Mojotone 5E3 Deluxe Kit

This was my first attempt at building a tube amp from a kit. I should state first off that building an amp like this is not easy to do and it is especially difficult to troubleshoot when you have no idea what you are doing. It is a learning process, start to finish. In the end, however, the amp sounds great. I had been thinking about building an amp kit for a couple of years and was debating between B.Y.O.C.'s Tweed Royal, or a 5E3 (Deluxe) or 5F1 (Champ) from Weber, Marsh, or Mojotone. Mojotone put several amps on sale the week after Thanksgiving and I picked up a complete 5E3 kit for $500 plus shipping. When the kit arrived there were a couple backordered parts (including the fiberboard) which arrived separately within a few days, and one part which was mispicked, which Mojotone replaced immediately. The kit components are all high quality--Carbon Comp, Sprague, TAD, Orange Drop, and JJ and EHX tubes. The cabinet is unlacquered tweed and not drilled for the chassis. The only component which I wish had been different was the Jensen C12Q ceramic speaker. I would have opted for a P12Q alnico speaker or perhaps no speaker and ordered a Weber 12a124a separately. The sale price did not allow for substitutions or deletions, however. Mojotone does not provide detailed instructions for their kit. There is a 5-page general instruction pdf available on their website, and the kit ships with a schematic and layout, the later of which was most useful in building the kit. I ended up relying on detailed instructions for other 5E3 kits and, well, figuring it out as I went along.

Soldering components to the board is pretty easy.

I won't bore you with all of the details about building the kit. Mojo's website claims that the kit will take about 5 hours to build. I took about a zillion hours to put this thing together. I spent several evenings and a weekend putting the kit together, and many hours more troubleshooting, researching problems on the web, resoldering, etc. Of course once you build one successfully, the amount of time would go down significantly. What I will do instead is to describe the the various problems that I had to sort out in case you run into the same things.

1. Ground the fiberboard properly. The Mojotone layout schematic does not include any direct instructions on how to internally ground different parts of the circuit. It took me a while to understand that the chassis itself serves as a ground and that there are three ground leads coming to from the assembled fiberboard that need to be soldered or bolted to the chassis, pots or jacks. My first attempt at grounding the circuit was to solder all three ground leads from the fiberboard to one lug which I then attached to one of the bolts from the choke. This did not work and the amp was very noisy. By chance I started prodding leads and the fiberboard with a chopstick and, completely randomly pressed the fiberboard near at the top left, according to Mojo's schematic, and grounded all three leads when one of the soldering points on the back of the fiberboard made contact with the chassis. The amp sounded better when I would do this so I knew that I had to rethink how to ground the leads. My "accidental" realization that there was something wrong with the grounding was only possible because I had not used the backing board that Mojo had supplied with the fiberboard (see #2 for more on this). My solution to the grounding issues was to buy new grounding lugs and install them in two places, first on the same choke bolt  where I had first soldered all three ground leads, and second on one of the mounting screws for V1. I relocated the ground that comes off the top right of the board to this screw. I then relocated the ground that comes off the top middle of the board to the ground lug on the normal circuit volume pot. This seemed to provide a better overall grounding scheme for the circuit and the amp started sounding better.

2. Use the backing board. Mojo's instructions didn't indicate what I should do with the backing board, so when I originally assembled the kit, I didn't use the board at all. After working through the grounding issues, I realized that the backing board was necessary to prevent the soldering points on the back of the fiberboard from shorting out against the chassis. I first "solved" this problem by unbolting the pots and jacks and pulling the top of the fiberboard out just enough to slide the backing board in behind the fiberboard and then pushing both boards back into place. This of course was only a temporary fix, and eventually I drilled the fiberboard, backing board and chassis so that the whole caboodle could be bolted to the chassis. This is a bit harder to do once then entire amp is built, so better to do this first before everything is wired in place.

3. Double-check your soldering. It is worth it to double-check your soldering as you are assembling the amp. When I was unbolting the jacks to squeeze the backing board in, I realized that I failed to solder the #1 jacks to  the #2 jacks such that that two of them fell off when I unbolted them. They had worked when I originally assembled the amp because the resistors leads I used to connect the jacks had made contact with the lugs even though they weren't properly soldered. I resoldered the jacks which fixed the intermittent cut-outs that I had in the #2 inputs.

4. Don't use brute force to seat tubes in tube sockets. In my case I had a lot of trouble seating the 12AY7 tube in the V1 socket. I ended up forcing the tube in force rather than trying to figure out why the tube wasn't seating properly and I bent the tube pins as well as bending and displacing the metal in one of the socket pin holes. After removing the tube, I managed to gently bend the tube pins back to their proper position and to open up the metal in the socket pin hole using a unbent paperclip (one of the most important tools ever invented), but after seating the tube again, I realized that some of the pins fit well, and others not so much. I ended up ordering a new tube socket from Mojo and replacing the original one. I was much more careful installing the tubes after this lesson.

