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Thread: mojo kit questions

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    mojo kit questions

    Hi,

    I am building my first amp. Its a 5E3 kit from Mojo.
    My only previous experience is building a few pedals from BYOC.
    I have a whole slew of newbish questions. Thanks in advance for your patience and help.

    The mojo kit doesnt come with instructions. I am having a hard time figuring out where a few things should go.
    1. There are two "3 lug terminal strips". They are not shown on the wiring diagram. Could these be for ground connections? maybe they screw under the power transformer nuts? are the three lugs connected inside the terminal? they dont appear to be from the outside. do i need to run a lead thru those three lugs to connect em?
    2. There are a bunch of little nuts and bolts in unlabeled bags. well okay, they are labeled as to size but not as to function and i cannot figure out their function. I know I need 10 nuts and bolts for the tube sockets but there are no sets of ten nuts and bolts. has anyone built a mojo kit and have any idea of what hardware goes where as far as the little nuts and bolts are concerned? The two chassis screws and nuts were the only ones labeled as to function. I had to go buy the screws needed to hold the eyelet board in place...is there any other hardware missing from this kit that i need to go buy?
    3. i have six jacks, one is mono, five are "shorting". Is the mono jack for the extension speaker?

    I have more questins but maybe I wil stop here for now.
    I am trying to build a dry run and fit the hardware before i solder the board.
    I am still waiting on the cabinet from mojo.

    Thanks again for the help, what a great forum!
    -Ben

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    Supporting Member loudthud's Avatar
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    Some less expensive kits require the builder to improvise. If you run into something you can't figure out, post it here and get help. Some kits require you to drill holes in the chassis to mount things. It may not be what you expected when you purchased the kit, but do the best you can. These kits require some tools and experience so they are not for everybody.

    1) I can only guess but prehaps they are to provide a place to solder unused wires from the transformers. Check the wires coming out of the transformers against the layout. Any extra or missing wires?

    2) Wait until the cabinet shows up. They may be to mount the baffle, speaker or chassis.

    3) I think you are correct that it is the extention speaker jack.

    Did you know there are people who sell kits for automobiles? Imagine trying to fit a sports car body on an old Volkswagen chassis.

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    Quote Originally Posted by loudthud View Post
    Some less expensive kits require the builder to improvise. If you run into something you can't figure out, post it here and get help. Some kits require you to drill holes in the chassis to mount things. It may not be what you expected when you purchased the kit, but do the best you can. These kits require some tools and experience so they are not for everybody.

    1) I can only guess but prehaps they are to provide a place to solder unused wires from the transformers. Check the wires coming out of the transformers against the layout. Any extra or missing wires?

    2) Wait until the cabinet shows up. They may be to mount the baffle, speaker or chassis.

    3) I think you are correct that it is the extention speaker jack.

    Did you know there are people who sell kits for automobiles? Imagine trying to fit a sports car body on an old Volkswagen chassis.
    Thanks Loudthud!
    actually the mojo was the most expensive kit i looked at but i am okay with trying to figure out stuff. Ideally I'd like to learn as I build my first amp, not just assemble, and not having instructions kind of forces some of that so its all good. Thanks again for the very helpful responses.

    Heres a picture of the 3 lug terminals

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    I built the mojo 5E3. I did not use the 3-lug terminal. I suppose you could use it for one of a variety of grounding schemes.

    The mojo kit doesn't have step by step instructions, but the components are generally good quality (carling switches, etc).

    Loudthud answered the questions rightly. Additionally, you may not use all of the nuts and bolts. But there are a variety of places they'll be needed: tube socket mounting, chassis mount to cabinet, speaker mounting nuts, and you'll need two nuts & screws to hold the eyelet board to the chassis (you drill the holes where you want them - I used a pic of a vintage chassis as a guide).

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    cool. thanks!

    I think I will place these three lug terminals under the power transformer bolts and use them to make ground connections. The layout shows a bunch of connections to ground at the top of the board. I think i need to better understand how all these ground wires should be connected. I've been trying to look at pictures to get some idea.

