Parts box turns Boombox

Transistorized

Member (SA)
Jun 19, 2012
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So I found a box online for a decent price and got a parts box for my M70. The parts box suffered what I like to call...blunt force trauma at some point in it's life. I knew about this in the purchase price. The description was accurate. However, it arrived in a few more pieces by the time it got to my house. The description said to assume you are buying this as not working at all. I based my decision to purchase based on the symptoms the box had. In the back of my mind I was fairly sure what was wrong with it and fairly sure it had enough good parts on it and to make it worth my while.

So it came and I originally intended for it to be a parts box. Put it on a shelf and wait for something to break on my other one to strip it. I guess it still could be....but as you are about to see below, I cared for it too much last night and now its a boombox today. Yes, I got carried away.

Powered it up and the radio played. Volume sliders / bass and treble all worked great. I thought, perfect (main reason for getting it). I have speakers and volume sliders if my other ones fail. When tape was selected the speakers would rapidly pulsate with a high pitched squeal and the tape deck would not play. The keys were bent all crooked and the mechanism just didn't look healthy. No offense to anyone who smokes (I used to smoke 12 years ago) but it was most definitely Marlboro country inside of this thing so...I delved right into it. Sorry guys....no pictures of progress. This entire job was done in 7 hours from 4PM to around 11PM. When I get on a roll I get so caught up in the progress that pictures get skipped. But this thing was in sad shape. So I stripped it down completely and washed all parts outside. I took out the speakers and meters and all of the wiring. I re-dyed the woofers because one had some nasty brown splatters on it. As I started putting it back together I started gluing all the broken pieces back in place. The old girl started responding with trim pieces glimmering and it encouraged me to keep going. The tuner window was missing the small metal trim that covers the slot the tuner needle operates through so yes....you got it. On went a piece of my aluminum HVAC tape...lol. I fixed the lighting circuit for the dial and re-glued the tuner window.

So after the cosmetics were completed, the main concern of mine was that issue of the tape deck function where the speakers would pulse and go into a wild squeal. This bothered me the most because I knew this was a switch and/or circuit issue (my weakness). I thought I would get lucky with my deoxit. I hosed down the record bar and every switch in the entire unit. Nope! Narrowed it down to two things. The ALC circuit and the left meter. So I started looking at what was happening when the symptom occurred. The left meter would peg out when it started. If I tapped on the left meter, the meter would go in and out and the noise followed it. Long story short, the meter was internally shorting and noise only occurred with ALC on. Since the left meter was internally shorted with spells of being open when tapped, I removed its ground and that removed a lot of the issue. I'm not planning to sink any more money into this. It's a parts box right? Anyway, after removing that meter from the circuit and selecting Manual for the record level all that nonsense went away. Yay! I can live with that.

After this was the tape mechanism. Ok....we are in my neck of the woods now. Tore it down almost all the way. Cleaned, oiled and lubed everything. All rubber parts looked good but glazed. Removed the nicotine glazed rubber components and cleaned them with 91% ISO. Not wanting to put any additional money into this thing and not knowing if the amplifier section was working for tape mode yet, I decided to reuse all belts and such. So with no new parts, I slapped it back together.

Wouldn't you know that this thing took off and played like a new machine. I didn't even have to adjust the motor speed. Music Search, FF, Rewind, Play..all good. It even records! It now works as good as it looks. So then I started tackling little things like the soft eject mechanism and such. Before I knew it...it was 11PM and I was staring at a fully functioning and decent looking "Parts box". The only issues being no antennas, no handle (but the strap clips were good so one of Joe's straps took care of that), a non working left meter (meh) and a few cosmetic issues and one missing slider cap.

This box lovingly responded with everything I did. I really enjoy that when it happens. It's like giving a kid who hasn't had much attention a toy. They seem to appreciate it more than another kid who is used to the attention. This box hadn't seen any love and I guess it warmed up to me. That, or I am finally starting to be a decent boombox tech from watching the experts here :-)

This is the best parts box I own. Video is on dropbox to avoid any copyright on YouTube. The tape may sound like it's playing fast here but it's recorded that way because its a DJ-Mix.

https://www.dropbox.com/s/5x2njxfhard1ze9/20190720_113346.mp4?dl=0

Picture of the two as of today :-)

20190720_113711.jpg
 

T-STER

Member (SA)
Jul 14, 2014
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Nice! Another one saved, that's great news and so cool you put it back together again. Certainly doesnt look like a parts box now!
 

Transistorized

Member (SA)
Jun 19, 2012
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Thanks T-STER. My wife said "So I guess you're not going to use it as a parts box now huh?" then fired into how we are running out of room...lol. I wish I could've taken a picture of her face when I made a common sense statement. I said, "You were fine with me purchasing it as a parts box. Wouldn't it take up as much room working as it would a parts box? The wife: :huh: :hmmm: :angelic: :yes:
 

retroclub

Member (SA)
Jan 25, 2019
75
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8
Awesome job Transistorized.

If I end up being half as good as you guys at restoring boxes, I'll be very happy. :)
 

Fatdog

Well-Known Member
Staff member
May 3, 2009
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Most excellent!! At first glance, I could not determine which one was the parts box. Great job, Ryan! :bow: :thumbsup: :rock: :hooray:
 

Transistorized

Member (SA)
Jun 19, 2012
1,838
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USA
Fatdog said:
Most excellent!! At first glance, I could not determine which one was the parts box. Great job, Ryan! :bow: :thumbsup: :rock: :hooray:
Thanks. Love taking the M70 boxes apart. It's a fun box to learn :yes:
 

Transistorized

Member (SA)
Jun 19, 2012
1,838
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In my drunken state..I have a question that I'm fairly sure I know the answer to. Been using the parts M70 box this evening.

If you can feel air puffing out from around the cassette function keys, does that mean the volume is loud enough? :lol:
 

Nickeccles

Member (SA)
Jan 26, 2016
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Littlehampton West Sussex
Video has great sound quality!! You just need a meter & a slider cap to finish it off! I spend hours quite often on something most would just throw away! I simply HAVE to get it working again if it was made during the early 80's - Save as many as you can people, low end mid range or high quality machines.........We won't be around forever................We need to leave as many boomers as we can behind fully working!!

I think I need to see a specialist :-D :-D :-D