[Robert St-Louis]

Hi all,

Quick question on my Nagra 4.2 and IV-S. When I record a steady 1 kHz
signal at 0 dB on the 4.2 (using line-in socket), the output on
playback is higher than when recording, when the potentiometer is left
at the same place. (I record at 0 dB, and playback is +4 dB). From
what I have read, this is normal and expected given the type of tape I
use, and what the machine is likely calibrated for.

However when I do the same with the IV-S, the output on playback is
much lower (-30 or -40 dB), and I have to increase the level of the
potentiometer considerably to bring the level back to 0 dB. This
happens on either of the two channels (when I record the test signal
on each separately).

It's been a while since I've owned a IV-S so I don't know if this is
normal or not. Is it?

If it isn't, do you have a suggestion about what adjustment needs to
be made? (I have the service manual but am not a tech).

Thanks a lot.

--Robert

[Scott Dorsey]

Robert St-Louis wrote:

Quick question on my Nagra 4.2 and IV-S. When I record a steady 1 kHz
signal at 0 dB on the 4.2 (using line-in socket), the output on
playback is higher than when recording, when the potentiometer is left
at the same place. (I record at 0 dB, and playback is +4 dB). From
what I have read, this is normal and expected given the type of tape I
use, and what the machine is likely calibrated for.

Sort of. It's a sign the machine is miscalibrated.

However when I do the same with the IV-S, the output on playback is
much lower (-30 or -40 dB), and I have to increase the level of the
potentiometer considerably to bring the level back to 0 dB. This
happens on either of the two channels (when I record the test signal
on each separately).

This is a sign the machine is even more miscalibrated.

It's been a while since I've owned a IV-S so I don't know if this is
normal or not. Is it?

If it isn't, do you have a suggestion about what adjustment needs to
be made? (I have the service manual but am not a tech).

Do the full alignment, start with the playback azimuth, the playback level,
the playback EQ. Then put on the exact kind of tape you're going to use,
do the record azimuth, the record bias, the record level, and the record EQ.

You're going to have to keep doing the full alignment on a regular basis,
too, so you might as well get the tools to do it now. You will need a cheap
scope, a signal generator (you can use a computer with a test tone generator
program), and the MRL alignment tape for the machine. The MRL tape is the
most expensive of the set.

The Nagra machines don't drift a lot unless they are really bumped around,
but they still drift some and you still need to touch up the alignment
now and then.

If the machine won't calibrate, THEN you have a problem to look into, but
my suspicion is that these have just drifted and probably weren't set up
for the same tape you're using.
--scott

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

[Mike Rivers[_2_]]

However when I do the same with the IV-S, the output on playback is
much lower (-30 or -40 dB),

This is a sign the machine is even more miscalibrated.

Or broken, either recording or playback, 30-40 dB seems way to far out
of whack to be within the calibration range. Play a tape on the 4S that
you recorded on the 4.2. If it plays back at near normal level, then the
4s isn't recording correctly. If it plays back at the low level, then
it's not playing back correctly.

[[email protected]]

On Tuesday, January 8, 2013 6:21:58 PM UTC-5, Mike Rivers wrote:
However when I do the same with the IV-S, the output on playback is

much lower (-30 or -40 dB),



This is a sign the machine is even more miscalibrated.



Or broken, either recording or playback, 30-40 dB seems way to far out

of whack to be within the calibration range. Play a tape on the 4S that

you recorded on the 4.2. If it plays back at near normal level, then the

4s isn't recording correctly. If it plays back at the low level, then

it's not playing back correctly.

Mike, good idea about recording and playing back tapes to and from the 4.2 and IV-S and checking playback levels. I'll do so today and report back. Could in fact be something wrong with the playback circuit on the IV-S. Cheers.

[Robert St-Louis]

Thanks a lot Scott, you're very helpful, as usual!
Both machines have likely not been calibrated in a long while, so
you're probably right about the need to go through them thoroughly at
this point.

I recently purchased a handheld signal generator, and handhelp mini-
scope.
http://www.amazon.com/VELLEMAN-HPG1-.../dp/B006YTWMZW
http://www.amazon.com/VELLEMAN-HPS14...589562-5434648

I also have a set of 250 nWb/m MRL tapes that I got with an Ampex 440,
that may or may not do the trick with the Nagras. Unfortunately, last
time I used it, it seems it has started to shed...

Sounds like this is an opportunity to get familiar with the service
manuals and the alignment procedure on these machines, and increase my
knowledge of tape recorder construction and maintenance.