    So i am guessing these three lug terminals were not in the original fender deluxes? they are probably just a conveniance for the kit builder?

    Thanks again for the help. Gonna get soldering later this afternoon I hope.
    Got a lawn to mow first

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    On these kits everything is pretty straight forward: you pretty much just follow the layout picture & schematic for connections, but there are two things these don't tell you:

    1) How to handle the physical placement (lead dress) of the wires, whether they are twisted, where they are positioned, etc. These are important considerations to minimize noise in the system. I recommend finding as many different pics of vintage and new 5E3 amps as you can to get an idea of what works well. Ebay is a great resource to see some pics.

    2) How to handle grounding. There are different methods and opinions. Search this forum as there are some good threads/discussions on the topic. Here's one thread, which has some pics of my layout.

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    Last edited by mbratch; 06-07-2009 at 11:30 PM.

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    1. One of those could be there to help you manage your heater (2 green) wires. The heaters are a major PITA to hook up, especially if the PT doesn't have a center tap.
    2. Those are probably the screws and bolts that hold the tube sockets.. and possibly the transformers on the chassis.
    3. 4 switched (3 lug) jacks for the inputs.. 1 switched jack for the main speaker jack & one 2 lug jack for the second speaker jack.

    I would encourage you to look up as many 5E3 gut/build pictures as possible..

    Best build tip: slide a tube into the tube socket your soldering on. It's fairly easy for solder to leak down into the tube pin hole and it's a PITA to clean it out once it's in there.

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    Quote Originally Posted by TommyTomcat View Post
    1. One of those could be there to help you manage your heater (2 green) wires. The heaters are a major PITA to hook up, especially if the PT doesn't have a center tap.
    2. Those are probably the screws and bolts that hold the tube sockets.. and possibly the transformers on the chassis.
    3. 4 switched (3 lug) jacks for the inputs.. 1 switched jack for the main speaker jack & one 2 lug jack for the second speaker jack.

    I would encourage you to look up as many 5E3 gut/build pictures as possible..

    Best build tip: slide a tube into the tube socket your soldering on. It's fairly easy for solder to leak down into the tube pin hole and it's a PITA to clean it out once it's in there.

    pardon my ignorance but regarding the tip...if you stick a tube in the tube socket before soldering and solder drips down into the socket hole...dont you then have a stuck tube?

    Thanks a ton for the help guys, Im gonna need lots more I am afraid.
    Ive looked at all the pictures of 5E3's i could find. Its really hard to see grounding and lead dress even in alot of em. most of em.

    I started soldering the board last night and ran out of wire before I could finish. I guess i was making the wires coming from the board a bit too long.
    Now I have to wait a week for more wire. Thats kind of frustrating, especially after waiting a week for the cabinet. Wire is .35 a foot., an extra foot or two woulda been nice mojo. my fault for making the wires too long I guess but how is a feeble newb like myself to know?

    anyway, I have treid and it looks like I am not going to be able to understand lead dress or grounding. In the end tho i just need to know how to wire the thing up, not fully understand how and why. i was hoping to fully understand but its not sinking in...

    My (very limited) understanding is i need to separate the ground for input from the grounds for power supply. So my plan is to just run the two ground wires from the power section of the board, the ac chord ground, the OT ground, the PT ground, and the pilot light ground under a single bolt of the PT.

    This makes the chasis grounded i guess...so now the pots and input jacks are automatically grounded as well by contact?
    So i can run the two ground wires coming from the input section of the board to the backs of those pots?

    I see some using a ground bus wire. I dont understand this. is it just for providing a long running surface for making other ground connections? why not just go direct to chassis or pot?

    another thing Im having trouble with is this "deathcap". Ive been told not to use it, but its in the kit...and I think if I dont use it, my layout wiring changes somehow? how am I to know how ot wire it if i remove that part?....If I dont use this deathcap, what does the ground switch do...actually what does it do in the first place if theres a three prong chord,(which there is)?

    thanks again...sorry for the newbishness. Im having fun building and trying to learn. wish my mind was a bit more agile..I was never good at the science and math end of things...hence the music
    Cheers!

