hadn't heard it for at least 10 years when I plugged it in a couple of weeks ago. To my amazement, the radio still works (somewhat) and the speakers still sound crystal clear with no distortion and a perfect balance of highs, mids and lows. No matter what the volume! Brought back some memories.

 

Anyway, the problem is I have to press and hold in the on/off switch for it to continue playing. Once I let go, it turns off. I also noticed that it plays all speakers in mono very clearly but when I switch to stereo it only plays the left speakers. It also cuts out sometimes and will continue to play but at a very low volume. The short wave section makes some static noise but I wasn't able to find any channels on any of the bands. I opened it up (cleaned and dusted too) and checked the fuse with a dmm and its still good. I don't know much about electronics but I'm willing to learn unless you all don't think I should mess with it. I would like to get the radio working if at all possible and not worry about the cassette deck at this time (or maybe never).

 

Any ideas of what could be wrong with it? Thanks.



#2 Superduper

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Posted 09 July 2017 - 10:44 PM

Oxidation builds up in all the metal contacts of switches and controls over time and results in poor electrical contact.  You need to remove the oxidation layer.  Just search the archives and do some reading.  Tons of information here regarding how to clean switches & controls.  Maybe use deoxit as a search term.



#3 gimp69

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Posted 10 July 2017 - 08:29 AM

Hello everyone, new to Boomboxery. I have a JVC rc-m90jw that I bought new when I was a young man. I used it until the tape deck no longer worked and then put it in a closet until now. I loved the sound that this machine can produce and hadn't heard it for at least 10 years when I plugged it in a couple of weeks ago. To my amazement, the radio still works (somewhat) and the speakers still sound crystal clear with no distortion and a perfect balance of highs, mids and lows. No matter what the volume! Brought back some memories.

 

Anyway, the problem is I have to press and hold in the on/off switch for it to continue playing. Once I let go, it turns off. I also noticed that it plays all speakers in mono very clearly but when I switch to stereo it only plays the left speakers. It also cuts out sometimes and will continue to play but at a very low volume. The short wave section makes some static noise but I wasn't able to find any channels on any of the bands. I opened it up (cleaned and dusted too) and checked the fuse with a dmm and its still good. I don't know much about electronics but I'm willing to learn unless you all don't think I should mess with it. I would like to get the radio working if at all possible and not worry about the cassette deck at this time (or maybe never).

 

Any ideas of what could be wrong with it? Thanks.

 

Servisol Super 10 has been very effective for me.  Take the case off the JVC so you can spray it into the switches, buttons and knobs.  Do one at a time, just a squirt or two into any gap there is into the switch, button, knob.  Then flick the switch, press the button, rotate the knob several dozen times to work it in.

 

Done it on two Sharp boomboxes, both came to life after what you described.



#4 Northerner

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Posted 10 July 2017 - 03:22 PM

Yep, what they say...fixes 90% of problems just like that :-)

#5 Rimmer36

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Posted 10 July 2017 - 07:40 PM

If it wasn't for servisol i doubt anything would be fixed around here lol

 

yes a good spray on all switches should solve the problem :-)



#6 gimp69

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Posted 11 July 2017 - 02:45 AM

Yeah it's was great being able to spray the stuff and then listen to a box spring back to life.  It gave me confidence to buy a "faulty" second one.

 

There will be many classic boomboxes getting thrown away when all they need is a squirt of spray.



#7 jimslim

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Posted 11 July 2017 - 07:28 AM

Thanks guys, I'll try to find either the deoxit or the servisol today and let you know the results. I need to go out of town so may not get back to you until next week. I really appreciate all the feedback.



#8 jimslim

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Posted 21 July 2017 - 09:12 AM

Well I finally had a chance to work on the boombox. I had to wait until my Deoxit arrived from Amazon. I disassembled the box into three parts by removing back cover and then all the blue screws, knobs and connectors. I used one squirt for each switch, knob, button, etc. and then flicked, pressed and rotated multiple times for each one. I did this one at a time. I then repeated the process and put everything back together. Turned it on and this time I could not get a single radio channel, not even static. I tried FM, AM and all the short wave channels. About the only positive is the power switch will sometimes stay on if I fiddle with it. Any ideas on what to do next?



