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My 3rd M70 Build


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#1 Transistorized

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Posted 14 January 2020 - 04:03 PM

Well I'm back at it with my 3rd M70 build. This one needed cassette deck work and treble potentiometer repair. I saved another one.

 

Here I have the pot removed from the board using my new soldering station. It made this much easier.

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Glued fingers back to nylon slider
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Very Happy with this solder job
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To my surprise the rear cover antenna supports are in perfect shape with the original antennas. The deck mechanism looks as if it was used very little as the tolerances were tight. Even the pinch roller looks and feels like new. All the idlers are fresh and new feeling...not hard and cracking like some. I lucked out. A lightly used M70 with common issues that are now all fixed. I can tell this one is going to go the distance.

 

 

Cosmetically its about a 8.5 out of 10 IMO.

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It's back together after repairs. Plays and looks like new during my testing. Installed new belts and fixed the treble on the the tone board. Cleaned it up and it's now 100%.

 

Video is prior to cleaning as I was sorting mechanical repairs first. This was the first test after all adjustments and repairs. Moment of truth time.

 



#2 Brutus442

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Posted 14 January 2020 - 04:41 PM

Always nice to see a resto in progress. Great job!



#3 Rimmer36

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Posted 16 January 2020 - 03:03 PM

what the heck would you want 3 m70's for lol, great work though dude



#4 caution

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Posted 16 January 2020 - 04:30 PM

Because they're awesome? I Have two and love them both.

Great work Ryan, glad to see another save!



#5 Transistorized

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Posted 16 January 2020 - 04:54 PM

Thanks guys!

 

After that dream I had with my volume potentiometers getting broke on my other M70, I knew I had to tackle this area of concern or I would forever be afraid of it. Those that know me know that I use my boxes like its 1980.

 

I evaluated my dream to find the meaning of it. I came to the realization that I had it because I was afraid of the tone board slider failure. I decided I didn't want to be afraid anymore so I got one that suffered with this issue to take it on.

 

I am glad I did because I can now use my M70s without fear and not be so concerned with its major flaw....The pesky tone board. I can now relax a little instead of cringe when I move the sliders and that makes all the difference in my enjoyment :-)

 

After I saw that it truly wasn't this mysterious thing and I got through it, it was almost like that moment in the Matrix where Neo starts to believe in himself and is able to take control over the situation within the Matrix program  :cool:

 

Why so many M70s? I tend to fall in love with boxes that I have torn down and repaired. I enjoy using a box that I know the ins and outs. In my mind I can see every moving part of the M70 during operation and can dissect it entirely and I enjoy having that knowledge. But, I need to move on to another box and learn another model,



#6 JVC Floyd

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Posted 16 January 2020 - 05:37 PM

Makes me wish I still had an m70 , mine had a dead channel so I traded it off to my good friend sinister4life.
We need people who can diagnosed and fix these boxes so hats off to you for doing your thing.

#7 Rimmer36

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Posted 16 January 2020 - 09:30 PM

Makes me wish I still had an m70 , mine had a dead channel so I traded it off to my good friend sinister4life.
We need people who can diagnosed and fix these boxes so hats off to you for doing your thing.

i wish you were my neighbour bro, you could have mine free :-)



#8 Tinman

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Posted 16 January 2020 - 11:07 PM

I've restored both an M71 and M70, they're great boxes.

You did a nice job all around.

 

Curious, what kind of glue did you use and do you use solder wick?



#9 Transistorized

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Posted 16 January 2020 - 11:31 PM

I've restored both an M71 and M70, they're great boxes.

You did a nice job all around.

 

Curious, what kind of glue did you use and do you use solder wick?

Thanks man.

 

I used a solder sucker to remove the solder from the board traces and for the potentiometer feelers I used 5 minute clear epoxy and let it dry for 24hrs.



We need people who can diagnosed and fix these boxes so hats off to you for doing your thing.

Thanks Floyd



#10 Tinman

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Posted 17 January 2020 - 02:09 PM

I bought one of those suckers from Radio Shack years ago but for some reason I've never used it.
You should buy a role of solder wick and give it a try, it works really well for normal solder connections.
The only time it's kind of a pain is when there's big globs of solder to clean off.

#11 caution

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Posted 17 January 2020 - 02:52 PM

Yes, yes YES!

Solder sniffers are good for large volumes of solder on big pins like pot/switch mounting posts, transformers, etc. but everything else, solder wick is the way to go.

