Mercury Epiphone Valve Junior Assembly Manual
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Mercury Epiphone Valve Junior Assembly Manual

Transformer demonstration project
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VERSION 012011

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Summary of Contents for Mercury Epiphone Valve Junior

  • Page 1 VERSION 012011...
  • Page 2 All Mercury Magnetics products are 100% handmade by us in California, USA. Copyright © 2006–2011 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics, Multi-Choke, Mini-Choke and “The Heart & Soul of Your Amp” slogan are trademarks licenced to Mercury Magnetics. Axiom, APS and ToneClone are registered trademarks licensed to Mercury Magnetics. Epiphone and Valve Jr. are trademarks of Gibson Guitar Corp. Mercury Magnetics is not affiliated with with Gibson Guitar Corp. 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. 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). OBJY8 component systems, electrical insulation, certified for Canada, class 130(b) – Class 200(n). Mercury Magnetics transformers and other products are in compliance with the European Union RoHS Directive 2020/95/EC with respect to the following substances: lead (Pb), mercury (Hg), cadmium (Cd, hexavalent chromium (CR (VI)), polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE). Attention: Modifying your Epiphone Valve Jr. amp voids the factory warranty! Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 3: Table Of Contents

    Indentifying which Version of the amp you own ..........4 The Story Behind Mercury’s First Transformer Demonstration Project ......5 Parts List .

  • Page 4: Indentifying Which Version Of The Amp You Own

    Stock Version 1 Chassis Also, Version 1 and 2 PCBs were green, whereas version 3 PCBs are dark brown (almost black). Other than the color of the PCBs, Versions 2 and 3 are nearly identical. However, Epiphone did change the values of some of the minor components from Version 2 to 3 (which are indicated in the Stock Version 2 & 3 illustrations in this manual). Chassis Note the relocation of Note: There are 2 tutorials on the tube sockets. the CD-ROM; one specifically for Version 1 and the other (this one) for Versions 2 and 3 PCBs. You’ll need to use the appropriate tutorial for the PCB version you have. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 5: The Story Behind Mercury's First Transformer Demonstration Project

    Mercury’s The Story Behind First Transformer Demonstration Project The Mercury Upgrades ay back in ’06 your friends at Mercury set out to create a basic demonstration The Mercury team spent about 3 months to show exactly what quality working on the little amp before deciding upon the transformers could do for your tone. Our goal best sounding combination of Upgrades and was to reveal the sonic capabilities of high quality adaptations. magnetics – i.e. properly designed vs. generic transformers. The project was headed by Sergio Hamernik, of Mercury Magnetics, and Los Angeles- What started out as a simple educational demo based amp wizard, Alan Cyr. After examining the ended up blowing the minds of virtually everyone original circuitry several custom Axiom-series who heard it. There was no denying how transformers and Mini-Choke sets were designed extraordinary our little test amp sounded after and tested. Alan was then able to clean up the the Mercury trannys were circuit, effectively opening up the installed..amp’s sound because much of...
  • Page 6 “State-of-the-Art” Studio Samples Follow these links to a selection of undoctored MP3 samples of the prototype Mercury Upgraded Valve Jr. Just for the fun of it these samples were made under primitive conditions (see the photo to the right). A special “Thank you!” goes out to LA musician Phil Woodward for his guitar work on these tracks: Mercury Upgrade Sample 1 Mercury Upgrade Sample 2 Mercury Upgrade Sample 3 Mercury Upgrade Sample 4 Mercury Upgrade Sample 5 Mercury You’ve made the – now you’re ready to play! Upgrade Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 7: Parts List

    Parts List Your Mercury Upgrade Kit for the Epiphone Valve Jr. (Version 2 or 3 PCBs) includes these components. Transformers: • Mercury Axiom Power Transformer (part #: EPJR-P) ....................1 • Mercury Axiom Output Transformer (part #: EPJR-OM) 4, 8 & 16W outputs ............1 • Mercury Axiom Mini-Choke (part #: EPJR-C-3H) ...................... 1 Capacitors: • 10mF 25V or 50V electrolytic (radial) ..........................1 • 22mF 40V electrolytic (axial) ............................. 1 • 22mF 450V electrolytic (axial) ............................2 • 22mF 450V electrolytic (radial) ............................2 • 270rF silver mica ................................1 • 680rF silver mica .

  • Page 8: Component Identification

    CAPACITORS (silver mica) CAPACITORS (ceramic disk) Mercury nameplate 47ρF Note that most capacitors have +/- polarity. Be sure to study the schematics for the correct directions when Upgrading your amp. 680ρF 500V 270ρF 500V Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 9 5. Mount transformers and choke. Install 6V6 socket and 15. Reattach main PCB to chassis. stand-off connector bracket if you are adding Alan’s 16. Using the supplied diagrams, triple-check your work 6V6 option. to ensure that all connections are made and are 6. Drill holes for filament wires and enlarge holes for correct. other connections into the main PCB. 17. Power up using a variac and amp meter. 7. Cut traces on the main PCB. CAUTION: DO NOT POWER UP THE AMP 8. Solder buss wire jumpers to the main PCB. WITHOUT THE SPEAKER CONNECTED!!!! 9. Solder in upgrade’s resistors and capacitors onto the 18. Arrange leads to minimize RF and noise. main PCB. 10. Make and solder in filament supply leads between V1 and V2 (EL84 and 12AX7) sockets. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 10: Chassis Modification Diagram

    Front of chassis 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.

  • Page 11: Transformer And Mini-Choke Specification Sheets

    NO: TC00273 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.
  • Page 12 (Call for more information.) 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.
  • Page 13 DATE: 04-24-07 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.

  • Page 14: Wiring Schematics

    Copyright © 2006–8 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics,ToneClone, FatStack & Mercury Vintage are trademarks of Mercury Magnetics. Axiom is a registered trademark of Mercury Magnetics. Epiphone is a registered trademark of Gibson Guitar Corp. or its subsidiaries.
  • Page 15 VERSION: 05-09-06 (original) 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 6V6 REV.
  • Page 16 Copyright © 2006–8 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics,ToneClone, FatStack & Mercury Vintage are trademarks of Mercury Magnetics. Axiom is a registered trademark of Mercury Magnetics. Epiphone is a registered trademark of Gibson Guitar Corp. or its subsidiaries.
  • Page 17 VERSION: 05-09-06 (original) 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 6V6 REV.

  • Page 18: An Overview Of The Upgrade Process

    5. Remove the following from the Main PCB (printed 8. The chassis needs to be modified to hold the circuit board): Upgraded power and output transformer and the a. Tubes Mini-Choke. If you will be adding the 6V6 Mod, you’ll b. Transformer clips need to add the tube socket as well. Reference the c. Unbolt the main PCB. chassis template, make the modifications and bolt on d. Unclip and/or unsolder all other direct connections the transformers and Mini-Choke. If you’ll be adding the to the main PCB. 6V6 Mod, see the special section regarding how. e. Unbolt and remove the stock output and power transformers 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 Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 19 6V6 REV. 07-28-08 (updated) 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.
  • Page 20 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.
  • Page 21 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.
  • Page 23 When the amp is working to your satisfaction use 6. Solder the green and black secondary leads the cable ties (supplied) to group and hold the from the OT to the speaker jack as indicated. various wires away from the Main PCB (especially 7. Solder the black primary OT lead to T4. the tubes). In particular, gather up Filament Supply Leads tying them as close to the power 8. Solder the yellow primary OT lead to T3. transformer as possible. See final photographs for 9. Solder the Mini-Choke’s leads to the locations examples. designed on the Main PCB. Apply Loctite 290 (green) to the two retaining bolts 10. Bolt the Main PCB back into the chassis. and screws of the Main PCB. 11. Connect the input jack and volume control Apply the Mercury metal place to properly I.D. leads to their jacks on the Main PCB. your Mercury Upgraded amp. And you are done! Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 24: Mercury Upgrade Bonus -- Alan Cyr's "6V6 Option

    Valve Junior – and while you’re at it, here’s Alan Cyr’s 6V6 Option Added tube socket for the 6V6 A Mercury Upgraded Valve Jr. with Alan’s 6V6 option installed. Note the additional tube socket. Here’s a simple additional 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 accompanying photos to show you how the add-on fits into the circuit. To make the mod, you’ll have to drill an additional hole in the chassis to support the new tube socket. The provided schematics, illustrations and photos show the complete Mercury Upgrade, including the parts needed to make the 6V6 option. Enjoy! Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 25 REVISED: 07-29-10 Copyright © 2008–2010 by Mercury Magnetics. All Rights Reserved. Mercury Magnetics, 6V6 Mod and Mercury Upgrade are trademarks 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.
  • Page 26 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.
  • Page 27 TO FILAMENTS POWER TRANSFORMER LEADS 480W 2W 270rF / 500V RESISTOR CAPACITOR STAND-OFF CONNECTOR 22mF CAPACITOR 1.5KW 1/2W RESISTOR 8-PIN SOCKET This sequence of photos shows the wiring and connections to the 6V6 socket. We suggest that you make the Mercury Upgrade first. Then run and 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 disk to a silver mica type. The white filament lead wires have been changed to orange. And, the green insulation shielding is now semi- transparent white. Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 28 Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 29 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. Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 30 Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 33 Solder the OT’s yellow primary lead to pin 3 of the working correctly. 6V6. When the amp is working to your satisfaction use Solder the two orange filament leads of the PT into the cable ties (supplied) to group and hold the pins 2 and 7 of the 6V6 socket. Note that these various wires away from the Main PCB (especially leads should be tightly twisted (see appendix). the tubes). In particular, gather up Filament Solder the OT’s secondary green and black leads Supply Leads tying them as close to the power to the speaker jack as indicated. transformer as possible. See final photographs for examples. Solder the OT’s primary black lead to T4 of the Main PCB. Apply Loctite 290 (green) to the two retaining bolts and screws of the Main PCB. Solder onto T1 and T2 the red leads from the PT. Apply the Mercury metal place to properly I.D. Solder the black and yellow PT leads onto the On/ your Mercury Upgraded amp. And you are done! 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. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 34: Tips 'N Tricks - Using A Variac & Current Meter

    AND/OR SERIOUS HARM TO YOURSELF! Using a Variac & Current Meter Don’t power-up your amp without ’em! NOTE: IF YOU ARE NOT A QUALIFIED AMP TECH, DO NOT ATTEMPT TO POWER UP YOUR MODIFIED AMPLIFER, YET. INSTEAD, Mercury RECOMMENDS THAT IT BE INSPECTED BY A QUALIFIED TECHNICIAN. AN AMP TECH WILL GO OVER YOUR WORK AND VERIFY THAT IT IS SAFE TO POWER IT UP. After modifying your amp, the next step is to power it up using a variac and current meter. The Variac and current meter allows you to slowly add voltage while checking the indicators to make sure that your handiwork is correct. Without a variac you run the extreme 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. Consider that the cost of a Variac is free, because a single error without one can easily cost more than the Variac itself! As the following instructions show, you’ll need to monitor the output current while increasing power to the amp with the Variac. If your Variac doesn’t have a self-contained current meter this can also be done with a separate amperes meter connected to the fuse-holder of the amp (with the fuse removed). Specific instructions for how to use Variacs and current meters are beyond the scope of this manual. Check the web or owner manuals of the devices for specific methods. Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 35 STEP A: Make sure that your amp is OFF. Plug it into the Variac. The Variac is OFF with the output voltage knob set to zero (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 protection. Variacs come in many shapes and sizes. But their function is basically the same. If your variac does not have an amperes (current) meter, you’ll need to use a separate meter. NOTE: The Variac in the photo to the left does not have an amperes meter whereas the Tenma model does. Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 36 STEP B: Turn on the amp’s power. STEP C: While watching the current (amp) meter, slowly roll on the Variac’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 reach 120 volts drawing less than half an amp, you are in good shape. NOTE: If you don’t have a current meter on your Variac, remove the fuse from the amp, and with an amp meter across the empty fuse holder socket, turn on the amp and perform the test above. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 37: Tips 'N Tricks - Making The Filmanent Supply Leads

    Tips ’n Tricks for Making the Filament Supply Leads Consistent, even twisting is important. Ideally you want about 10 twists per inch. And 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 quality transformers, combined with Alan’s reworking of the circuit, this “solution” is no longer necessary. The above illustrations show how to create new filament supply leads which you’ll be using to make the conversion. The leads are then soldered into the locations indicated on the schematics. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 38: Tips 'N Tricks - Making The "Rc Network

    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. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 39: Tips 'N Tricks - Alan's "Anti-Squeal" Circuit Option

    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 unlucky ones, install this anti-squeal option. Refer to the schematics for specific connection information. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 40: Tips 'N Tricks - Working On Pcbs

    Repair to a damaged eyelet: The lead from component bypass- es the damaged eyelet and is soldered to either a revealed trace or another terminal on the same trace (as in this example). require patching and repair work as you make the Upgrade. This is normal, and easy to do – as long as you know a few tricks. Revealing a Trace: Sometimes we need to “reveal” traces so that the PCB can be modified or repaired. An easy way to do this is to take a sharp knife or Exacto and carefully scrape away the lamination to “reveal” the copper foil under it. Use high-grade (99%) Isopropyl alcohol and a Q-tip to clean these new contacts before soldering to them. Various examples: 1. Jumper. 2. Jumper. 3. Trace repair (jumper soldered from terminal to terminal on same trace). 4. How to Repair Damaged Eyelets: The PCB’s Trace repair (ditto). 5. Damaged eyelet repair (lead is soldered to conductive eyelets are easily damaged and a revealed trace). Continued on next page è Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 41 Various examples: This photo shows a cut trace, and a com- ponent lead jumpered and soldered to a revealed trace. It’s best If an eyelet is damaged or missing or the trace to not drill a hole directly into a trace. Instead make the hole off to the side of the trace and then, as in this example, solder the material around it is very thin, then you may component’s leg to the trace. consider soldering a reinforcement jumper across it. How to Cut a Trace: A “trace” is the conductive A trace cut severes the embedded metal laminent strip (foil) on a printed circuit board. It has a very on a PCB. The purpose of a trace cut is to modify or thin laminate or lacquer layer over it. Cutting a trace re-route the electrical flow of the circuit. is like clipping a wire. Use a box knife, Exacto knife or a Dremel Tool with a cutting or grinding edge attachment to make the cuts. Here’s two different ways to cut a trace: Dremel Tool Trace Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 42: Tips 'N Tricks - Reducing Rf & Other Noise In The Circuit

    1. With the amp powered-up, turn its volume control off and unlplug the guitar. 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—about 10 twists per inch. Symetry is important. 5. Try to follow our examples as closely as possible. 6. The output transformer’s primary YELLOW lead is another source of noise. Keep it under and away from as many components and other leads as possible, but close to the chassis. 7. Make sure that the twin RED B+ leads from the PT are NOT TWISTED together. Tips ’n Tricks for Drilling the Tube Socket for the 6v6 Mod To create the proper-sized hole for the 6V6 tube socket, you’ll need varibit or stepped drill bits similar to these. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

  • Page 43: The Output Transformer Circuit

    The Output Transformer Circuit Mercury’s circuit equivalent of an Output Transformer Primary Self Capacitance Primary Inductance Secondary Self Capacitance Primary Resistance Interwinding Capacitance Secondary Resistance Primary Leakage Inductance Core Eddy Current Losses Secondary Leakage Inductance Core Hysteresis Losses “Blessed are the Tone Makers”...

  • Page 44: Discharging Filter Capacitors

    * * * soldering supplies and a volt/ohm meter (learn how to use them!). “Filter” caps can store fatal amounts of electrical current. The caps are connected near the rectifier Start by unplugging the amp from the wall, the and are part of the power supply, and aid in speakers from the amp, and removing the amp converting AC to DC. In fact, they are a standard chassis from the case. For Fender amps, removing component in any power supply. the chassis involves unscrewing the upper back case panel, then unscrewing the chassis from the If you’re completely lost, and don’t understand this, top of the case. Put the screws, nuts, and lock DON’T MODIFY YOUR AMP. You haven’t enough washers where they won’t get lost. knowledge to work on high voltage/current circuits With the chassis out of the case, you can locate safely. the filter capacitors you’ll want to avoid touching as you perform the tune-up. These will be cardboard Several ways to discharge caps: cylinders (usually orange or tan or vintage Fenders) FIRST, UNPLUG THE AMP! (But that doesn’t with “+” printed near one terminal. It’s also a good make it safe!) idea to steer clear of wiring connected to the power transformer because it’s a discharge path for the THEN, take a screwdriver or a jumper and short filter capacitors. the capacitors leads. Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 45 Instructions Level of difficulty: Moderate Step 1: Strip about 1/4 inch of insulation off each end of a 2-foot length of insulated copper wire, and solder one end of the wire to one of the leads of a high wattage resistor. The resistance required can be determined by adding 5 to 50 ohms per volt of the capacitor’s rating. For instance, a 100V capacitor would require a resistor rated anywhere from 500 to 5k ohms. Step 2: Attach the other end of the wire to an alligator clip. Filter Capacitor Discharge Tool Step 3: Solder the free lead of the resistor to a short piece of bare copper wire. 1. Safety glasses. Always use safety glasses. If you wire a capacitor in backwards there is a very Step 4: Tape the resistor and bare copper wire to good chance that it will explode in your face. one end of a length of non-conductive material, Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 46 3. From the chassis to a tube pin. This can be (about 5 minutes, if the amp has bleeder resistors this time will be shorter) then, while the discharge done at pin 3 of any power tube, or pins 1 or 6 of any preamp tube. By shorting the chassis tool is still in place recheck all the capacitors with your multi-meter and keep that other hand behind to the correct pin the caps will be forced to drain through the plate load of that tube. This you. Keep checking until the voltage has reached prevents sparking from high current. a safe level. Note: This procedure must be done every time you turn the amp on then off. IMPORTANT NOTE, HOW NOT TO DO IT: In old Remember to remove the discharge tool before electronics books they tell you to use a screw driver with an insulated handle to short out the caps. powering on the amp. Make it a bright color like Epiphone Valve Jr. • Mercury Upgrade Kit 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.
  • Page 47 1. Never work on an amp if you’re tired, fatigued, fuse in series with the resistor on the discharge frustrated or intoxicated. tool in case you forget to remove it. 2. Never work while distracted. Filter capacitors are wired in parallel, so draining one should drain them all, but never assume. 3. Never work on an amp around small children. Always recheck for residual voltage in every filter There are just too many dangers involved to capacitor until there’s absolutely no doubt in your take that chance. mind that all are drained. 4. Try to have a plan in case something does go Less than 5 volts is safe, but I prefer to drain mine wrong. You might consider asking someone in to 1 volt for peace of mind. Don’t be surprised if you your household to take a CPR class. find the capacitors slowly recharging themselves. 5. Take your time and don’t rush. This phenomenon is known as dielectric absorption and is quite normal in electrolytic capacitors. The 6. Use common sense. filter caps shouldn’t recharge to a lethal level, but http://tubenewbie.com/discharge_capacitors.html leave the discharge tool in place while working on the amp. Epiphone Valve Jr. • Mercury Upgrade Kit 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.

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