Revox PR99 MkII; Speed change

[Ty Ford]

Last night Scott Dorsey, Mike Rivers, Richard Kuschel, John Vengouski myself
and several spouses had a wonderful Moroccan dinner in Washington DC.

Many things were discussed, oddly enough including audio.

One thing remains a question to me. There are hard-wired "speed selector"
jumpers on the PR99 Locator MPU Printed Circuit board. There's also a
notation about two different capstan diameters.

Has anyone ever downshifted a Revox PR99 from 7.5/15ips to a lower speed
using these jumpers? Was a new capstan required? Any thoughts would be
appreciated. The maintenance manual doesn't really go into it in detail.


Regards,

Ty Ford





For Ty Ford V/O demos, audio services and equipment reviews,
click on http://www.jagunet.com/~tford

[David Satz]

Ty Ford wrote:

> Has anyone ever downshifted a Revox PR99 from 7.5/15ips to a lower speed
> using these jumpers? Was a new capstan required? Any thoughts would be
> appreciated. The maintenance manual doesn't really go into it in detail.

At the risk of being quite wrong, I'd extrapolate from the A 77 series
in which a new (smaller diameter) capstan was needed as well as new
record and playback amplifier PC boards when changing speeds. If not
installing new cards then at least a fair number of components would
need swapping around because of the different EQ curves.

Since there is some demand for the high speed model, while standard-speed
B 77s come up from time to time on the used market, it may be a lot easier
to sell yours and buy a unit that's already got the right parts in it.

--best regards

[Mike Rivers]

In article <tford.1411534339B@news.jagunet.com> tford@jagunet.com writes:

> Many things were discussed, oddly enough including audio.

Yeah, but the food was better than the audio in the restaurant.

> One thing remains a question to me. There are hard-wired "speed selector"
> jumpers on the PR99 Locator MPU Printed Circuit board. There's also a
> notation about two different capstan diameters.

It could be that the jumpers change equalization and you have to
resort to mechanics to change the speed, but I suppose that if you can
identify anything useful about the jumpers, you could change them to
what you think is the low speed and see what happens. If the tape
doesn't run slower, then you need the different capstan.



--
I'm really Mike Rivers - (mrivers@d-and-d.com)

[Scott Dorsey]

Ty Ford <tford@jagunet.com> wrote:
>Last night Scott Dorsey, Mike Rivers, Richard Kuschel, John Vengouski myself
>and several spouses had a wonderful Moroccan dinner in Washington DC.
>
>Many things were discussed, oddly enough including audio.
>
>One thing remains a question to me. There are hard-wired "speed selector"
>jumpers on the PR99 Locator MPU Printed Circuit board. There's also a
>notation about two different capstan diameters.

Okay, on the A77, you need to swap capstans in order to change speeds.
You also ought to swap motors so the capstan is shifted a bit, but you
can redrill the mounting bracket on one motor to make it fit in the new
position.

I didn't think you needed to swap the capstans on the B77. I thought it
was just a jumper on the servo control board.

The electronics on the A77 can be tweaked so that it will run at 30 ips
on 15 ips speed, but the motor sounds like it's going to explode at any
minute. Likewise it can be run down to 1 7/8 ips if you can deal with
the flutter.

>Has anyone ever downshifted a Revox PR99 from 7.5/15ips to a lower speed
>using these jumpers? Was a new capstan required? Any thoughts would be
>appreciated. The maintenance manual doesn't really go into it in detail.

Check the parts list on the manual and see if there are two part numbers
for the capstan or not. If there is no jumper that you change on the servo
control board, you probably need to change the capstan.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Edi Zubovic]

On 18 Aug 2003 11:22:13 -0400, kludge@panix.com (Scott Dorsey) wrote:

>>One thing remains a question to me. There are hard-wired "speed selector"
>>jumpers on the PR99 Locator MPU Printed Circuit board. There's also a
>>notation about two different capstan diameters.
>

Well, it must have been a Bon Appetite indeed.

