Bad Cat - Volume Loss, Crackling after 45 min.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by MountainJam, Aug 14, 2019 at 4:11 PM.

  1. MountainJam

    MountainJam Member

    Messages:
    3
    Joined:
    Wednesday
    Amp:
    early 2000's Bad Cat Hot Cat 1x12 Combo

    Issue:
    A week ago I noticed an intermittent crackling, even without the guitar or effects plugged into amp. Turned amp off for 10 minutes; turned back on and didn't notice issue again over next 20 minutes of playing.

    A day or so later, after 40 min. or so of sounding perfect, there was immediate volume loss. You could still hear the guitar through the speaker, but without gain and at 10% of what it was, and it wasn't responding to the master volume knob. I put the amp in standby mode while I removed the guitar cable from the pedal board and plugged directly into the amp, thinking it could be an issue with my effects. Turned standby off, and the amp was back at full volume and gain, but the same crackling noise mentioned previously started, so I turned the amp off.

    The next day, the exact same scenario occurred. This time I timed it to exactly 45 minutes after starting to play, and again there was immediate volume loss after sounding perfect, so I hit the standby switch and heard a fading sizzle like bacon frying on a pan, then turned the standby off and the volume and gain were instantly back. I hit the tubes again with a pencil and heard no crackling or noise.

    Tubes:

    The power tubes are Ruby EL34s that are 14 months old with about 250-300 hours on them. They look fine, even at the 45 minute mark. No red platting or arcs when the standby is switched. No audible sounds when the speaker is on and I hit them with a pencil.

    Recent work:

    After 12 years of working flawlessly, in 2018 my amp sounded like **** and one of the tubes began red plating. I brought it to a fairly new tech who was under the supervision of a veteran tech and electronics engineer who found a shorted coupling capacitor feeding into the red-platting tube. He replaced the cap and the bias resistors it fried and it's corresponding capacitor on the other tube socket due to the stress from the original shorted coupling cap. He also put in the new power tubes.

    Worth noting:

    The tech noted that my power chord was very loose fitting on the AC output and could fail. I'm still using that chord, but as I said, their is a volume loss, not a volume cut-out like the amp is intermittently losing power.

    Another note: while this could just be in my head, lately I've felt that the tubes and the area around the tubes has been getting hotter than I remember, but I'm not 100% confident that's the case.
     
  2. Rod

    Rod Tone is Paramount Supporting Member

    Messages:
    18,123
    Joined:
    Nov 29, 2004
    Location:
    Area 51 & Seacoast ME
    1....Get a new power cord....and throw that one away....that cord could be your problem!
    2... Spray Deoxit into all the jacks the 1/4” ones on the amp.....front and rear.....
    3.....””””””””””””””””””” all the tube socket pin holders (with of course the tubes removed.).....
    The amp is 12 years old.. it needs general maintenance
     
  3. pdf64

    pdf64 Member

    Messages:
    5,721
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    I don’t think you should expect a long life from power tubes in that amp. Try another pair.
     
    Blue Strat, gldtp99 and Rod like this.
  4. Rod

    Rod Tone is Paramount Supporting Member

    Messages:
    18,123
    Joined:
    Nov 29, 2004
    Location:
    Area 51 & Seacoast ME
    Good point..... my old Hot Cat ran very hot.....
     
  5. gunslinger

    gunslinger Member

    Messages:
    1,456
    Joined:
    Mar 28, 2010
    Location:
    Louis XVI ville, KY.
    It sounds like a bad tube. But this is just a guess.
     
  6. MountainJam

    MountainJam Member

    Messages:
    3
    Joined:
    Wednesday
    Thank you for your replies. I appreciate the help.

    Just went out and bought a new IEC power cable from an electronics store, though it's not as beefy as the one that came with the amp. It definetely fits much tighter.

    The new power cord says 10A - 125V, the old thicker Bad Cat cord says 10A - 250v. Should I be concerned, or are these universal chords interchangeable?

    I also picked up CRC QD Electric Cleaner, as I couldn't find Deoxit. Should I order some online, or are all contact cleaners created equal?

    I'll start by cleaning what you mentioned and using the new power cord.

    If that doesn't help then I'll order a new pair of power tubes.
     
