820Ω

100K

V1-A

330

uF

1

2

3VOL 2(dark)

1M L

OG

VOL 1(bright)

1M L

OG

.0022uF

.022uF 470K

.0047uF

470K

470pF

2.7K

100K

0.68

uF

6

7

8

12AX7V1-B

2.7K

100K

0.68

uF

1

2

312AX7V2-A

10K

6

7

8

V2-B

100p

F

.022uF

470p

F

470K

1M L

OG

VOL

470p

F

470K

470K

.022uF

.001

uF

1M L

OG

820Ω

100K

12AX7V3-A

0.68

uF

1

2

3

6

7

8

100K

TREBLE

470pF

C9.022uF

C11.022uF

33K

1M L

OG

25K

LIN

V3-B

250K

LIN MSTR VOL

BASS

MID

toPower Amp

100K

47K

1M

47K

NOTE 2 NOTE 3

NOTE 4

NOTE 1

NOTE 1

Marshall JMP Series 1987 and JCM-800 2204Switchable Dual PreampsDrawn by Steve Luckey

D

F

E

E

F

NOTE 2 JMP series uses .0022uFJCM-800 series uses .022uF90's Reissue series uses .022uF

NOTE 3 JMP series uses .005uFJCM-800 series uses 220pF90's Reissue series uses .0047uF

NOTE 4 The 0.68uF cap is only present in the JMP 1987 series.

NOTE 1 Value not critical. Use 33K to 68K.

NOTE 5 Alternate Switching. Remove the channel selector switch and put a 470K mixing resistor in the JCM-800 signal path as shown. Replace the single input jack with two separate jacks and use an external A/B switch to select channels.

470K

NOTE 5

JCM800 2204

PLEXI 1987

NEUTRALLINE

GROUND

3 AMPSLO BLO POWER

6.3 VAC

50/50uF50uF

10K / 3W 10K / 3W

C

C

0.022

.1

10K

470

1M

1M

Presence5K-L

100K 0.022

5600

220K

0.022

220K

82K 5600

47K

1Ω

1Ω

1K/5W

1K/5W

SPEAKER(8 OHMS)

1

2

3

8

7

6 5

3

4

1, 8

5

3

4

V4-A

V4-B

V5

V6

B A

From PREAMP

1N4007

BIAS25K-L

15K

BIAS RANGE220K / 1W

+ 10uF

12AX7PHASE

INVERTER

POWER AMPLIFIER

.5 AMP

50/50uF

Plates Screens Phase Inverter Tone Stack Driver

10K / 3W 10K / 3W

50uF 50uF

Plexi preamp JCM-800 preamp

+ 10uF47K

A B C D E F

.1

47pF

Marshall JMP Series 1987 PLEXI LeadPower Amp and Power Supply

Drawn by Steve Luckey

1, 8

4 5

67

81

23

4 5

67

812

3

TS

G

Plexi Normal1M-A

Plexi Bright1M-A

JCM 8001M-A

Presence5K-L

Master1M-A

Bass1M-A

Mid25K-L

Treble250K-L

Ground #5

+ +

330µ

F 25

V

0.68

uF

0.02

2µF

0.02

2µF

0.02

2µF

100p

+ +

50µF

45

0V

0.68

uF

470p

0.02

2µF

0.02

2µF

+ +

50µF

45

0V

B+Node C

0.1µF

0.02

2µF

0.1µ

F

NFB

0.02

2µF

0.02

2µF

V1Plexi Preamp

V2JCM800 2204 Preamp

V3Tone Stack Driver

V4Phase Inverter

V5PA Output

V6PA Output

Gnd #1Gnd #2Gnd #3

0.68

uF

+ +

10µF

100

V

+ +

10µF

100

V

B+to fuse

AC from STBY switch Gnd #4

470p

470p 47

0p

BIAS

+ +

50µF

45

0V

E

.0047µF 630v

.002

2µF

630v

F

.001µF 630v

D

47

B

C

3.13

Turret --- drill size is 3/32"

Hole for wire pass thru – drill size to fit

Standoff – drill size to fit

Dashed lines are underboard jumpers

INSTRUCTIONS FOR PRINTING DRILL GUIDE

NOTE… This drawing contains layers. Insure all layers are turned on for printing.

Board size is 3 1/8" X 13". Print two copies of this drill guide FULL SIZE on legal size paper. One copy will be used as a drill guide. The other copy will be used for installing jumpers. Measure the board length of the printout to verify it is 13". Attach to blank board using double sided carpet tape. Use a center punch to put a mark at the cross hairs of each turret, standoff, and hole. Use a 3/32" drill bit to drill all holes. Then enlarge holes as needed for standoff screws and wire pass thru.

13.00