#9 Northerner

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Posted 21 July 2017 - 10:27 AM

Maybe a cable didn't get reconnected?

#10 Superduper

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Posted 21 July 2017 - 10:48 AM

Sounds like classic symptoms of highly oxidized controls & switches. I think more aggressive cleaning is in order. Also, the tuner band selector switches are notorious for poor contact due to oxidation. Those frequently need lots of work to restore, often removing the board can provide better access as those switches are partially sealed.

#11 jimslim

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Posted 21 July 2017 - 11:08 AM

Thanks, when I get a chance I'll open her up again and do another cleaning as well as a check to see if I left any cables unconnected. Should I use deoxit on the inside of the cord connection and also the area of the plug inside the box?



#12 Superduper

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Posted 21 July 2017 - 03:15 PM

It can't hurt but your problems are more likely dirty switch or controls.

#13 caution

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Posted 21 July 2017 - 07:40 PM

Does line-in or tape work? Any hiss when you crank it?



#14 Superduper

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Posted 21 July 2017 - 08:05 PM

Since we are on subject of line-in, the line/phono switch on rear is also prone to become dirty too.

#15 gimp69

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Posted 23 July 2017 - 06:50 AM

Well I finally had a chance to work on the boombox. I had to wait until my Deoxit arrived from Amazon. I disassembled the box into three parts by removing back cover and then all the blue screws, knobs and connectors. I used one squirt for each switch, knob, button, etc. and then flicked, pressed and rotated multiple times for each one. I did this one at a time. I then repeated the process and put everything back together. Turned it on and this time I could not get a single radio channel, not even static. I tried FM, AM and all the short wave channels. About the only positive is the power switch will sometimes stay on if I fiddle with it. Any ideas on what to do next?

 

D5 or F5?



#16 jimslim

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Posted 25 July 2017 - 02:21 PM

I used D5 and I'm not sure if the line in still works. It did when I last tried it along with the phono in. However, that was at least 10 years ago.Tape does not work but I don't really care about that right now. I'll try another cleaning this weekend. 



#17 Transistorized

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Posted 27 July 2017 - 09:24 PM

This might sound silly but also make sure the headphone jack gets sprayed. A bad connection there will cause no sound on the speakers as well.

Those frequency selectors on the tuner board can really be a pain to get cleaned. Most of the time that and the stereo/mono selector will cure all. Sounds like the tuner selectors need more work.

#18 JVC Floyd

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Posted 28 July 2017 - 04:35 AM

This might sound silly but also make sure the headphone jack gets sprayed. A bad connection there will cause no sound on the speakers as well.

Those frequency selectors on the tuner board can really be a pain to get cleaned. Most of the time that and the stereo/mono selector will cure all. Sounds like the tuner selectors need more work.



I agree, the band selector switches and the function switch still act up on mine because I'm too lazy to do anything about it lol. But these are the culprit every time the sound cuts in and out.

#19 jimslim

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Posted 31 July 2017 - 09:34 AM

I opened up my box yesterday and in the process very carefully checked to see if I had left a cable loose or unconnected. I didn't, they were all secure. So with the box now separated into 3 parts I again sprayed (deoxit d5) all the knobs, switches, etc. I took out the power on/off switch separately and sprayed, cleaned and worked it, let it dry and repeated the process at least 5 times. It would engage on and off normally and I could feel and hear it smoothly working. I also concentrated on the Stereo/Mono, Function Switch, Band Selector Switches, Loudness and Dolby switches spraying and working all these at least 5 times. When they all seemed to be working smoothly I put it all back together and turned it on. 

 

Although I was expecting disappointment, I was happy to hear the radio working again. This time the radio did NOT cut out at all and it plays in stereo as well as mono! This is a big plus which I was happy to hear. All the bands now receive channels so overall I'm a happy camper. The only negative is that the power switch will not stay on. I have to keep it pressed in and once I let go it turns off. I can feel and hear it clicking on/off but it just won't stay on. I suppose I could tape it down and just plug the cord in when I want to use it but I'd like to get it working. So in conclusion, the radio is now functioning normally and the speakers are all working great so the only problem left is the power switch. Should I continue to spray and clean it or start hunting for a new switch?

 

Thank you all for your help, I really appreciate it.