Onkyo TA-2550 Service Manual

TA-2550
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 safety. 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 4
direction
direction
2. Insulating resistance measurement
Connect the insulating-resistance tester between the plug of
power supply cord and chassis.
Specifications; SOOV more than 1OMQ
HX PRO CIRCUIT OPERATION
EXPLANATION
1. Regarding recording frequency characteristic and bias
Ordinarily, if the recording bias current is increased, REC/PB
frequency response level in the high frequency region (about
10KHz and above) drops, and if the bias is decreased, the
response rises.
ai Bias decrease 4
Frequency >
ene
<—_———_
Bias increase
REC/PB level
2. Regarding the basic operation of HX PRO (Refer to Fig. 1)
The HX PRO uses the ~% PC1297CA IC. 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.
The signal of 1) preserves the frequency response with
the integrated circuit of (b).
R450 + R448 (2.1)
2m xX C426 x R450 x R448 *”
By means of the frequency of Fig. 1, the frequency which
is effective from the beginning is determined. In the
ordinary situation, this is half the audio band (10KHz),
(1OKHz ~ 7.5KHz).
At (c), in order to use the affected waveform after-ward,
absolute detection is carried out.
Frequency =
Rise
a
Frequency —>
4) At (d), the waveform peak value is detected. The output
becomes the peak DC voltage.
5) At (e), 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 1) ~ 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 HX PRO
With equation (2. 1) noted above, the effect begins at the
frequency thus determined.
Above a certain level the effect begins.
(Substantially 0 dB: In the vicinity of 500mV line out)
The audio signal component level is dependent upon the
waveform after point (c).
2)

Onkyo TA-2550 Specifications

General

Brand	Onkyo
Model	TA-2550
Category	Tape Deck
Language	English