RCA 18V100 service manual Components, Coaxial cable from the console to the twin lead and com

50 ohms resistance with negative ohmmeter polarity on the

center conductor. (With positive polarity on center conductor,

resistance should be between 20 and 30k ohms.) See "Coaxial

Cable Replacement".

r	Selector Switch Unit Tests
	The quickest test for a troublesome Selector Switch Unit is
	substitution with a new unit (see Parts List). If a new unit is
	unavailable, use a DC voltmeter and ohmmeter to check unit
	circuitry (see schematic of Fig. 19) for open or short-circuited
	components.
				TWINLEAD
				TV	SET
				CONNECTION
	GAME INPUT			A A		TRANSFER
						SWITCH
	TERMINALS
	(PHONO	>-9-			O	1-	TV ANTENNA
		J1				J3
	JACK)	N	H				TERMINALS
				0=	o
						r

<**

STUDIO

RFC 2

to the metal box or rivets holding terminal board. If either antenna lead touches the box or rivets, snowy pictures may

result. (Late production units use insulated rivets which

eliminate problem))

Power Supply Unit Tests

The Power Supply Unit operates between carefully chosen

voltage and ripple limits. To check unit for satisfactory opera-

tion, connect unit as shown in Fig. 20. DC output under

these conditions ranges between 8.5 and 10V. Ripple on this

DC (measured with oscilloscope) must not exceed 1 V peak-to-

peak. Replace unit if beyond these specifications (see Parts

List).

Leakage Current Test

With the Power Supply Unit plugged into an AC outlet,

check for leakage current to earth ground on both poles of the phone plug, as shown in Fig. 21 , using an AC milliam- meter. Leakage current must not exceed 0.5mA. Reverse AC

plug polarity and recheck leakage current.

	A A
	DC INPUT
	TERMINALS
	(PHONE JACK)
	Figure 19. Schematic, Selector Switch Unit
r	When the switch is in the "Studio II" position, it connects
	the coaxial cable from the console to the twin lead and com-
	pletes the DC circuit between the console and power supply.
	With the switch in the "TV" position, it disconnects the con-
	sole and forms a circuit between the antenna terminals and
	the twin lead for normal TV reception.
	If the Selector Switch Unit is defective, it must be replaced
	(see Parts List) since it cannot be satisfactorily repaired in the
	field. It is carefully manufactured so as not to exceed the RF
	radiation limits specified by the FCC.
	If snowy pictures occur in the "TV" position or Studio II
	cannot be shut off, check antenna connections for short circuits

r

-ft-

\

TO 120V

ACADJUST FOR

LINE

250 mA ON

MILLIAMMETER

—^Figure 20. Testing Power Unit Output for Voltage and

EARTH

GROUND

Figure 21. AC Leakage Test

NOTE: If power unit checks out OK but is inoper-

ative with operable Studio II console, check fit of

plug-in jack. Some early production plugs and jacks

have tolerances that conflict and prevent adequate

plug penetration. Solution to problem is often simply

to increase effective length of plug by filing the jack

slightly as shown in Fig. 22. (Use sharp knife to

remove any untrimmed mold flash from plug if

present.)

FILE OR SHAVE

SLIGHTLY

TO INCREASE

PLUG PENETRATION

Figure 22. Removal of Material from Front Edge of Jack

Ripple Content