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Champion 600 noob issues

Discussion in 'Amp Central Station' started by Mrmudd_Mrgold, Jun 22, 2018.

  1. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Hi all:

    Long time player, first time tube amp owner here. I've been following the Champion 600 mods here the past few years, and finally picked one up a few months ago (used). Mine appeared to be stock, so I changed the speaker, grill cloth, and tubes. All was running just fine 'til yesterday. I had changed the functional power tube from an RCA to a Sylvania I had just to hear the difference (both old tubes rated around 95%). The Sylvania worked fine on the low input. Then when I switched to the high input it gave me some weird harmonics, made kind of a "crinkly" sound, and then the amp cut out. I am wondering if the tube was just dying/old and couldn't handle being put back into service (got it as part of an eBay lot). No burnt smell from either preamp or power tube, though.

    I put the RCA and another JJ preamp tube back in the amp, powered it back up and get no guitar signal. The amp hums still, but it's a very low hum that is fixed i.e. does not increase as the amp warms up (like before) and the volume knob doesn't affect it. The amp lamp is behaving normally.

    I haven't opened up the chassis yet to check for burnt stuff but will do that. Am just wondering what issue this might sound like to more experienced folks here. :) Did I possibly fry one of the transformers?

    Btw I bought this little amp to mod and learn more about amp circuits (kinda like the guitars I've built from various Squier guts). I guess be careful what you wish for!
     

  2. Doctorx33

    Doctorx33 Tele-Afflicted

    Jun 8, 2014
    atlanta
    I'm not an expert but open it up and check the screen resistor. Either the tube was bad or went bad and took something out. I doubt if it was a transformer.
     
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  3. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    `
    That'd be a good place to start...

    DSC06936.jpg
     
    Last edited: Jun 22, 2018

  4. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Thanks! I'll check that screen resistor.
     

  5. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    `
    Be sure to let us know what you find!


    `
     

  6. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Ok. Opened it up and the fuse looks okay. R3 was definitely fried and some residue formed around preamp tube (see pic). I took out R3 and replaced with a jumper wire as a test. Amp still not working BUT when I plug into high input and turn volume to about 3 O clock position am getting some low, farty noises when I pick strings. Some progress. :/ 34D707B0-916F-4753-8AF3-817C2F526C6E.jpeg
     

  7. scelestus

    scelestus TDPRI Member

    Age:
    34
    4
    Jun 24, 2018
    Michigan
    I'm only just learning about this stuff but R3 looks like the bias resistor for one triode in that tube. You will need some resistance there to get signal - replacing that resistor with another one (instead of just a lead) might help a lot.

    Again, though, I'm just getting started down this amp road so I'm happy to be corrected by those more knowledgeable.
     
    Last edited: Jun 24, 2018

  8. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Thanks. I'll put a replacement in R3. Anyone know the wattage on this resistor? Looks to be 1.5k ohm but is it 1/4 or 1/2w?
     

  9. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    C600.JPG
    C600b.JPG
     
    Last edited: Jun 25, 2018

  10. Schematic
     

    Attached Files:

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  11. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    R3 resistors are on order now. In the meantime here's a clip of the aforementioned "farty" noises. The actual open notes heard are coming from the acoustic sound of the guitar nearby; the amp is only outputting the buzzy noise:

     

  12. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    I have replaced R3 as well as a new fuse. Also put a new JJ 6v6S that I had in there as an additional factor to rule out (so both tubes are new). I'm still getting the same result -nothing on the low input, but on the high input turned to about 3 o'clock I get the crackle/buzz noise. It seems to react to the guitar input, i.e. it's a little noisier with the guitar's volume pot up and/or when I switched to the bridge humbucker on an HSS Strat fwiw.

    I've read that R10 is pretty notorious for failing in these amps bc they run so hot. That would be consistent with the Sylvania that I had fail initially. Mine looks okay but have not tested or inspected closely yet. Anyone else have issues with R10?
     

  13. AxemanVR

    AxemanVR Tele-Afflicted Ad Free Member

    Dec 27, 2011
    Minnesota USA
    `
    Unfortunately it sounds like the "quick fix" attempts failed to deliver for you. :(

    It's appears you have no choice but to systematically go through everything. I'd start by checking voltage levels at each "Test Point" (TP) shown on the schematic in order to narrow down where the failure occurred in the circuit, starting with the power supply.

    Be especially careful due to high voltages though... we'd hate to have something bad happen to you!

    Good Luck...


    `
     
    Last edited: Jul 12, 2018

  14. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Thanks for the quick reply. It's back to the garage bench, then. :(
     

  15. tombm3

    tombm3 Tele-Holic

    591
    Apr 24, 2003
    USA
    I just recently picked up a used 600 from the bay. I didn’t notice it until after I won that it was a not working/ parts amp. Ugh, need to learn not to bid on items from my phone. Anyway, once it arrived I opened it up and didn’t see any crispy components. I found a bad fuse. Obviously something caused the fuse to blow. Thanks to this thread I carefully inspected R3 and R10 and didn’t see any damage.

    Spare fuses arrived today so I got to work. I replaced the pre-amp tube but didn’t have a spare 6V6. So I re-used the China made on dated 2014.

    With fingers crossed, I powered it up with nothing plugged into it. Actually the amp was just resting in the cabinet and not secured. There was a solid buzz that didn’t change with the volume.

    I plugged a guitar in and it made amp sounds. I’ve had champs before but nothing as small with tubes as this 600.

    Ok, seems to be working. Decided to button it up. When the chassis was secure in the cabinet the buzzing was essentially gone. I know what the single ended amp sounds like so it appears to be working. I didn’t do a long test. Maybe a 5 minute run through. There could be a cold solder joint somewhere. I’ll have to keep investigating this one.

    Thanks again for your thread and I hope you can get your amp figured out soon.
     

  16. tombm3

    tombm3 Tele-Holic

    591
    Apr 24, 2003
    USA
    Kinda sounds like a blown speaker.
     

  17. Mrmudd_Mrgold

    Mrmudd_Mrgold TDPRI Member

    Age:
    42
    9
    Feb 28, 2018
    South Carolina
    Upon testing R10 it was sure 'nuff dead- no resistance, no continuity. That one is a little tricky to get to but I removed it and replaced with the proper 2w 470ohm, fired up the amp, plugged in, and... success! Amp sounds at least as clear as I remember from a few weeks back! This 600 is now back pretty close to stock specs, so I'm gonna keep it as is for now. Thanks for the sage advice everybody! :D:D
     
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  18. gusfinley

    gusfinley Tele-Meister

    265
    Jun 11, 2014
    SLC, UT
    Glad you got it up and running. Its a great sense of accomplishment to fix something yourself!
     
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