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Biasing, setting up for different tape and capacitors ....

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June 8, 2005 9:58:56 AM

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

Hello,

Can someone here please explain or point me to a site (which explains) on
HOW to set up an open reel recorder (TEAC 3440 and TASCAM 388 in my case)
for different tape formulations ? I also would like to know precisely HOW to
change capacitors and any other things that may fail due to age of the
recorder. I asked about capacitors 'cause they seem to fail first on an
otherwise good, low use machine.

I'm a total NEWBIE with regards to these 2 issues but I have the
operations/service manuals for all of my machines and a willingness to learn
to do these myself. I'm certainly not dumb but it would be nice to have a
not-too-technical explanation of how to perform the above so that I don't
have to get "lost in the woods" for the lack of a better term.

Thanks in advance,

Daniel
June 8, 2005 9:58:57 AM

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

On Wed, 08 Jun 2005 05:58:56 GMT, "Daniel" <NotReal@yahoo.com> wrote:

>Hello,
>
>Can someone here please explain or point me to a site (which explains) on
>HOW to set up an open reel recorder (TEAC 3440 and TASCAM 388 in my case)
>for different tape formulations ?

You over bias by an amount that differs from one tape formulation to
another and also recording speed. That means you turn the bias all
the way down and then bring it up til you see a peak in record /
playback level and keep turning it up past that point until it drops
again slightly. I seem to remember over biasing 2 - 3 dB at 10kHz on
an Otari 5050BXII using Ampex Grand Master tape at 15 ips and then
adjusting the record eq for linear frequency response. At 7.5 ips
over bias by like only 0.5 dB. That would probably get you close
enough. There wasn't much difference on Teac machines except they
didn't have very good record eq and sometimes you would have to trade
off more linear frequency response for greater distortion. If you
have a distortion analyzer, it is easy, just bias for minimum
distortion.

> I also would like to know precisely HOW to
>change capacitors and any other things that may fail due to age of the
>recorder. I asked about capacitors 'cause they seem to fail first on an
>otherwise good, low use machine.

Can't help much there.

Julian
Anonymous
June 8, 2005 11:06:38 AM

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

"Julian" <JulianPAdamsNo@SpamHotmail.Com> wrote in message
news:ju4da1lm4otslkpc7fp8uo2lf5ff7h8fmk@4ax.com...

> You over bias by an amount that differs from one tape formulation to
> another and also recording speed. That means you turn the bias all
> the way down and then bring it up til you see a peak in record /
> playback level and keep turning it up past that point until it drops
> again slightly. I seem to remember over biasing 2 - 3 dB at 10kHz on
> an Otari 5050BXII using Ampex Grand Master tape at 15 ips and then
> adjusting the record eq for linear frequency response. At 7.5 ips
> over bias by like only 0.5 dB. That would probably get you close
> enough. There wasn't much difference on Teac machines except they
> didn't have very good record eq and sometimes you would have to trade
> off more linear frequency response for greater distortion. If you
> have a distortion analyzer, it is easy, just bias for minimum
> distortion.

On the Studer I used to use, you'd overbias 3dB @ 10kHz for 15 ips, 4dB for
7.5 ips, and who the hell cared at 3.75 ips.

But we need to backtrack. Original poster, you're gonna need one crucial
item: a playback alignment tape, so you can set the playback head azimuth
(that's the head gap's angle to the tape path, ideally perpendicular),
playback levels and playback EQ. You need to do those things before you
start messing with the record controls (azimuth, bias, level and EQ).

Peace,
Paul
Related resources
Anonymous
June 8, 2005 12:37:02 PM

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

Daniel <NotReal@yahoo.com> wrote:
>
>Can someone here please explain or point me to a site (which explains) on
>HOW to set up an open reel recorder (TEAC 3440 and TASCAM 388 in my case)
>for different tape formulations?

There is an introduction in the FAQ. You also will want the service manuals
for the recorders, which are available from Tascam.

>I also would like to know precisely HOW to
>change capacitors and any other things that may fail due to age of the
>recorder. I asked about capacitors 'cause they seem to fail first on an
>otherwise good, low use machine.

Learn to solder before doing anything else. Spend a good while practicing
making cables, and soldering and desoldering some junk boards before you
do anything else. Learn to be able to remove a part and replace it without
lifting the pads. Then start thinking about working on the machines.

>I'm a total NEWBIE with regards to these 2 issues but I have the
>operations/service manuals for all of my machines and a willingness to learn
>to do these myself. I'm certainly not dumb but it would be nice to have a
>not-too-technical explanation of how to perform the above so that I don't
>have to get "lost in the woods" for the lack of a better term.

Capacitor replacement is something that you really need to be a tech for.
First you need to learn how the circuit works to some extent, so you can
diagnose a problem. Secondly you need very good soldering skills to be
able to fix it. This is not something you will learn overnight, but it is
a good thing to learn.

Alignment is something that you need no real tech experience for. You
just need a scope, a signal generator and an alignment tape. It's something
you should practice on so you can do it in a few minutes, and it's
something that needs to be done on a regular basis (weekly or daily for
regular studio operation).
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 8, 2005 5:07:15 PM

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

Daniel wrote:
>
> Can someone here please explain or point me to a site (which explains) on
> HOW to set up an open reel recorder

Your answer is in your hands:

"I have the operations/service manuals for all of my
machines"

It's explained in detail, with all the tools and equipment
you need.