As to the B77 and speed change by exchanging the capstan; I do it
sometimes just to bring some 38 cm/s tape into the PC. By changing the
normal speed capstan to the fat HS one, the following is what I
noticed (from purely mechanical point of view): -- The band does not
touch the tape guide before the capstan. The solenoids can't latch to
the end position but they do hold. So there is a change of sound when
they engage in comparison with the normal "clack" with the 19 cm/s
capstan. I think the capstan roller is under increased load (normal
pressure should be abt 1,5 kg when I remembered right). But the sound
is OK and at least here, I didn't notice some azimuth problems (I can
do posibble eq. corrections later in the PC).

I have both the motors of a PR99 and of a B77 MKII and there is indeed
the difference in motor housings ie. mounting plates; the bores for
screws at PR99 are slightly offset in comparison to the B77's which
are centered. So the capstan is offset slightly too. Now I don't know
whether the Low Speed version has an offset base plate but it may well
be so.

Edi Zubovic, Crikvenica, Croatia


PS. I just haver to exchange the Nvidia's Nforce2-based motherboard
for a VIA's one. I can't get rid of small glitches whatever I try and
until the exchange, I can't work at all. Looks like a PCI
transport/buffer problem. I did everything, even changed from ACPI
BIOS to "normal" but no help. Perhaps there's a hidden IRQ conflict
because Nforce2 presented me with some 25 "Interrupt Steerings"
instead of 4 at VIA!

The glitches when zoomed in look as the shark's teeth, awful! -- With
VIA everything was fine.

[Justin Ulysses Morse]

Ty Ford <tford@jagunet.com> wrote:

> Has anyone ever downshifted a Revox PR99 from 7.5/15ips

Hold it right there. If you sell your 7.5/15ips PR99, you should be
able to buy two or three lower-speed machines. I may have access to
one if you'd like to just trade.


ulysses

[Ty Ford]

In Article <180820031845333479%ulysses@rollmusic.com>, Justin Ulysses Morse
<ulysses@rollmusic.com> wrote:
>Ty Ford <tford@jagunet.com> wrote:
>
>> Has anyone ever downshifted a Revox PR99 from 7.5/15ips
>
>Hold it right there. If you sell your 7.5/15ips PR99, you should be
>able to buy two or three lower-speed machines. I may have access to
>one if you'd like to just trade.
>
>
>ulysses

Hmmmm. I found a guy in nashville who worked for Studer Revox. $400 for the
conversion (plus shipping).

I'm going to wait to see if this job comes in that may require the 3 3/4ips
first, but thanks for the offer! What do you have?

Regards,

Ty Ford

BTW, it's not just about jumpers, as one might suspect. It is about capstan
size and EQ adjustments and bias adjustments and moving a belt to another
goove on the wheel. The jumpers just change the timing display.

Regards,

Ty Ford

For Ty Ford V/O demos, audio services and equipment reviews,
click on http://www.jagunet.com/~tford

[Justin Ulysses Morse]

Justin Ulysses Morse <ulysses@rollmusic.com> wrote:

> >Hold it right there. If you sell your 7.5/15ips PR99, you should be
> >able to buy two or three lower-speed machines. I may have access to
> >one if you'd like to just trade.


Ty Ford <tford@jagunet.com> wrote:
> Hmmmm. I found a guy in nashville who worked for Studer Revox. $400 for the
> conversion (plus shipping).
>
> I'm going to wait to see if this job comes in that may require the 3 3/4ips
> first, but thanks for the offer! What do you have?

My old college radio station unloaded a whole bunch of PR99s in the
last few years, along with some AG440s and MX5050s and other stuff.
Their bureaucracy prevents them from selling stuff, but allows them to
throw things away, pay to have them disposed of, or given away to
whoever volunteered to do the lifting. I got many of those machines,
and most are long gone, but I think there was one left that an
associate of mine grabbed and I know he has no use for it. He'd be
happy to move up to a faster machine if it didn't cost him much.

$400 for the conversion to low speed seems silly when you can't sell a
3.75/7.5ips PR99 for more than about $150 on a good day. I think I may
have gotten $250 for one of the 15ips machines, but that was two or
three years ago. If they said Studer instead of Revox it would be
different.

ulysses