Sony 6557-03n, 03s,43n,43s ibm chassis n3 서비스 매뉴얼

3-1

Part Replaced (

[)

RV901

HV ADJ

When replacing or repairing the shown below table, the follow-

ing operational checks must be performed as a safety precaution

against X-rays emissions from the unit.

•

(1) Hardware logic circuit

•

Turn the POWER SW on, and check that the RAS-

TER fades in.

•

Connect a variable resistor (20 k

Ω

 or more) and an

ammeter in series between FBT pin !¡ and – 15 V

line (– side of C637). Decrease gradually the resis-

tance of the variable resistor from maximum to mini-

mum, and confirm that the Beam Current Protector

Circuite works (TV Raster disappears). The current

must be within the range shown below.

Standard current: Less than 1.09 mA

(2) Software logic circuit

•

Turn the POWER SW on, and check that the RAS-

TER fades in.

•

Short between + of C639 and GND.

•

Connect a variable resistor (20 k

Ω

 or more) and an

ammeter in series between FBT pin !¡ and – 15 V

line (– side of C637). Decrease gradually the resis-

tance of the variable resistor form maximum to mini-

mum, and confirm that the Beam Current Protector

Circuite works (TV Raster disappears). The current

must be within the range shown below.

Standard current: Less than 1.14 mA

HV Regulator
Circuit

HV HOLD
DOWN Circuit

Beam Current
Protector Circuit

Part Replaced (

])

D board

IC901, R903,

R922,

T901,

RV901

• Mounted D board

D board

D913,

D916,

C923,

R920,

R927,

R935,

R936,

T901

• Mounted D board

D board

IC901, D901,

D902,

D918,

R053,

R918,

R923,

R928,

R932,

R933,

R934,

R939,

T901
• Mounted D board

* Confirm one minute later turning on the power.

•

(1) Confirm that the voltage between cathode of D913

and GND is more than 17.5 V DC.

(2) Using external DC Power Supply, apply the voltage

shown below between cathode of D913 and GND,

and confirm that the HV HOLD DOWN circuite

works. (TV Raster disappears)

Standard voltage: Less than 23.40 V DC