Another Akai MG1212.......

It's ALIVE!!!!!!!!!!!!!!!

It works! Cool.
I got the idler tire in the mail today. Intalled and put in a tape......first off, about the tapes I have. The guy I got the machine from said he had a bunch of tapes. New and used. When I went to pick up the Akai, he only had one used one on hand. He just moved into his place and had boxes from floor to ceiling all over his basement. He said the rest of them are buried away and said he will contact me when he finds them.
The tape he gave me has a song on it he recorded back in '97 with a female singer.
The other tape I got used from ebay for $18. It also has music on it.

So, back to the first press of play. I put in the ebay tape with great excitement. Put on the headphones. Pressed play. And 10 of the LED meters started to dance up and down. The tape transport is functioning real smoothly.
I'm surprised. And I sounds real good. The fun part is I get to mix the song that's on there. It's kind of a soul, R&B type thing with some female vocals.This was recorded at the slower of the two speeds.

The tape I got with the machine has a song with 10 tracks recorded with the faster speed. It sounds great. No real drums or bass though. Those were done with keys. And there is only one song on that tape. So I'm thinking the rest is virgin tape afterwords.
Rewind and FFW aren't the quickest. I also noticed that the tape is still against the record/play head when rewinding. I can hear it slightly in the headphones. Not sure if that is supposed to be like that.

So, I'm thinking the idler tire could be one of the main issues with the notorious transport problems on this machine. The one I have hasn't been used in ages as the guy told me. But with a new small capacitor, idler tire and a fix to a broken section to the cam, this unit is up and running. But I'm am gonna expect other issues in the future.
I haven't tried recording yet. Will try some tests tomorrow. Fingers crossed.
But for now, the rest is just cosmetic. Won't be able to do any calibration that's for sure.

Im guessing these tapes can be easily erased with a bulk eraser.

Here is a picture of the meters in action....

IMG_20161215_195608.jpg

As you can see the faders are down. I didn't have the switch selected to track.
I'm really looking forward to recording a song on this sucker.
 
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Okay. Another problem has popped up. I still haven't got to the eject button problem yet, but there is a problem with the eject function. I fixed the cam that moves the door up and down, but there is a problem that happens every now and then. When closing the door, it sometimes stalls and then quickly slams shut. This is another problem I have heard of while searching around.
I found the problem, and there is also something mentioned about it in the service manual(thanks Sweetbeats for the link). Must be a common problem if the part being bent is mentioned in the manual.
There is a part called the slide eject action part. Mine has become bent. I think its made out of aluminium. Maybe cast steel. Not sure. This is causing the door to slam shut sometimes. Now I gotta figure a way to straighten it without breaking it. It a vital component for the eject system and I can't risk snapping it.
Here is a picture....what do you guys think? maybe some heat???

IMG_20161215_230251.jpg

IMG_20161215_224121.jpg
 
Excellent that you got it working with minimal effort.

Most likely that metal part is cast pot metal.....maybe aluminum. Doesnt look like steel from the pics.

Ive had luck with such parts in the past.

Automotive related. Not audio. But anyway.... no need to get into details.

My fix for straightening deformed cast parts has been to put it in a vise and slowly heat it up with a heatgun on high, as I'm slowly tightening the vice till its straight. Cooling it is rapidly in a bowl filled with water helps the process.

Good luck and congrats on the progress so far.

Edit: a good long term solution is to have one machined out of aircraft grade billet aluminum.

Second edit: Almost forgot. Gibson bridges would collapse and bow like that because of years of string tension. I'd fix those the same way. But........it wouldnt be a permanent fix.
But in all fairness they have a lot of downward stress from the string tension.
 
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DAMN j.harv...I'm impressed. Nice work!! :D:D:D

I second RFR's recommendations. It looks like cast aluminum. Getting it warm is a good security measure, and using a vice is good because it provides even pressure over a larger area, and it is easy to advance the pressure. Often the vice won't get a part like that totally straight again...like pressure *past* the centerpoint has to be gently applied so that the part comes to rest straightened out. You can still do this in the vice using some nails, one at the center point, and the other two placed one on each end on the opposite side. I can sketch a pic if that doesn't make sense.

Anyway...wow!

