JVC-RC-M70

[prg333]

I have several boom boxes.. My favorite is probably the M 70 which I got back in 2010.
It did develop a problem recently. When I push play, it doesn’t start up on the first try in fact it takes somewhere between half a dozen to 15 tries of pushing play and then stop until the reels start moving. It always seems like more than a dozen times recently.

Sometimes it’ll start when I flip the tape over. Other times I have to go through the whole ritual again.

It seems like the motor is still good. But something is wearing out or needs adjustment. It probably could use new belts, even though it seems to play at the correct speed once the tape deck gets going.

Anyone experienced this problem with their M 70?

Luckily, about 40 minutes from where I live there’s a very nice and experienced electronics TV repair shop. At first, he didn’t wanna even attempt to work on a Boombox. But after I brought them an open wheel tape recorder and several other tape decks for the home and a couple amplifiers.

He was willing to take a shot at my Boombox. A very nice Magnavox that was made in Austria. The keys were stuck down, but it was able to open it up and fix the keys, clean it up put in new belts and do some soldering.

So I’m hoping you’ll be able to do the necessary repairs adjustments for my M 70

Fresh belts some lubrication. Fix whatever is preventing it from starting to play on the first try.

Any thoughts. Thank you for your help.

 

[Tinman]

Yeah, most likely needs new belts, cleaning and lubrication.

 

[aiwapanasonic]

I would first source the right belts because chances are they won't have good ones. This machine deserves the best belts because the deck is one of the best in a boombox. You can also send them the service manual, it can be found online. There are also two good videos on YouTube.

I rebelted my m70 on the weekend and found that it has 4 rubber idlers in the mechanism. Normally a deck would have one and you would always change it. But here I didn't know the size, plus they seem to not go wrong because not many people write about them. However, they should be inspected for cracking and cleaned during a belt change.

As for the main belt - this model used very narrow belts. I believe my m70 had the original belt from Japan, and its width is less tham 3mm. The belt just looks tiny compared to the size of the flywheel. I did measure the path - see below.

Based on what people have written before on this forum: this is the replacement belt by one manufacturer: FBS 9.6: 9.6" x 0.125" Wide x 0.034" Thick. A potential replacement is FRM 9.6: 9.6'' x 0.139'' Wide x 0.035'' Thick. The last letter stands for Small or Medium, but they may be different manufacturers. People here have successfully used the FRM with good results. Just don't be like me and get the FRW version - this one is Wide, and it is too wide and won't fit the motor pulley. Try to find the FBS ideally; or otherwise, the FRM

My old belt in millimetres: internal circumference 270 mm x 2.9mm x 0.5mm
Belt path in millimetres: 276mm

So the old belt was about 2% shorter than the path; it was also very smooth so it would slip. It could not start a cassette. The new ones are 10% shorter than the belt path. If I used a wider/thicker belt, I would stick to about 5% or 7% of the path to avoid too much tension.

Good luck!

so I would ask/check for:
- oiling the capstan path - they need to take out the capstan, and for this they need to partially disassemble the back of the deck, with the solenoid and some finicky little springs. Best thing to do is take detailed photos from each angle
- oil the motor from the front as much as possible - just a drop of fine oil; to get to the back of the motor, you need to pull it apart, desolder etc so the front should be sufficient.
- check the metal moving parts for thickened grease and add new grease if needed (why not ceramic/silicone, it is good on both plastic and metal)
- clean all rubber parts like the four idlers and the pinch roller
- change the main belt; put everything back together
- check if the counter belt needs changing; the size is published on the forums here too;

 

[Transistorized]

I have a parts M70 that does this. WIth mine, I know it isn't belts because a hum can be heard through the speakers and it's like the drive motor isn't getting the full voltage. Sometimes it will start to turn the flywheel and then come to a stop. The power light (if the power selector is in the off/sleep position) is dim like the entire radio is not getting full power. Pressing stop and play several times on the deck results in it eventually taking off with a bright power light and working as it should.

 

[aiwapanasonic]

I have a parts M70 that does this. WIth mine, I know it isn't belts because a hum can be heard through the speakers and it's like the drive motor isn't getting the full voltage. Sometimes it will start to turn the flywheel and then come to a stop. The power light (if the power selector is in the off/sleep position) is dim like the entire radio is not getting full power. Pressing stop and play several times on the deck results in it eventually taking off with a bright power light and working as it should.

What could this be - poor electrical connection or a faulty cap? These aren't known for faulty caps.

 

[prg333]

I would first source the right belts because chances are they won't have good ones. This machine deserves the best belts because the deck is one of the best in a boombox. You can also send them the service manual, it can be found online. There are also two good videos on YouTube.

I rebelted my m70 on the weekend and found that it has 4 rubber idlers in the mechanism. Normally a deck would have one and you would always change it. But here I didn't know the size, plus they seem to not go wrong because not many people write about them. However, they should be inspected for cracking and cleaned during a belt change.