> I also would like to know precisely HOW to
> change capacitors and any other things

Here are the precise steps, considering "I'm a total NEWBIE
with regards to these 2 issues":

1. Find someone who is highly skilled with this task.

2. Take your machine and yourself to them.

3. Watch while they do what you want them to do. Watching
them do it will give you an appreciation for the skills and
knowledge required, and justify in your mind why you will be
paying them what they will ask to be paid. This is not a
task for a "NEWBIE". Or you could practice on many, many
other pieces of junk equipment until you gain the skills.
But then you wouldn't know if you had been successful.
Changing capacitors, or for that matter any board level
component on these machines is incredibly difficult for an
amateur. These aren't beginner level Heathkits.

There are way too many ways you can screw this up. If you
intend on having machines that will work for you for any
length of time, keep your hands busy with head cleaning,
lubrication, de-magging and maybe alignment chores. On the
other hand, if you decide to go ahead, find out what scrap
3440s and 388s are selling for so you'll have an idea of
what you'll be able to get for the machines.



TM
June 9, 2005 9:21:05 PM

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

On 8 Jun 2005 08:37:02 -0400, kludge@panix.com (Scott Dorsey) wrote:

>

>Alignment is something that you need no real tech experience for. You
>just need a scope, a signal generator and an alignment tape. It's something
>you should practice on so you can do it in a few minutes, and it's
>something that needs to be done on a regular basis (weekly or daily for
>regular studio operation).
>--scott

Scott, You don't really need a scope to align a tape deck. Yes, I
know you can get more precise head alignment, but the difference is
slight indeed, and I don't want to scare the OP off if he doesn't have
one or know what to do with it.

Julian
Anonymous
June 10, 2005 1:35:39 AM

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

Julian <JulianPAdamsNo@SpamHotmail.Com> wrote:
Kludge writes:
>>Alignment is something that you need no real tech experience for. You
>>just need a scope, a signal generator and an alignment tape. It's something
>>you should practice on so you can do it in a few minutes, and it's
>>something that needs to be done on a regular basis (weekly or daily for
>>regular studio operation).
>
>Scott, You don't really need a scope to align a tape deck. Yes, I
>know you can get more precise head alignment, but the difference is
>slight indeed, and I don't want to scare the OP off if he doesn't have
>one or know what to do with it.

It's not slight at all! Honestly, you really need to do it right with
a scope. If you don't have the azimuth absolutely perfect, you can't
do the high end EQ correctly and the errors just get compounded. Alignment
isn't really all that difficult and there is _no_ reason to cut corners.

With a scope you also learn things about your head condition and tape
path stability that are important to know... if you can't keep the loop
closed at 16 KHz you won't notice it at all by listening to the playback,
but you'll sure see it on the scope.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
June 10, 2005 10:53:36 AM

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

Ok, I perhaps under-estimated the value of a competent pro to do this type
of work. Thanks very much for all of your replies and helpful suggestions
and I'll definitely have a tech look at my machines. Hopefully I'll learn
something from them ...

Thanks again for shedding light on this issue.

~Daniel
June 10, 2005 10:53:37 AM

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

On Fri, 10 Jun 2005 06:53:36 GMT, "Daniel" <NotReal@yahoo.com> wrote:

>Ok, I perhaps under-estimated the value of a competent pro to do this type
>of work. Thanks very much for all of your replies and helpful suggestions
>and I'll definitely have a tech look at my machines. Hopefully I'll learn
>something from them ...

Like most things it depends on your expectations. If you need 100% as
good quality as the machines you have can possibly produce, yes you'd
best not to try on your own. If learning how the machines work is one
of your goals and you're willing to accept 90 - 95% as good as you can
get at least to begin with, you just might be able to achieve it on
your own if the machines are in good shape. It's certainly at least
worth a try! I wouldn't let these guys get away with scaring you off.
They're not telling you the complete story. There are reasons why it
is actually better NOT to mess very much with a scope and head
alignment on a machine whose heads are worn, for example. If your
record and play back always on the same machine, playback head
alignment isn't critical if you tweak the record head to match
wherever the playback head is currently set to. Even if you don't
have a test tape, assume the playback eq is probably at least close
and see if you can't tweak the bias and record parameters a little bit
and improve teh record quality. Get the manuals and see what you can
accomplish. If it looks like the machine is in good shape and you are
happy with your response measurements and if it sounds pretty good to
your ears and the heads don't show too much wear, THEN invest in a
test tape. That's something no one talked about. If the heads are
badly worn, it just isn't worth spending the money to have a pro fix
it up for you unless you are ready to spend big bucks. Run your
finger nail across the head and see how much of a groove is worn where
the edges of the tape contact the heads. A little click is OK, no
groove is perfect. On extremely badly worn heads you'll actually see
the black head gap gets wider. If the machine is basically blown, you
haven't lost anything by trying to tweak it a bit and if it is in
pretty good shape you'll know and either get it closer or decide it is
worth the money to take it to someone to get perfect. I definitely
think you should try first on your own! I don't recommend changing
components with your amount of expertise, but if you stick to just
tweaking the record head alignment and electronics, you aren't going
to ruin the machine. Be systematic, read the instructions carefully
and mark your starting points on each adjustment so if you do get
confused, you can at least put it back to where it was before you
started. If you simply can't figure it out THEN pay someone.

Go for it!

Julian
Anonymous
June 10, 2005 12:01:01 PM

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

Daniel <NotReal@yahoo.com> wrote:
>Ok, I perhaps under-estimated the value of a competent pro to do this type
>of work. Thanks very much for all of your replies and helpful suggestions
>and I'll definitely have a tech look at my machines. Hopefully I'll learn
>something from them ...

It's not that bad, but it is something you want someone to show you. But
read the FAQ on the subject... it is a little dated but describes the
process well.
--scott


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