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    Mojo doesn't supply enough wire IMHO, and you may want to use different colors like the Fender girls did back in the day to ensure you get the grids wired right, etc. Since this is a vintage style amp I like to use the old Fender style brass grounding plates. However, you can use a ground buss soldered across the pots ala Marshall and will probably have a better long-term setup.

    I've found that having some very good pictures of the insides of the vintage amp you're building serves as a great compliment to the schematic and layout diagrams. Bear in mind that the original amps usually did not use twisted pairs for the filament wires and usually had a center tap wire for the filaments as well.

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    I did a 5E3 mojo kit. It had plenty of wire. In fact, I had to redo something once I built it and had to use more wire than normal, and it was all there. Mojo will provide a little extra if you ask, I'm sure, so I wouldn't use that as a gauge for whether to use their kit. They don't do the brass plate. I did the buss ground back of the pots, which works fine.

    I'd follow SoK66's advice and look at gut shots of vintage 5E3's or other kits for guidance. The factory amps have excellent lead dress and neat wiring. There are some clone examples that are, frankly, a bit of a rat's nest so avoid that. As noted, the filament wires in the new 5E3's and clones are twisted pair rather than one wire. I chose to run my twisted pair against the chassis as in the vintage tweed wiring. Some choose to have it be "up in the air" as in blackface wiring. Either seems to work great, just a matter of preference.

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    Last edited by mbratch; 12-19-2009 at 05:25 PM. Reason: Added more info.

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    Hi Everyone. This thread is old. The deluxe has long since been completed and sounds fantastic. Mojo did not provide enough wire, not even close. They did not provide all the hardware necessary to complete the kit (self tapping board mounting screws) but managed to provide hardware that was completely unnecessary (chassis strap screws? but there are no chassis straps on a tweed deluxe?). The rectifier tube they supply is not acceptable. but these are minor isssues. I would sill recommend the mojo 5E3 kit.

    Since the mojo 5E3 came out well, months later I decided to try their 18 watt kit when it was on sale in october. Big mistake! The mojo 18 watt kit is just poorly conceived and implemented. The schematic has errrors and omissions, they changed the layout from the original and it is fundamentally flawed because they put the trem footswitch jack in the worst possible place just so they could use the same chassis they use for their jtm. The layout does not show any grounding scheeme , it doesnt even show the heater wires. It calls for sheilded wire yet none is provided and mojo doesnt even sell non external braided sheilded wire. That is failure right there. I order a kit and immediately have to order form somewhere else to get the parts necessary to complete it? lame. But the big problem is the layout. I wil be trying to fix this thing in the next couple weeks...argh!

    so to sum up:
    mojo 5E3: thumbs up with some minor issues. order more wire with your kit and a decent rectifier tube.


    mojo 18 watt kit: stop! do not buy! try brown note, gds ...anyone but mojo.

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    Last edited by Ben; 12-19-2009 at 05:25 PM. Reason: spelling

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    Glad you got your build going Ben!

    Yeah, the Sovtek 5Y3 generates a higher plate voltage than a NOS 5Y3. So it makes the amp a bit different in sound. The JJ 6V6S can handle it, but it is not quite a "stock" sound. I still keep the Sovtek in case I want more gain, etc. I use it in conjunction with my JJ's. But I also bought a NOS 5Y3 to swap out now and then.

    I'm a little surprised about the severe shortage of wire; but they did provide (in my kit) what I would say is "just enough" as long as you do everything very efficiently and waste very little. I actually measured everything out as I went so as to have very little waste. I still think your suggestion to ask for extra wire is good, though.

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    If you're thinking about a Mojo kit, you're better off with a kit from Marsh. There are decent instructions with the Marsh kit, and it includes everything you'll need to build the amp. It also is based on the Mojo kit and a few hundred $ less.

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    Quote Originally Posted by Diablo View Post
    If you're thinking about a Mojo kit, you're better off with a kit from Marsh. There are decent instructions with the Marsh kit, and it includes everything you'll need to build the amp. It also is based on the Mojo kit and a few hundred $ less.
    I've read that the Marsh kit instructions are excellent. But the price is not "a few hundred $ less". Marsh is currently posted at $635, and Mojo is posted at $701. Both kits use good quality components.

