Question About Building My Own Amp

Discussion in 'Amps' started by jhull54, Dec 3, 2019.

  1. jhull54

    jhull54 Well-Known Member

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    Question for the DIY amp guys.

    I have a big 1x12 Line 6 combo cabinet (chassis is long gone) and am using it with a 5 watt head. I would like to build a 5e3 combo out of it. Since I don't need cab/speaker, or tubes, I took a look at Mojotone and their kits for this particular amp.

    Question is--for a relative amp building n00b like myself, is soldering the main headache in building these, or is there more I need to look out for regarding difficulty, and, does anyone have an opinion on the Mojotone kits? I'm mainly wanting to make sure the transformers are pretty robust, as I've heard these can be the weak links in these kits.

    Thanks to any and all who can give their thoughts!
     
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  2. mozz

    mozz Well-Known Member Supporting Member

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    Take measurements first to be sure that chassis will fit. Transformers on one side and tubes sticking out the bottom.
     
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  3. Mickey

    Mickey Gandalf the Intonationer

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    If you can get a copy of the instructions FIRST you should see whether you want to attack this project or not.
    I seriously doubt they are up to Heathkit standards but I do not honestly know how good their instructions are.
    I've built kits where the instructions were like:
    locate resistors, install
    locate capacitors, install
    etc.

    I would call routing of wires and locating components a much bigger hassle than soldering as it can make the difference between
    a quiet amp or one that hums like mad, as an example.
     
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  4. Chocol8

    Chocol8 Well-Known Member

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    A 5e3 is a fairly easy circuit and both circuit diagrams and layouts are widely available. That said, many people have managed to not get it right on the first try.

    Careful following of the diagrams and good solder technique is key.
     
  5. andrewsrea

    andrewsrea Well-Known Member

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    Good advice above. Additionally, these are high and lethal voltages. If you really are a noob, do the Mojotone or similar building workshop.
     
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  6. nomadh

    nomadh Well-Known Member

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    Good question. Is there any amp kit of any size that has outstanding explanation/ troubleshooting / guide book instructions? I'd love something that would explain what we are doing, then how to do it then how to test the section you just built. Like every few steps it says "now check the ohms between here and here and from there to there it should be 200 ohms because you can see r6 is in parallel with r4 and r9 in series". "If not check steps 9a to 12b again" Then "this needs to be 200 because it will be x percent of this voltage for 12ax7 pin5" or whatever
    I'm thinking the beginners here read this and think "wow nomad must be a pro amp builder" The amp builders here are reading this and saying "i think nomad had a monkey randomly typed this" :)
     
  7. jimytheassassin

    jimytheassassin Well-Known Member

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    There’s plenty of documentation on the mojotone 5e3 to get you started and answer many of your questions. FWIW there’s endless amounts of info on these in general as well, not to mention mods galore (which is something worth looking into after you finish your build and get adventurous again). It’s worth watching and reading all the relevant materials until it really sinks in. On the one hand you can simply go through the instructions and end up with a decent amp, but learn very little about what’s goin on technically. The nature of these “paint by numbers” kits makes that possible. But if you really get bit by the bug, the 5e3 is a great amp to start working on to realize what really makes these things tick.






    Sent from my iPhone using Tapatalk
     
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  8. Mickey

    Mickey Gandalf the Intonationer

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    @nomadh what you are wishing for is what I referred to as "Heathkit standards" they had instructions with a drawing at the top of the page and step-by-step how to at the bottom.
    And their step-by-step directions were things like:
    1.- cut a 6" piece of the RED hookup wire, strip 1/4" from one end and 1/2" from the other.
    2.- connect the 1/4" stripped end to V1 Pin 5 and the 1/2" stripped end to V3 Pins 6 & 7. Route the wire as shown in drawing D1.
    3.- Solder the V3 end of the of the wire.
    4.- Cut a 3" piece of the RED hookup wire. Strip 1/4" from each end.
    .....

    If you followed their directions to the letter you could build any of their products successfully.
    Unfortunately, they got bought out by Zenith (remember them?) and are no longer with us.
     
  9. Manodano

    Manodano Well-Known Member Supporting Member

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    If you are going to build amps, you need to be able to solder. read a schematic diagram. identify color coded resistors and cryptically labeled capacitors, mount and properly solder pots and transformers, and probably do some metal work before its over with. And unless you are a talented scrounge hound, these days you can buy a good amp a hell of a lot cheaper than you can build one.

