Scott 480A Service Manual

Page 1

GENERAL SERVICING INFORMATION

The following information applies to all players in this volume, and should be followed
before any adjustments are made or trouble diagnosis is attempted. Any exceptions or
additions will be found in the detailed servicing procedures for each player.

POWER SOURCES

Many players require full supply voltage for proper operation Be sure the supply
voltage is maintained at the rated value under load while making adjustments.

CLEANING

Head faces should be cleaned with head cleaner to remove dust and accumulated
oxide. (An applicator may be fashioned from absorbent cotton.) Do not use a screw-
driver or any metallic object near the head faces.

CAUTION: Avoid getting head cleaner on an y plastic surface.

Clean capstans, pressure rollers, and tape guides with alcohol using a soft lint-free
cloth. Also use alcohol to remove oil and grease from drive belts and other driving
surfaces.

LUBRICATING

Clean all surfaces before lubricating. Apply a few drops of #20 machine oil to all
bearings and rotating bushings. Apply a thin film of light, nonhardening grease to all
cam surfaces and pawls, if they have been factory lubricated. Always wipe excess
oil or grease from parts that have been lubricated.

CAUTION: Oil and grease must be kept ofl all driving surfaces as well as any parts
which may transfer oil or grease to them.

DEMAGNETIZING

Heads require demagnetizing at regular intervals to maintain high-frequency response,
dynamic range, and low distortion. (Follow instructions included with the demag-
netizing unit.) After demagnetizing the heads, keep all screwdrivers and other metallic
objects away from the head faces. Tape guides may also require occasional demag-
netizing:

IMPORTANT: Be sure to demagnetize the heads after making resistance measurements
in the head circuits.

CARTRIDGES

Many problems associated with tape players result from defective cartridges. Always
try a cartridge known to be good before attempting repairs.

Page 2

Scott 460A,480A

oae=w
I. 23.7
POWER AMPLIFIER / (26.1w
5 v +240i24.8)d8

Aux, TUNER, VOLUME AMPLIFIER
115391-- +2039
" l50rnV /:f TOTAL

PHONO =79.s(eo.4)da-

/ EOUALIZER

_PHONO / 3-5
.___, _ _ _
-2.5mv

TONE CONTROL- 1: 0 :18

Level Diagram:
460A (480A) [1 kHz Input]

ADJUSTMENT

Equipment Required

Audio signal generator.

DC voltmeter.

Speaker load resistors, 8 ohm, 100 wart.

Digital voltmeter or DC milliammeter.

The following adjustments are the same for both the left and
the right channel.

Bias Adjustment

1) Connect 8 ohm resistors to the speaker A terminals, and
set the Speaker Mode switch to A position.

2) Turn the Volume control fully counter-clockwise.

3) Turn RV] fully counterclockwise.

4) Depending on available equipment, use A or B:

A. Set digital voltmeter to most sensitive voltage range.
Connect probes across R37 and R39 (Voltmeter bias
test points, L channel).

Turn unit on. Let it idle for at'least one minute. Ad-
just RVl for 40 mV across the resistors.

B. With unit off, remove jumper between PC board ter-
minals E and E, and connect ammeter, set to 100 mA
range.

Turn unit on and let it idle for at least one minute.
Adjust RVl for 40 mA.

5) Perform the same procedure for the right channel, except
measure voltage across R38 and R40 (voltmeter bias test
points, R channel) or replace jumper from D to D with
ammeter. Adjustment is made with RVZ.