1. Remove the 5 mounting screws.
2. Lift the board upwards.
1. Remove black ribbon cables from J502, J601, and J901 by pulling up edge of connector housing, then gently pulling cable from connector.
2. Remove wire connectors from J802, JN01, and J801 by pulling white cable connector out of PC board connector.
3. Remove wide white ribbon cables from J501 and JF01 by gently pulling ribbon cable out of connector.
4. Pull off the volume knob, then remove control nut from volume control. A 7/16 nut driver can be used.
5. Remove the three board mounting screws.
6. Using a long-nosed pliers, release the two white nylon PC standoffs.
7. Cut wire tie from the transformer wires nearest the main board. This leaves room to remove the board.
8. Lifting from the back, remove the main board.
1. Remove C617, C618, C619, C620 (100uF, 50V electrolytics). Connect a 2.2uF 50 or 100V polyester capacitor from the + terminal of C617 to the + terminal of C619. Similarly, connect a 2.2uF 50 or 100V polyester capacitor from the + terminal of C618 to the + terminal of C620.
2. Remove C655, C656 (2.2uF 630V Dynaco-brand capacitors). Replace each capacitor with a jumper wire.
3. If desired, replace C653, C654 (2.2uF 630V Dynaco-brand capacitors) with 2.2uF, 250V WIMA MKP-10 capacitors. C653 will have to be laid down sideways.
4. Temporarily remove R663, R664, R657, R658 (2-watt metal oxide resistors just behind the tube sockets). This allows access to the components below.
5. Remove R653, R654, R667, R668, C651, C652, R665, R666 (all the components below the resistors removed in the previous step.
6. Replace R653, R654 with 37.4K 1/4W 1% resistors.
7. Replace R667, R668 with 221K 1/4W 1% resistors.
8. Replace R665, R666 with 100K 1/4W 5% resistors.
9. Leave C651, C652 empty.
10. Re-install R663, R664, R657, R658.
11. Power Supply updates:
a) connect two wires (about 5 inches long) to pins 1 and 3 of the 7812 regulator (Q801). Connect the other end of these wires to a 15 ohm 5 Watt resistor.
b) connect two wires (about 5 inches long) to pins 1 and 3 of the 7812 regulator (Q804). Connect the other end of these wires to a 50 ohm 3 Watt resistor.
c) Position these resistors away from the PC boards so that their heat does not get near the boards.
d) Replace R801 with a 1.5 ohm 3 Watt resistor. The holes in the PC may have to be drilled larger to accomodate the bigger resistor.
e) Tack-solder a short piece of wire across the leads of D805. This shorts out this diode.
RK51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 81, 82, 83, 84, 85, 86, 87, 88
QK55, 56, 57, 58, 59, 60, 61, 62, 65, 66
CK51, 52, 53, 54, 55, 56, 57, 58
2. Put wire jumpers in the following resistor locations:
RK53, RK54, RK63, RK64, RK65, RK66, RK85, RK86
3. Put the specified new components in the following locations:
5.62K (1/4W 1%): RK51, RK52, RK59, RK60
2.21K (1/4W 1%): RK75, RK76
1000pF (mica, polystyrene, or polypropylene): CK51, CK52
4. Put a jumper wire from the left hole of RK81 to the left lead of RK51. Similarly, put a jumper wire from the left hole of RK82 to the left lead of RK52. This is best done on the bottom of the board.
5. Install a 6.81K 1/4W 1% resistor from the left hole of QK55 to the right hole of RK55. Similarly, install a 6.81K resistor from the left hole of QK56 to the right hole of RK56.
6. Install a 2.87K 1/4W 1% resistor from the center hole of QK65 to the bottom hole of RK 87. Similarly, install a 2.87K resistor from the left hole of QK66 to the bottom hole of RK88.
Reverse the removal process. Take care that the blue stripe of the 3- and 4-conductor black ribbon cables match the locating arrow on the main board.