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Thinking in building a tweed amp - 1st timer

Discussion in 'Shock Brother's DIY Amps' started by tube.tone, Jul 23, 2009.

  1. tube.tone

    tube.tone Tele-Meister

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    Thanks a lot guys!

    I just wanted to make sure. Yesterday I received the speaker from weber. Looks really nice. Photos do not make justice... I thought that it was a 12A150 but in matter of fact is a 12A125.

    I did a test ride on my blues junior and it sounded brighter than stock speaker but all the vintage juice is there...

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  2. Tuxedo

    Tuxedo Tele-Holic

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    I'm thinking about building a Deluxe, too. As a noob like myself—how difficult was it for you so far?
     
  3. tube.tone

    tube.tone Tele-Meister

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    Hey Tuxedo, very very straight-forward. I just had to keep a certain flow, take step by step and I tried to keep things tidy.

    [​IMG]

    I have used the layout and other built threads as a reference. Now, I'm a bit anxious with the testing before first fire up...
     
  4. tube.tone

    tube.tone Tele-Meister

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    Update,

    I would like to tank you all for your impute in this topic. Below are few pics last details,
    The rectifier and power tubes sockets:
    [​IMG]

    Pre-amp socket right before I soldered the filaments heaters:
    [​IMG]

    Inptut jack layout, I like the way it looks wired this way:
    [​IMG]

    Finaly a perspective of finished interior:
    [​IMG]

    Everything went smoothly. I had a couple issues, though. A pin inside a power socket was damaged... the bad part is that I have only noticed when the board was in place and soldered. So, I had to remove the socket and replace the pin.

    Also, I have noticed that I can't tight the board to the chassis much, because it bends in the fasteners spots. I am afraid that it might get loose with vibrations. What do you would do?

    More coming soon!
     
    Last edited: Sep 19, 2009
  5. tube.tone

    tube.tone Tele-Meister

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    First Fire Up,

    After installing the chassis in the cabinet I have checked once more time the wiring layout, components values and ground connections.

    Everything was fine with the exception of the 500 pf tone cap that was soldered to the wrong lug. There's no reason to go wrong since I have followed the layout... I don't want to be creative here!! :)
    [​IMG]

    After comtempling this funtional sculture for 2 secounds I cound not resist in fire it up. So, I did it with no tubes at first. The pilot light turned up and no smoke and neither sparks!!!
    [​IMG]

    After, I tried the amp with the chinese tubes All valves light up with the exception of one power tune that came dead. I was scared for a moment!!! in any event the want worked and i managed to plug my guitar a take out a few tunes.... couldn't go far with experiments because it was a little late. So, went back and I have installed the RCA 5Y3GT and RCA 6V6gt and 2 GE 12AX7. I fire the amp once more time and all tubes were lite.

    I have played at very low volumes, great vintage tone. The hum is there when I crank the volume but I think is not enough to bother me... I have to test it better when there's no one around at home.

    [​IMG]
    [​IMG]
     
    Last edited: Sep 19, 2009
  6. tube.tone

    tube.tone Tele-Meister

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    One extra detail! so that 50 years from now my grandsons know what tubes to plug in. :lol:
    [​IMG]
    [​IMG]
    [​IMG]

    regards
     
  7. Jelle

    Jelle Tele-Meister

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    Very nice and looks clean. I love the tube-charts! Thanks for making the effort to document your progress.
     
  8. tube.tone

    tube.tone Tele-Meister

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    first screw up....

    Thanks Jelle! ;) It’s my pleasure!

    Unfortunately, everything was going well until yesterday. The amp was sounding very nice, full, loud!!. There was some hum above 4 (definitely more hum than my silent blues Junior improved by Billm), nothing major I think and there’s still some more room fore improvements with grounding.

    The big [email protected] up happened when I fire up the amp with no speaker load... it toke a few second until I figured out that it was not my guitar cables to late.

    I notice a bit a burnt smell, after opening the amplifier I surveyed for damages and I saw a discolored 4.7k 2w cement resister between power capacitors.
    [​IMG]

    I have measured the resistance and it stills measure 4.7k. The amp works although, now there is a crackling noise even when the volume is totally down. The power tubes give the impression to be intermittent, there's a blue glow inside one (no matter the position) and there is a light burn smell... but amp works.

    I am looking for opinions in the cause and extend of the damages?

    Sorry for my English, I hope I made my self clear.

    Thanks guys,
     
  9. backalleyblues

    backalleyblues Friend of Leo's

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    Replace that cement resistor, that's the source of your crackle and intermittance. Blue glow in a power tube (especially NOS) is pretty common, and nothing to worry about.

    Franc Robert
     
  10. tube.tone

    tube.tone Tele-Meister

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    Thanks backalleyblues... it's sounding golden again. Luckily It was just a bad resistor. Although it's a pain in the ass desoldring and soldering without being able to remove the board out completely.

    I toke this chance and I have ended up replacing the 250ohm cathode resistor with a 270ohm. Also, I have soldered two 100 Ohm resistors between 6v6 filaments and cathode resistor cap, runs much more silent now.

    ;)

    Regards to all
     
  11. tube.tone

    tube.tone Tele-Meister

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    Hi Guys

    Here goes an update.

    I had a little hum issue that now is resolved. The 5e3 runs very quiet now. I believe it was a reversed rectifier and OT wires at the standby switch. Just in case I rearranged the ground wire and re flowed a few solder joints.