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    I had excellent results and straightforward builds with my Mission Amps kits.

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    Quote Originally Posted by mbratch View Post
    I've read that the Marsh kit instructions are excellent. But the price is not "a few hundred $ less". Marsh is currently posted at $635, and Mojo is posted at $701. Both kits use good quality components.
    You're correct about the 5E3 kit. Not as much of a bargain as I thought.

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    Quote Originally Posted by Ben View Post
    1. There are two "3 lug terminal strips". They are not shown on the wiring diagram. Could these be for ground connections? maybe they screw under the power transformer nuts? are the three lugs connected inside the terminal? they dont appear to be from the outside. do i need to run a lead thru those three lugs to connect em?
    I guess you have a ground bus, that would be a bare wire grounding every pot, the board, etc. You can use the 3 lug strip to connect ground from power cord, ground bus, etc.
    Quote Originally Posted by Ben View Post
    2. There are a bunch of little nuts and bolts in unlabeled bags. well okay, they are labeled as to size but not as to function and i cannot figure out their function. I know I need 10 nuts and bolts for the tube sockets but there are no sets of ten nuts and bolts. has anyone built a mojo kit and have any idea of what hardware goes where as far as the little nuts and bolts are concerned? The two chassis screws and nuts were the only ones labeled as to function. I had to go buy the screws needed to hold the eyelet board in place...is there any other hardware missing from this kit that i need to go buy?
    Why don't you start with a mail to mojotones. I guess they would be eager to help you out. Either shipping the missing parts or point you in the right direction.
    Quote Originally Posted by Ben View Post
    3. i have six jacks, one is mono, five are "shorting". Is the mono jack for the extension speaker?
    Take a close look at the circuit layout, you should be able to make out what jack to use in the different places. Google(images) 5E3 layout
    Quote Originally Posted by Ben View Post
    I have more questins but maybe I wil stop here for now.
    I am trying to build a dry run and fit the hardware before i solder the board.
    I am still waiting on the cabinet from mojo.
    I believe there's as many ways of building an amp as there are builders. Your way might be an easy way, but solder might help you as it holds everything in place. If you go wrong you can resolder...

    Edit, I didn't see any reply to this thread last time I was logged in. I do now, and my reply is somewhat redundant.

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    Last edited by überfuzz; 02-15-2010 at 09:18 AM. Reason: reply out of date

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    Quote Originally Posted by Ben View Post
    Hi Everyone. This thread is old. The deluxe has long since been completed and sounds fantastic. Mojo did not provide enough wire, not even close. They did not provide all the hardware necessary to complete the kit (self tapping board mounting screws) but managed to provide hardware that was completely unnecessary (chassis strap screws? but there are no chassis straps on a tweed deluxe?). The rectifier tube they supply is not acceptable. but these are minor isssues. I would sill recommend the mojo 5E3 kit.

    Since the mojo 5E3 came out well, months later I decided to try their 18 watt kit when it was on sale in october. Big mistake! The mojo 18 watt kit is just poorly conceived and implemented. The schematic has errrors and omissions, they changed the layout from the original and it is fundamentally flawed because they put the trem footswitch jack in the worst possible place just so they could use the same chassis they use for their jtm. The layout does not show any grounding scheeme , it doesnt even show the heater wires. It calls for sheilded wire yet none is provided and mojo doesnt even sell non external braided sheilded wire. That is failure right there. I order a kit and immediately have to order form somewhere else to get the parts necessary to complete it? lame. But the big problem is the layout. I wil be trying to fix this thing in the next couple weeks...argh!

    so to sum up:
    mojo 5E3: thumbs up with some minor issues. order more wire with your kit and a decent rectifier tube.


    mojo 18 watt kit: stop! do not buy! try brown note, gds ...anyone but mojo.
    Hey Ben, I ordered a Mojotone 18 watt kit and you are absolutely right on everything you just said. I am having the exact issues you had. I tried to start up the amp today and no luck. Is the wiring really messed up?

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