TubeDepot JTM45+ User manual

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Learn Build Play
JTM45+ “ ” Styled
ASSEMBLY MANUAL
with some great “ ” styled mods)
50W Tube Guitar Amp Kit
1686 Barcrest Dr., Memphis, TN 38177
www.tubedepot.com
Version 4.2
24 January 2014
recommended level of difficulty

This manual was developed and
published by:
TubeDepot.com LLC, Memphis, TN
Written by:
Robert Hull
Edited by:
Robert Hull
Josh Phelps
Design and Artwork by:
Robert Hull
Christia Magee
Special thanks to following for their design help:
Joe Austi Bria Overstreet Da iel Yakel
Matt Kirby Mike Taylor Aaro Coppage
He ry Lum Be Siler
Special thanks to the following for their excellent amp building and proofreading skills:
Matt We dt Brad Jo es Michael Wa g
Terry Gayle Richard I gold Scott McMilli
Copyright © 2011
TubeDepot.com LLC
1686 Barcrest Dr.
Memphis, TN 38134
[phone]
i [email protected]
REGARDING THESE BOOK MATERIALS
Reproductio , publicatio , or duplicatio of this booklet, or a y part thereof, i a y ma er, mecha ically,
electro ically, or photographically is prohibited without the express writte permissio of the publisher.
The Author, Publisher or Seller assume o liability with respect to the use of the i formatio co tai ed herei .
For permissio a d other rights u der this copyright, co tact TubeDepot.com.
Acknowledgements
ii TubeDepot.com

Preface …...........................................................................................................
Chapter 1
Safety ….........................................................................................................
Chapter 2
Tools a d Supplies .........................................................................................
Chapter 3
Parts I ve tory …...........................................................................................
Chapter 4
Cabi et Preparatio …...................................................................................
Chapter 5
Chassis Preparatio , Assembly a d Wiri g .......................................…......
Chapter 6
Turret Board Co structio …........................................................................
Chapter 7
Turret Board / Chassis a d Wiri g …...........................................................
Chapter 8
Testi g …......................................................................................................
Chapter 9
Fi al Assembly ….........................................................................................
Chapter 10
Schematic ….…..................…......................................................................
Appe dix
A) Resistor a d Capacitor Codes ...............................................................
B) Solderi g Hi ts .......................................................................................
C) Amplifier Care a d Feedi g ....................................................................
D) Mods …...................................................................................................
Table of Contents
iv
1
2
3
28
6
10
24
35
38
30
33
34
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41

Marshall amplifiers have always bee the forefro t i the sou d of rock ' roll.
Si ce the early 1960's, Marshall has take simple circuits a d tur ed them i to
extraordi ary, amplifiers that to this day, co ti ue to defi e great to e.
I the early 60's, the JTM45 established Marshall as the ew leader i guitar
amplifiers. While all the other amplifier ma ufacturers were desig i g their
amps to be clea er, Marshall took a differe t path. With a simple circuit (from
the Fe der 1959 4x10 Bassma ), Marshall “cru ched” it full of harmo ically rich
to e a d built a amplifier that set the sta dard for everyo e to follow.
This British JTM45+ kit is our od to the origi al JTM45 a d MkII 50W
amplifiers. With turret board, poi t-to-poi t co structio , quality compo e ts,
a d just a touch of America upgradi g, this kit is ready to become your sou d.
U like previous assembly ma uals, we have desig ed this ma ual for the
more adva ced builder i mi d. This ma ual is lite o step-by-step i structio s,
but filled with detailed drawi gs a d photos. We are leavi g these drawi gs a d
photos to speak for themselves. If you have previous amp buildi g experie ce,
you will e joy the challe ge that this kit provides.
But before we get started, a safety review …
Robert Hull
Director of Tech ical Services
TubeDepot.com
Before continuing, PLEASE READ the following:
We are continually making improvements to this assembly manual in
an effort to provide the best instructions possible. Therefore, when
the manual's instructions differ from the video, I recommend following
this written manual as this will be more up-to-date and accurate.
NOTE
iv TubeDepot.com
Preface