    Thanks for the advice Johnnycrash, Below are the voltage measurements I did:

    Filament =6.3V AC
    V5 Rectifier
    Pin 2= 334VDC
    Pin 3= 336VDC

    V4 6v6
    Pin 3= 323VDC
    V3 6v6
    Pin 3= 326VDC

    After 4.7K resistor 330V
    After 22K resister 245V

    Tonight, I will measure the 6V6's screens (pin 4), and cathode (pin 8)
    to figure out bias and output and V1 and V2 voltages.

    I have placed a RCA 12AY7 into V1 and performed another late night playing test, it sounds full and rich. I couldn't bring it into distortion though... :twisted: tomorrow I'll be alone all day:rolleyes:

    Regards to all
     
  12. tube.tone

    tube.tone Tele-Meister

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    Very inspiring. Don't you think? Neil Young's rig in Australia photo taken by Andrew Kidman.

    [​IMG]
     
  13. fernando

    fernando Tele-Afflicted

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    >Champs are really cramped in the chassis. Simpler circuit, but much less space.

    but... you are not stuck to the chassis or cabinet size of the original model! You are free! :p

    You can build whatever... a 5F1 Champ with a 10'' in a wider than taller cabinet á la Vox, or a 5F2A, or a AA764 Champ or VibroChamp...
     
  14. tube.tone

    tube.tone Tele-Meister

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    Hey guys, I am back with my project update.

    I have bumped in a couple issues that were causing some weird voltages measurements. I noticed that the bias was running way too hot, my rca 6v6 were steaming with no apparent explanation... I have reviewed the wiring and searched for defective parts and everything was ok.

    [​IMG]

    I figured that I was in the edge of my knowledge, so I toke the amp to a knowledgeable guy in vintage amps. He checked the amp and said that everything was looking very clean and well thought.

    The reason of the unstable bias was in the two 100ohms resistors from 6v6 socket to the cathode resistor... in this case is was point less and prejudicial due to the fact that the power transformer has a central tap for filaments. After clipping these two resistor the amp came back to normal. No more ugly distortion nither red plating.

    Luckily the RCAs survive to some testing under the stress they were submitted to...

    [​IMG]
    [​IMG]


    I'll come back after more testings :)

    [​IMG]
     
  15. tube.tone

    tube.tone Tele-Meister

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    Ok guys, It takes a lot of courage to post this clip here. One day I learn how to handle a guitar... :)

     
  16. fstempleton

    fstempleton Tele-Meister

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    Any thoughts re the following for a first build:
    1. I was leaning toward a Mission 5e3 because the price was similar to Mojo's, and Mission's customer service is apparently awesome. Now, however, Mojo has cut their 5e3 kit to $575 for October - so it's temporarily $144 less than the Mission kit [which I understand is based on the Mojo kit]. Any reason NOT to go with the Mojo kit? [Bruce, if you'll match Mojo's price drop I'll reconsider, but the Mojo deal is hard to beat....]
    2. Are there any consensus "mandatory mods" that should be done to a 5e3 build? I plan to compare whatever diagram and layout I get against the Fender originals, but except for a grounded power cord, am uncertain if anything else should change from the Fender design. Any thoughts?
    Thanks! ST
     
  17. tube.tone

    tube.tone Tele-Meister

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    Hi there,

    Good! I didn't scare all of you with my clip :D

    You should be fine with any kit, you can always upgrade the components to your taste. I have done that starting with a Weber Kit (chassis, transformers, cabinet and a good speaker).

    Mojo seems a very nice kit, Mission has the advantage of Bruce's support... If you feel comfy with your research and help you get in the forums you will be very ok with Mojo's kit.

    If you notice most layouts out there are a slightly improved version of the original tweed. This is not exactly a mod, the filaments heater wiring is improved they run twisted from pilot lamp and filaments to filaments in order to avoid undesirable hum.

    If you power transformer don't have a central tap for filaments it's recommended to wire two 100ohm resistors from filaments to ground to create an artificial central tap.

    Also, in order to keep the amp quieter it's also recommend to rethink the grounding off all stages.
    Basically, it's recommended to connect all ground to one point or separate them by stages and make currents floes like a river instead moving freely on the chassis.

    see here a good explanation:

    http://www.aikenamps.com/StarGround.html

    Again, I don't think this is considered a mod, the tweed character remains it just sounds less noisy.

    I hope this helps,

    Best
     
  18. tube.tone

    tube.tone Tele-Meister

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    Hi again, Yesterday I have took final voltage readings on my amp.

    My bias probe shows me now 38ma with a 270ohms cathode resistor. What do you think, considering the voltages below?

    By my calculations my plate dissipations is around 13w-14w

    Thanks
    5Y3
    Pin 2: 388V
    Pin 8: 388V

    6V6's
    Pin 3: 383V
    Pin 4: 340V
    Pin 8: 20V
    Pin 3 to Pin 8: 360V

    12ax7
    Pin 1: 157V
    Pin 6: 158 V

    12ay7
    Pin 1: 116V
    Pin 6: 176V
     
  19. fstempleton

    fstempleton Tele-Meister

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    Thanks for all the info - it's going to be very helpful when I do my 5E3 build.
    I'm also thinking about, as a "warm up project," taking apart a Crate v8 Palomino that I picked up a couple of years ago, which has never really worked well [primarily a bad gain pot I think]. I'd reuse whatever I can, and would aim to convert it into a hand-wired champ circuit. I figure that at minimum I can reuse the PT, OT and tubes, plus the chassis, cab, speaker and cord. That should keep my cots minimal.
    Any thoughts?
    Thanks
    ST
     
  20. tube.tone

    tube.tone Tele-Meister

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    one more clip to give a better sense of how it sound... not bad hum?! :D
     
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