2SC1815 datasheet(13/54 Pages) TOSHIBA

13 / 54 page

– 13 –

CIRCUIT CHECKS

Troubleshooting Guide for Fail Safe Circuit

HIGH VOLTAGE CHECK

CAUTION: There is no HIGH VOLTAGE ADJUSTMENT on

this chassis. Checking should be done following the steps

below.

1. Connect an accurate high voltage meter to the second an-

ode of the picture tube.

2. Turn on the receiver. Set the BRIGHTNESS and CON-

TRAST controls to minimum (zero beam current).

3. High voltage must be measured below (B) kV.

Refer to table-1 for high voltage (B).

(See SETTING & ADJUSTING DATA on page 14)

4. Vary the BRIGHTNESS control to both extremes to be sure

the high voltage does not exceed the limit under any con-

ditions.

FS CIRCUIT CHECK

The Fail Safe (FS) circuit check is indispensable for the final

check in servicing. Checking should be done following the

steps below.

1. Turn the receiver on and press the RESET button.

2. Temporarily short TP-(R) and TP-(X) with a jumper wire.

Raster and sound will disappear.

3. The receiver must remain in this state even after removing

the jumper wire. This is the evidence that the FS circuit is

functioning properly.

4. To obtain a picture again, temporarily turn the receiver off

and allow the FS circuit more than 5 seconds to reset.

Then turn the power switch on to produce a normal pic-

ture.

Check that the set returns to normal operation when pin 12

of Z801(or emitter of Q472) is grounded with jumper wire.

Check the voltage across

Capacitor C471 is

approximately (C) volts.

Refer to table –4 for

FBT detection voltage (C) .

Faulty power

circuit or hori-

zontal circuit.

Defective Fail Safe Circuit

(See SETTING & ADJUSTING

DATA on page14)

YES

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