5. Clean up internal lead dress. The amp still didn't sound right and after often reading about how lead dress affects an amp's sound, I decided to rewire most of my connections to the tube sockets, jacks, and pots. It's pretty easy to find pictures of the various ways to dress leads online--pick one and try your best to follow it. Shorter leads are best, and avoid crossing over leads if at all possible. Common practice also seems to be to run leads against the chassis wherever possible. This is more an art than a science. I ended up shortening most leads, especially to the pre-amp tubes, jacks, and pots. In the end, the inside of the amp looked much better, and seemed to be less noisy as well.

Messy!

6. Double-check your soldering again. After all these problems the amp still didn't sound right, the biggest problem now seemed to be that the amp's volume was really loud with very little distortion, and seemed to reach maximum volume at around 3-4 in both the normal and bright circuits. I decided to check all my soldering again, and this time I found another loose wire, from pin 4 of V3 which connects the power tubes screens to the caps on the left of the fiberboard. While I am only beginning to understand how this amp works electronically, this seemed to have the effect of producing no screen voltage and no attenuation of the power tubes, thus producing full undistorted power at 4 on the volume pots in either circuit. I resoldered this lead and the amp was significantly quieter and, for the first time since I had assembled the kit, the amp would distort with both volume controls at about midway. I was making progress, but I wasn't quite there.

7. Use Voltage charts. I finally decided to compare voltage readings from my amp with what was available online, in particular Doug Hoffman's Valve Data Page. There are several users who have posted voltages from their 5E3 amps to make comparisons easy. I was hesitant to check the voltages in my amp because I didn't want to stick anything conductive in the amp and kill myself, but once I got over my fear of death and got voltage readings from the amp using a cheap Radio Shack multimeter, it became pretty clear that the voltages for V2 were not correct. Everything else, the rectifier, power tubes, and V1 were more or less within tolerances of what different users posted on the Hoffman site. After thinking about this for a while I decided to double check all the cap and resistor values on the fiberboard, especially in the phase inverter section to see if I had made a mistake with the components. After everything checked out O.K. I thought that there might be a problem with the 12AX7 tube, probably due to my own repeated installation and removal of the tube. I decided to order a new 12AX7 tube just to be sure. While I was waiting for the tube to arrive, I realized that I could use a 12AX7 tube from my Fender Champ 600 reissue amp to see if this would give proper voltage readings. When I removed the suspect V2 tube I realized that I had, in fact, installed the 12AY7 tube in the V2 socket, which doesn't provide nearly the amplification factor that a 12AX7 tube would. Which leads to:

8. Install the V1 (12AY7) and V2 (12AX7) tubes in the correct socket. Just double check this as you are installing the tubes. I ended up with two identical 12AX7 tubes since I thought one was bad, and a common substitution for the V1 12AY7 is a 12AX7 which increases preamp gain significantly.

9. Crank it up! In the end, after much trial and error, the amp sounds great. I'm still learning how to use the interactive controls, but the classic Fender tweed sound is amazing. It's also given me the desire to build more amps, and I am considering a 5F1 Champ kit, a blackface Deluxe Reverb kit, and a tube reverb unit kit to give the tweed amps a little twang. The folks at Mojotone provide an excellent kit and are super responsive to issues with parts. They do not provide detailed instructions, but I sure learned a lot as I put together the amp!

DIY Fuzz Pedal

More kit love. This one is the B.Y.O.C. extra special vintage fuzz kit which is based on a Fuzz Ace and is available here. This is the second B.Y.O.C. kit I have put together and it was an easy build. The board layout is great and the instructions are easy to follow. One caveat with this kit, however, which is that you need to carefully adjust the bias trimpot to get the pedal to work properly. If you do not you will get a thin sound out of the pedal which may lead you to believe that you have done something wrong in the build, which with me is always the mostly likely cause. In this case I started troubleshooting the pedal before I adjusted the trimpot, which the instructions clearly state that you should do first. In my haste, I thought that I had inserted the germanium transistors incorrectly and in attempting to reseat them (I won't tell you how many times I did this), I broke off one of the leads. Fortunately the kit comes supplied with two SS-9013 transistors for testing and troubleshooting and I am currently running these in the pedal until I buy replacement germanium transistors. You can get these through B.Y.O.C.'s parts store here. The pedal sounds awesome as is and I expect it to sound more awesomer when I get the germanium transistors. I'll update the post when I get around to buying them.

UPDATE (1/2014): I have finally gotten around to sorting out the problems with this pedal. I purchased a second set of AC127 germanium transistors (which were used in the original version [rev 2.0] of the pedal) and later a set of  AC128 germanium transistors (which are used in the new version [rev 3.0 of the pedal), neither of which worked. Meanwhile, B.Y.O.C. came out with a new version of the pedal (rev 3.0), which among other significant differences, has replaced the 0.1uf film capacitor (the yellow capacitor in the photos above) with a 0.01uf film capacitor. I thought swapping out the cap for one with the new value would work, and it did the trick. I ordered a .01uf film cap from Mouser, soldered it in, and the circuit worked as originally intended. The internal bias pot now has plenty of range. I still have not gotten the AC128 transistors to work, but the original AC127 transistors work well. I would recommend making this change if you have rev. 2.0 of the pedal and have had problems getting the germanium transistors to work.

