5F2A home build

Discussion in 'Shock Brother's DIY Amps' started by Lindsay, Dec 10, 2017.

  1. Lindsay

    Lindsay TDPRI Member

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    I look at this forum a lot but seldom post. Here's a few pic's of recent builds and a video of the end result. The specs are home bent and welded aluminium chassis, Hoffman layout, own wind transformers and choke. 5Y3, 6V6, 12AX7. Output transformer, grain orientated core, switchable plate load (5K and 7K). Power transformer puts out 315V on plate with 5Y3 or 340V using 5AR4 rectifier. Switched gain stage bypass cap and NFB. Sounds best at lower voltage. Video was just a bit of fun and not intended to be an amp test as such. One of my mates playing, using a loop pedal and a hit of OD pedal at 1.56.

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    D'tar likes this.
  2. dan40

    dan40 Tele-Afflicted

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    Great looking builds you have there!
     
  3. Lindsay

    Lindsay TDPRI Member

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    Thanks Dan, I put a lot of effort into the builds. I've now built four of these so it gets easier each time.
     
  4. tombob

    tombob Tele-Holic

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    I have a cabinet from a early 50's Alamo 1x10 amp that my dad originally bought somewhere around 53'. The chassis has been taken out and long lost but I want to use it for a 5f2 Princeton cab (that's actually close to what it was originally, except with a 6SL7). The cutout for the chassis is closer to the size of a 5F1 though. I don't see why it wouldn't be easy to use a 5F1 kit add another pot with the 500pf and .0047uf caps for the tone control. The only other different I see is more filtering in the 5F2 but I should be able to use a bigger cap to make up for the Princeton having one more cap.
    Lindsay... It looks like you are using 3 filter caps instead of 4, is that correct or am I just missing one in the pictures? If you are using 3, what values are you using? If you don't mind me asking.
     
  5. JORear

    JORear Tele-Meister

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    Didn't miss a beat when you lost your eye glasses. Love it.
     
  6. Lindsay

    Lindsay TDPRI Member

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    [QUOTE="
    Lindsay... It looks like you are using 3 filter caps instead of 4, is that correct or am I just missing one in the pictures? If you are using 3, what values are you using? If you don't mind me asking.[/QUOTE]

    Yes 3 caps : 33 uF reservoir cap, 15H choke (Screen supply) 8 uF - (22K dropping resistor) 8 uF
     
  7. tombob

    tombob Tele-Holic

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    Thanks Lindsay, I didn't see the choke although I like a choke on 5f1/5f2a amps, it does smooth things out. The circuits are so close between a Champ and Princeton I really don't see why adding the tone and using a single bigger reservoir cap instead of a pair of them in a 5f1 wouldn't make a compact 5f2. I've been wanting to do something with that old Alamo just because it was my dads, I'd love to have it a working amp again.
     
  8. jmp81sc

    jmp81sc Tele-Meister

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    Nice looking amps. Did I read it correctly that you wound your own transformers? If so that is really next level stuff.
    congrats
    John
     
  9. tombob

    tombob Tele-Holic

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    Me getting to amp building has been a slow process. The closest decent amp tech I knew was 175 miles away for years so I started reading and doing small repairs (filter caps, biasing, burnt resistors and so on). After I got more comfortable I started doing mods to change things I didn't like. Once I started wondering why the mods did what they did I actually started to learn some about them is when I really started enjoying it. Building amps is a lot of fun to me and really interesting, not to mention addictive :) but I'm a long ways from winding my own transformers.
     
  10. Lindsay

    Lindsay TDPRI Member

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    Like you said, there are that many variants amongst these amps it won't matter Tom. The parts count is that small you won't need a kit, just grab what you need. With these builds I incorporated a few of those changes on switches. The input uses the typical Fender dual input with 68K resistors. The preamp cathode has a switchable bypass cap which gives a boost and the negative feedback(22K) is switchable.

    Yes John, they are my own design and winds. Thanks
     
  11. tombob

    tombob Tele-Holic

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    I found a source for a 5f1 kit for $150. The transformers and chassis are nearly as much buying them separate. If I find a cheaper source to put one together I'll probably go that way, I haven't done a lot of looking yet for parts for it, there's really not much to them so I might have most of the small parts already. I need to look through my parts boxes and see.
     
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