Sony ta 5650 service manual

Page 1

Service Bulletin No.49

SONY CORPORATION OF AMERICA Model:

Technical Publications Department
47-47 V." Dun Sim-t. Lonl Ill-mi (my, Nut Vurk 11101

TA-4650,-5650

Subpct V-FET Replacement
Data: August 16, 1976

The TA-4650 uses two V-FETs (ZSJ18 and ZSK60) and the TA-5650 uses
four V-FETs, in each channel of its power amplifier. Both the
ZSJ18 and ZSKGO are divided into six ranks (-53 to -58) according
to their ng0 (gate-source voltage) and Vp (out-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.

s()ray
ZSKGO
A56

rank

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

Page 2

hi - ii
Service Bulletin No.62

90m CORPORATION or AMERICA Medan $342225 452226 8650
Technical mbh'carions Department _ _

0747 v." Dun smut, Lou Island City. Now York 11101

Subwct V-FET Replacement

Date: 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.
0 VOM set to X19 range.
<3 S to D _______ Approx. 1~20
S to G _______ Same as a diode
D G S D to G _______ Same as a diode

23.118. ZSKGO

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 ViFET
conductor patterns on the board as follows:

V-FET Source gate
28.118 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 - RTvSOl (RT-351)
TA-8650, TAN-8550 - ET-70l (RT-751)
TAN-5550 - RT-501 (RT7601)

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.