phase variance on half track (pr99)

[mr c deckard]

i posted about this a few days ago: i hooked the pr99 up to a scope,
and the phase at 16khz "warbles" by as much as 90degs . . . is this at
all normal? i get a new pinch roller tomorrow, but i swapped it out
for another one, and it still didn't really improve.

when i look closely at the tape, it shifts up and down as it goes
across the heads ever so slightly. i can't seem to figure out what is
causing it. i pulled back the pinch roller, but it still does it . .
..

thanks,
chris

[Peter Larsen]

mr c deckard wrote:

> i posted about this a few days ago: i hooked the pr99 up to a scope,
> and the phase at 16khz "warbles" by as much as 90degs . . . is this at
> all normal? i get a new pinch roller tomorrow, but i swapped it out
> for another one, and it still didn't really improve.

> when i look closely at the tape, it shifts up and down as it goes
> across the heads ever so slightly. i can't seem to figure out what is
> causing it. i pulled back the pinch roller, but it still does it . .

Il Manuale will help you and so will experience in getting a tape path
right. I don't have picture perfect 16 kHz stability on my Revox A77 but
that is because the IDIOT who converted it to 15" couldn't drill a
straight hole and thus caused the capstan axis to tilt. Unfortunately I
didn't find that out when it mattered. Strangely the people who fought
with adjusting it also didn't grasp that something so basically wrong
was the cause of the transport being less good that usual for the
pedigree. I am not suggesting that something equally severe is wrong
with your machine, but a tape path adjustment problem does appear to
exist. First get a service manual prior to doing anything else. Next get
a degausser so that you have demagged tools.

> thanks,
> chris


Kind regards

Peter Larsen

--
************************************************** ***********
* My site is at: http://www.muyiovatki.dk *
************************************************** ***********

[Scott Dorsey]

mr c deckard > wrote:
>i posted about this a few days ago: i hooked the pr99 up to a scope,
>and the phase at 16khz "warbles" by as much as 90degs . . . is this at
>all normal? i get a new pinch roller tomorrow, but i swapped it out
>for another one, and it still didn't really improve.

That bis a little excessive, yeah.

>when i look closely at the tape, it shifts up and down as it goes
>across the heads ever so slightly. i can't seem to figure out what is
>causing it. i pulled back the pinch roller, but it still does it . .

Could be a bad roller still. Could be bad guides, bad heads. How old
is the MRL? If it's been sitting on a shelf for 20 years it could be bad.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

In article > writes:

> i posted about this a few days ago: i hooked the pr99 up to a scope,
> and the phase at 16khz "warbles" by as much as 90degs . . . is this at
> all normal?

> when i look closely at the tape, it shifts up and down as it goes
> across the heads ever so slightly.

That will do it. It doesn't take very much skew to get 90 degrees
phase shift between channels at 16 kHz. You might be able to improve
on it with a new pinch roller and getting the tension just right. Worn
guides can also cause this, but it's unlikely that they're worn that
badly. When aligning a recorder that I can't get any better than that
without extensive rebuilding, I just take an eyeball average when
doing an azimuth alignment.

Try a different tape (is this a standard alignment tape?) Back
coated tape is more mechanically stable than uncoated tape, and Agfa
(and I assume BASF) tape tends to be more consistent in width than
othe brands.


--
I'm really Mike Rivers - )
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

[mr c deckard]

thanks for the replies all, i'm still trying to meet up with the
postman to get the new pinch roller . . . but i've JUST had the heads
relapped, and JUST bought the mrl tape.

the guides (the rollers that the head cover clips to) seem to be
engineered to allow a bit of variance in the tape, there's also the
dark red guide between the repro head and the capstan, but it seems
fine, too.

here's something strange, tho. the sync and repro head are encased in
a metal shield. it seems that the tape hits this case when it comes
off the sync head (although i can't tell for *sure*) . . . the
worrisome thing is that there doesn't seem to be anyway to adjust
this.

and i can't find a manual at all for a reasonable price ($250usd !=
reasonable) -- although a german gentleman posted a link to a
download, but alas, the manual for the A77 only has the front cover in
the zip file . . ., and the pr99 is available only in german.

