MTR90II alignment

Archived from groups: rec.audio.pro (More info?)

J.P. Ambrogi wrote:

>
> The problem started with Bias calibration: I loaded a blank tape and
> recorded a
> 10 khz signal (from the console oscillator), with the remote set to
> REPRO and started turning the bias pot just to discover that the
> needle on the meter goes all the way to right (past +3) before
> reaching the point of going back. Is it normal behaviour?
>
> Then I went to do REC gain! Again recording a 1khz tone with the
> remote set to REPRO, all tracks armed, and the needle (on all 24
> meters) don't go past -20, no matter how much I turn the REC gain pot.

Your problem, as you state, starts with the bias adjustment. If your
meters are pinning before you get a peak reading, back off the input
level of the 10kHz tone. It does not need to read 0vu for the bias
adjustment. Try sending the 10kHz tone to the machine -3vu and see if
you can get a peak then. If not, back it off further.

Once you have the bias set properly, I'll bet your record gain alignment
will work fine. It sounds like you aren't biasing the tape enough to get
it to actually record a healthy level.

--
Eric

Practice Your Mixing Skills
Multi-Track Masters on CD-ROM
www.Raw-Tracks.com

Archived from groups: rec.audio.pro (More info?)

J.P. Ambrogi <jpambrogi@ig.com.br> wrote:
>
>I started with the playback alignment playing the 1khz signal on the
>MRL tape and tweaking the repro gain pot 'till the meters read 0 Vu
>(The reference fluxivity of my MRL is 355 nW and I was going for a +6
>alignment). No problems here!

Umm... did you do the azimuth first? You need to make sure the azimuth is
correct before setting the repro gain and the repro EQ.

>The problem started with Bias calibration: I loaded a blank tape and
>recorded a
>10 khz signal (from the console oscillator), with the remote set to
>REPRO and started turning the bias pot just to discover that the
>needle on the meter goes all the way to right (past +3) before
>reaching the point of going back. Is it normal behaviour?

It is if you are feeding too hot a signal into it. Turn the level on the
oscillator down... all you need is to find the peak, so it does not matter
what the actual level on the oscillator is as long as you can find the peak
with it.

>Then I went to do REC gain! Again recording a 1khz tone with the
>remote set to REPRO, all tracks armed, and the needle (on all 24
>meters) don't go past -20, no matter how much I turn the REC gain pot.
>The tone was recorded and reproduced, but obviously very low. Looking
>at the meters on the console set to read BUSS OUT I could see the tone
>at 0 Vu. Switching the console meters to read the signal coming back
>from the recorder showed a very weak signal. The funny thing is that
>when I change de console oscillator to 10khz, the OTARI needles go
>midway and then its easy to get to 0 Vu with a little tweak in the REC
>gain pot.

If your bias is set wrong, trying to set gain is not going to work. If your
azimuth is set wrong, setting gain or EQ is futile. Go back and get the
azimuth and bias points right.

If before when you were setting the bias, the levels off-tape were too high,
and when you are trying to set the record levels, the levels off-tape are
too low, almost certainly you did something wrong in the process of setting
the bias.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

In article <3254de3c.0410012018.5e766931@posting.google.com> jpambrogi@ig.com.br writes:

> I started with the playback alignment playing the 1khz signal on the
> MRL tape and tweaking the repro gain pot 'till the meters read 0 Vu
> (The reference fluxivity of my MRL is 355 nW and I was going for a +6
> alignment). No problems here!

That's the right place to start. Actually, that's "+5.7" but no reason
to quibble about it.

> recorded a
> 10 khz signal (from the console oscillator), with the remote set to
> REPRO and started turning the bias pot just to discover that the
> needle on the meter goes all the way to right (past +3) before
> reaching the point of going back. Is it normal behaviour?

Yes. This means you need to adjust the record level. It's a little
inconvenient if you're using the internal oscillator because that's
usually at a fixed level and you can't adjust it. Back off the Record
Level pot until you can keep the meter on scale through the peak. You
can get pretty close to make two adjustments at once if you find the
bias peak, set the record level so that the meter goes up to +3 VU,
then increase the bias so that the meter comes back down to 0 VU
(assuming you're adjusing for "3 dB over peak" - otherwise compensate
accordingly.)

You'll probalby have to tweak the record level again (it should be the
last thing you do) after you adjust the high frequency EQ, but you'll
be in the ballpark.

> Then I went to do REC gain! Again recording a 1khz tone with the
> remote set to REPRO, all tracks armed, and the needle (on all 24
> meters) don't go past -20, no matter how much I turn the REC gain pot.

Either the HF equalization is way off or something is very wrong. Are
the heads clean? Do you have the tape threaded correctly? Are you
using the same tape as you used for adjusting the bias? (not the
calibration tape, I hope!)


