DH-502 Installation Instructions

1.3 Disconnect AC power from the DH-500 and remove all connect- ing cables.

2.3 Remove the 17 screws which secure the cover along the top front, sides and rear. Set cover aside. DO NOT GRAB THE AMPLI-

FIER PANEL OR HANDLES WHEN THE COVER IS RE- MOVED. You might bend the chassis.

3.cl Turn the amplifier over, or stand it on the nansformer end. Loosen, but do not remove the two front screws which secure the amplifier module near the front (center) of the chassis. Remove the two screws at the rear which secure the module. Return the amplifier t o its upright position.

4.El Prepare one each red and green wires each 16” long. Twist them together throughout their length.

5.Select the PC-7A circuit board. Note that the eyelets arcnumbered on the circuit side of the board, with eyelet #l to the left when the row of eyelets is nearest you, and the board is upside down to make soldering easier. Connect the wires from the components side of he board, and be sure each is securely soldered to the circuitry.

6.0 Connect the red wire of the twisted pair to eyelet # 1 of PC-7A. (S) Connect the green wire to eyelet #3. (S)

7.Prepare a 3-l/2” green wire and a 4” red wire. With one pair of ends even, twist these together. At the uneven ends, connect the green wire to cyelet #4 of PC-7A. (S). Place the pair off toward eyelet #l, and connect the red wire to eyelet #6. (S)

8.c! Prepare a 5” red wire and a 6” green wire. Twist these together with one pair of ends even. At the even ends connect the red wire to eyelet #2. (S) Connect the green wire to eyelet #5. (S)

9.3Unsolder the twistcd pair of leads from eyelets 1 and2 of the right amplifier module at the center rear of the amplifier. This pair of leads which connects to the right inputsocket, will no longer be used while the amplifier is funtioning monophonically. These leads must be taped securely so that there is no possibility for the bare wire to contact any portion of the circuit. Masking tape is sufficient, but electrical tape is preferred. These leads may be removed if desired.

10.Remove the rear rop screw securing the right channel amplifier circuit board to the hear sink just above where the twisted pair was disconnected. Do nor lose the fiber spacing washer which is between the circuit board and the heat sink. This washer is not used on later production DH-500s. Select one of the screws from the bridging kit, and the mounting bracket. The bracket is anchored at this location, flat surface up, with the screw inserted fust through the single tab from inside the bracket. then through the circuit board. the fiber spacing washer, (optional) and into the heat sink.

11.Select the two screws and nuts and the circuit board PC-7A. With the components facing out, secure the board t o the outer surface of the bracket tabs.

12.0Select the short twisted pair of wires connected to eyelets 4 and 6. Connect the red wire to the upper eyelet #l of the right circuit

board at the center rear. (S) Connect the green wire t o the lower eyelet #2. (S)

13.Place the long pair of wires from eyelets 1 and 3 down between the amplifier module mounting bracket and the back of the chassis. The module can be tilted forward t o facilitate this. Connect the red wiret o the lower ey elet #l on the left circuit board. (S) The easiest way is to wrap it in a tight loop around t h e bare stub of the wire presently connected to this eyelet. Be sure both wires are soldered securely to he board. Connect the green wire t o the upper eyelet #2 in the same fashion. (S)

14.0Making sure that no wires are trapped by the mounting bracket, reinstall the. two screws securing the rear of the module to the chassis. Tighten all 4 screws.

15.0Connect the red wire of the remaining twisted pair from PC-7A to eyelet #6 of the PC-9 circuit board behind the power trans- former, (S)This wire may be connecred t o the stub of the existing wire as before. Connect the green wire to eyelet #4 of PC-9. (S) Eyelei #I of PC-9 is nearest the edge of the chassis.

16.0 Reinstall the amplifier cover.

PC-7A PARTS LIST

	COMPONENT SIDE PC-‘IA
c Rl’		0 6		0 5	c R2-0
c RID-a		v c c2-A			c R2-0
	cR12-0				- R13-
.-- Rll-		A - R5--r		v - R3-
c R6-0		0 4		0 2	- R7-
c R6-0		c R9+		0 2	- R7-
		c R9+
				t-Cl_
	i	)- R6+		i
+c4-+	R15	A	D--R&	Rl v
+c4-+					*C3+
	1	0 3		J 01
	1
- R17-					- R16--,
		.			.
		6	: 1 ;	:	1

Rl 22.1K, l%, metal film

R2 2.2K. 1/4w, 5% carbon film

R3 2.2K, 1/4w, 5% carbon film

R4 47 ohms, 1/4w. 5% carbon film

R5 47 ohms, 1/4w. 5% carbon film

R6 8.2K, 1/4w, 5%, carbon film

R7 8.2K, 1/4w, 5 % , carbon film

R8 47 ohms, 1/4w, 5% carbon film

R9 47 ohms, 1/4w, 5% carbon film RlO 2.2K, 1/4w, 5% carbon film Rll 2.2K, 1/4w, 5% carbon film R12 22.1K, l%, metal film

R13 IO0 ohms, 1/4w, 5% carbon film

R14 100 ohms, 1/4w, 5% carbon film

R15 47 ohms, 1/4w, 5% carbon film

R16 3.3K, lw, 5% metal film

R17 3.3K, lw, 5%. metal film

Cl 1 OmF, 16V. non-polarized

c 2 6.8pF. 1 00V, dipped mica

c3 22mF. 25V, electrolyte

c4 22mF. 25V, electrolyte

Ql BC55OC NPN nansistor

Q2 BC55OC NPN transistor

Q3 BC56OC PNP transistor

Q4 BC56OC PNP transistor

Q5 MPSA63 PNP transistor

Q6 MPSA13 NPN transistor

RMP/4-2212 RC/4-222 RC/4 -222 RC/4-470 RC/4-470 RC/2-822 RC/2-822 RC/4-770 RC/4-770 RC/4-222 RC/4-222 RMP/4-2212 RC/4-101 RC/4-101 RC/4-770 RM l-332 RMl-332

CERNP-106 CM -068 CER-226AA CER-226AA

SSH-650

SSH-65 1

SSH-695

SSH-645