!!! Read these safety precautions before continuing !!!
ALL tube amplifiers co tai LETHAL VOLTAGES, ofte several hu dred volts which WILL
leave bur t e tra ce a d exit wou ds i ski if accide tally touched. These voltages have the
pote tial to cause permanent physical damage and death. These voltages are prese t
whe the amp is tur ed o a d also for some time after the amp has bee tur ed off. You
can still get shocked with a tube amp turned off and disconnected from AC power.
The above stateme t is a bit scary, but we wa t to stress that every piece of electro ic
equipme t must be treated with respect. Whe AC power is applied, there is always a cha ce
for i jury or death. With tube amps, eve whe the AC power is ot applied there is still
da ger. Bei g shocked with high voltage is very pai ful a d we do ot wa t a yo e fi di g
out the hard way.
Whe buildi g this kit, we wa t your experie ces to be both e joyable a d safe. There are
more kits to assemble a d we wa t you to e joy buildi g a d playi g them all.
Throughout this ma ual at key poi ts i the co structio , we have a otated importa t
steps with the below alerts. For your safety a d to improve co structio quality, It is importa t
that you become familiar with each of these alerts a d adhere to a y safety recomme datio s
whe they appear.
Explanation of Alerts
Safety
1
- DISCLAIMER -
TubeDepot.com, it's employees, officers, shareholders, investors and
subsidiaries accept no liability for any damage s), injury s) or death incurred
from or while building or using this kit.
WARNING
CAUTION
NOTE
MOD
sed when identifying an action that may cause physical injury or death.
sed when identifying an action that may cause damage to components
and/or equipment.
sed when identifying general points of interest.
sed when identifying potential modification point(s)
TubeDepot.com 1

As with a y co structio project, there are certai recomme ded tools a d supplies. The
followi g are the tools a d supplies NOT provided with the kit but are eeded for completio .
These are expected to be provided by the builder.
TubeDepot.com
The following is our recommended list part number
Phillips screwdriver, #1 a d #2 TL-VTSCRSET8
Slip joi t pliers
Needle ose pliers TL-VT33
Wire cutters, diago al TL-VT33
Wire strippers, for 18 a d 20 awg wire TL-VT5021
Electric Drill (cordless recomme ded)
Drill bit, 1/8” - AC receptacle i stallatio ; turret board wire routi g TL-DB-40125
Drill bit, 5/32” - turret board mou ti g TL-DB-40156
Drill bit, 9/32” - Chassis mou ti g i cabi et
Drill bit, 5/16” - i set ut i stallatio i to chassis
Drill bit, 7/16” - impeda ce selector i stallatio
Drill bit, 1/4” - shock mou ted tube socket mou ti g holes
Cou tersi k bit
Maski g tape, 2” or 3”
Ruler or scale, 12” w/ 1/16” marki gs
Perma e t marker, fi e tip
Solderi g iro , 25W – 40W (35W recomme ded) TL-WP35
Solder, electro ics safe (60/40 w/ rosi core recomme ded) TS-24-6040-0027
Flux, electro ic – liquid or paste (must be safe for electro ic work) TS-83-1000-0186
De-solderi g pump / solder extractor TS-384-1000
Solder wick or desolderi g braid TS-1817-10F
Spo ge or solderi g iro tip clea er TL-TIP-CLEANER
The following are tools that really nice to have on hand
Solderi g statio w/ temperature co trol TL-WTCPT
Multimeter w/ DC ra ge of at least 500V TL-DVM850BL
Variable AC supply (Variac® style)
Curre t Limiti g AC source (dim bulb tester) – self built
Needle ose pliers – small size, for electro ics work TL-NN7776
Wire cutters, diago al – small size, for electro ics work TL-170M
Ce ter pu ch – a automatic ce ter pu ch is great
Nutdrivers - 5/16”, 11/32”, 7/16”, 1/2”
Square, 9”
Scratch Awl
De-burri g tool TL-DB-1
Fi ger ail polish (for holdi g uts a d screws i place)
Step drill bit (1/8” - 1/2”)
Ora ge wood stick – for movi g compo e ts a d wires i to place TS-OWS
2Tools and Supplies
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Make sure the followi g items are i cluded with your kit. Let us k ow if there are a y missi g
items or if you have a y questio s regardi g a particular part(s).
1 chassis, alumi um Marshall style JTM45 CH-MARJTM45
1 pa el, fro t a d back, Marshall style JTM45, plastic CH-MARJTM45-FP
1 TR-PW-05
118025
118058
1 JJ-GZ34
1 JJ-EL34
3
xfmr, power, 45W Marshall style w/ rectifier tap
xfmr, output, 50W Marshall style by Classictone
choke, Marshall style 3 HY, 250mA by Classictone
GZ34 JJ dual-diode rectifier
EL34 beam power tetrode (sold i pairs) 12AX7 /
ECC83 dual triode preamp tube JJ-ECC83
7 k ob, Marshall style w/ set screw P-MAR-1-4-BRASS
1 k ob, chicke head, vi tage w/ set screw P-VSCH
2 fuse holder, low profile screwdriver cap, 3AG P-FH-LOWPRO
2 fuse, 3AG 500mA slow blow (HT fuse) P-BK-MDL-.5A (o e spare)
2 fuse, 3AG 3A fast blow (Mai s fuse) P-BK-AGC-3A (o e spare)
1 I dicator lamp, 6.3V i ca desce t P-PL-MARSHALL-1
1 push ut-flat rou d 5/16" stud (i cluded w/ above lamp)
6 jack, 1/4", Amphe ol mo o P-ACJM-IHS
2 washer, chassis grou di g for above jack GW-CL1442
1 switch, toggle SPST; Carli g P-110-63
1 switch, toggle DPST, Carli g P-2BK62-73
2 washer, lock 1/2", i ter al tooth LW-IT-1-2
2 switch, mi i toggle, DPDT, (o -o ) P-108-MINI-2
1 switch, mi i toggle, SPDT (o -off-o ) P-108-MINI-3
1 switch, 3 positio rotary P-ROTARY-SWITCH
1 plug, AC chassis mou t, press fit P-IEC-1
1 power cord, with IEC co ector P-12PWI
3 diode, 1N4007 D-1N4007
2 diode, GP02-30-E3/73 D-R3000
3 socket, tube, mi iature 9 pi SK-B-VT9-ST-C
3 shield, tube socket, mi iature 9 pi SK-PCP
3 socket, tube, octal chassis mou t SK-B-VT8-ST
3 grommets, rubber 1/2" chassis hole P-GROMMET-1/2
4 bolt, metric, M6x30mm, stai less steel MS-M6X30MM
4 flat washer, metric, M6, stai less steel BP-M6-WASHER
4 captive uts, M6 BP-M6-CAPTIVENUT
3Parts Inventory
TubeDepot.com 3
qty description TD part number

