Onkyo TA 2800 Service Manual

Page 1

ONKYO

TA-2800

SEFIIAL NO. 3302

SERVICE MANUAL

STEREO CASSETTE

TAPE DECK
MODEL TA-2800
Black model
UDN, UDC, UD 120V AC, 60Hz
UG 220V AC, SUI-I2
UW 120 or 220V AC . 50/60l-Iz
UQA. UQB 240V AC. SOHZ

SAFETY-RELATED COMPONENT WARNING

COMPONENTS IDENTIFIED BY MARK 4, ON
THE SCHEMATIC DIAGRAM AND IN THE PARTS
LIST ARE CRITICAL FOR RISK OF FIRE AND
ELECTRIC SHOCK. REPLACE THESE COM-
PONENTS WITH ONKYO PARTS WHOSE PARTS
NUMBERS APPEAR AS SHOWN IN THIS MANUAL

MAKE LEAKAGE-CURRENT OR RESISTANCE
MEASUREMENTS TO DETERMINE THAT
EXPOSED PARTS ARE ACCEPTABLY IN-
SULATED FROM THE SUPPLY CIRCUIT BEFORE
RETURNING THE APPLIANCE TO THE
CUSTOMER.

ON KYO:
MIIIIII IIIIMPIIIIIIIIS

SPECIFICATIONS

Track Formal: 4-lrecks. 2~chennels
Erasing Syslem: AC erase

Tape Speed: 4.8 cmlsec. (1-7/6 I:p.e.)
Wow and Flutter: 0.04% (WRMS)

Frequency Response: 20-17,000Hz (Normal)
(30- 16.000H1 1-3dB)
20-18,!)sz (High)
(so-17,000Hz :SdB)
15-21.000Hz (Melnl)
(20 40.000142 : ada)
SIN Ratio: GOdB (metal lepe, Dolby NFl oil)
A nolse reduction ol 10dB above Em:
and 5d B at (Hz ls possible wilh Dolby B
NR. A nolse reducllon of 20:15 el 5kHz Ie
posslbla with Dolby O NH.
Input Jacks: Une IN: 2
lnpul senslllvily: 60mV
Input Impedance: 50kolims
Ouipuls: Une OUT: 2
Standard oulpul level: 1100mV (DdB)
Opllmurn load Impedance: over
50 kohms
Headphone Jack: 1
Opllmum load Impedance: 8 to 200

ohms
Moiors: DC servo molor: 1
DC molor: 2
Heads: REC/PB: Special Herd Permelloyx 1:

Erase heed: Ferrlle x 1
Power Supply Rating: U.K. and Auslrellan models:

AC 240V, 50Hz

U.S.A. and Canadian models:

AC 120V, 60Hz

Worldwlde models:

AC 120V and 220V switchable, 50/ 60H:
Power Consumpllon: 24 wells

Dimensions: 4350M) x 132(H) x 366(D)rnm
7-1/8" x 5-3/16' x 14-7/16")
Welghl: 6.2 kg: (13.7 lbs.)

Specilicallons and exlernal appearance are subject In change
wllhoul notice because 0! producl Improvemenls.

Page 2

-2800

REC/PB level ->

SERVICE PROCEDURES

1. Replacement of power supply cord

There are two power supply cord outlets on the strainrelief.
Insert them in prescribed direction to ensure safEIy. AS-UC-
3 (UD<120V> model) should be inserted lengthwise and
other types of cords should be inserted horizontally.

Power Supply Cord Power Supply Cord

Horizontal

length Wise
directlon

direction

2. Insulating resistance measurement

Connect the insulatingeresistance tester between the plug of
power supply cord and chassrs.

Specifications: 500V more than iOMQ

HX PRO CIRCUIT OPERATION
EXPLANATION

1. Regarding recording frequency characteristic and bias
Ordinarily. ifthc recording bias current is increased. REC/PB
frequency response level in the high frequency region (about
lthHz and abovc) drops. and if the bias is decreased. the
response rises.

Rise

Drop Bias decrease? T
\ E _/\
<-- 1'
Bias increase E
5
Frequency - E Frequency -->

2. Regarding the basic operation ofHX PRO (Refer to Fig. l)
The HX PRO uses the ,u PC1297CA 1C. The operation is
in accordance with the following.

1) At (a). the recording bias is added onto the audio signal.
and the recording signal is detected. This is the same as
the recording head recording the signal on the tape.

2) The signal of l) preserves thc frequency response with
the integrated circuit of (h).

R450 + R448 (,7 I)
27: x C426 x R450 x R448 "
By means of the frequency of Fig, l. the frequency which
is effective from the beginning is determined. In the
ordinary situation. this is half the audio hand (lUKHZ).
(lllKHz ~ 7.5KH2).

3) At (c). in order to use the affected waveform afterward.

absolute detection is carried out.

Frequency :

4) At (d). the waveform peak value is detected. The output
becomes the peak DC voltage.

5) At (6). the standard voltage and the voltage of (4) are
compared.

6) With the output of (e). the frequency generation level is
controlled (voltage controlled amplifier). That is. the bias
size is varied.

7) Summing up I) ~ 6):

At (a). the time constant (frequency) that is detected in
the recording signal is preserved. and above a certain
frequency and above a certain level. the VCA controls
the bias current by causeing its reduction. When this is
done. in the maner shown in the explanation of Item I
above. the frequency high region is raised, With this
control. the audio signal is instantaneously dealt with.

Regarding the operating conditions of the fix PRO

With equation (2. 1) noted above. the effect be'gins at the
frequency thus determined.

Above a certain level the effect begins.

(Substantially 0 dB: In the vicinity of SOUmV line out)
The audio signal component level is dependent upon the
waveform after point (c).

2)