first build 5e3 - question on tubes and parts

Discussion in 'Shock Brother's DIY Amps' started by agent_zed, Aug 22, 2019.

  1. agent_zed

    agent_zed TDPRI Member

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    Hi,

    new to forum and building amps so hopefully not too many dumb questions.

    I've decided to put my own parts together and i just want to check a few details to ensure i get it right.

    1. I've read a few other threads so my understanding is that 22awg wire is fine for most of the circuitry with 18awg for the power to the tubes. It has to be rated over 600v. Is this correct?

    2. Is multistrand cable ok for this or does it have to be solid core?

    I've found 'equipment wire' which is multistrand 20awg rated at 1kv would this be more than adequate for most of the build? with the 18awg for the high power as above.

    3. The plans i am following list an eyelet board and an insulation board. Are these both phenolic resin boards? The insulation board simply covering the back of the main board?

    4. I've found some capacitors that are correct uf but rated at 630v instead of 600v. I assume that is not an issue as it can take more than needed?

    5. I want to try and use some old tubes that i already have. I have a Mallard ECC83 which i believe is a direct replacement for the 12AX7. I also have some more but not sure if they can be used in any way:-

    12BH7A USA - preamp tube?
    Hammond 6BQ5 (I think it is a Q but it looked like an O so i assume it has rubbed off) which is = EL84
    5u4gb - this seems to be a TV tube? from my googling.
    12AL 7AECC8 G17 BOH5 - lettering has rubbed off so I think it is probably an 12AL5 at a guess as that comes up in a google search.
    Hammond 22-12 (I think as lettering rubbing off - if that makes any sense)

    I'm sure I'll have more questions but if anyone can help answering these that would be much appreciated.

    Thanks
     
  2. boredguy6060

    boredguy6060 Friend of Leo's

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    #1. 22 awg is standard for everything except heater wiring which is 18awg, single or multi strand is your choice. Yes, over 600v.
    #3, Yes, the insulation board is just to cover the bottom of the eyelet board.

    #4, 630v is fine, anything over 600v.
    #5 ok to use old tubes, try them and see if they work,
    Can’t help with the rest , good luck,
     
  3. wabashslim

    wabashslim Tele-Holic

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    You gave your age as 118. That's probably way too old to delve into this hobby, given the intricacies & dangers of tube electronics (or valves, as you Brits are supposed to say with a slightly condescending demeanor). Not to mention the ways that a close proximity power transformer can induct harmful frequencies into a pacemaker. I would first study how you lived to reach that age and see if you can develop a formula (legit or not) to sell on daytime TV commercials when us retired folks are watching.
    Hope this helps. And welcome to the forum!
     
  4. theprofessor

    theprofessor Friend of Leo's

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    Welcome to the forum!
    1. What most folks do is 22 AWG for everything except the heater wire that runs from the lamp to the power tubes to the preamp tubes, connecting all filament pins. For that, use 18 AWG.

    2. Multistrand cable is fine. I've found that I generally like solid-core the best, but that is really just a matter of preference.

    3. The eyelet and backer board are not likely phenolic. They are more than likely vulcanized fiberboard.

    4. Extra voltage rating is perfectly fine.

    5. Your Mullard ECC83 is indeed a direct replacement for a 12AX7. The former is the European system of coding, the latter American. None of the other tubes you listed is used in a typical 5e3 tweed Deluxe. The 5U4GB is a rectifier in some guitar amps, however, and I believe the 6BQ5 is used in some circuits as well. But only the ECC83 in a tweed Deluxe.

    I hope that helps!
     
  5. agent_zed

    agent_zed TDPRI Member

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    Thanks for the quick responses. So by the sounds of it I am on the right lines.

    Pretty pleased as just found another ECC83 (12AX7) in the garage. Which is a useful spare if the first doesn't work.

    I just read a bit on another forum about using another 12AX7 instead of the 12AY7 but it seems it adds too much gain.

    I've managed to get to 118 years old by being careful with electric and not publishing personal details on the internet :)

    I kinda get the idea from every thread i've read that there is the serious potential for death, which is giving me a healthy fear of doing it right and being very careful with health and safety. I will be reading and re-reading all the safety stuff before i put any electric into the system and subsequently energising parts.