so i'm going to replace the roller, but the sync shield thing concerns
me.

thanks,
chris


> That will do it. It doesn't take very much skew to get 90 degrees
> phase shift between channels at 16 kHz. You might be able to improve
> on it with a new pinch roller and getting the tension just right. Worn
> guides can also cause this, but it's unlikely that they're worn that
> badly. When aligning a recorder that I can't get any better than that
> without extensive rebuilding, I just take an eyeball average when
> doing an azimuth alignment.
>
> Try a different tape (is this a standard alignment tape?) Back
> coated tape is more mechanically stable than uncoated tape, and Agfa
> (and I assume BASF) tape tends to be more consistent in width than
> othe brands.

[Scott Dorsey]

mr c deckard > wrote:
>
>here's something strange, tho. the sync and repro head are encased in
>a metal shield. it seems that the tape hits this case when it comes
>off the sync head (although i can't tell for *sure*) . . . the
>worrisome thing is that there doesn't seem to be anyway to adjust
>this.

Is the head height okay? On a 2-track you can probably adjust it visually
and just leave it at that.

>and i can't find a manual at all for a reasonable price ($250usd !=
>reasonable) -- although a german gentleman posted a link to a
>download, but alas, the manual for the A77 only has the front cover in
>the zip file . . ., and the pr99 is available only in german.

Last I looked they were only around $20. Try a broadcast supply house.
--scott

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

[mr c deckard]

the head height seems ok, the tape is right between the two "cut-outs"
on the head, and it doesn't hit the shield on the top or bottom, just
on the egress from the sync head, it seems like it might be hitting
it, which reminds me, when JRF relapped the heads, i remember them
doing some sort of alignment -- i'm a little weary of moving the heads
around on the mounting place since i'm unclear on what, exactly, they
did. . .

-chris


>
> Is the head height okay? On a 2-track you can probably adjust it visually
> and just leave it at that.
>
> >and i can't find a manual at all for a reasonable price ($250usd !=
> >reasonable) -- although a german gentleman posted a link to a
> >download, but alas, the manual for the A77 only has the front cover in
> >the zip file . . ., and the pr99 is available only in german.
>
> Last I looked they were only around $20. Try a broadcast supply house.
> --scott

[Edi Zubovic]

On 22 Nov 2003 12:19:52 -0800, (mr c deckard)
wrote:

------<snip>---

>and i can't find a manual at all for a reasonable price ($250usd !=
>reasonable) -- although a german gentleman posted a link to a
>download, but alas, the manual for the A77 only has the front cover in
>the zip file . . ., and the pr99 is available only in german.
>
>so i'm going to replace the roller, but the sync shield thing concerns
> me.

A manual for $250?! Or the whole machine with 2 manuals? God
Allmighty.

While I don't quite second posting manuals free online as they're
copyrighted too (Revox still sells the operating and service manuals
but certainly for a tenth of the above price at maximum), my inner
myself always giggles a bit when I find one at the web.

So here you'll find a service manual for the PR99 (MKII) for, khem,
free:

http://www.arky.ru/audio/

Now when you're at that site, look at the black links bar where stands
something like "cxembi". That's Schematics in Russian. When you're at
the page, the Revox PR99 Service Manual is #59. It's a zip containing
gif pictures of pages and it's abt. 18,5 MB.

If the tape swimms on new heads, check for clearances at guide roller
bearings, which should be medically clean so and so, clean the
capstan with a isopropyl alcohol and wash the capstan roller in a mild
detergent then dry, but only if the roller is of older type ie. pure
rubber (it has an arrow for the rotation direction then). Often the
newer rollers are made of a greenish rubber-like synthetics. It's so
hygroscopic that you'll get something like Blue Tack of the material
until you bake it at 70 degrees C and let dry.

A dirty capstan, or some other tape run problem, excels at the very
end of the tape: you can clearly hear wow at 1 or 3 KHz.

Edi Zubovic, Crikvenica, Croatia

[Edi Zubovic]

:
>
>http://www.arky.ru/audio/
>

Ow. The manual is in German only, I see. Sorry.