As for the main belt - this model used very narrow belts. I believe my m70 had the original belt from Japan, and its width is less tham 3mm. The belt just looks tiny compared to the size of the flywheel. I did measure the path - see below.

Based on what people have written before on this forum: this is the replacement belt by one manufacturer: FBS 9.6: 9.6" x 0.125" Wide x 0.034" Thick. A potential replacement is FRM 9.6: 9.6'' x 0.139'' Wide x 0.035'' Thick. The last letter stands for Small or Medium, but they may be different manufacturers. People here have successfully used the FRM with good results. Just don't be like me and get the FRW version - this one is Wide, and it is too wide and won't fit the motor pulley. Try to find the FBS ideally; or otherwise, the FRM

My old belt in millimetres: internal circumference 270 mm x 2.9mm x 0.5mm
Belt path in millimetres: 276mm

So the old belt was about 2% shorter than the path; it was also very smooth so it would slip. It could not start a cassette. The new ones are 10% shorter than the belt path. If I used a wider/thicker belt, I would stick to about 5% or 7% of the path to avoid too much tension.

Good luck!

so I would ask/check for:
- oiling the capstan path - they need to take out the capstan, and for this they need to partially disassemble the back of the deck, with the solenoid and some finicky little springs. Best thing to do is take detailed photos from each angle
- oil the motor from the front as much as possible - just a drop of fine oil; to get to the back of the motor, you need to pull it apart, desolder etc so the front should be sufficient.
- check the metal moving parts for thickened grease and add new grease if needed (why not ceramic/silicone, it is good on both plastic and metal)
- clean all rubber parts like the four idlers and the pinch roller
- change the main belt; put everything back together
- check if the counter belt needs changing; the size is published on the forums here too;

Thank you for that. Very good and detailed advice. Wow four idlers. That’s more than I thought were in there. I bet that rubber is wearing away too, but maybe I can show the guy all the measurements and he can order the right belts or I can. Then if he’s willing to put a lot of work and effort it might be 300 bucks for him to do it but if he does it right, that would be great. Really is an excellent Boombox.

 

[Transistorized]

What could this be - poor electrical connection or a faulty cap? These aren't known for faulty caps.

I always assumed it was a dirty or faulty power power leaf switch on the deck or a poor connection somewhere. Since it is a beater parts box, I never really investigated it. Not saying yours is the same issue as mine but with my parts machine, it appears to be an issue getting full power as even the radio doesn't come on when the issue occurs in the sleep setting and the power light goes dim or almost off. This doesn't happen when the power switch is on. The fault still occurs with the cassette deck not engaging but the power light (with the swtich on) stays bright and the FM radio and speakers will work with enough power. The deck still requires several play and stop cycles to get it to take off and sometimes it absolutely refuses to take off with the power switch in the on position. I am more successful when it is in sleep/off and press stop and play over and over until the power light comes on bright and it takes off.

The only thing I can tell you is that on my radio when this issue first started manifesting itself, I found it by putting the radio into off/sleep because I wanted it to shut off after playing a tape. I noticed when I would place it in off/sleep the deck would auto-stop and the radio shut down. While in the off/sleep selection, when I went to press play, the power light was bright and the cassette started to play but then the speed started to slow and the power light started getting dimmer and dimmer as the tape slowed and eventually even the amp couldn't even produce sound as it faded away to only a hum. Once this issue started, it continued and got worse and worse until I discovered that keeping the radio off and cycling back and forth from stop to play would eventually get it working. Once it worked in the sleep/off selection it continues to play perfectly regardless of the power switch selection until the tape reaches the end and stops. Then it's up in the air again as to if you will need to perform this process again to get it to play the next tape.

 

[aiwapanasonic]

I'd clean every pot and switch and leaf switch when disassembled. How? there is a deOxit version for pots and sliders - and this machine has lots of sliders at the top that can get dust. Some compressed air and then deoxit. For the leaf switches, some deoxit should be ok for a while, but people recommend a physical clean - just a thin screwdriver/swiss knife; or very thin sandpaper like 5000+ or even better - some polishing cloth. I'd also test the machine disassembled and try wiggling the connectors.

With the new belt (low-quality one I had handy) the W&F on my machine is 0.17% WRMS, which is a bit high. The service manual gives it 0.05%, I will try experimenting with different belts; wish I had a FRM or FBS.

Also I faced some static noise issue because there is a front Aluminum panel, really part of the face that is used as an antenna. Inside, it connects to an antenna cable with a very tiny fiddly joint: aluminum to copper. They need to be pressed hard together to make good contact. I could tell it is loose by touching the front panel, just above the right speaker (when you look at it from the front), just next to the FM stereo light. I forgot to mention my model is a Victor, but it should be about the same.