    Oh another question it seems you need to put a metal shield over one of the tubes. Is that for electrical safety? I was planning on making it a standalone head unit and having it with mesh front and back so no possible way anyone could touch anything. Would i still need the tube covered?

    many thanks all
     
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  6. Telekarster

    Telekarster Tele-Meister

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    I'm really interested to see how your project turns out. I've had something like this on my mind for a while, and 5e3 is what I've had in mind. Please keep us posted on your progress and good luck!!!
     
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  7. jtcnj

    jtcnj Tele-Holic

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    good luck in getting started.
    shields are for noise reduction; repulse outside noise sources.
    Watch the safety vids.



    1 hand in pocket.
    make and always use the capacitor voltage drain tool.
    make and use the light bulb current limiter.
     
    Last edited: Aug 22, 2019
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  8. wabashslim

    wabashslim Tele-Holic

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    That's one PG video I can agree with completely....except he should have mentioned - BE SOBER! Using beer as my bench helper I once ran a running Twin Reverb's B+ supply from fingers to the same (left) arm's elbow grazing the chassis. Had a gig later and had spasms & tightness in that arm all night.
     
  9. theprofessor

    theprofessor Friend of Leo's

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    A healthy respect and even fear is a good thing. Take all precautions you can. If you're already a worry-wart, don't let it keep you up at night, though. I am a fan of 12ay7's and their subs in the first position of tweed amps that call for them. The tube shields are for radio frequency shielding. They're not absolutely necessary, and sometimes they can rattle, too. But if you can use them, use them.
     
  10. dan40

    dan40 Tele-Afflicted Silver Supporter

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    Many builders use 18awg wire for the heaters which is perfectly fine, but I have found it to be a bit hard to work with in the small 5e3 chassis. Marshall used 22awg wire for everything in their amps and that is what I have gotten in the habit of using on all of my builds. Solid core wire holds it shape well and is easy to work. Hoffman sells some very nice cloth covered solid core if that is what you go with. I really love topcoat, pretinned stranded wire in my builds. It also holds it shape well and since it's pretinned, it solders up very easily. If you decide to use plain wire, be sure to tin the ends before connecting it. Valvestorm sells the topcoat wire if you are interested in trying it. They also sell several types of bare buss wire that you may need for grounding buss.

    http://valvestorm.com/Products/Wire

    https://hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=WireCable&ORDER_ID=244729630
     
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  11. Wyatt

    Wyatt Tele-Afflicted

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    22 AWG is fine for everything in a 5E3. The combined current draw for the 5E3 heaters and pilot lamp is ~2amps, less than one third the 7A maximum current rating for 22AWG.

    No reason to add extra headache and supply cost with the thicker 18 AWG, it completely unnecessary.
     
  12. agent_zed

    agent_zed TDPRI Member

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    awesome thanks for all the info. Looking forward to getting started. I think i'll print out a safety sheet and pin it on the wall in front of my work space so i can't miss it.

    Is there an alternative to the metal shields? perhaps a mesh version? completely for vanity sake but i like the idea of being able to see the tubes.

    For the wiring i've noticed from pics on the web that different build use different colour wires. Is there a standard colour scheme that is best to follow? Or doesn't it matter. The plan i am following has green cable but I don't really like that as I am used to green cable being for earth (ground) so i'd rather use something like brown which is the live cable in UK wiring.

    thanks for the links but I'm in the UK so postage would be huge, but useful for reference.

    I had a closer look at the random valves i have and realised there was more numbering on the ones i could properly identify. So i have a pair of 7246's and the 12al5 is actually a 12AU7A. But having googled them it doesn't look like either would work. The 12AU7A is too low a gain. So i'll have to buy the other valves. Perhaps they will come in useful for a different build if this goes well and i get the bug :)
     
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  13. dan40

    dan40 Tele-Afflicted Silver Supporter

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    I don't use the shields on many of my amps and they are normally pretty quiet. I'm sure they do help in some situations but I have never been able to hear much difference with or without.

