Sony ta 4650 schematic

Page 1

Service Bylletin No.49_

SONY CORPORATION 01" AMERICA Model:

Technical Publications Department
4747 VIII Dlm Sin-l, Lon. Illlrld Olly, NM York 11101

TA-4650,-5650

Subpct V-FET Replacement
Datm August 16, 1976

The TA-4650 uses two V-FETs (ZSJ18 and ZSKGO) and the TA-5650 uses
four V-FETs, in each channel of its power amplifier Both the
ZSJ18 and ZSK6O are divided into six ranks (-53 to -58) according
to their ng0 (gate-source voltage) and Vp (cut-off voltage). It
is necessary to use the same rank V-FETs in the same channel. The
rank is indicated on each V-FET as shown. If the correct rank is
not available, replace with a complete set of another rank.

scnuy
ZSKGO
A58

rank

It should be noted that only the ranks from -54 to -57 are usable
in the TA-4650/5650.

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hi - ii
Service Bulletin No.62

SONY CORPORATION or- AMERICA Model: 32134326 425536 8650
Technical Publications Department _ _
.747 VIII DIM Slit... Long Island CRY. N" Y 11101

Subhct V-FET Replacement
Dam: August 15, 1977

Refer also to Hi-Fi Service Bulletins No. 41, 49, and 51.

Perform the following procedure if V-FET failure is suspected.
To avoid damage to a replacement V-FET, do not replace without
first making this check.

1. Turn off the power and remove the suspect V-FET.

2. Check resistance readings of this V-FET using a VOM set to the
X19 range. See illustration below.

<3 VOM set to X19 range.
<3 S to D _______ Approx. 1~ZQ
S to G _______ Same as a diode
D G S D to G _______ Same as a diode

2SJ18.2SK60

If readings appear normal, the V-FET is probably okay, and
other circuit components should be checked.

3. If readings are not normal, turn on the power with the V-FET
still out of the circuit. Set the VOM to the 50 VDC range
(or as close as possible) and connect the leads to the V-FET
conductor patterns on the board as follows:

V-FET Source gate
ZSJ18 VOM (+) VOM (-)
ZSKGO VOM (_) VOM (+)

4. Set the dc bias adjust resistor (see below) on the Power Amp
Board for maximum reading.

TA-4650, -5650 - RTw301 (RTcSSl)
TA-8650, TAN-8550 - RT-701 (RT-751)
TAN-5550 - RT-SOl (RT-601)

5. Turn off the power and install the replacement V-FET. Reapply
power and reset the dc bias according to the service manual for
the respective model.

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