1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

1975 Silver Face Champ- snap, crackle and pop!

Discussion in 'Amp Tech Center' started by SanAnTex, Nov 18, 2017.

  1. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Do you think I should resolder the large cap?
    It is a 4 ohm speaker... between a Chevy and a dead calf? Nice find!
     
  2. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Wiggling the tube didn’t make a difference in sound... maybe I should be looking for some good local “Tex” haha. Thanks for the welcome!
     
    robrob likes this.
  3. Darkness

    Darkness Tele-Afflicted

    Age:
    52
    Posts:
    1,131
    Joined:
    Apr 7, 2016
    Location:
    Stygian Gulf
    As mentioned by @keithb7 , there’s some nasty solder joints in that amp. Death cap needs to be removed. Another thing I’ve done is to remove the snubber cap (330pf) on the 6V6. Fender put these in due to sloppy lead work. Remove it and see if you have any oscillation. All the SF champs I’ve worked on had this cap. I had no problems with oscillation on any of them after removing it. Also, a screen resistor 1K-1watt is a really good addition for the 6V6. A little extra protection never hurts.
     
  4. Slim Chance

    Slim Chance Tele-Afflicted

    Posts:
    1,456
    Joined:
    Mar 1, 2011
    Location:
    Beltway, USA
    SanAnTex take heart knowing that when you get the amp sorted, you will have a little gem. Take heed in what those above have said. All good advice there.
     
    SanAnTex likes this.
  5. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas

    Thanks slim chance. With all of this help, I hope to have this gem running in tip top shape soon!
     
  6. keithb7

    keithb7 Poster Extraordinaire

    Posts:
    5,003
    Joined:
    Jan 9, 2010
    Location:
    Western Canada
    It probably works as is, just looks like a poor connection. The cathode cap off the 6V6 has been replaced. Probably not too long ago. Green arrow in pic is pointing to cathode cap I am referring to. However it is right up beside the cathode resistor that gets pretty hot. Resistor is show with red arrow pointing to it.

    The cathode cap could be cooked already. I'd change it, and the resistor to a 3W or maybe the 5W white square type. Then separate them from each other. Get another NOS 6V6 and try things then. Stock is 25uf at 25V. Up it to 25uf at 50V. Stock resistor us 470 ohm 1W. Get that out.

    [​IMG]

    You can see here, the same resistor and cap in a Vibro Champ separated further apart:

    [​IMG]

    Or here is another example in a Vibro-King. I used a 5W resistor in this amp. See the separation distance?

    [​IMG]
     
  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    68
    Posts:
    9,794
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    Should be no big deal...and no, the cap solder joints may not be perfect but unless you have a 100+ watt soldering iron don't try to fix them. It takes a LOT of heat to solder properly to the chassis.

    I'd clean and retension the sockets just because (I'd use cleaner/lube - it tends to work better); then replace the plate and cathode resistors. Rice Krispie noises are usually caused by one - or more - of those 3. Easy fix - hopefully.
     
    Thin69 likes this.
  8. Nightclub Dwight

    Nightclub Dwight Tele-Afflicted

    Posts:
    1,649
    Joined:
    Aug 12, 2016
    Location:
    Pittsburgh
    Hey! Welcome back muchxs. We missed you.
     
  9. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Thanks a million for the identifying these components for me. Like you and muchxs have suggested, I will be replacing these in the very near future (and spreading them apart). Hopefully I can source these at a local electronics store. I will beef up the reisitor and cap like you suggested.. does brand matter with these small parts or aslong as the specs are ok they will work? Thanks again! Y’all are awesome.
     
  10. keithb7

    keithb7 Poster Extraordinaire

    Posts:
    5,003
    Joined:
    Jan 9, 2010
    Location:
    Western Canada
    Cheaper will work. Cheapest will mean +/- 50% of posted values. I’d pay a little more for tighter tolerances.
     
  11. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Ok, thanks. They have the resister here in town, but only have a 22uF at 50V for the cap. I suppose I will order from mojotone or another vender. Thanks again!
     
  12. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    i see where the cathode resistor is, but what or where is the plate resistor? Thanks!
     
  13. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    68
    Posts:
    9,794
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    There are two - the 100k and 2.7 k connected to pins 1 & 6 of the 12AX7.
     
  14. RLee77

    RLee77 Friend of Leo's

    Posts:
    4,361
    Joined:
    May 15, 2016
    Location:
    Nevada
    This needs to be a song lyric.
     
    theprofessor, SanAnTex and BobbyZ like this.
  15. keithb7

    keithb7 Poster Extraordinaire

    Posts:
    5,003
    Joined:
    Jan 9, 2010
    Location:
    Western Canada
    These caps really seem to be a going concern these days. Tonight another broke musician and a broke 70's Fender amp showed up at my door at 7 PM. "Dude, can you fix this? Please."

    I opened it up immediately to find a cathode cap blown to bits. 25uF/25V. It took all of 5 mins to swap in a 25uf/50V and he was off...And down $20.

    @SanAnTex this is a test. See if you can spot the new cathode cap in this 1979 Musicmaster Bass amp:

    [​IMG]
     
    robrob likes this.
  16. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Thanks!
     
  17. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    Did I pass? FAAAA7BC-2F31-4694-B6FC-3750BE475BF4.png
     
    Darkness and keithb7 like this.
  18. keithb7

    keithb7 Poster Extraordinaire

    Posts:
    5,003
    Joined:
    Jan 9, 2010
    Location:
    Western Canada
    You passed. Are you comfortable draining high voltage from caps and soldering in new parts?
     
  19. SanAnTex

    SanAnTex TDPRI Member

    Age:
    32
    Posts:
    80
    Joined:
    Nov 18, 2017
    Location:
    Texas
    I have some experience with a soldering iron but haven’t yet had to drain caps. I will find a tutorial online and make sure the caps are drained with a multimeter.
     
  20. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    68
    Posts:
    9,794
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    That will work fine in place of a 25uf. The low-voltage bypass cap values are not critical like the filter caps or power tube bypass cap. 22 and 25 uf are interchangeable.

    Wow - that's very unusual. And if it was "blown to bits" I'd be looking for the cause. Low voltage caps rarely "blow to bits" - they are only passing 1-2 volts.

    IMO that indicates the cap was hit with excessive voltage, something shorted or there's an intermittent problem with tube itself . Not just the cap.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.