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Mercury Epiphone Valve Junior, Assembly Manual

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Mercury Epiphone Valve Junior Assembly Manual Download Page 21

Epiphone V

alve Jr

.

 • 

Mercury Upgrade Kit

 

21

This
 project

 and
 its

 documentation

 is

 the
 result

 of

 technical

 investigations

 made

 by

 the
 engineering

 staf
f of

 

Mercury Magnetics

. The
 disclosure

 of

 the
 information

 herein

 may
 pertain

 to

 proprietary

 rights

 and
 

the
 furnishing

 of

 these

 documents

 does

 not
 constitute

 an

 expresed

 or

 implied

 license

 to

 use
 such
 materials.

T7 

T8 

T9 

T3 

V2 

V1 

T10 

T11 

T12 

GND 

C6 

C9 

C7 

C8 

T1 

T2 

D3 

T4 

T5 

R10 

R11 

T6 

B1 

C12 

D4 

D1 

D2 

IN 

G 

IN  S10  G 

VALVE JUNIOR 

VER051122 

HBO1570 

9 

8 

7 

6 

5 

4 

3 

2 

1 

1 

9 

8 

7 

6 

5 

4 

3 

2 

1 

1 

R12 

R14 

C3 

C5 

JP3 

C4 

R2 

R15 

R5 

R4 

R3 

C1 

R13 

R1 

R8 

JP1 

JP2 

R9 

R6  R7 

C2 

C11 

MAIN PCB UPGRADE SEQUENCE: 
1.  If necessary, swap R1 with 1M

Ω

 resistor. 

2.  If necessary swap R8 with 1.5K

Ω

 resistor. 

3.  If necessary, swap R9 with 2.2K

Ω

 resistor. 

4.  Replace R7 with 470K

Ω

 resistor. 

5.  Replace R12 with 3.3K

Ω

 resistor. 

6.  Replace C4 with 10

µ

F capacitor. 

7.  Replace C12 with 22

µ

F capacitor. 

8.  Build RC Network as indicated and solder  
 

into R6. 

9.  Build Filament Supply Leads as indicated  
 

and solder into position (use holes made 

 

in previous sequence). 

 
 
 

 

1.5K

Ω 

resistor 

2.2K

Ω 

resistor 

1M

Ω 

resistor 

100K

Ω 

resistor 

470K

Ω 

resistor 

1M

Ω 

resistor 

10

µ

F 

capacitor 

(note polarity!) 

22

µ

F 

capacitor 

(note polarity!) 

RC network at R6 

RC network (R6) 

RC network 

Filament supply leads 

680

ρ

F 

capacitor 

680 

3.3K

Ω 

resistor 

VERSION: 05-09-06 (original) 

6V6 REV. 12-30-08 (updated) 

www.MercuryMagnetics.com 

www.Amp-Exchange.com 

Copyright © 2008 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics, 6V6 Mod and Mercury Upgrade are trademarks of Mercury Magnetics.  Epiphone is a registered trademark of Gibson Guitar Corp.  or its subsidiaries. Mercury Magnetics is not affiliated with Gibson Guitar Corp. 

Valve Jr. 

VERSION 2 & 3 MAIN PCBs 

Tip: How to install resistors 

Non-flame-proof resistors should 

be mounted flush to the PCB. 

Flame-proof resistors should 

be mounted 2~3mm off the PCB. 

Summary of Contents for Epiphone Valve Junior

Page 1: ...VERSION 012011 ...

Page 2: ...y Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials Mercury Magnetics products are UL Underwriters Laboratories Inc recognized components for the USA and Canada OBJY2 component systems electrical insulation E120568 UL Recognition class 130 b Class 200 n ...

Page 3: ... damaged or fall off If this happens you ll have to fabricate a repair or created a jumper to a trace See this manual s appendices for tips POWERING UP A GUITAR AMP After making any modifications to an amp s circuit e g this Upgrade use a Variac along with an current meter some have both to slowly apply power to the amp while checking for warning signs of circuitry errors or shorts See the section...

Page 4: ...owever the original Version 1 Valve Jrs came with a single 4 ohm output whereas the later Versions 2 and 3 were given 4 8 and 16 ohm outputs Another clue to determining which version you have is the chassis Examine the chassis photos on the left Notice the location of the tube sockets Also Version 1 and 2 PCBs were green whereas version 3 PCBs are dark brown almost black Other than the color of th...

Page 5: ...nobs no added f x circuits nothin you just can t get any more elementary and still have a playable tube amp All this for around 100 00 150 00 retail Yes but as you might expect the stock amp is rather dull and anemic sounding The Mercury Upgrades The Mercury team spent about 3 months working on the little amp before deciding upon the best sounding combination of Upgrades and adaptations The projec...