Regarding erasing the tapes, yes I agree a bulk eraser should do the job just fine.

Regarding calibration, I'd like to reach out to Jay McKnight at MRL and see if they could make even a simple short 100Hz/1kHz, 10kHz test tape on 1/2" LPR35 (does that even come in 1/2"?) that could then be loaded in an empty cassette shell...would work at least to get the playback level calibrated. Won't help with frequency response sweeps...but that's what I'm thinking of doing in order to get one of mine calibrated.
 
The good and the bad..........

The good.
I got the eject mechanism part mostly straight. With a vice and some heat as mentioned earlier. Thanks.
I also added some aluminium putty to the part for added strength. The part is constantly under tension from a bigger sized spring. Here it is with the putty. It dries in to solid aluminum

IMG_20161216_160609.jpg


The bad....
My repair job on the cam failed:mad::mad::mad::mad: Back to the clicking door again.
The little piece of jb weld broke off. There is probably a lot of pressure on that spot from the spring loaded arm. So now I gotta figure out what else I could use to fix it. I'm thinking epoxy putty might be stronger. Or I might be able to use the aluminium putty I have to build it up.
Anyway, I got the part out, and now can show a picture of the broken spot. Look carefully. You'll see a break in the wall of the channel....That's where the arm guide is dropping in to.

IMG_20161216_164819.jpg


I think I could add the epoxy all the way to the outside wall of the channel behind the break so it won't snap off. Just fill up that whole section.
 
Do you know anyone with a 3d printer?

On that piece broken off, you could get some plastic and heat and bend it to shape, file and sand the bottom to fit and glue it with CA with a catalyst. It would be a pain, but it 'could" be reconstructed.
 
So it rides on that outside track??

Looks a bit messy, but let's hope it works.
:D


Yeah. It ain't pretty. And I'm not sure this ones gonna work either. I used plastic epoxy this time, and I just realised this is the kind that dries to a rubbery feel. Not hard and solid. I have a few tubes of different epoxys lying around. I think I used the wrong one. But I remember this stuff is easy to remove.
Does anyone know what kind of plastic this cam would be made of? from what I have been reading on some of these epoxys is that they won't adhere to polyethylene or polypropylene plastics.

I think I'm gonna go out and by some Tamiya epoxy putty from the hobby store tomorrow. I have used this stuff in the past with good results. I dries hard like solid plastic.
 
Could be wrong but i think it's a nylon based plastic. Durable with somewhat 'slippery' gualities.
 
This might be crazy talk, but is it feasible to create a mould using a temporary fix and cast a replacement part from something?
 
That could be done. Maybe.
Heres another idea.
Get out your dremel. Drill, cut, file......whatever you want to call it, all the way through the broken section.
Get some plastic, bend it with low heat and put it in place of the missing chunk.

Glue it in and re enforce the back side. Not the bottom, but the side where nothing is riding on.

This way it won't snap off because it's integral to the cam piece now as it goes through.

That's the way I'd do it. It will take a bit of work, time and patience, but would be solid.

Basically you are reconstructing the part with new plastic.
 
I think if it was me I'd be doing something similar to what you are doing with the cam, but making some little forms out of something epoxy wouldn't stick to, and using standard 2-part epoxy cement...using the little forms to create as smooth a wall on the follower side of the channel, and then building it all the way over to that other wall like you just did. That's a good idea.

3-D printer is an intriguing idea.

I suspect, as has been suggested, the cam/gear is nylon-based.

Where do you get aluminum putty?

[EDIT]

Thanks again for taking the time to post all this info, and for your resourcefulness and willingness to really dig in. I honestly think the chronic problems with these units are isolated to a small number of maladies that haven't been teased out and resolved. I think you are doing just that. Some are waiting for me to go ape-crap on the issues with my "Story" thread, but honestly I think this thread is the "Story".
 
Thanks for the repair suggestions guys. I'm gonna try the epoxy putty this time. It turns into a solid piece when dry and can be carved with an exato knife to shape it. I'm just hoping it sticks and doesn't just drop out.
I will post a pic when it has cured.


Where do you get aluminum putty?

I got the putty at local bolt and nut supplier. It's good stuff that can come in handy. When cured you can drill into it and you can also machine it.

