marshall 5010 different version schematic attached

Mar 2, 2022
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i was chillin' on the ssguitar forum recently, hoping to find a schematic for the 30 watt "redbox" combo... i'd picked up a "scrap" board on ebay, and rebuilt it to get it running.
my friend tassieviking took the info i supplied him and drew up an actual schematic for the jm pcb-78 5010 variant, which marshall doesn't have and has never been on the net.
so here's the schematic for this odd rare beast.... this is for the one with hi and lo ins, and the line out/headphone jack on the front panel with presence control which is literally a simple treble booster between the output of the treble control and the input of the master volume. i guess they call 'em redbox's cuzza all the little red mylar box caps used for blocking/coupling.
these are great amps! i really diggit.

5010 early version BOM
board jm78-2

vr1 gain b22k
vr2 volume al00k
vr3 treble b220k
vr4 mids b22k
vr5 bass a1m
vr6 pres b22k

ic 1 mc1458e

q1 bc184
q2 bc182
q3 bc182
q4 bc212
q5 bc184

q6 mj3001 darlington
q7 mj2501 darlington

zd1 9.1v <4739>
db1 br62

r= red box cap
t= tantalum
e= electro
c= ceramic

c1 [email protected] r
c2 [email protected] t
c3 [email protected] t
c4 2.2n c
c5 100n c
c6 [email protected] t
c7 2.2n c
c8 [email protected] r
c9 4.7n c
c10 220p c
c11 [email protected] r
c12 [email protected] r
c13 [email protected] r
c14 [email protected] t
c15 [email protected] e
c16 [email protected] e
c17 [email protected] r
c18 [email protected] e, axial
c19 2.2n c
c20 220p c
c21 [email protected] e, axial
c22 non existant
c23 [email protected] e, radial
c24 [email protected] e, radial

all resistors 5% cc 1/4 watt unless specified

r1 1m
r2 68k
r3 68k
r4 10k
r5 100r
r6 22k
r7 10k
r8 470r
r9 non existant
r10 22k
r11 68k
r12 10k
r13 33k
r14 4.7k
r15 2.7k
r16 2.7k
r17 10r
r18 6r 1 watt
r19 270r 3 watt
r20 470r
r21 10k
r22 3.9k
r23 4.7k
r24 680r
r25 10r
r26 2.2k
r27 1.5k
r28 1.5k
r29 1.5k
r30 10r
r31 39r

Hammond Power Transformers 166J28 28vac center tapped (14-0-14)

Marshall 5010 PCB 78-2 Schematic.jpg

gerber files available by request if needed by anyone.

hope this helps someone out... big props to tassieviking for the drafting and files to recreate this beast!

a couple mods i found that seem to help are

make all preamp resistors 1% metal film resistors
make the big power supply filter caps bigger... 2200 is ok, but a lot of ripple when the amp is pegged. 4400uf, 6800uf are good, i have 10,000uf in the last one i did.
make the two filter caps for the preamp 220uf or 470uf instead of 100. that makes it "sag" a bit less, and gives slightly better bass response, or seem like it.
my bro mark says standard marshall values in the tone stack are an improvement, but i haven't tried doing that yet.

you can hack an fx loop in between the output of the master volume and the input to the driver. i've been experimenting, but nothing i'm truly happy with yet. even a passive one works fairly well, but i like the amp to be dead quiet when pegged, and the fx loop seemed to add noise a bit so i removed it.

anyways... onwards n upwards... and happy 420, if so inclined.