Mercury Epiphone Valve Junior User Manual

Epiphone Valve Jr. • Mercury Upgrade Kit 3
This project and its documentation 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.
SOLDERING NOTE: Depending upon the version your Valve Jr. may be assembled using RoHS compliant, lead-free solder. Working
with lead-free solder is different than standard solder. Generally a hotter iron is necessary. For more information we recommend doing
a web-earch for “lead-free soldering techniques.”
CAPACITOR DISCHARGE WARNING: Safe discharging of lter capacitors matters. It is essential for your safety and to prevent
damage to the amp’s circuitry, that large or high voltage capacitors be fully discharged before measurements are made, soldering is
attempted, or the circuitry is touched in any way. For information on how to do this, web-search “capacitor discharging.” Also see the
appendix for additional information.
CAPACITOR POLARITY: Note that many capacitors have positive and negative polarity, and are stamped accordingly. Be sure that
their polarity is correct when soldering to a PCB.
BRAIDING, TWISTING AND COILING LEADS: Do not braid, twist or coil the power transformer’s B+ lead wire. Check our reference
illustrations and photos to see which leads are twisted together. Typically only the lament leads of the power transformer. Other posi-
tioning of leads may be necessary to minimize amp noise. Follow are diagrams and instructs for optimal performance.
TRIMMING TRANSFORMER LEADS: To minimize noise, measure and trim the solderable lead lengths of the transformers and Mini-
Choke
™
. Route all wires cleaning around the tubes, chassis, etc.
CLIPPING vs. UNSOLDERING PCB COMPONENTS: To make this Upgrade it will be necessary to remove several components from
the Main PCB of the amp. Due to quality issues with modern off-shore PCB manufacturing, it can be difcult to unsolder an item without
creating other problems, the most typical of which is an eyelet detaching from the PCB. Therefore we’ve indicated which components
should be clipped vs. unsoldered. To unsolder heat your iron to 800ºF, then very quickly heating up one side of the existing solder con-
nection while pulling it through on the other. If the iron is not hot enough, or you linger too long, the eyelet will get 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 modications 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 on “Using a Variac” at the end of this manual.
LOADING OUTPUT TRANSFORMERS: You must connect a speaker or speaker cab to your amp before powering it up. Without a
load the output transformer will blow.
MINI-CHOKE FACTOID: A Mercury Mini-Choke
™
replaces a resistor and adds a disernable amount of tonal dimension to the circuit.
TRANSFORMER BREAK IN PERIOD: As a general rule, transformers require approximately 30 hours of playing time to be fully
broken in. Please refer to Mercury’s website for more information.
BE SAFE! ALWAYS USE PROTECTIVE EYEWEAR!
Table of Contents
Indentifying which Version of the amp you own . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
The Story Behind Mercury’s First Transformer Demonstration Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Component Identication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chassis Modication Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Transformer and Mini-Choke specication sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Wiring Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
An Overview of the Upgrade Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Mercury Upgrade Bonus -- Alan Cyr’s “6v6 Option” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Appendices:
Tips ’n Tricks – Using a Variac & Current Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Tips ’n Tricks – Making the Filmanent Supply Leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Tips ’n Tricks – Making the “RC Network” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Tips ’n Tricks – Alan’s “Anti-Squeal” Circuit Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Tips ’n Tricks – Working on PCBs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Tips ’n Tricks – Reducing RF & Other Noise in the Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Tips ’n Tricks – Drilling the Tube Socket for the 6V6 Mod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
The Output Transformer Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Discharging Filter Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
CAUTION! The voltages in your amplier can be dangerous. Transformers and chokes are not user servicable
parts. Installation of these components should always be performed by an experienced technician. The simple ability
to use a soldering iron is not enough to qualify a “do-it-yourself person.” Those who are inexperienced in working
with electronic circuits should never attempt to service their ampliers. Household line currents can be deadly!!
Transformers, chokes and large lter capacitors can store dangerous charges for several days, or longer, after the
amplier has been unplugged. Never touch the terminals of these components without being certain of their charge
status. Risk of shock and damage to equipment may result from mishandling and/or improper use of these compo-
nents. Please use common sense and always think safety rst. After all, great tone is most enjoyed when you are
alive to hear it.

Mercury Epiphone Valve Junior Specifications

General

Brand	Mercury
Model	Epiphone Valve Junior
Category	Amplifier
Language	English