Power switch

[Macs]

My M71 has a few weird things going on. First, it wont turn off.
Is the power switch breaking a common thing with these?
Is it easy to get to ? I’m going to open it up soon. I got the service manual. I had started a post In general chat describing some of the issues but forgot to mention the power switch. Thanks.

 

[hopey]

Yes it has open contacts easy to clean with fine grade wet and dry sand paper.

 

[Superduper]

It’s most likely not the main power switch. There is a 2nd power switch which is part of the tape deck power system. If the deck is powered on, that second switch will also be switched on. It won’t turn off unless you reset the deck.

Don’t mess with the main switch using sandpaper. That WON’T do anything to correct an always on condition and as the copper leafs are rather fragile, you risk breaking it and then you’ll have a really bad day. The only time you should even consider polishing the contacts on the main switch is if there is a poor connection at the leafs.

 

[dubout]

The M70 / M71 doesn't need to be turned on to play cassettes. The cassette mech has it's own power switch so to speak. Your problem seems to be that your belts failed while the cassette deck was switched on. Superduper tried to explain that to you above and in your other thread. The flywheel needs to complete it's turn to disengage the leaf switch. Open up the box, turn the flywheel by hand and the motor will stop.

In fact, I don't think that there is much wrong with your box. Exchange the belts – also the belt from the counter as it controls the auto stop – and I am sure it will eliminate most of the problems.

Also I recommend contact cleaner / washer. The one that evaporates completely. Flood all potis, sliders and switches, then move them several times. Let it dry off. Use only a little Deoxit afterwards for conservation. Maybe that's all your box needs.

One other thing: The feelers inside the sliders can break off. When spraying the sliders, try not to spray underneath the sliderpods at full blast but only on the carbon track. For example pull the slider to the lowest setting and flood the upper area, then push the slider to the highest setting and spray the lower area. Then move the slider several times up and down. I hope my explanation isn't to confusing ...

 

[Macs]

Excellent, thank you all for taking the time to help.

 

[hopey]

Don't forget the normally closed contact for the sleep function.

 

[Macs]

Hey hopey, is the sleep function part of the main power switch ?
I’m going to take a close careful look at the power switch and try to located the second one also.
The problem started after I sprayed the heck out of everything.
the radio works even with the power off.
I got belts on the way.
if anyone wants to take the time to explain, Is sleep function the same as being off or like a timer that turns it off in case you fall asleep?
Also how does the program select on the tape work ? Or rather what does it do? I would think that thing is complicated and wouldn’t work well after all these years. Thanks, im reading back as many old post as I can. You guys are great.

 

[Macs]

Never mind. I saw a similar post now about sleep function. And I think it clicked what you all been saying about the tape still running.

 

[hopey]

The tape acts as a timer, when the tape ends it switches off the radio or tape. The power switch has a normally closed contact in series with the reed switch for the tape mech.

 

[Macs]

Last night I opened the back of box and looked at the belt and switch.
The main belt didn’t look terrible but it did have a kink in it that came around when I rotated the wheel. I have both new belts on the way. The switch had a tiny bit of green that I sprayed, I let it dry over night and the green was gone this morning.
I then plugged it in and the hum seems to be coming from the transformer. The deck clicked away. I got video and a few pictures. Please let me know what I should do next.

 

[hopey]

That's in great condition your lucky sounds like the auto stop is trying to engage replacement belts should fix this. You can help with deck logic by pushing it with your finger. I would just disconnect the mech until you replace the belts.

 

[Macs]

That's in great condition your lucky sounds like the auto stop is trying to engage replacement belts should fix this. You can help with deck logic by pushing it with your finger. I would just disconnect the mech until you replace the belts.

Alright, I’ll get on it. Thanks

 

[Macs]

Does anyone think the transformer is messed up ?
you can hear on the video What it sounds like.

 

[hopey]

I find the best way to diagnose is by process of elimination. Disconnect the tape mech first then try on battery or dc to confirm the AC tx is making the noise.

 

[Macs]

Hello all, I just got done replacing the belts on the M71 and the problem is still there.
can someone tell me what is going on with this thing? Has anyone seen this before?
How do I reset the deck and what does that mean exactly?
Here’s a vid. If anyone has any ideas, thanks.

 

[hopey]

Hard to tell can you remove the deck and take photos of all the belts and post. Is the tape counter working as this forms part of the auto stop logic and I think is what is making that tapping sound. Do the tape spindles spin freely? Did you replace or clean the idler tires they press up against the flywheel, These can be resurfaced with fine grade sandpaper and cleaned with alcohol if split will need to be replaced.

 

[Macs]

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

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- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

youtube.com

Seems to be from the pause button area ?

 

[Macs]

I used these belts.
the tape counter is working
All the rubber wheel parts looked good. I cleaned them with a q-tip and alcohol.

 

[Macs]

- YouTube

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

youtube.com

 

[Superduper]

Your deck is clearly not resetting, which is why the capstan flywheel continually runs. I think you need to remove the deck and inspect it carefully for mechanical issues such as sticking or binding levers.. Even without power, you can usually manually reset the deck by spinning the flywheel (in the proper direction). One revolution is all it takes. Typically there is a effort hump in the rotation immediately before it resets. With the deck out of the unit, you can inspect it more closely. As the deck gets old, dust and grime can work it's way into the mechanism and old grease dries up and sticks. This is a purely mechanical deck and quite complicated as you will see so it does get affected by binding, sticking and dirty assembly. You should also make sure that the belt is installed correctly. If the capstan is running in reverse, it will never reset and can make clicking noises like you hear.