Query failed: connection to localhost:9312 failed (errno=111, msg=Connection refused). Champ clone build - troubleshooting help needed! - Amps Discussions on The Fretboard
›
UNPLANNED DOWNTIME: 12th Oct 23:45

Champ clone build - troubleshooting help needed!

What's Hot
jamesxryanjamesxryan Frets: 1
in Amps
Hello! First post here, so please forgive any newbie gaffes. I bought and have stuck together a Fender Champ 5F1 kit from Marsh amps. It now turns on and makes a sound, but is very very quiet - I have to turn all the way to get anything audible. I'm getting I've got a short to ground somewhere or something, but before I take it all apart and start from scratch, has anyone come across something like this before and can tell me where to look? It's not the tubes - I've replaced all and nothing changes.
0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter

Comments

  • MistergMisterg Frets: 212
    Hi,

    Double check your wiring first (then check it again).

    Favourite things to mess up that give these symptoms are the wiring of the input jacks - check these carefully.

    I don't know if the Marsh amps kit includes any shielded cable, but if it does, it's easy to melt the insulation around the inner conductor when you solder it which shorts the signal to ground.

    Ground connections to the cathode resistor on the 6V6 are another 'gotcha' - check whether there needs to be a link under the board.

    Have you got the means to check voltages (likely 300V+) inside the amp without killing yourself?


    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ICBMICBM Frets: 69426
    Can you post a pic of the insides, large and clear enough to see the wiring connections and resistor values etc?

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • jamesxryanjamesxryan Frets: 1
    Ok here are some pics of the guts. Any thoughts would be much appreciated. I can take voltage readings too, if you tell me what I'm looking for. (As you may be able to tell, this is my first amp build.) As you'll see, no shielded cable, so that's not the problem.

    image
    image


    image


    image
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • MistergMisterg Frets: 212
    edited August 2013
    jamesxryan said:
    image



    Assuming your kit is the classic 5F1 circuit: http://www.kbapps.com/audio/schematics/tubeamps/fender/images/champ5f1layout.gif

    There are two 1500 ohm resistors (1k5) - one on the far right  of your photo connected to the cathode of V1, one top centre connected to ground with the big 470 ohm cathode resistor.

    Double-check that these are the correct value - they should have the colour code brown/green/red. It may be something funny with the colours in the photo, but yours look like brown/green/orange (15k). That would make your amp very quiet!

    Will keep looking...

    0reaction image LOL 0reaction image Wow! 1reaction image Wisdom · Share on Twitter
  • ESchapESchap Frets: 1427
    I'd say MisterG has nailed it if you look at the blown up image, those definitely appear to have an orange band rather than red as the third, making them 15k.  If they came in the kit, the company has supplied you with the wrong resistors!
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ESchapESchap Frets: 1427
    I've just checked and I've got spare 1k5 carbon comps.  If you want a couple posted to you foc.  PM me your address.
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ICBMICBM Frets: 69426
    edited August 2013
    Yes, that's the only thing I can see that doesn't look right - at least with little pics on my phone :).

    There should really be a 25uF/25V cap in parallel with the V1a cathode resistor too. The 5F1 schematic shows it omitted, but the original 5F1 I owned had it, as do a lot of others I've seen, definitely factory fitted. They sound better with the cap.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 1reaction image Wisdom · Share on Twitter
  • jamesxryanjamesxryan Frets: 1
    You're right, it looks like they are the wrong value resistors. I'll make sure I complain to Marsh Amps. ESchap, thanks for the offer, which may be more generous than you realise as I live on a small island in the Pacific so postage would be steep! I'm actually putting together an order for some electronic bits I need for another build, so I'll add the resistors and extra cap.

    I'm a bit blown away by the speed and quality of advice - thanks all. Watch this space to see what the final result looks/sounds like (which may be a while yet since I have to wait for post which takes weeks in general). Assuming I don't find any other problems...
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • MistergMisterg Frets: 212
    edited August 2013

    jamesxryan said:
    ...Watch this space to see what the final result looks/sounds like (which may be a while yet since I have to wait for post which takes weeks in general). Assuming I don't find any other problems...
    We'll be waiting ;)

    If you contact Marsh Amps, I would hope that they'd do the decent thing and air-mail the correct resistors to you.

    Keep us posted :)
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • jamesxryanjamesxryan Frets: 1
    Correct resistors in the post from Marsh. Hopefully will be at full volume in a few weeks! (must get around to building cab...)
    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ICBMICBM Frets: 69426
    Assuming this is the fault and that there's nothing else wrong (I don't see any reason why there should be) it's a bit worrying that the kit wasn't checked properly. In this case, the wrong value will just make the amp quiet and do no harm, but there are other mistakes that would not be so benign and could cook a valve, or possibly blow a cap.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • jamesxryanjamesxryan Frets: 1
    It's taken a while (a function of the length of time it takes post to get here, full time job and two little kids), but it's finally finished: image
    0reaction image LOL 1reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ESchapESchap Frets: 1427

    A Hula Champ! 

    That is very cool, hope it sounds as good as it looks.  Great first build!

    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • MistergMisterg Frets: 212
    Great stuff!

    It's loud even before you turn it on ;)
    1reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
  • ICBMICBM Frets: 69426
    Definitely needs a hula girl graphic on the grille cloth :).

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

    0reaction image LOL 0reaction image Wow! 0reaction image Wisdom · Share on Twitter
Sign In or Register to comment.