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Friday, 24 June 2016

Mitsubish MC8000 audio system repairs.

Sadly, my friend Richard's dad passed away a while ago...

"There's some stuff here Andy, would you like it? I'd rather it went to a good home."

So it's now my duty to the man, to get it all going.....

This interesting audio unit was amongst the gear. It's a Mitsubishi MC-8000, originally sold by my old employer, B.V.Harrod (sadly long gone), and has it's original speakers and cabinet.

 ... and yes, that's the right way up, it has a vertical linear tracking turntable.


After some cursory checks, I give it some mains. There's a motor running somewhere, the turntable doesn't work, neither does the cassette, but the radio works fine!













Off with the back, and it's immediately obvious why the turntable doesn't work .... the belt's missing!

Actually it's not... Some of it is in the bottom of the cabinet, and some has stuck to the turntable flywheel. I quickly clean it up, with some wipes and a bit of IPA. Sizing of these things can be a pain, but it's easy really. Get a piece of string, and wrap it round the motor shaft and flywheel, where the belt would run, and cut the string. This will be the approximate circumference of the belt. Now belts are sold in dimensions of diameter, width and thickness, so divide the length of your string by Pi... in this case it's 200mm, and about 5mm wide.

The arm is driven by two other motors too. One raises and lowers the arm, and the other is used to track the arm across the record.

The belts that drive these functions are also in a bad way... just touching them leaves a nasty sticky black mess. A bit of IPA to clean up, and some replacement belts see the turntable working....













... now the motor continuously running is the motor in the cassette deck.... probably another belt!  It's buried right in the bottom of the cabinet. See that brown, spotted thing lying across the circuit board? That's a bit of turntable belt!







... the motor nicely dates the unit from 1980...












Getting the transport out requires a lot of disassembly, and quite a considerable amount of cussing....


















... but eventually yields ... I will not be beaten by mere machinery!












... sure enough the capstan belt has gone the same way as all the others! I'll change the lot...



















The tape transport is carefully disassembled to gain access to the belts..












..which involved removal of the record switch actuator lever. Capstan flywheel is removed to clean the remains of the belt off...










... and some suitable replacements found from the belt box. The capstan belt measures in at 71mm. There's a 2.8mm wide belt which will do nicely.










The deck is repaired, and time to contemplate re-uniting it with the rest ... look at all those screws!











Finally back into the lower part of the cabinet!


























... and that reunited with the top...

Thankfully, all the plugs are nicely labelled...


















... and once the transformer is re-fitted, speakers connected, it's tested...




A new stylus is fitted, and the turntable works a treat. Sounds far better than I had expected... unfortunately there's nothing but a nasty hum from the cassette deck. It appears either the wiring to the tape head, or the head itself is open circuit.... I dread having to remove the transport again. Closer inspection reveals the wiring to the head is broken, and it's been repaired before.. there's some evidence of a poor soldering job, and the wires have been left very short. Thankfully, access, although difficult, is possible through the front, after removal of the door, and the repair is completed.








Here's a quick video of the turntable in action....

And, finally, a few photo's of the original dealership who supplied the unit. These were taken on the last day of trading, back in November 2005.. a sad day.

Shop front...














Interior... looking sadly empty :(






























and the workshop...
















18 comments:

  1. I hear that they had a brilliant 1st class service technician working there...

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  2. I have an MC-8000 as well. It will play 45RPM singles very well, but it refuses to play 33RPM longplay recored. Any idea what might be wrong? Easy to fix?
    Many thanks, Louis

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    Replies
    1. Hi. You need to replace all 3 bulbs on the back of arm.

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  3. Good job on your mc-8000

    I have the x-10 here in the states and also have the repair manual. I got the turntable working great after finally figuring out that the 12v bulb in the tone arm needed replacing. That was no fun!

    The cassette player needed 4 new belts so I’m tackling that now. I think I got everything back correctly. I’d like to test the deck before putting it back in. I’m concerned that when I push the play button(no power) the pinch roller doesn’t move and when I push the stop bottom it won’t make the play bottom pop up.

    I hot wired the red and black wires from the power supply to the cassette motor but only got a hum without the motor turning.

    Any suggestions?




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    Replies
    1. Cocked up the reply, Jim... it's below... ;)

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  4. Hi Jim,
    I'd see if the mech is free first, by gently turning the motor pulley with the end of a screwdriver. If the mech has jammed for some reason, you'll need to strip it again to see what's stopping it from turning. I didn't have the manual, but it all seemed straight forward... except getting it in and out of the case!!!