4 screw, zi c plated 6-32 x 1/4", phillips pa head BP-632-1/4
18 screw, zi c plated 6-32 x 3/8", phillips pa head BP-632-3/8
2 uts, sta dard 6x32 BP-632
12 uts, KEPS 6x32 BP-632-KEPS
4 sta doff, alumi um hex, #6 threaded, 1/2" lo g BP-ALSTDOFF-6-FF-1/2"
7 uts, KEPS 8x32 BP-832-KEPS
3 uts, 8-32 sta dard BP-832-NUT
6 screw, zi c plated 8-32 x 3/8", phillips pa head BP-832-3/8
4 solder lug, locki g, #8 screw P-TERMLOCK-8
4 solder lug, locki g, #6 screw P-TERMLOCK-6
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - yellow HTPVC-20-STR-YELLOW
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - red HTPVC-20-STR-RED
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - black HTPVC-20-STR-BLACK
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - white HTPVC-20-STR-WHITE
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - blue HTPVC-20-STR-BLUE
10 ft wire, 20 AWG, stra ded, hi-temp PVC - violet HTPVC-20-STR-VIOLET
10 ft. wire, 20 AWG, stra ded, hi-temp PVC - ora ge HTPVC-20-STR-ORANGE
10 ft. wire, 18 AWG, stra ded, hi-temp PVC - black HTPVC-18-STR-BLACK
2 ft wire, 20 AWG, solid bare buss wire, ti ed copper BW-20
2 ft wire, 16 AWG, solid bare buss wire, ti ed copper BW-16
2 ft shielded wire, i terco ect IW-2330
5 ft alumi um tape, 2" width, self adhesive P-TAPE-ALUM
1 ft double stick tape, 1" wide ( ot listed i stock – applied to back of plastic back plate)
1 heat shri k, 1/8" - BLACK, 6" piece TS-HS-1-8
11 i . G10 glass epoxy board (11”x 3-1/8”) BP-125BOARD-RED
68 turret, hollow Keysto e 1540-4 BP-TURRET
1 470 / 1/2W, 1% metal film R-273-470
2 820 / 1/2W, 1% metal film R-273-820
2 1.5K / 1/2W, 1% metal film R-273-1.5K ← mod.
1 2.7K / 1/2W, 1% metal film R-273-2.7K
2 5.6K / 1/2W, 1% metal film R-273-5.6K
1 22K / 1/2W, 1% metal film R-273-22K
1 27K / 1/2W, 1% metal film R-273-27K
2 33K / 1/2W, 1% metal film R-273-33K
1 47K / 1/2W, 1% metal film R-273-47K
1 51K / 1/2W, 1% metal film R-273-51K
1 56K / 1/2W, 1% metal film R-273-56K ← mod.
4 68K / 1/2W, 1% metal film R-273-68K
1 82K / 1/2W, 1% metal film R-273-82K
5 100K / 1/2W, 1% metal film R-273-100K
4 TubeDepot.com
qty description TD part number