IMG_20161217_113152.jpg


Some are waiting for me to go ape-crap on the issues with my "Story" thread, but honestly I think this thread is the "Story".

NOOOOOO!!!!
Your threads are epic Cory. A multimeter hasn't even made an apperance in this thread :)
I didn't even want to go this deep with detail, but once I discovered the problem of the eject issues, I wanted to share the fix as I have read in other forums of people having this problem. So hopefully if anyone out there encounters the phantom, clicking tape door, they can look into it without having to take it to a tech. If they're brave enough to dig in that is ;)
I hope this cam is the last of the problems, which I think it is as the playback on this thing sounds great. Then I can put it back together, polish it up and make some music with it.

I'm really looking forward to your thread on this machine when you get around to it. I'm curious to see if there are any similar problems and I'm also curious about the modification that has been done to yours[/QUOTE]
 
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Okay.... repair attempt #3

Tamiya Epoxy putty. Filled it in real good and it's pretty much rock hard now. So I can't see it breaking in any way. The only thing that could happen, is it could just drop out in one piece if it doesn't adhere to the part properly.

IMG_20161217_153635.jpg
 
Best of luck. If it fails I'm sure you'll get some support. I could experiment on one of my cam gears to determine what will adhere. But hopefully you've got it licked!
 
Just an update on what's going on. The good and the bad.

The good....The repair to the cam with the epoxy putty seems to be holding well and the eject function works smoothly. Tape transport runs smooth. No tapes have been eaten. Playback of the previously recorded material on the used tapes I have play back nicely, EQ works and all LEDs lghting up as they should.

The not so good....
Record function.... When I first tried to record something and play it back, I was either getting nothing upon playback, or, on some tracks, a very faint distorted sound that would kind of fade in and out.
I was pretty sure it's not the heads as they playback the previously recorded tapes fine. The first thing I thought was to go back to the power supply pcb, as I changed out a bad capacitor which remedied the no sound output problem I was having when I first got the machine.
The psu did have a leaky battery as I mentioned earlier and it made a mess of the board on the underside. This made a mess to a number of the solder points. I did clean a bunch of them up, but I went back in and found some more that could use a good reflowing. I also replace a few more capacitors.

After that, I tried recording and low and behold, I get clean recording and playback....on ten of the twelve tracks.Tracks 7 and 11 are bad. So here's the wierd thing that is happening...

While recording on track 10, the channel 11 LED meter constantly peaks and the overload light also come on.
When I turn up the monitor volume on channel 11, while still recording track 10,I'm getting a constant nasty rumbling distortion.
Upon playback, the track 10 recording sounds good.

When I try to record something on track 11, all seems normal while in record mode. The meter doesn't peak like when recoding on tr.10. But when I playback what I just recorded on track 11, the sound kinda fades in and out now and then or it's just silent. I may get 10 seconds of silence, then it fades in and then quickly dissapears.

This also happens with track 7. While recording on track 6, channel 7 LED peaks and distorts through track 7
monitor. Recording on track 7 does the same. Fades in and sometimes nothing. But it's not as bad as the track 11 issue, as I have gotten a consistent recording on Tr 7 at one point, but the problem does pop up.

So I'm thinking track 7 and 11 must share the same circuit or buss somehow???? They are both odd numbered tracks, even though, in the user manual, it doesn't say anything about panning fully left or right when recording.

I went back and checked the solder points thinking I may have bridged 2 points together, but I don't see anything like that. I tried swapping pb/rec cards, but no go. So I'm thinking the problem may still lie within the powersupply. Just gotta find a way to track it down. I know I could just use ten tracks, but that would just bother me knowing there are 2 extra tracks sittng idle :)
 
Hmmmm, got no answers. But good on fixing what you have so far.
Probably between you and Cory addressing issues, sooner or later two, mabye3 units will breathe fire again.
 
Are the record amps on individual cards, one per track?

When you did your swap what cards did you swap?

Some of what you describe sounds like relay issues to me.

And on your power supply board repairs, based on what I saw of the battery leakage damage, I'd strongly consider bypassing the effected solder traces and adding jumper wires instead. Battery acid will eat foil.
 
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