 

It's like a sponge soaking up water. It's indispensible on those bent pins on heavier components, like pots and switches. They're bent over to keep the part from falling off the board before it goes through the wave solder machine. If you don't remove all the solder between the side of the pin and the pad it's sitting on, you risk lifting the pad off the board when straightening the pin for removal. Once all pins are straignt, and you can nudge it from the side and see it wiggling freely in the hole, it just falls out. :yes:



#12 Transistorized

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Posted 17 January 2020 - 03:03 PM

I bought one of those suckers from Radio Shack years ago but for some reason I've never used it.
You should buy a role of solder wick and give it a try, it works really well for normal solder connections.
The only time it's kind of a pain is when there's big globs of solder to clean off.

Yes, yes YES!

Solder sniffers are good for large volumes of solder on big pins like pot/switch mounting posts, transformers, etc. but everything else, solder wick is the way to go.

 

It's like a sponge soaking up water. It's indispensable on those bent pins on heavier components, like pots and switches. They're bent over to keep the part from falling off the board before it goes through the wave solder machine. If you don't remove all the solder between the side of the pin and the pad it's sitting on, you risk lifting the pad off the board when straightening the pin for removal. Once all pins are straight, and you can nudge it from the side and see it wiggling freely in the hole, it just falls out. :yes:

That sounds like a great idea guys. My B-Day is rapidly approaching. I told my wife I would like a fume extractor. Looks like I can add solder wick to the equation. I just informed my wife. She is looking at me like I am speaking French...lol. I'm going to have to explain to her what soldering wick is :-) BRB 

 

Update: Looks like I did the right thing by de-tuning the deck motor speed by just a tad. When I say tad I am talking about being 1/2 second slower towards the end of a 3 minute song. What usually happens is I get the radio back together and then find later that the motor speed has changed slightly. The problem with the M70 is (unless you have the model with pitch control) you have to remove the entire chassis from the case to adjust the speed again. Even if I did have pitch control, my OCD would require that the speed be perfect with it centered. What a pain. I really wish they had installed the motor to where you could get to the speed control simply by removing the rear cover like other radios. 

 

Anyway, when I was putting the deck back together I noticed that the flywheel was a tad stiffer to turn with the new belt than a mechanism with a worn in belt. So when adjusting the motor speed I went just a tiny bit slower. I am glad I did. At first I could tell that my tapes were just a bit slow but my assumption of resistance decreasing once the lube and belts settled in were correct. The tape speed after 2 hours of playing has increased slightly. Tape speed is now perfect. With a tape that is not dragging and not stretched, I can pull up the MP3 on YouTube of the song playing, match it to the tape and it plays side by side the whole way through. Spot on.

 

I couldn't be happier. And the tapes were all recorded on my Sony 850ES which was perfectly calibrated last year. 



#13 JVC Floyd

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Posted 17 January 2020 - 06:35 PM


Makes me wish I still had an m70 , mine had a dead channel so I traded it off to my good friend sinister4life.
We need people who can diagnosed and fix these boxes so hats off to you for doing your thing.

i wish you were my neighbour bro, you could have mine free :-)

Thank man , I know you would do it too.

Ryan I still have the RX 5050 you gave me , I managed to put a nice set of woofers on it and with minimal work she's a great box and fully working . thank you brother.

#14 Transistorized

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Posted 18 January 2020 - 10:54 AM

Ryan I still have the RX 5050 you gave me , I managed to put a nice set of woofers on it and with minimal work she's a great box and fully working . thank you brother.


You're so welcome Floyd. I am glad it went to a good home and that you got it 100%. Those little Pannys will Rock and they go Loud. I bet it vibrates the concrete with those better woofers!

#15 Lasonic TRC-920

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Posted 19 January 2020 - 04:27 PM

Nice save, thankfully they made tons of M70's so even the modest collector can have the opportunity to experience this fantastic box without having to sell a kidney. 

 

QUESTION: How different are the M70 sliders compared to the 838? I have some spare M70's and a wrecked 838 that could use the love.



#16 BoomboxLover48

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Posted 20 January 2020 - 11:11 AM

Nice save, thankfully they made tons of M70's so even the modest collector can have the opportunity to experience this fantastic box without having to sell a kidney. 

 

QUESTION: How different are the M70 sliders compared to the 838? I have some spare M70's and a wrecked 838 that could use the love.

Sell a Kidney.......  :lol:  :w00t:  :lol:  I fell off my chair laughing! Hope I didn't damage my kidney from the fall! :lol: