Mercury Magnetics Epiphone Valve JR Upgrade Kit Build Part One

 

I had heard many good things about the Mercury Magnetics kit for modifying a Epiphone Valve JR amplifier. I believe my first encounter with the company was via an ad in Vintage Guitar Magazine (proof advertising actually works!), which prompted a little Internet sleuthing on the subject. My initial searches lead me directly to YouTube, where I found a good collection of demo videos on both the stock Epiphone Valve JR and Mercury modified version.

 

I will say right off the bat that the stock Epiphone (for its price point) is no slouch; it has a good tone for blues and rock and a classic look to it. But after watching some before-and-after videos I was convinced that it would be a worthwhile project.

 

So with that I purchased two Epiphone Valve JR heads and requested a kit from Mercury so we could modify the amp and then see how it stacked up against a stock unit. Phil Manley was the perfect guy to take on this project for GuitarFixation. Phil has a wealth of experience with electronics from building his own fuzz pedals to repairing amplifiers. Phil also has a well-stocked workbench in his garage (yes, a garage in San Francisco- there will never be a time that I don’t covet his garage) that includes a quality soldering iron with adjustable heat and a large assortment of tools, parts, and meters. Again, this is really a project for an intermediate; I would not recommend this to someone who is picking up a soldering iron for the first time.

With all of the parts together I headed over to Phil’s on a foggy San Francisco morning and we began the modification. Pulling the amplifier apart and removing the components was a simple enough task, as Mercury includes a disk with the kit that contains a huge manual and some videos. The only real issue with the instruction manual was that it had almost too much information. The manual is for all three versions of the head (current production is version three) and that made them a little hard to read because the document was referencing all the versions on one diagram. That being said, the instructions are very thorough and it is a good idea for you to read them a few times before you start. (Editor’s Note: Always RTFM, boys!)

Discharging the caps on the main board is a fairly simple task; you just want to ensure that they are totally drained as to avoid any chance of a shock. We didn’t plug in the amp before we started the modification so there was no juice to be found, but if you are going to use the old screw driver technique, you should remember to ground it. A good way to do this is by getting two alligator clips with a wire in between them and connecting one side to the screw driver and the other to a grounded source. It reminded me of when I use to work on tube television: one had to discharge the picture tube with a flat blade screwdriver – POP!

An indispensable tool for this kind of work is a solder sucker that is used to remove hot solder from a board or component. You simply heat the area till it flows and then you load the solder sucker by compressing the spring. Then simply put it over the area in question and hit the button. This will remove most of the solder from the area (you may have to do it twice to get it all), well worth it, as makes adding the new components much easier.  You can get one from Radio Shack, but beware their tiny under-$10 model. Be sure to get a half decent one that has a lot of suction to clear away the solder. I recommend the “Edsyn Solder Sucker” it is the one Phil is using in the video. You can get an Edsyn from MarkerTek for about $24 - you can get it HERE.

A Dremel tool will also serve you very well for the modification of the amp. I ended up buying one after Phil had already completed all of the trace cuts on the board (sorry Phil!) The Dremel would have made these cuts worlds easier when compared to using a flat head to scrape away at the trace. If you are not going to use a Dremel then you will want to double check the trace cuts with a meter set to continuity and to ensure that the cuts are 100% or you’re in for some trouble down the road. You will also need a step bit if you decide to do the 6V6 mod, but you could always use a drill and Dremel like we ended up doing when the local hardware store came up flat in the step bit selection (see the video).

So to this point Phil had been working on the amp for a total of five hours, but we had taken a few minutes for lunch and had to make a trip to the hardware store. So in reality I would say this first section took Phil roughly two and a half hours. If you were working alone without someone pointing a camera in your face I think you could have it done in less than two hours. So far the kit is straightforward and easy enough to work on with a reasonably clear set of directions to work from (but be sure to print them in color!) The fun will continue in part two as Phil really gets into the nitty gritty of  this amp mod.