    With wire color, it is totally up to you but using certain color schemes will help us to easier spot problems should you have any issues after the build. Marshall used green for grid wires, yellow for cathode and blue for the plate wires in most of their amps. Fender used yellow cloth wiring for most all of the preamp runs in the tweed amps. Here is a google search page with many 5e3 chassis pics that will give you an idea of different wiring color schemes. Also pay close attention to the lead dress in the original amps. Clean, neat and short wiring are important for a quiet amp.

    https://www.google.com/search?q=fen...8KHai2DLkQ9QEwAHoECAgQBg#imgrc=7SYOWp5pBrB6pM:
     
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  14. agent_zed

    agent_zed TDPRI Member

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    oh cool. I guess you can add them later if there is interference.

    next question and i know it is debated hotly but I think i've decided to use metal film resistors. So i've been looking at these and the website i'm on some of the resistors say they have a fire retardant coating and others don't. In terms of expense it is not going to be a huge outlay but they are about twice the price but is there a specific need in this instance to use a certain type.

    for example
    with the fire coating..
    https://www.digikey.co.uk/product-d...onents/PR01000105602JA100/BC4742CT-ND/7352172

    without
    https://www.digikey.co.uk/product-d...onents/MBB02070C5602FCT00/BC3838CT-ND/7351268

    The datasheet on the bottom one lists industrial, medical, telecommunication and automotive so it doesn't suggest to me there is a problem using the cheaper one in an amp. But figure it's better to ask than burn my house down.

    thanks
     
  15. Nickfl

    Nickfl Tele-Afflicted

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    Those are both a little pricey, I wouldn't pay the extra for the fire resistant ones.

    Tayda doesn't have a very good selection of 1/2 watt metal film, but if you want to go carbon film, they have the full range and they are less than 1/10 the price of what you are looking at: https://www.taydaelectronics.com/resistors/1-2w-carbon-film-resistors.html
     
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  16. sds1

    sds1 Tele-Afflicted

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    What Nick said, in either case those are expensive resistors.

    Rather than worry about fire resistance, I'd rather see you up-rate everything -- 1W minimum and 3W where higher current is flowing (PSU dropping, screens).

    I see you are shopping Digikey but they don't carry the resistors I like:

    https://www.mouser.com/Xicon/Carbon...h-Hole/CF-RC-Series/_/N-1z0zls8Z7gz3yZ1yzv52p

    I use those everywhere and then any metal film 3W for power and screens. And get a 10W or 15W wirewound for your power tube cathode.

    Notice the Xicon 294's are only $0.03 a piece when buying 10+. Never buy less than 10!! :)

    Sorry to steer you off your current path of execution but I hope it helps.

    P.S. if you can find some 22AWG topcoat wire you will be super pleased with how easy it is to work with. Colors are up to you, it may cost you more to diversify.
     
  17. dan40

    dan40 Tele-Afflicted Silver Supporter

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  18. agent_zed

    agent_zed TDPRI Member

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    oh cool thanks both. I've tried a few websites but the postage seems to be a killer as i am in the UK and anything from the US is expensive on the shipping. mouser is £12! Think i'll use cpc as i use them regularly for other things and whilst each part is more expensive its free postage over £8 so it will work out cheaper in the long run and they have been really good so far.

    I'll upgrade to 1w as suggested.

    The next problem i am having is finding '3 lug shorting jacks'. They don't seem to be very common over here even ebay is drawing a blank.

    I've read that shorting jacks are a type of switching jack. So can i use a 3 contact switching jack? I am assuming it need to be normally closed, as my understanding is that it is shorting the jack until a plug is inserted?

    would this be correct/work?

    https://cpc.farnell.com/unbranded/t-214j/jack-socket-stereo-switched/dp/CN01611

    (it doesn't say but again from what i've googled they are normally closed)

    many thanks all
     
  19. BobSmith

    BobSmith Tele-Meister

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    I believe this will not work. This looks like a TRS plug (tip ring sleeve) connection used for stereo audio (L and R).

    Switchcraft 12a is what you want, if you can get it.
     
  20. agent_zed

    agent_zed TDPRI Member

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