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

Archived from groups: rec.audio.pro (More info?)

In article <9b30ebb8.0410021504.458c62c2@posting.google.com> mike@monsterisland.com writes:

> On thing to know about Otari heads - as the get wornd and need
> relapping the put out more high end. IF you're having wierdness at
> 10k, there is a possiblity that your heads need relapping.

There are two conflicting forces at work when heads wear. First is
that there's less metal in the core of the inductor, so the inductance
of the head goes down, and therefore the high frequency response
rises. But when you get too far down, the gap widens, and that reduces
the high frequency response.

Fortunately the rise due to metal wear comes enough before the drop
due to metal wear, so if you pay attention to what's happening when
you tweak up the alignment, you'll have warning that it's time to get
the heads fixed up. Of course this removes some metal, so you'll have
a high frequency rise (that you can take care of with the EQ
adjustment) after getting the heads relapped.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

Archived from groups: rec.audio.pro (More info?)

In article <41616160.29A29E3@soc.soton.ac.uk>,
James.R.Perrett@soc.soton.ac.uk says...
> "J.P. Ambrogi" wrote:
> >
> > Hi,
> >
> > I had troubles trying to do the alignment on a MTR90 II.
> >
>
> First get hold of the manual - there is a pdf version around on the net
> so there's no excuse not to have it (although it is a 20MB or so
> download). I'd follow the proceedure in the manual step by step to start
> with - an MTR90 in decent shape is very easy to calibrate. If you get
> into real problems then hopefully Chris Notton will appear - he's the
> real Otari expert around here.
>
> Cheers.
>
> James.
>
Well you've all been so eloquent & helpful!
The only dodge I might add is that you might find it easier to set a
(any) master bias pot in the middle (turn all one way until "click click"

is heard then back 5 turns), select it, and "peak-up" all the individual
biases at the highest frequency on your oscillator then go back to 10k.
to do your over-bias, all your tracks will now track the master-bias pot
perfectly.

Pip pip
--
Chris Notton
Replace "nospam" with my surname to reply by email
Sostituisca il "nospam" con il mio cognome per rispondere
}<////(*>

Archived from groups: rec.audio.pro (More info?)

J.P. Ambrogi <jpambrogi@ig.com.br> wrote:
>
>Anyway, you guys were right! For any reason, I was assuming that I
>should use the 1 khz at nominal level to do the Bias adjustment.
>Trimming down the oscillator level did the trick!

What tape are you using?

With most modern tapes, you will do better by using 10 KHz with overbias
than looking for the peak at 1 KHz. For one thing, the 10 KHz peak is
much narrower. But unless you are using an old-style red-oxide tape,
using the peak at 1 KHz is apt to give you too high a bias level.

With overbias, you find the peak, then you increase the bias until the
playback level drops by a particular amount (which is fudge factor that
is specific to the tape formulation and head gap width and which you can
get off the tape data sheet).

>I'd be very happy to pay each one of you a drink as long as you don't
>mind taking a plane to Brazil to get it...

It is cold and damp this time of year here, and I assure you I would much
rather be on a beach in Brazil. I do have maracuja tea, though, which is
better than nothing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

kludge@panix.com (Scott Dorsey) wrote in message news:<cju9nk$le2>

> It is cold and damp this time of year here, and I assure you I would much
> rather be on a beach in Brazil. I do have maracuja tea, though, which is
> better than nothing.
> --scott

Yeah! It has a nice and subtle sedative effect with the advantage of
not having to hide it from the police!

J.P. Ambrogi
Jardim Elétrico
BRAZIL

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> J.P. Ambrogi <jpambrogi@ig.com.br> wrote:
>
>>kludge@panix.com (Scott Dorsey) wrote in message news:<cju9nk$le2
>>
>>
>>>What tape are you using?
>>
>>An old, but still virgin, 3M 996!
>
>
> Definitely go the 10 KHz route. The Otari has .25 mil heads, so with
> 996 try 3 dB of overbias at 15 ips. Watch out for sticky shed, though.
> I have had old 996 go sticky.
> --scott
>

I'm a 996 fan and have used a few older reels. Almost
none exhibit sticky shed, although I've had one or two
that did, but it wasn't too bad. Still very playable.

--
--
John Noll
Retromedia Sound Studios
Red Bank, NJ

jn145_deletethisfirst_@verizon.net

visit the new website: http://www.retromedia.net

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James Perrett <James.R.Perrett@soc.soton.ac.uk> wrote in message

> I really can't remember where I found it but if you have an email
> address that can accept very large attachments then I could send you a
> copy.

I would be grateful, James!
My e-mail is: jeletrico@ig.com.br

Regards,

J.P. Ambrogi
Estudio Jardim Elétrico
BRAZIL