    Good luck, and keep us posted!

    Andy Doz.

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  5. Thanks for your thoughts, Andy.

    Nothing seems to be jammed so I took a chance and put it all back together. What a nightmare but I got it.

    Well the pinch roller comes up when play is pushed but tape does not move. After about 3 seconds the play lever pops up and the motor turns off. Same happens with fast forward/rewind.

    I think I may have found the problem by looking over the mechanism before I put it back in. There is pulley just to the left of the motor(the belt motor goes right in front of it). A belt goes to it from the flywheel. BUT, the pulley only turns on it’s shaft! The shaft does not turn! I can move it on the shaft. That just doesn’t seem right. There is no washer/keeper on it either. I was thinking at first maybe it was just for balance. In the parts list, I can see other stuff on the other end of the shaft but I can’t tell for sure what’s what as the diagram is small.

    After tying this, I am more convinced that the pulls should be attached to the shaft.

    I was hoping someone reading this could verify that the pulley IS attached to the shaft by looking at their unit.

    If so, I’ll have to try to glue it on. All ideas are welcome!

    Thanks for your time.

    Jim







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    Replies
    1. Sadly Jim, I passed my unit on... The pulley hasn't got a felt pad underneath it, has it? To form a slipping clutch to provide some low-torque to the take-up spool? I somehow doubt it from your description. Sounds like you've hit the nail on the head!

      Good luck!

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  6. Getting ready to tackle repairing an X10 that wandered into the record shop I work at. Same issues as yours; weird motor running in cassette section when powered on, turntable belts are gone. I just wanted to say thanks for posting everything on here, it's been EXTREMELY helpful in giving me the courage to (as a young amateur) try to repair this unit.

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    Replies
    1. Congratulations Alan! Another saved from landfill! You are now officially a hero.

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    2. Happy to report that my X-10 turntable is working like a champ! I re-wired the incandescent sensors to LED, replaced the belts, and I'm back in business. Tape deck is still out of order, but I'll tackle that beast at a later date. Thanks again for the help!

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  7. Good going Alan!

    I got mine repaired also, both the record player and the cassette. Yep, I was right that that pulley on the tape deck was suppose to be attached to the shaft. It took JB Weld and some thinking on how to do it. Plus getting the cassette unit in and out 3 times was no fun.

    I also had to replace the light sensor bulbs including the one in tnr tone arm. I opted to use incondescences as I really didn’t know how to sub LEDS.

    If you get a chance and the time, I’d be interested in what you had to do to use LEDs.





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    Replies
    1. My friend, Andy at North Hill audio had one with a failed lamp. He used a yellow LED, and with a 1K current limiting resistor in series. You'll need to work out the polarity, or it won't light (just reverse it, if it doesn't)

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    2. Hi Jim! Like Andy said, polarity is key :) I ended up having to wire mine up twice to figure that out. Looking top down at the main circuit board on top of the tonearm, you'll see a red wire soldered to the left, with one leg of each incandescent going to a pad connected to the red wire. That's the negative side. What threw me for a loop was the fact that I didn't realize I can wire a resistor to either side of an LED leg, anode or cathode, and it'll still put the resistance on the circuit. I just assumed you have to put the resistor on the positive side, and I also assumed the side with the red wire was positive, leading to me having to wire the LED's up twice.

      SO, all that said, what you'll want to do is wire from the pad on the left, to one leg of a resistor (I used 1/4w 470 ohm), the other leg of the resistor goes to the cathode (negative) side of the LED, and the anode (positive) side of the LED goes to the pad on the right that corresponds to where the incandescent leg was soldered. You'll want to use 3mm LEDs as 5mm won't fit, and I don't think color really matters as long as light is emitted (I used red). Hope that helps, let me know if you have any more questions!

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  8. Hey there, I have an X-10 and it has a grey wire coming from the E part of the power switch PCB. I always take pics but I didn't take one of where that one goes. Any help?

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    Replies
    1. Sadly I've never seen an X-10. It wasn't available here :( Sorry...

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    2. I went back and looked at my pics from earlier in the year when I repaired my X-10. I think the gray wire is a chassis ground; here's a pic I took that shows it: https://imgur.com/a/D9Fshpe

      Hope that helps!

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  9. I have the schematics for the X-10 and I don’t see any gray wire coming off the PS-41 power switch. It shows only 2 white wires coming off of it and going to the power transformer. I don’t know what you mean be the “E” section.

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