CLIMBING THE ALPS
3: The large spring in the center is a "mod-ification"
to the Alps DAT loading mechanism, the success of which assumes
the loading mechanism and transport have not been damaged.
Tascam’s TC DAT decks
are more affordable than Sony’s, so the former find their way into many
audio facilities while the latter are more common in video houses. All
of Tascam’s DAT transports are made by Alps, an original equipment manufacturer
(OEM) that supplies the mechanisms found in the Otari DTR-90, the Fostex
PD-2 (portable) and D-30 (rackmount) TC DAT recorders. By some stroke
of luck—or genius—Fostex bypassed the problematic front-loading “elevator,”
opting instead for a simple, trouble-free hinged loading door. (Sony,
Panasonic and Pioneer make their own DAT transports. The Fostex D-5 and
Tascam DA-20 are entirely made by Pioneer. The transport in those machines
found its way into the Fostex D-15 and PD-4 as well.)
The Alps loading mechanism is a little too delicate for impatient Americans
who are accustomed to slamming VHS tapes into their home VCRs. Cassettes
not gently inserted will easily bend metal parts, pushing electromechanical
tolerances beyond the machine’s ability to compensate.
4: The yellow arrow points th "The Claw." Highlight-ed in
green is a metal spring that can also be damaged by impatience.
Four common symptoms
plague the Alps front-loading mechanism: It can either be sluggish or
too hungry during feeding, the latter being least desirable. On a good
day, a cassette sucked in before being securely engaged will be ejected.
(On a bad day, the machine will jam.) During the unload process, the “Central
Scrutinizer” may not sense that the tape is fully ejected, causing an
endless “déja` vu” of load and unload. To spare you some mental anguish,
the fourth symptom is described below, under the heading, “The Claw.”
SPRING INTO ACTION
Three sensing switches are hidden on the underside of the DA-60’s right
“junction” PCB as shown in the upper half of Fig. 2. (The lower portion
of this figure shows the visible side of this PCB.) No adjustments are
provided, and initial attempts at creating an adjustment “window” yielded
mixed results. As mechanical friction seems inconsistent among the various
mechanisms, a more basic “fix,” shown in Fig. 3, involves adding a spring
that serves a double purpose. As the cassette is loaded, the spring creates
resistance so that the tape is fully engaged before tripping the sensor
switch. On the return trip, the spring ensures that the mechanism returns
to the same “at rest” position, positively disengaging the switch.
Note: Under normal conditions, the job of the capstan motor is to maintain
exact speed. Alps also uses the capstan motor to power the loading mechanism!
A series of reduction gears convert the relatively weak rotational energy
into a force barely powerful enough to raise and lower the cassette. The
design is far from elegant.
I searched high and low for the perfect spring, finally settling on the
type used by Tascam for the loading drawer of the DA-30 and DA-30 MKII
(part number 5801396801). Cut the spring in half, fold out the last coil
so that it can be easily hooked and attach as shown in Fig. 3.
5: The horizontal support beam triggers the release of the claw (click
for larger view).
All DAT shells have
a rectangular slot designed to accept a claw that, when implemented, can
assist in the positioning process. Fig. 4 shows the black plastic assembly
on which the claw pivots (indicated by the yellow arrow). If users yank
the tape before it is fully released, the claw will break. This DA-60
subassembly does not have a part number so it can not be replaced. Instead,
it is necessary to purchase the entire loading mechanism (a $400 part).
After installing the spring, if the claw still doesn’t reliably disengage,
the final tweak is to apply a slight bit of pressure to the “thrust and
support” beam as indicated by the purple arrow in Fig. 5. This horizontal
bar provides structural stability to the loading mechanism as well as
“thrust” to trigger the claw’s release. Gently apply pressure and let
go. Then load and unload a tape repeating the “pressure process” until
the tape is consistently released.
END OF TAPE
In providing this information, it is not my intention to take away business
either from myself or from my friendly competitors. Tape machine repair
requires experience, patience, fine tools (in good condition), a steady
hand, test equipment and test tapes, ample illumination, good vision and/or
optical magnifiers. That said, an educated consumer is the best customer.
Get to know what’s on the inside, be good to your gear, be happy on the
outside and save a hug for your technician!
to Page 1
month, Mix debuts “The Tech’s Files,” a regular column focusing on maintenance,
mods, DIY and technical issues. Written by freelance author and noted
tech wizard Eddie Ciletti, this new column will emphasize how to achieve
optimum performance from the gear you already own. Read on, and enjoy.
Eddie Ciletti relocated his service facility from New York City to the
Twin Cities in 1999. While this is his first column for Mix, you can find
many of his tape- and audio-related articles at www.tangible-technology.com.
Reprinted with permission from Mix Magazine, April, 2000
© 2000, Intertec Publishing, A Primedia Company All Rights Reserved