Page 6: ... is much more than a simple inductor It can also store energy like a capacitor Better voltage regulation results from using a choke that puts less stress on your power transformer helping it to live longer Chokes permit higher load currents to be drawn from vacuum tube rectifiers without exceeding their peak current rating This means life extension for your tube rectifier Solid state rectifiers ru...

Page 7: ...te yellow red and blue wire 5 coils Mercury metal badge 1 Mercury guitar case sticker 1 Alan s 6V6 option components In addition to the standard Mercury Upgrade you may also want to install Alan s 6V6 option It s fairly simple to do but requires adding a socket to the circuit another hole inthe chassis There is a special section of this manual dedicated to making Alan s 6V6 option Here is the list...

Page 8: ...ssis 8 32 1 2 bolt nut washer lock washer for attaching the output power transformers to the chassis EPJR P power transformer EPJR O 4Ω EPJR OM 4 8 16Ω output transformer EPJR C 3H Mini Choke 1x 2x 1x 1x 1x 2x 2x 2x 6x 12 in coils 1x 1x 1x 1x 1x 1x 2 2KΩ 1 2W red red red RESISTORS carbon film NUTS N BOLTS OTHER COMPONENTS RESISTORS flame proof Component Identification Use these photos to identify ...

Page 9: ...PCB 7 Cut traces on the main PCB 8 Solder buss wire jumpers to the main PCB 9 Solder in upgrade s resistors and capacitors onto the main PCB 10 Make and solder in filament supply leads between V1 and V2 EL84 and 12AX7 sockets Sharp knife for scraping insulation layer from traces Electric drill with 1 16 and 11 64 bits 1 and 9 16 Varibit or stepped drill bit Silicon goo Loctite 290 green Pure isopr...

Page 10: ...f the chassis Hole location 4 x 2 3 16 from the front left hand corner of the chassis Enlarge existing hole Mercury s Axiom EPJR C 3H CHOKE mounting hole locations 2 Hole location 9 1 8 x 4 1 4 from the front left hand corner of the chassis 6V6 Mod only Hole location 6 1 2 x 5 1 4 from the front left hand corner of the chassis 1 dia From the center of the 1 dia hole drill 2 mounting screw holes ex...

Page 11: ...ion Mercury Magnetics 9167 Independence Ave Chatsworth CA 91311 818 998 7791 FAX 818 998 7835 info MercuryMagnetics com www MercuryMagnetics com 100 of our products are designed handmade in So California USA Established in 1954 TM All dimensions are nominal EPJR P EPJR P CLASS Axiom TYPE Power Transformer PART NO EPJR P ORIGINAL EPIPHONE PART NO TC00273 MOUNTING Horizontal A Frame VA RATING 30VA D...

Page 12: ...ablished in 1954 TM Copyright 2006 2010 by Mercury Magnetics All Rights Reserved Mercury Magnetics ToneClone FatStack Mercury Vintage are trademarks licensed to Mercury Magnetics Axiom is a registered trademark licensed to Mercury Magnetics Epiphone is a registered trademark of Gibson Guitar Corp or its subsidiaries Mercury Magnetics is not affiliated with Gibson Guitar Corp Epiphone Valve Jr Orig...

Page 13: ... CA 91311 818 998 7791 FAX 818 998 7835 info MercuryMagnetics com www MercuryMagnetics com 100 of our products are designed handmade in So California USA Established in 1954 TM All dimensions are nominal EPJR OM MULTI TAPVERSION EPJR OM CLASS Axiom TYPE Output Transformer PART NO EPJR OM ORIGINAL EPIPHONE PART NO YW TF VALVE JUNIOR 5W MOUNTING Horizontal L Bracket POWER RANGE Our OTs are rated to ...

Page 14: ...unior Head DRAWN BY MERCURY MAGNETICS 08 03 07 REV 04 09 10 www MercuryMagnetics com www Amp Exchange com This project and its documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expressed or implied license ...

Page 15: ...AX7 12AX7 12AX7 EL84 7189 6V6 12AX7 VERSION 05 09 06 original 6V6 REV 07 28 08 updated REV 12 02 10 Valve Jr head Mercury Upgrade with 6V6 Mod This project and its documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not consti...

Page 16: ...mbo DRAWN BY MERCURY MAGNETICS 05 09 06 REV 04 09 10 www MercuryMagnetics com www Amp Exchange com This project and its documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expressed or implied license to use ...

Page 17: ...2AX7 EL84 7189 6V6 12AX7 FILAMENT CONNECTION TYPE EL84 6V6 You can use 6V6 6L6 6550 etc PINS 4 5 2 7 VERSION 05 09 06 original 6V6 REV 07 28 08 updated REV 04 09 10 Valve Jr head Mercury Upgrade with 6V6 Mod This project and its documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprie...

