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5E3 first build boothill

Discussion in 'Shock Brother's DIY Amps' started by sethberrett4, Feb 18, 2019.

  1. sethberrett4

    sethberrett4 TDPRI Member

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    Well, first off thanks so much to all the tdpri community for the incredible support and advice they give This is my first post and although I'm sure my questions have been answered in other posts which I can't find, any help/suggestions would be much appreciated. I finally go's my chassis all wired up (first time ever soldering) except for the ground bus on the left side. I used the boothill wiring diagram, as well as robrobs 5E3 deluxe amplifier one from his website.

    My biggest confusion now is exactly how to ground the power transformer, and where the ground bus for the left side of the circuit board hooks up too. I think I understand how the output transformer.

    There is also a mysterious 3 prong price that I haven't seen pictures of or diagrams of anywhere, I feel like it has something to do with the grounding, but any pictures or information would be much appreciated. I have no clue where it goes or what it hooks onto, so I will attach a picture of it.

    Again Thanks so much, I'm just a 20 year old building an amp for the first time with little knowledge about electronics, but a love for tube amplifiers.
     

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  2. sethberrett4

    sethberrett4 TDPRI Member

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    Here are the transformers
     

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  3. Mr Ridesglide

    Mr Ridesglide Friend of Leo's Silver Supporter

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    The mysterious piece could be used for a few different things. It's called a terminal strip most of the time. It's likely it was sent for you to use as a ground. Note that if you were to drill a hole, or put this over an existing bolt, as it stands only the middle soldering lug is grounded. You would need to put a piece of bus wire or other wire to the other two to also have them grounded. Or, you may not use it all, depending on how you go about laying out your build.

    The power transformer; 18021 classic tone - that will need the red/yellow and the green/yellow center taps grounded to get your intended voltages from the red pair (rectifier) and the green pair (filaments). Many folks put these on a transformer bolt. I think the general consensus on this is to drill a separate hole and mount these not on the transformer bolt. You could use your mysterious piece for this, and you would still have an extra spot for your power supply ground to go to.

    Don't forget that for sure you don't want your A/C ground going to a transformer bolt, but put a ring terminal connector on that, and put it on it's own bolt in the chassis.

    Make sure to connect them with star washers, or locking washers/nuts so that they never come loose.
     
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  4. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    As this is your first rodeo, I'd recommend reading through these instructions for building a 5e3. If you scroll down to the layout, you can see that you need to connect the 1st and 2nd filter caps, which will eventually ground somewhere near the transformer. This keeps the filter hum to a minimum. The 3rd one is grounded by the bus bar, which the Stewmac version doesn't have.

    https://www.stewmac.com/How-To/Onli...Wiring/59_Tweed_15W_Amp_Kit_Instructions.html
     
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  5. Mr Ridesglide

    Mr Ridesglide Friend of Leo's Silver Supporter

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    IMG_0566.JPG
    You may be able to make out here how there is one of the terminal connectors on the upper right transformer bolt. There are also single terminal connectors on the power tubes where a 1 ohm resister is grounded from the power tube cathode to easier measure the current.
     
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  6. Urshurak776

    Urshurak776 Tele-Afflicted

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    Taken from the link Uncle Daddy posted above:

    2-18-2019 3-39-26 PM.jpg
     
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  7. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    You might want to look at this- it's the Fender schematic and layout for the current Tweed deluxe.
     

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  8. flyswatter

    flyswatter Friend of Leo's

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    Stewmac_5E3_incorrect_LI.jpg
    The Stewmac layout has a few serious problems, not least of which is showing how not to connect the safety ground to the chassis.

    SAFETY GROUND:
    On the Stewmac layout, it shows the green (ground) wire for the AC cord trimmed short and soldered to a terminal strip bolted to the southwest transformer bolt. This is dangerous, because if the strain relief for the power cord were to ever to fail (such as if the cord were violently yanked or the amp fell off a stage while plugged in), the safety ground would be the first of the AC leads to break free, leaving an ungrounded chassis and potentially dangerous situation.

    I've used those bakelite (or whatever) terminal strips on point-to-point builds and restorations and can't count the number of times they have broken with the slightest bend or tug.

