Combo chassis as head- ok for tubes to be run in horizontal position?

Discussion in 'Shock Brother's DIY Amps' started by jtcnj, Jan 28, 2018.

  1. jtcnj

    jtcnj Tele-Holic

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    I built an 18w TMB from the VHT parts clearance at Ubuyguitars.
    The chassis is meant for a combo.

    I want to build a head cab for it instead.
    I have searched, am getting conflicting info.

    A while back I researched this a bit and believe it to be ok,
    I have been running the chassis sitting on a cabinet with the tubes horizontal for some time now.
    No issues.

    It has the following tubes:
    5y3, 12ax7, el84.

    Looking to confirm this before I start on the cabinet.
     
  2. Finck

    Finck Tele-Afflicted

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    No problem at all, tubes can work in any position. Just use some adequate retainers to make the tubes in place.
     
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  3. hackworth1

    hackworth1 Friend of Leo's Vendor Member

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    Just a thought. We sometimes run light bulbs horizontally without a second thought. It seems weird to run tubes that way, but tube data sheets indicate that any position is fine.
     
  4. radiocaster

    radiocaster Poster Extraordinaire

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    Depends on the ventilation and how you have it set up. I've heard the Marshall JTM60 and 30 had some problems due to this.
     
  5. Nickfl

    Nickfl Tele-Afflicted

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    There are some tubes that aren't meant to be run horizontally iirc, but I'm pretty sure any of the common guitar amp tubes are ok. If in doubt check the datasheet.
     
  6. Finck

    Finck Tele-Afflicted

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    Actually, ventilation has to be a concern no matter what's the position of the tubes.

    It's good to install a grill right over the tubes, what will help with dissipation of heat. Anyway, I guess it's easier to take care of this issue in a head than in a combo, because there are no acoustic matters to think about.
     
  7. Old Tele man

    Old Tele man Friend of Leo's

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    Just remember that heat "rises" more easily than it wants to move horizontally.
     
  8. clintj

    clintj Friend of Leo's

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    The 5Y3 is sensitive to orientation. Depending on the datasheet writer, either pins 2 and 8 have to be horizontal, or 2 and 4 have to be vertical if the tube is mounted horizontally (same thing, written another way). 12**7 and EL84 sheets list the operating position as "any".

    The reason is so the filament doesn't sag and create havoc in the tube.
     
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  9. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Bah - came here to say this and he beat me to it :D

    The tube datasheets that are commonly available typically list the mounting positions or any requirements so you can always check there in the future.
     
  10. clintj

    clintj Friend of Leo's

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    I had to look for an old RCA one to find that data. It takes some hunting sometimes.
     
  11. hackworth1

    hackworth1 Friend of Leo's Vendor Member

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  12. Senor C

    Senor C TDPRI Member

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    Have a few couple of these to build. How’d it turn out? We’re you true the the schematics?
     
  13. jtcnj

    jtcnj Tele-Holic

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    Glad I asked. My pins 2 and 4 are at 10:00 and 4:00.

    I'll give some thought to either turning the socket or moving it to the PT side of the chassis.
    Either will be extra work so I will probably just build
    the cab vertical.

    Thanks for the help.
     
  14. jtcnj

    jtcnj Tele-Holic

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    I used the VHT populated board and their PT,

    I changed the ground scheme to break up the pre-amp and power sections Fender-like.

    I used plain old switchcraft shorting jacks, not the Marshall style, and put a switch for 8 or 16 ohm output. I did not employ a standby switch.

    It turned out great.

    Just shut it down a little while ago :D:D
     
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