Yamaha MT8XII - Will not record!

M

Moonroom72

New member
Hi, this is my first post on here, and any help at all would be greatly appreciated!

I just got a Yamaha MT8XII off eBay - everything seems to work perfectly fine on it, other than one thing: It will not record audio!
I plugged a synth into each of the 8 channels one at a time, routed everything just as it instructs in the manual, was getting signal prior and subsequent to recording, but nothing was actually put onto the tape.
Well, that's not true actually, when I maxed the headphones I could hear a very faint, very distorted and crumbly imprint of what I recorded. It wasn't even loud enough for one of the signal bars on the screen to light up. However when setting up the tracks, I had the signal bars going just about up to the very top. It was a strong signal, routed through the corresponding group and brought up to full level via the group volume knob, as instructed in the manual. So I had the signal assigned properly, had the track armed to record (blinking circle around the track number on the screen), and had the circle stop blinking and become solid when I hit the record/pause button. Even while recording, the signal bars were lighting up, but upon playback, only that tiny tiny crumbly signal remained on the tape.
I checked listening to it through the different mix options - the cue and monitor mix and all of that, tried flipping the input button on the track from mic/line to tape and every possible option to hear the recorded sound properly - it just wasn't there.

Any idea what might be going on? I cleaned the heads, have not demagnetized them though I don't imagine that would really solve this problem, but I do plan on trying.

Any suggestions would be great, as well as any recommendations for a source of replacement parts if I do indeed need to replace something.

I'm keeping my fingers crossed that I'm just somehow operating this thing wrong and nothing needs to be fixed...
 
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Not sure I can help much as I don't know this machine but thoughts are:

Is the line out just as bad as the headphone output for the recordings?
Do you get the same effect on every channel?
Have you tried to play back a recording on a standard cassette deck?
Is it the same with different tapes - you are not using a metal cassette by any chance?


If none of these show anything I would suspect the bias oscillator. Does the erase work?
 
Thanks for your reply!

- I have not tried the line out, only the headphone out...all I know is, the volume bars of the recorded tracks, as shown on the screen, are so low (barely even produce any bars) that I don't think the lone out would make a difference.
- I do get the same effect on every channel. I tried recording on all 8.
- I haven't played back a recording on a normal tape deck but will give it a try. I do know that other recordings play back just fine on the machine.
- I'm not using a metal tape, I'm using the recommended kind. The type II ones.

Bias oscillator huh? Interesting...where would one begin fixing that if that was the source of the problem?
 
I assume this device has a Source/Tape switch. On recorders I've got, if that switch is in the wrong place, I get a very similar effect to what you describe.

If you want to listen to what's coming in, you need SOURCE selected. Once the tape is in motion, and recording, selecting TAPE will give you what's already recorded on the tape. If the tape is paused, you may get what you describe. If you play the tape, and there's no input, and you select SOURCE, then ditto You can get a little bit of bleed through between the two. I'm assuming it's a 3 head machine??

Depending on the layout of the machine, and how clear the manual is, it could be easy to miss this.

Otherwise, I guess you've got a BIG problem.

Geoff
 
I would first check it can erase. The erase circuit normally uses the same oscillator as the record bias circuit just at higher level. If it can erase it may just be that the bias level is way out. This seems very unlikely for all 8 tracks but maybe there is just one trimmer for them all. You will need the service manual to locate the bias trimmers. Just had a thought that the dbx may not be working or be disconnected. Is there a dbx in out switch you can clean and toggle a bit?
 
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