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Some questions about tape machine calibration Recorders, Players & Tape Machines
Old 18th December 2010
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Joao B.'s Avatar

Some questions about tape machine calibration

So I got a Otari MTR90mkII and have some questions about calibration.

I'm using the manual to do this, but there's somethings I don't quite understand.

The first step is Repro align. I'm using a home made calibration tape until I get my MRLs.

While monitoring repro, I used the 1K tone to set the repro gain to 0VU (the tape is +8db/200nWb). After all the channels are aligned, I moved to the 10K tone.

Now here's the thing: on some channels, the VU needle is reading -10 and I can't rotate the REPRO HI SPEED EQ screw further to get it to zero! It seems to have reached the end and it just clicks. On the other channels (where the meters are closer to zero, the gain screw works fine).

What can I do?

Sync alignment with 1K is fine too.

The other problem is with bias setting. I'm feeding the Otari bias TS input with a sinewave from my computer. The thing is that when I rotate the channel bias screw counterclockwise the needle rises and exceeds the +3VU mark before dropping. So I can't tell how much I need to turn to get it down 3dB.

What am I doing wrong?

Thanks guys
Old 18th December 2010
1. you cannot make up your own tone tape. I suppose you could borrow an MRL, align your deck and make your own tone reel with your aligned deck, but even that is bogus. Really you can't get past this to align your deck right. So I'd stop now. who knows what the deal is with the homemade tape, so it's hard to say what's happening with the 10k alignment. It's possible your azimuth is off from the deck that made the tone tape. If when you get a proper MRL if you still have the same issue it could well be that you need to get the heads relapped. Does the 10k tone bounce around or is it steady? Is it the same with sync? As far as the bias goes you don't have to send the 10k tone to your deck at Odb, you should send it lower so that you have some travel to make the bias adjustment. But really you have to get a real MRL
Old 19th December 2010
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Joao B.'s Avatar

Thanks Lou,

I think I'll ditch this tapes and wait (rr) for the real thing.
Old 19th December 2010
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Knox's Avatar

yea . . no one wants to buy a MRL tape, but it is necessary
Old 19th December 2010
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Joao B.'s Avatar

Actually I bought 3 MRL tapes from a fellow GS'er before I even posted this, but they are going to take a while to get here.

I didn't buy them before because the store that sold me the machine said that they were going to include some calibration tapes (they even called them MRL). But they are just some tapes printed at some studio (the tapes say Snake Ranch studios, London)

I guess I'll have to wait some more.
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