Edi

[Peter Larsen]

Edi Zubovic wrote:

> >http://www.arky.ru/audio/

> Ow. The manual is in German only, I see. Sorry.

It may still suffice, at the price it is better than not having it.

> Edi

--
************************************************** ***********
* My site is at: http://www.muyiovatki.dk *
************************************************** ***********

[Edi Zubovic]

On Sun, 23 Nov 2003 13:54:58 +0100, Peter Larsen
> wrote:

>Edi Zubovic wrote:
>
>> >http://www.arky.ru/audio/
>
>> Ow. The manual is in German only, I see. Sorry.
>
>It may still suffice, at the price it is better than not having it.
>
>> Edi

.... and unfortunately, after downloading it, I've found it's an Users
Manual, not a Service Manual... pity but nevertheless, it's a pretty
good scan and still containing useful info which could be generally
useful for B77 series also.

Edi Zubovic, Crikvenica, Croatia

[Mike Rivers]

In article > writes:

> Ow. The manual is in German only, I see. Sorry.

But the pictures and numbers should work pretty well in any language.



--
I'm really Mike Rivers - )
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

[mr c deckard]

hey, thanks for the info edi. but my problems are solved - i
thought calibration would be covered in the users manual, and things
like part numbers were covered in the service manual. the reason i
thought this is that i actually successfully downloaded a service
manual, but since it's in .tiff format, it's really really hard to
view -- i just saw pc board layouts, mods, schematics and exploded
views, but on second look, i see some instructional text.

i suppose i'll site down and print it all out. i'd really much rather
pay $50, but so it goes.

thanks again,
chris deckard
saint louis, mo


>
> A manual for $250?! Or the whole machine with 2 manuals? God
> Allmighty.
>
> While I don't quite second posting manuals free online as they're
> copyrighted too (Revox still sells the operating and service manuals
> but certainly for a tenth of the above price at maximum), my inner
> myself always giggles a bit when I find one at the web.
>
> So here you'll find a service manual for the PR99 (MKII) for, khem,
> free:
>
> http://www.arky.ru/audio/
>
> Now when you're at that site, look at the black links bar where stands
> something like "cxembi". That's Schematics in Russian. When you're at
> the page, the Revox PR99 Service Manual is #59. It's a zip containing
> gif pictures of pages and it's abt. 18,5 MB.
>
> If the tape swimms on new heads, check for clearances at guide roller
> bearings, which should be medically clean so and so, clean the
> capstan with a isopropyl alcohol and wash the capstan roller in a mild
> detergent then dry, but only if the roller is of older type ie. pure
> rubber (it has an arrow for the rotation direction then). Often the
> newer rollers are made of a greenish rubber-like synthetics. It's so
> hygroscopic that you'll get something like Blue Tack of the material
> until you bake it at 70 degrees C and let dry.
>
> A dirty capstan, or some other tape run problem, excels at the very
> end of the tape: you can clearly hear wow at 1 or 3 KHz.
>
> Edi Zubovic, Crikvenica, Croatia

[Steve]

Peter Larsen > wrote in message >...
> Edi Zubovic wrote:
>
> > >http://www.arky.ru/audio/
>
> > Ow. The manual is in German only, I see. Sorry.
>
> It may still suffice, at the price it is better than not having it.
>
> > Edi

You could allways try a small chunk of relevant text on

http://babelfish.altavista.com/translate.dyn

It may not help but it my give you a laugh.

Steve Lane

[Edi Zubovic]

On 23 Nov 2003 11:26:20 -0800, (mr c deckard)
wrote:

>hey, thanks for the info edi. but my problems are solved - i
>thought calibration would be covered in the users manual, and things
>like part numbers were covered in the service manual. the reason i
>thought this is that i actually successfully downloaded a service
>manual, but since it's in .tiff format, it's really really hard to
>view -- i just saw pc board layouts, mods, schematics and exploded
>views, but on second look, i see some instructional text.
>
>i suppose i'll site down and print it all out. i'd really much rather
>pay $50, but so it goes.
>
>thanks again,
>chris deckard
>saint louis, mo
>

You're welcome Chris!

Edi