DIY Overdrive/Boost Pedal

More kit love. This one is the overdrive 2 kit from Build Your Own Clone available here. This is the first kit that I have put together from Build Your Own Clone and it was a great experience. The kit came complete with all parts including chassis and extra parts for the most common mods. The board was laid out clearly including labels for cap and resistor values. The web site has easy to follow directions, including the most common mods. There is an optional MOSFET conversion kit which can be ordered for an additional few dollars. Here are a couple photos of the kit going together. The magnifying loop in the first photo is only there because of my poor eyesight. I have trouble seeing color stripes on resistors and the loop helps.


The folks at Build Your Own Clone clearly put a lot of effort into the design of this pedal. It it based on the Ibanez Tube Screamer with a host of mods as well as an additional boost channel which can be used separately from or in conjunction with the overdrive channel. There are also two toggle switches, one which lets you select additional silicon or led clipping and a second 3-way EQ switch which adds highs and lows or lows to the tone stack. The kit comes with two op amps which you can choose from, a JRC4558D op amp which was in the original Tube Screamer and the Burr Brown OPA2134 op amp. The chip is socketed so you can swap them out as easily as changing the battery. In addition there are three trimpots on the board for minimum and maximum distortion as well as level in the overdrive channel. You can build the kit according to the original Tube Screamer specs or tweak it however you want. What is truly amazing is that all of this is crammed into a standard 125b chassis.


Building the kit took about three hours, included sorting out the resistors and caps. I am still getting a handle on all of options for the pedal. My wife ran hiding when I first plugged in the pedal and had the pots all opened up. My son nodded knowingly when I got the level turned down with the overdrive all the way up. I recently got a Fender Champion 600 amp and wanted to have a classic overdrive pedal to drive the front end of the amp. This is an awesome kit and is highly recommended.

DIY Envelope Filter Pedal

More kit love. This one is a General Guitar Gadgets DOD 440 Envelope Filter replica kit. I can't say enough about these kits. Super easy to put together. This pedal is subtle, and I still haven't worked out the best sounds for it. It is an autowah and you have to fine tune the knobs to come up with something useful. There isn't much on the web about the DOD original, although I found a pdf of an original manual here. The manual really doesn't give much information. The left knob is level, the right range. If the range knob is turned up too high there is a fair bit of distortion. A lower setting, up to maybe 2:00 or so seems to work better. I actually prefer using the pedal with a bass rather than with a guitar. Think Bootsy Collins. I had the notion of replacing one of the resistors with a pot to get more variation, something along the lines of the Q control on an Electro-Harmonix Q-Tron, following some vague instructions I found on the web. I desoldered the resistor, resoldered it to the bottom of the board and soldered the pot in parallel on the topside. This didn't seem to do much so I removed it. You can see the space where the 430K resistor would be in the close up (it still soldered to the bottom of the board). If anyone has any ideas about modding this circuit send me an email and I'll try it. I also had half a notion to try to install the guts of one of these kits directly in my Jaguar. Jaguars have plenty of extra space in the various control cavities to do this, including space for a 9v battery in the trem cavity. This would involve rewiring the entire guitar and using the rhythm circuit controls on the upper bout to control the effect. In theory you could do this with any effect that had only two controls and a small enough board. I went so far as to order some pots and switches to try this, but once I started tweaking the kit itself, I never got around to it. I really didn't want to get to the point where I started chiseling out wood to get everything to fit. I may try this in the future.

DIY Tremolo Pedal

I finally got around to adding tremolo to my guitar setup this past weekend thanks to the EA tremolo kit offered by General Guitar Gadgets. The kit included the resistors, caps, transistors, LED, PCB, jacks, pots, knobs, footswitch, wire, and case--everything to put together a complete stomp pedal. The instructions are downloaded from their site. The build took about 4 hours from start to finish with a couple breaks and was a lot easier than it first appeared when I opened the box. The most time-consuming part was figuring out the resistor values. I have red-green colorblindness and it took a magnifying glass. The pedal sounds great. It has a volume control which allows you to match the volume when the pedal is bypassed. The speed control has a wide range, as does the depth control. The led flashes at the speed rate when on. I have an 80s-era Fender solid-state amp that has a great clean channel and spring reverb but no tremolo. The amp has an effects loop located before the power amp so I patched the tremolo pedal in. At first I thought that something was wrong in the build, as the pedal only worked when in bypass, but I realized that I had reversed the cables into and out of the pedal. So I quickly fixed that problem. Make sure you use a new battery--I used an old one and didn't realize how great the pedal is until I switched it out. Highly recommended. I am not a great solderer, but this actually wasn't too hard. I used small diameter solder for the first time which works great. It also helped to clip off the extra length of the components as I went along to make more room to get at the next point. Once you start cramming everything into the case the soldering gets a little harder, so measure all the wires carefully to make as much room as possible. I might swap out the red LED for a blue or green one just for fun. I don't have any interest in finishing it--nothing wrong with raw aluminum and masking tape.