Thanks again!
--Robert

[PStamler]

Everything Scott says is right, but there's one more thing you need to do before you start the alignment procedu clean the bejasus out of the heads. Encrusted crud on the heads (particularly the playback head) can cause severe losses.

Also, before you put your MRL tape on the IV-S, find somebody with a magnetometer and see if any of your heads are magnetized.

Peace,
Paul

[[email protected]]

On Wednesday, January 9, 2013 2:36:07 AM UTC-5, PStamler wrote:
Everything Scott says is right, but there's one more thing you need to do before you start the alignment procedu clean the bejasus out of the heads. Encrusted crud on the heads (particularly the playback head) can cause severe losses.



Also, before you put your MRL tape on the IV-S, find somebody with a magnetometer and see if any of your heads are magnetized.



Peace,

Paul

Thanks Paul. I've been cleaning the tape path with isopropyl before each test run. But it looks like some of my 966 stock is starting to shed (damn!) so I'll pay particular attention to it. My MRL tape was shedding oxide last time I used it, I'll read into baking it to possibly reverse the trend, if that will preserve the tape.

I also demag the tape path before tests (have a couple of demag'ers). Would that not prevent a head from becoming magnetized?

[Mike Rivers[_2_]]

On 1/9/2013 10:44 AM, wrote:

My MRL tape was
shedding oxide last time I used it, I'll read into baking it to
possibly reverse the trend, if that will preserve the tape.

MRL will give you a discount off a new tape, but go ahead and bake the
one you have first. At this point, its use isn't critical, you just want
to see where you stand. And for personal use, you can afford a half a dB
of loss here and there if that happens. I suggested comparing recordings
made on one recorder with the other because I didn't know (or forgot)
that you had an MRL reference tape.

I also demag the tape path before tests (have a couple of demag'ers).
Would that not prevent a head from becoming magnetized?

There's a paper on the MRL web site http://www.mrltapes.com/ about
demagnetization. The short story (and why Paul recommended checking with
a magnetometer) is that if you don't do it right, you can magnetize the
heads when you're trying to demagnetize them.

I think you asked about calibration tapes and reference levels, unless
that was someone else. There's a paper on the MRL web sit called
something like Choosing and Using a Calibration Tape that has a table of
offsets that let you use a tape made at one reference fluxivity to
calibrate to a different reference fluxivity.

[PStamler]

On Wednesday, January 9, 2013 9:44:39 AM UTC-6, wrote:

I also demag the tape path before tests (have a couple of demag'ers). Would that not prevent a head from becoming magnetized?

Not necessarily. Sometimes the head gets magnetized because there's a defective capacitor connecting it to the amplifier. If that's the case, then the head will get re-magnetized every time you turn the machine on.

Peace,
Paul

[Scott Dorsey]

wrote:

I also demag the tape path before tests (have a couple of demag'ers). Woul=
d that not prevent a head from becoming magnetized?

Heads don't normally become magnetized... it's actually a very rare event
and most of the time I have seen residual magnetism it's because of someone
degaussing the heads and being sloppy about it.

If you don't have a magnetometer, you're better off not degaussing at all
than doing it all the time, because without the magnetometer you don't know
if you're making things better or inadvertently making them worse.

Head magnetization is a very rare problem, but it does happen.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[PenaL]

On 8.1.2013 23:57, Robert St-Louis wrote:
Hi all,

Quick question on my Nagra 4.2 and IV-S. When I record a steady 1 kHz
signal at 0 dB on the 4.2 (using line-in socket), the output on
playback is higher than when recording, when the potentiometer is left
at the same place. (I record at 0 dB, and playback is +4 dB). From
what I have read, this is normal and expected given the type of tape I
use, and what the machine is likely calibrated for.

However when I do the same with the IV-S, the output on playback is
much lower (-30 or -40 dB), and I have to increase the level of the
potentiometer considerably to bring the level back to 0 dB. This
happens on either of the two channels (when I record the test signal
on each separately).

It's been a while since I've owned a IV-S so I don't know if this is
normal or not. Is it?

If it isn't, do you have a suggestion about what adjustment needs to
be made? (I have the service manual but am not a tech).

Thanks a lot.

--Robert

Maybe some part of chain is out of tune or broken. You should have the
test tape for tuning so you notice is the "fail" recording or payback
amp or somewhere else.
Also the tape you use will affect, so you should tune the recorder
according exactly the the tape you use.

It has gone about two decades while I used the Nagras - a lot on these
times. Really nice and lovely tools... :-)

-Pentti