Page 18: ...s Special note The solder used in these amps is RoHS compliant a term for a new industry standard that basically means the solder is lead free This also means that you ll need to use a good quality iron running hotter than traditional solder melting temperatures set it for about 800 F RoHS compliant solder melts at higher temps than the original soldering alloys but it s likely you ll be using reg...

Page 19: ...00KΩ 10KΩ 4 7KΩ 220Ω 220KΩ 220KΩ 220Ω 1 5KΩ V2 2 2KΩ V3 1 5KΩ V2 2 2KΩ V3 1 5KΩ 1MΩ 1MΩ 22µF 22µF V2 4700µF V3 470µF 22µF 22µF 22µF 22µF 22µF 022µF 022µF 1µF VERSION 05 09 06 original 6V6 REV 07 28 08 updated www MercuryMagnetics com www Amp Exchange com Valve Jr STOCK MAIN PCB VERSIONS 2 3 Copyright 2008 by Mercury Magnetics All Rights Reserved Mercury Magnetics 6V6 Mod and Mercury Upgrade are tr...

Page 20: ...s R1 7 8 9 10 11 12 Remove for Version 2 PCBs Do not remove for Version 3 PCBs Remove for Version 3 PCBs Do not remove for Version 2 PCBs 5 Make 5 trace cuts as indicated 6 Drill new 5 64 holes as indicated holes 1 to 6 7 If you will be installing the 6V6 Mod then enlarge holes 7 8 with 1 16 bit 8 Add 2 buss wire jumpers as indicated Hole 1 Hole 2 Holes 3 4 Jumper 1 Enlarge hole 7 Jumper 2 before ...

Page 21: ...or 6 Replace C4 with 10µF capacitor 7 Replace C12 with 22µF capacitor 8 Build RC Network as indicated and solder into R6 9 Build Filament Supply Leads as indicated and solder into position use holes made in previous sequence 1 5KΩ resistor 2 2KΩ resistor 1MΩ resistor 100KΩ resistor 470KΩ resistor 1MΩ resistor 10µF capacitor note polarity 22µF capacitor note polarity RC network at R6 RC network R6 ...

Page 22: ...is the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials ...

Page 23: ...ni Choke s leads to the locations designed on the Main PCB 10 Bolt the Main PCB back into the chassis 11 Connect the input jack and volume control leads to their jacks on the Main PCB Triple check your modifications If you have any questions the time to get them answered is now Call Mercury if you are in doubt about anything Finish re assembling the unit including reinstalling the tubes putting th...

Page 24: ...ditional mod you can make to your project amp from Alan Cyr It adds a tube socket that gives you a lot more flexibility with the little amp s tone When we debuted the mod at the LA Amp Show 2007 we demonstrated it with the EL84 and 6V6 in tandem you can run either tube independently or at the same time and it was the clear favorite of all who attended On the following pages are the schematics and ...

Page 25: ...RY VALVE JR UPGRADE VERSION 07 25 08 REVISED 07 29 10 TO RESISTOR R12 LEFT SIDE TOWARD TUBE SOCKETS TO RESISTOR R15 LEFT SIDE TOWARD THE JACK 470Ω 2W FLAME PROOF RESISTOR GROUND TO PIN 7 OF EL84 SOCKET STAND OFF 1 5KΩ 1 2W CARBON FILM RESISTOR Mercury Magnetics 9167 Independence Ave Chatsworth CA 91311 818 998 7791 FAX 818 998 7835 www MercuryMagnetics com TM Copyright 2008 2010 by Mercury Magneti...

Page 26: ...ate instructions 1 Thread the various transformers and choke lead wires through the original chassis holes as indicated 2 Solder yellow and black leads from PT s primary to the ON OFF switch as indicated twist these leads 3 Solder the 2 orange filament wires from the PT to the 6V6 s pins 2 and 7 as indicated twist these leads 4 Solder OT s primary black wire to T4 as indicated 5 Solder OT s second...

Page 27: ...nd fully test your amp After you have tested played in the amp and are accustomed to its new and improved tone make the 6V6 option You can run the amp with both the 6V6 and EL84 in parallel or remove either tube from the socket and run the amp on a solo tube Notes The components of the current kit differ slightly from those shown in these photos The 270rF capacitor has been changed from a ceramic ...

Page 28: ...is the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials ...

Page 29: ...the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials The next 4 photos show an Upgraded Version 2 PCB of a Valve Jr with the 6V6 option Note An error resulted in the OT s black primary lead being cut short The 6V6 option s stand off connector was used to remedy the problem ...

Page 30: ...is the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials ...

Page 31: ...is the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials ...

Page 32: ...is the result of technical investigations made by the engineering staff of Mercury Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials ...

Page 33: ...the Main PCB Solder onto T1 and T2 the red leads from the PT Solder the black and yellow PT leads onto the On Off switch Solder the orange white striped center tap lead from the PT and the ground chassis lead to the back of the board see special instruction page Solder the Mini Chokes leads to the locations designed on the Main PCB Connect the input jack and volume control leads to their jacks on ...

