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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

5E3 Build using 1951 Radio parts

Discussion in 'Shock Brother's DIY Amps' started by kneedeepinit, Oct 25, 2017.

  1. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I have recently built a 5F1 and absolutely love the sound that it produces. I used a Boothills kit and, by taking my time, everything went as smooth as I could have hoped.

    I now have the bug and this is my 2nd of (hopefully) many more to come. I have a collection of tubes to choose from and a few organ pull chassis. I also have a few old radio chassis. I think I have the parts to build a 5E3 but I would sure appreciate some direction from the experts here.

    My starting point is the transformers from a Viking 51-06 radio. It was apparently working but I did not turn it on. Here is the schematic

    [​IMG]
     
    Last edited: Oct 25, 2017

  2. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I have purchased a mojotones turret board kit and am waiting to pick it up. I have all of the necessary tubes. I plan to use the output transformer and speaker from the radio. I hooked up the speaker to my 5F1 and it sounded great so I think it is a good starting point. I have a cabinet ready for a 12" speaker.

    My plan is to use a chassis from my boneyard. I was given a dead Guild guitar amp and I used the cabinet for my 5F1. I gutted the amp chassis and it is ready to have some holes drilled for the tubes.

    [​IMG]

    [​IMG]
    [​IMG]

    [​IMG]
    [​IMG]
     
    Last edited: Oct 25, 2017

  3. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I applied 120VAC to the input of the power transformer and I got 320 - 0 - 320. I think this is going to work for the 5E3 build but would like some advice. Can I use the standard mojotone filter capacitors with this transformer to get proper voltages?
     

  4. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    The Mercury Magnetics FTPD power transformer shows 380VAC on each winding, and that is supposedly their "vintage correct" model. This guy shows 330V:

    https://tubedepot.com/products/clas...MIrJrOipmN1wIVELjACh0fuQPpEAQYASABEgJn8vD_BwE

    so I'm thinking you'll be alright with the 320. Might need to adjust the cathode resistor, but should work out well. The amp was driving 2x6V6 before, so I would expect it to do it again.
     

  5. Dacious

    Dacious Friend of Leo's

    Mar 16, 2003
    Godzone
    A lot depends on va of the transformer. I think you will be fine with that. I built a 5E3 with a marginal 275-0-275 volt transformer driving a 6X4 rectifier tube at its design limits. Later I changed it for a bigger radio console unit driving a 5Y3 and there was almost no change in sound or level even though B+ jumped about 20 volts. Cathode bias circuits and early Fenders seem very tolerant.
     

  6. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    thanks guys. I agree about the 5E3 circuit being tolerant. I have seen builds with a very wide range of B+ and that is one of the reasons I ended up going down this path.
     

  7. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    That transformer will probably be fine. You can use something other than a 5Y3 if you need to boost B+ voltage.
     

  8. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    robrob, I have a few alternatives to the 5Y3. I have a 5QB5 and a 5U4GB / 5AS4A. Do you think any of these would be better?

    I have a number of 6 volt rectifier tubes but I was thinking of picking one of them for my next build.

    edit - after looking at the data sheets, I think the 5y3 is the way to go.
     
    Last edited: Oct 26, 2017

  9. Tonetele

    Tonetele Friend of Leo's

    Jun 2, 2009
    South Australia
    Good on ya kneedeepinit ! Seen uncle Doug on building a 5F1 from old radio parts? That Viking radio must have been something else in it's day- our family kitchen radio was like a 5F1- guess who blew it when I tried to make it a guitar amp?
     
    robrob and kneedeepinit like this.

  10. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    I would start with a 5Y3 and if you need to lower the B+ voltage then try the others.
     
    Bob Mc likes this.

  11. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I am making a bit of progress while I wait to pick up my turret board kit. I drilled out the remaining hole in the front for the 2nd power switch. I drilled out the hole for the transformers. I installed two grommets for the secondary transformer wires.

    [​IMG]

    [​IMG]
     

  12. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I also decided to use a computer power cable. I like the idea of being able to remove the power chord completely instead of having it dangle around. I do have a question though. The plug I used had a 1.0K 275V capacotir between the hot and the neutral. It is a pretty heavy duty 3M unit. What is its purpose and should I keep it?

    [​IMG]
     

  13. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Probably a surge protection cap. I'd leave it there.
     

  14. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    thanks Rob. I don't think it will do any harm. It might be duplicated in the mojotone circuit but I am just going to leave it there.

    One lesson learned already is not to paint prior to drilling holes. I got a bunch of scratches on the chassis because I have not clear coated it yet. Looks like I am going to need another couple of coats of paint but I am going to wait until I am completely done with the prep.

    I am toying with the idea of adding a few red 6 volt led lights under the chassis. There are a few holes left over from the previous application so it might look cool to have a warm red glow coming from within the chassis. Could I use the 6.3 volt heater wires to do this?
     

  15. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    Sure - as long as you have enough extra current in your heater line that'll be fine.
     

  16. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I should be ok. The transformer was supplying 6 volts to 8 tubes in the old chassis, this one is 4 tubes. Two of the 5E3 are 12 volt so I would count them as double and get 6 total 6 volt circuits, still less than 8.
     
    corliss1 likes this.

  17. hackworth1

    hackworth1 Friend of Leo's Vendor Member

    12ax7 type dual triode tubes can be wired in parallel for 6 volts OR in series for 12 volts.

    They're typically wired in parallel for 6 volts.

    If the old amp had eight 6 volt tubes to heat, you are correct in thinking that the heater circuit will have an easy job.

    http://www.valvewizard.co.uk/heater.html
     

  18. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I double checked the Viking 51-06 schematic and I found that it had three 6 volt bulbs in addition to the 6 volt heater circuits. One is the front panel power indicator and I think two were to back light the radio dial. That tells me that the transformer is going to have lots of 6 volt amperage available for my needs.

    I pulled the two 6 volt bulbs from the old radio. The sockets and bulbs work but the bulbs are clear. I am looking for a soft red glow. A trick I learned from a radio tech was to use permanent marker to change the color of clear bulbs. I now have two red 6 volt bulbs and sockets ready to install after all of the other electronics get done.
     

  19. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I have now gone as far as I go until I get my turret board kit. It is at my post office box in Montana because I did not want to spend the extra to ship it to Canada.

    I printed off the faceplate decal. I tried using Gimp but I could not get it to orientate correctly. My wife uses Excel for her work so I got her to print one off. It took about 20 tries to get the margins correct but it is done. I cannot put it on until I do the final paint.
     

  20. kneedeepinit

    kneedeepinit TDPRI Member

    Age:
    54
    34
    Oct 3, 2017
    calgary
    I wonder if anyone can provide feedback on my proposed layout. The layout I have come up with has several objectives. The first is to separate the 12ax7 preamp tubes from sources of interference as much as possible. I have placed them as far away from the 6V6 and transformers as I can.

    The second goal was to uses as many existing chassis cutouts as possible. To do this, I have the front panel very spread out and this will result in some longish wires from the turret board.

    I have also located the power supply input and the speaker output as close to the transformers as possible. This was done because the wires from the existing transformers are quite short and I was trying to avoid adding connections to lengthen them

    https://image.ibb.co/mNocLm/20171030_101237_1.jpg
     

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