CLIMBING THE ALPS

Figure 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.

Figure 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.

THE CLAW

Figure 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). Ouch!

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!

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Note: This 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.            —Ed.

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