Page 34: ...xtreme risk of frying your amp or some of its components getting hurt electrocuted etc A Variac is a standard amp tech tool No amp tech should be without one They are available from many electronic stores or online eBay etc Prices start at about 50 and go up from there The better units such as the Tenma isolated variable AC power supply shown in these photos include output current metering Conside...

Page 35: ...o 0 Turn on the Variac s power Then turn on the amp s power Variac A variable transformer used to vary AC voltages Also the tradename for a brand of variable AC transformer There are other brands but the term is generically used to describe all of them A variac allows adjustment of the incoming AC mains voltage The better quality units have meters for voltage and current or both and fuses for prot...

Page 36: ...ariac s output voltage knob The amp should turn on at about 45 volts When you get to about 60 volts you don t want to see more than a few hundred milliamps If the current meter reaches anywhere above half an amp roll the Variac back to zero shut everything down discharge the caps and look for the error short or bad component Correct the problem and repeat until this test passes STEP D Once you can...

Page 37: ... bring the twist of the leads as close as possible to the terminals they ll be soldered to The Valve Jr s original circuit ran the filaments to DC we re converting it back to AC Running the filaments to DC is a common enough technique intended to reduce excessive noise problems Unfortunately this method also cooks the tubes and cuts their working life up to about a third Because you re now using q...

Page 38: ...Magnetics The disclosure of the information herein may pertain to proprietary rights and the furnishing of these documents does not constitute an expresed or implied license to use such materials Tips n Tricks for Making the RC Network These photos detail the making and installation of the RC Network Refer to the schematic for specific connection information ...

Page 39: ...itute an expresed or implied license to use such materials Tips n Tricks for Alan s Anti Squeal Circuit Option Join the provided 47rF ceramic disk capacitor to the 220KW resistor and jump them across pins 6 and 7 of the V1 socket 12AX7 as shown Due to quality issues with some of the Chinese materials being used some but not all Version 3 Valve Jr amps will emit a squeal If you re one of the unluck...

Page 40: ...intain affordable prices for consumers On a PCB components are often attached to the top of the board and then soldered from the back via pass through conductive eyelets where they follow the traces that make up the circuit Asian made PCBs are typically not as resilient as those made in the west Therefore they re likely to Continued on next page è Damaged eyelet Intact eyelet Repair to a damaged e...

Page 41: ...f in the process of making repairs and modifications If this happens the easiest workaround is to reveal about 1 8 of trace material near the eyelet hole on the same circuit and solder the component s lead connection directly to that Or if there s a nearby soldered connection on the same trace you can use the component s lead to jumper directly to the terminal If an eyelet is damaged or missing or...

Page 42: ...ar 2 Listen Do you hear an unusual amount of extra noise 3 The key to reducing noise is the layout of the wiring Looking at the supplied photos of a finished amp you ll notice patterns as to how the filament leads and other leads are twisted together How some are not twisted Their lengths The use of wire ties and the positions of others 4 The filmament wires should be as evenly twisted as possible...

Page 43: ...y Resistance Secondary Resistance Core Eddy Current Losses Core Hysteresis Losses Blessed are the Tone Makers The above circuit reveals the properties of an audio output transformer The transformer is a reactive component its values change depending upon the information feeding it Transformers for tube based electric guitar amps are designed to intentionally provoke the tubes into distortion the p...

Page 44: ... high voltage current circuits safely Several ways to discharge caps FIRST UNPLUG THE AMP But that doesn t make it safe THEN take a screwdriver or a jumper and short the capacitors leads OR jumper the power amp tube plate pin to ground for a minute or so Class A single power tube only OR jumper the positive lead of each large cap to ground for several seconds A jumper with a built in resistor 10K ...

Page 45: ...ery good chance that it will explode in your face If you haven t given the capacitors a couple of days to discharge or if you just want to be cautious you can use a short length of insulated wire with alligator clips on the ends to discharge them First make certain that the amp is unplugged Attach one alligator clip to a capacitor s positive lead then touch the other clip to the amp chassis severa...

Page 46: ...TO DO IT In old electronics books they tell you to use a screw driver with an insulated handle to short out the caps Shorting with a screwdriver will almost instantly drain the caps to zero volts causing sparks from high current This is not acceptable If there are several hundred volts stored in the caps be prepared for a nice sized spark It will most likely leave a black mark on the chassis and i...

Page 47: ...or until there s absolutely no doubt in your mind that all are drained Less than 5 volts is safe but I prefer to drain mine to 1 volt for peace of mind Don t be surprised if you find the capacitors slowly recharging themselves This phenomenon is known as dielectric absorption and is quite normal in electrolytic capacitors The filter caps shouldn t recharge to a lethal level but leave the discharge...

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