    Also, transformer bolts can sometimes come loose from the friction of a heavy component vibrating the bolt on the smooth surface of the chassis.

    The right way to attach a safety ground, is to keep the safety ground wire untrimmed (just curl it into the otherwise unoccupied chassis corner... so it would be the last of the 3 conductors to break free), soldered crimped and soldered to a ring terminal and mounted on its own dedicated bolt with lock washers on both sides. In some countries (including mine), it is actually the law to have the dedicated bolt. --- as Mr Ridesglide has already stipulated above.

    Soldering the safety ground to the chassis (original 50s 5E3s do this for the PT centre taps as well) is also accepted by many, but for this you need a high powered soldering iron with a wide tip -- the regular wand or soldering station running at 30ish watts or 700 degrees won't do it.

    Safety grounds sometimes will be bolted to a transformer bolt -- again on a ring terminal with lock washers, not a terminal strip -- if it is a vintage amp of some value where the owner has denied permission to drill a hole for a safety ground bolt. However, there is no reason to accept this second-best option on a new build.

    (BTW: This isn't just my opinion... it is the consensus among every experienced tech I know. The Stewmac layout came up for criticism recently on another (private) forum, many of whose members are commercial builders.)

    -----------------------------

    Stewmac layout also gives no indication of how to ground the preamp. The best way is to run a bus (which I see the OP already has with his kit) from the 3rd (preamp) 16uF filter capacitor to the ground lug on one of the input jacks.

    -----------------------------

    Stewmac also wires its inputs unconventionally for modern builds (though I have seen it on some vintage amps). They have the white (neutral AC) wire going through the fuse to the transformer. Normally, the white neutral connects directly to one of the PT primaries. The black (hot) AC lead goes first to the fuse, then jumpers over to the power switch, then the other lug of the power switch carries the other PT primary. Again, I don't know any other builder or tech who does it any other way, unless it's a vintage amp being restored to common practices of a half-century ago.[/QUOTE]
     
    Last edited: Feb 18, 2019
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  9. SacDAve

    SacDAve Poster Extraordinaire

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  10. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Welcome. I don’t know from StewMac's 5e3, and the instructions may be good, but the layout you want is Rob's.

    [​IMG]
     
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  11. SacDAve

    SacDAve Poster Extraordinaire

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    You should also build a light bulb current limiter before you fire the Amp up.

    Also Robs page "Tube Amplifier startup Procedure"
     
  12. robrob

    robrob Poster Extraordinaire Ad Free Member

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    In my 5E3 layout above the power amp ground is a bolt on the chassis. You can use a transformer bolt or a dedicated ground bolt. The preamp bus wire is soldered to one of the input jack's ground terminal. That jack should use a star washer for a good ground-chassis contact.
     
  13. sethberrett4

    sethberrett4 TDPRI Member

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    Thanks so much for all the advice! I finally got it all wired up and everything good to go (or it appears to be anyway). I'm going through robrobs pre amp start up check list checking everything. Here's a few pictures if anyone can see anything out of place or have any questions.

    For the grounding I grounded the power amp bus, red/yellow, and green/Yellow wires from the power transformer to that three prong piece, and grounded all prongs together and bolted it to a power transformer bolt. I grounded the power cord to a separate power transformer screw.

    The preamp bus is grounded to one of the imput Jack's.

    Questions:
    I hooked together the white power cord wire with a black wire from a the power transformer together and heat shirnked it. Just making sure that is the correct thing to do? I believe that's what it shows on robrobs diagram.

    Also with wiring the switches, fuse, and light, does it matter which leads go to which prongs? For example the fuse has one prong in front and one in back. I hooked the one in front to one prong on the main power switch, and the rear fuse prong to the black power cord. Would it have mattered it if wired them to the opposite prongs?

    Thanks again everyone! If you need any more pictures of thing specifically let me know. I plan on firing it up later today.
     

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  14. robrob

    robrob Poster Extraordinaire Ad Free Member

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    The fuse wiring matters, the pilot light, power and standby switch don't. You have it correct, we want the hot from the power cord to the center of the fuse. That will keep from shocking someone when they try to replace the fuse with the amp plugged in.
     
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