2 220K / 1/2W, 1% metal film R-273-220K
2 470K / 1/2W, 1% metal film R-273-470K
4 1M / 1/2W, 1% metal film R-273-1M
2 1.0 / 1W metal oxide R-273-1
3 10K / 1W, metal oxide power resistor R-273-10K
1 15K / 1W, metal oxide power resistor R-273-15K
1 220K / 1W, metal oxide power resistor R-273-220K
2 470 / 3W metal oxide R-282-470
1 1K / 3W metal oxide R-282-1K
2 10K / 3W metal oxide R-282-10K
1 22K / 3W metal oxide R-282-22K
1 47pfd / 500V; silver mica CP-SM-47-500V
1 100 pF / 500V; silver mica CP-SM-100-500V
1 250pfd / 500V; polystyre e CP-PFC-250-500V
1 500pfd / 500V; polystyre e CP-PFC-500-500V
1 .0022ufd / 630V; Mallory 150 CP-M150-0022-630V ← mod.
7 .022ufd / 630V; Mallory 150 CP-M150-022-630V
2 .1ufd / 630V; Mallory 150 CP-M150-1-630V
2 .68 / 100V, Mallory 150 CP-M150-68-100V
2 50ufd / 50ufd @ 500V CP-JJ-50X2-500V
2 capacitor clamp, small CP-CLAMP1
1 16ufd / 475V CP-FT-16-475V
1 47ufd / 500V CP-FT-47-500V
1 330uF / 16V CP-ST-330-16V
2 10uF / 160V CP-ST-10-160V
1 5K li ear RV24A-10D2-15R1-B-5K
1 25K li ear RV24A-10D2-15R1-B-25K
1 250K li ear RV24A-10D2-15R1-B-250K
4 1M audio RV24A-10D2-15R1-A-1M
1 50K trimmer pot BP-BIASPOT-50K
1 Turret setter kit DIY-PFT-KIT
The following additional parts are particular to your choice of head or combo kits:
head kit -
1 cabi et, small box black tolex Marshall style CAB-MAR-SMBOX
combo kit -
1 cabi et, 1x12 combo Marshall style CAB-MAR18
1 speaker, 12",(various 75W speakers) our secret hidde stock
1 1/4" pho e plug, Switchcraft P-280 P-280
1 ft. techflex, yellow TS-PTNO-1-4
2 ft. wire, 18 AWG, stra ded, hi-temp PVC - white HTPVC-18-STR-WHITE
TubeDepot.com 5
qty description TD part number

This chapter deals with prepari g the cabi et for i stallatio of the completed chassis. But
first, we eed to take i ve tory of the parts that came i stalled with the cabi et.
Cabinet Inventory
Combo Cabinet
1. Handle w/ mounting hardware – There should be a si gle flat black ha dle with two
gold e d covers mou ted to the top of the cabi et.
2. Feet, rubber – There should be four rubber feet attached with screws.
3. Back panels, upper and lower with screws – There should be two back pa els. The
top back pa el should be secured with four pa el screws, the bottom pa el should be
secured with five pa el screws. All pa el screws should have a fi ishi g washer.
4. Baffle screws – There should be eight black oxide coated screws with matchi g
black fi ishi g washers holdi g the baffle i the cabi et.
5. Speaker bolts – There should be four black oxide coated bolts for securi g the
speaker to the baffle board.
Head Cabinet
1. Handle w/ mounting hardware – There should be a si gle flat black ha dle with two
gold e d covers mou ted to the top of the cabi et.
2. Feet, rubber – There should be four rubber feet attached with screws.
3. Back panel w/ screws – The back pa el should be secured with four pa el screws.
With either cabi et, i spect all screws. I've fou d screws that were 't fully tighte ed duri g
assembly. These loose screws will buzz whe vibrated by the speaker or speaker cab.
Drilling the Four Chassis Mounting Bolts
4.2.1 Combo Cabinet
Step 1 – Remove the back pa el a d lay the pa el o
the work table with the vi yl coveri g faci g dow .
Step 2 – With the alumi um chassis, ce ter the chassis
o the back pa el with the co trol pa el side of the
chassis flush agai st the back pa el cutout (photo 4.2a).
Step 3 – Make a mark through each of the four mou ti g
holes of the chassis o to the back pa el (photo 4.2a).
Step 4 – Drill a small 1/8” pilot hole i the ce ter of each of these marks.
Step 5 – O ce the pilot holes have bee drilled, drill the fi al 5/16” hole dow the ce ter of
each of these holes.
Step 6 – With a hobby k ife, clea the edges of the holes by cutti g off a y excess vi yl
coveri g left from the drilli g operatio .
4.2
4.1
CAUTION The following steps call for drilling the mounting holes in the cabinet for the chassis. Make
sure to review, reread and remeasure at each step to reduce potential drilling errors.
Because (as the wise old amp builder's saying goes) what is drilled, cannot be undrilled.
photo 4.2a
4Cabinet Preparation
photo 4.2b
6 TubeDepot.com