    If I were cutting my teeth, I'd start with a 5F1 Tweed Champ kit. The second input channel on the Deluxe and the second output tube really make the 5E3 Deluxe quite a bit more work and aggravation to assemble than a 5F1. There are more ways to screw up a 5E3, in other words.

    Another challenge is that the 5E3 chassis is pretty compact, and needs to be assembled in a certain order to avoid problems getting it all packed in there.

    Your goal is to complete an amp that works, not start an overwhelming project that gets abandoned early on.

    ALSO the tip about making sure you can mount a completed 5E3 chassis in that cabinet is a very good one. The 5E3 is oriented to be top mounted, and there is a very high probability that the tubes and transformers (bottom and side mounted) may not clear the speaker frame and/or magnet. I've tried to stick 'em in all sorts of cabinets, and most modern cabinets are simply a no-go for a 5E3.
     
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  10. jhull54

    jhull54 Well-Known Member

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    Yeah, after looking at the schematic, it does appear that the chassis will not work in that cabinet. The chassis in this cab was forward facing, so looks like this is a no-go for sure for that amp.
     
  11. AnotherJim

    AnotherJim Well-Known Member

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    Anyone here ever build the boy electronics kit? I was checking their stuff it because of this post and their directions seem pretty goo.
     
  12. Mickey

    Mickey Gandalf the Intonationer

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    Linky????????
     
  13. jtcnj

    jtcnj Well-Known Member

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    All the above advice +1!

    I have not used kits; I hear mostly good things about the Mojotone ones.
    I too, would / I did start with the Tweed Champ 5F1 as well, then try a 5E3 if you have contracted the amp building disease.

    Most important is to build the amp in a manner that you do not:
    A. Get yourself killed.
    B. Burn the house down.

    You will need a decent multi-meter, a decent soldering station ($30 on Amazon can get you there), a capacitor discharge tool (easily made), clip leads.
    Strongly recommend the light bulb type current limiter for startup - also easily made.






    There are lots of good reads for general good build practices - they are important as was said.
    Reduced noise / hum, motorboating or other unwanted oscillations.
    The sub forum on TDPRI called Shock Brothers DIY amps is a really good one.
    Search it; you will get lots of hits.
    Merlin Blencowe's pages called The Valve Wizard has a lot of good info too.

    Wiring / hum for heater / filament circuits:
    http://www.valvewizard.co.uk/heater.html

    very good beginner explanation on tube operation:
    http://www.valvewizard.co.uk/Common_Gain_Stage.pdf

    and lots of great stuff from a Rob Robinette, also a member at that site.
    https://robrobinette.com/How_The_5E3_Deluxe_Works.htm
     
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  14. AnotherJim

    AnotherJim Well-Known Member

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  15. andrewsrea

    andrewsrea Well-Known Member

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    Everyone should have this experience at least once. Okay maybe not the whole house, but an amp fire is a learning experience.

    Alligator clips and a 150 ohm 5w resistor. One end to ground and the other to the resistor lead. With the amp off and unplugged, touch the exposed resistor lead to what ever you are draining. I recommend a 5w as you can hold it bare hand with out having to be over concerned with your skin touching the lead.

    Can't hurt when bringing new high volt- high microfarad filter caps to life. But don't get too wrapped up with it. Most production amps get plugged in straight and turned on in final test and quality control. Rare that they get burned-in. Test then - box - then ship.
     
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  16. jtcnj

    jtcnj Well-Known Member

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    The light bulb will take the current spike if your start up has a short - likely saving your transformers in the process, or anything else, from starting that first amp fire.
    Fun, maybe, but expensive.
     
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  17. nomadh

    nomadh Well-Known Member

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    At least once :)
     
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  18. Chocol8

    Chocol8 Well-Known Member

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    Safety measures are a sign of doubt and weakness. Attack with confidence!
     
  19. jimytheassassin

    jimytheassassin Well-Known Member

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    Ya just go for it. What could go wrong
    It’s hard to believe he’s still alive. A lightbulb limiter might have helped but it won’t save you from burning your nose with a soldering iron



    Sent from my iPhone using Tapatalk
     
    Last edited: Dec 4, 2019
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  20. Manodano

    Manodano Well-Known Member Supporting Member

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    A good stiff 300 volt DC shock sends me up to the couch where I sit quietly and thank the Maker for sparing my ass. Done for the night. I've experienced bad shocks twice, and the second time I reacted so violently that I knocked the chassis I was working on off the workbench and threw my soldering iron across the room.

    You don't want any bad bites - they aren't kidding, that shit can really kill you. Comes right up your arm heading straight for your heart. At the speed of light, no less.
     

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