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New 5e3 kit build

Discussion in 'Shock Brother's DIY Amps' started by Romartin, Oct 16, 2017.

  1. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    Btw, I have a tweed hot rod deluxe extension cab I never use (I don't have the HRDLX amp anymore) that I'm pondering turning into a combo cab for the 5e3. I'd have to build a 2 piece back panel to replace the closed back one and cut out for the chassis. It's a 1x12 but it's big enough to recut the baffle to a 1x15 or build a new baffle as a 2x10. It's unfinished tweed so I just wonder how hard it would be to pull back the tweed, cut the chassis cutout, reglue it then shellac/laquer the cab. Has anyone here tried lifting then reglueing tweed onto a cab? That's my only concern is getting it up enough to cut out for the chassis without tearing the tweed.
     

  2. rocksmoot

    rocksmoot Tele-Meister

    172
    May 6, 2012
    Rogers, Arkansas
    I know you didn't ask, but personally I'd consider a matching head to go with that cab.
     
    tombob likes this.

  3. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    I've actually been thinking about building a head cab and covering it in matching tweed. I will shellac/laquer them both if I do. I also thought if I did I might cut about 1/3 of the back off and make a removable section to make it open/closed back convertible. It always seemed like tweed type amps sound better with a open back cab.
     

  4. rocksmoot

    rocksmoot Tele-Meister

    172
    May 6, 2012
    Rogers, Arkansas
    Ampeg makes a flip-top bass cab. You can attach one of several amp heads to the cabinet and you flip it out to play or flip it in to transport/store.

    http://www.ampeg.com/products/portaflex/pf-115he/

    Never seen a guitar amp like that but it would be cool.
     

  5. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    A flip-top guitar amp would be cool. I've seen the Ampeg bass amps and it is a good idea, it makes a more compact amp to carry without losing cab volume. The size of the standard 5e3 cab is really on the small side, I know they were never intended to be run at the volume people run them at now though. They were designed back when overdrive was still considered "unwanted distortion".
     

  6. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    I sit down and drew a layout for my build with the minor mods drawn in. I'm not planning to do a lot of mods, it's easy to get where I'm spending more time playing with switches than playing. Once I find the sound I'm wanting from the amp there's no reason to have a hundred other options anyway. I do like a grid stop resistor on the phase inverter and a NFB loop option to add a little headroom, and maybe add a little more filtering, those are the biggest mods. I wouldn't mind adding a mid-cut but I don't want to delete the tone to do it so I'd have to make a place for it.
     

  7. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    I checked my voltages again today and the B+ voltages have increased by 10-15 volts since the last time I checked. I haven’t made any changes. Is it normal for voltages to change?
     

  8. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    I'm interested in what everyone thinks about that too, I haven't had a lot of experience with cathode biased amps so anything I can learn helps, especially since my kit is supposed to be here Thursday :)
    I do know that tubes themselves will fluctuate a little after 24 hours or so of use. From what I've seen modern electrolytic caps and film resistors don't change much at all with "burn-in". Those big paper red Atom caps from the 60's look cool but I really like the way the modern ones perform, I've heard they're supposed to last 30+ years before you need a filter cap job.
     

  9. DrPepper

    DrPepper Tele-Meister

    Age:
    59
    244
    Nov 24, 2017
    Texas
    What is the wall voltage at your house?
     

  10. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    124v
     

  11. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    Well I’m still having trouble getting the right bias value, and having high b+ voltages. I’m cutrently using the classic transformer 40-18021. I’m thinking about switching to the 40-18016 which has 330-0-330v. What do you all think?
     

  12. tombob

    tombob Tele-Holic

    Age:
    45
    510
    Jun 25, 2010
    Sonora, TX
    Have you tried using larger dropping resistors on the B+? It seems like it's a lot cheaper to try it first anyway. As long as you can get the bias good all the new 6V6s are made to run in blackface amps without problems and they run up to 425v plate voltage.
    I started my build now too, I'm taking my time, adding a ground bus (it doesn't have the brass plate like the original) and trying to get everything just right.
     

  13. Wyatt

    Wyatt Tele-Holic

    913
    Nov 3, 2004
    What are your numbers currently?

    B+ voltages from 330-395 are all considered "normal" for a 5E3 build thanks to varying viewpoints on "ideal" operating conditions. Most of the ones we've heard of records probably ran somewhere in that upper range (370+). My 1960 ran around 395VDC and was much more "rawK" than most of the lower voltage clones.

    That said, I've used the 40-18078 and tried both the high voltage and low voltage taps and the difference is not night and day.
     
    King Fan likes this.

  14. Wyatt

    Wyatt Tele-Holic

    913
    Nov 3, 2004
    What are your numbers currently?

    B+ voltages from 330-395 are all considered "normal" for a 5E3 build thanks to varying viewpoints on "ideal" operating conditions. Most of the ones we've heard of records probably ran somewhere in that upper range (370+). My 1960 ran around 395VDC and was much more "rawk" than most of the lower voltage clones.
     

  15. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    Okay so here is my current voltage chart. This is using a JJ 5y3 rectifier. By the way, I ordered an NOS RCA 5y3 tube and it put out 10 volts higher than the JJ 5y3. Interesting.

    V3/4
    Pin 3: 371/371
    Pin 4: 329/ 329
    Pin 8: 21.3/21.3

    B+1: 378
    B+2: 328
    B+3: 239

    Cathode resistor measures 250 ohm
     

  16. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY

  17. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    they are Tung-sol. Which are 12watt. I tried putting in the 300ohm resistor, but the plate dissipation was still over 100% and the plate voltage was at or near 400. So I don’t know what I should do next. Any suggestions?
     

  18. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    Let's try something different here. Drain the caps, and measure the OT resistance from the center tap to each plate connection. Then with the amp idling, measure the B+ at the first filter cap and the voltage at each plate. Post those numbers with as much accuracy as your meter will give you (tenths, hundredths, etc)

    Let's see what the actual plate current and dissipation is at each power tube, and reevaluate from there.
     

  19. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    So the OT resistance at v3 is 209.2ohm. The B+1 voltage is 377. And the plate voltage at v3 is 367. So if my calculations are right, I’m running at 47mA plate current. Smoking hot!
     

  20. Romartin

    Romartin TDPRI Member

    Age:
    32
    68
    Aug 7, 2017
    USA
    I have a 350ohm cathode resistor on the way. Maybe this will do the trick
     

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