On 2014-03-28 1:49 PM, Ted Kendall wrote:
> Is it not true that all tape guidance is "forced" to some extent? The
> most elegant system I have seen is that on the old Philips Pro51, where
> the roller guides are convex and the tape runs to the point of maximum
> pressure, without touching the flanges. That said, I reckon the A80 to
> be about the best general purpose transport there is - in my experience,
> it has never done violence to a tape. The only major drawback is that it
> deals about a well as any single capstan transport with severely warped
> or cupped tape - which is not very well at all. The Telefunken M10 is
> better here, as it has a trailing capstan, and I suppose a reworked
> A80QC might do a good job...
As you are undoubtedly aware, the roller entering the head assembly on
the A80 is convex / crowned and it also has an eddy current brake on it.
So, in reality, in fast wind modes, that guide is semi-stationary and
the tape slips over it on an air film (we hope). During playback, this
rotating component adds drag. While that is not as good as a slightly
slower capstan (relative to the one to the right of the head assembly),
but it does interesting things.
Additionally, the roller that pushes the tape into the head assembly on
the A80 does a magnificent job of "breaking the back" of the curl on
cupped (mostly acetate) tapes and this has become a magic solution for
me in reproducing many of these old acetate tapes. This is especially
true with full-track mono recordings that are cupped.
As an aside, it is interesting to note that I believe (it was about
three months ago I looked into this) that the supply-side capstan on the
A80QC sets the speed and the takeup side capstan is run a little faster.
Also interestingly, the direction change is accomplished at the capstan
motor lead level where the supply and takeup servo boards always remain
the same and the motors and tach heads are switched by the
forward/reverse play logic!
I also find judicious use of the tension pots sometimes assist in
playing a tape. The A80 (and A810 and other) tension sensors provide a
good indication of what you are doing.
The worst two tapes I've recovered that had been substantially warped by
long-term damp storage were greatly aided by using velour on a stick as
a pressure pad. These were both reels of acetate Scotch 201, one was
one-inch and the other was 1/2-inch. On the one-inch tape the top tracks
were the only ones recorded and of course those had the most warpage.
The bottom of the tape was tight against the heads and the top was
fluttering like a flag in the wind. We got most of it except where there
was a huge "pimple" forced through the first 1/2 to 3/4 inch radius by
the hub slot. The anomalies there were ably covered by the producer,
editing in other note fragments. This recovery was done on the Sony
APR-16 and I had to manually increase the pinch roller pressure to
counteract the drag that "pressure pad" caused.
-- Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm Quality tape transfers --
even from hard-to-play tapes.