  7. sickboy79

    sickboy79 Member

    Messages:
    11,351
    Joined:
    Aug 17, 2006
    Location:
    Chicago
  8. xtian

    xtian Member

    Messages:
    1,911
    Joined:
    Dec 15, 2010
    Location:
    NorCal
    re: power cord, 125vAC rated is fine, assuming you're in the USA.

    re: CRC spray--do NOT used this for your pots. Pots need lubrication. Use Caig DeOxIt F5 for pots.

    The best DeOxIt for contacts (jacks, tube pins, etc.) is D5 or D100.
     
    Rod likes this.
  9. jthomas666

    jthomas666 Member

    Messages:
    321
    Joined:
    Jun 26, 2016
    Location:
    Downeast Maine
    I am assuming that you have verified that it is not a fuse. That is, the tubes are heating up and the pilot light comes on. You often cannot tell that a fuse is good simply by looking at it.

    If an amp that has been working well stops working for no reason, and if it hasn't been dropped or otherwise injured.... it is almost always a tube. That doesn't hold for new builds.

    You generally cannot tell that a tube has failed just by looking at it. That said, if the tubes look silvery or maybe milky, then the tube may have lost its vacuum. Then you just need a new tube (or tubes). A shorted tube does not have any unusual appearance.

    With a sudden failure it IS smart to make sure that the signal is getting in (i.e. guitar cord is good and the input jack is not loose). It also is smart to make sure that the connection to the speaker is ok. After that, I'd replace the power tubes with known good tubes and see if that fixes the problem. If that doesn't fix the problem, I'd replace the preamp tubes, one by one, with a known good tube. Take out one preamp tube, put the replacement in. If that doesn't help, then put the original tube back in and move on to the next preamp tube, and repeat. Being systematic is helpful.

    If these things do not fix it, you need a tech... or you need to become a tech. Best wishes.
     
    Rod likes this.
  10. Steppin' Wolfe

    Steppin' Wolfe Member

    Messages:
    4,014
    Joined:
    Jul 19, 2007
    Tech time....experienced tech. Full evaluation is necessary, imho. I agree that the power tubes may have been used up in that cathode biased circuit, but I would want a good review...and a voltage chart done with the new tubes IF the tubes are indeed the problem. Just for grins, have you tried subbing in fresh tubes in the preamp and PI? V1 is common to both channels. V2 is dedicated to the gain mode.
     
    Rod likes this.
  11. MountainJam

    MountainJam Member

    Messages:
    3
    Joined:
    Wednesday
    Thanks again for the additional replies.

    1. I used the CRC spray on the toggle switch on my SG and it sounds better (quieter) and switches much smoother than it has in a while, but I stopped there. I will get the DeOxit before I clean anything on my amp.

    2. I just ordered new Ruby EL34s and will try those out when I get them in a couple days. I currently don't have any extra power tubes sitting around to test. If that isn't the issue, I'll at least have extra tubes for when they do fail.

    3. If the cleaning mentioned above, and the new power tubes don't resolve the issue, I will order a new pre-amp tube and systematically replace and test the old ones one at a time as someone suggested.

    4. Tech time...as for this suggestion, I will keep this in the back of my mind as I do the above steps. I don't think the steps above are out of my wheelhouse.

    If I get to a point where I don't feel comfortable doing something I'll pay the $75 (plus parts) for a tech to fix it. I just live in the woods, a few hours from a metro area and don't know any reputable techs in New Hampshire.

    How do you folks find techs to work on high-end gear when you live no-where near the manufacturer (Bad Cat is in California), and when they don't have any certified techs anywhere outside of their state (California)?

    Plus, I need to step up and take responsibility for doing basic maintenance and repairs on equipment I've owned for 14 years. No excuse on my part. I'm just lucky Bad Cat makes amps that work flawlessly for almost 14 years running every day.
     
    Steppin' Wolfe likes this.
  12. Steppin' Wolfe

    Steppin' Wolfe Member

    Messages:
    4,014
    Joined:
    Jul 19, 2007
    A good, experienced tech should be able to deal with any problems in that Bad Cat. Ask questions before giving the amp up for work. Too bad you didn’t order a noval tube or two with the power tubes....saves on shipping and time. And..as you note, you might need them some ime anyway.
     
    Rod and pdf64 like this.
  13. Rod

    Rod Tone is Paramount Supporting Member

    Messages:
    18,123
    Joined:
    Nov 29, 2004
    Location:
    Area 51 & Seacoast ME
    Techs in NH.... I would bring it to Music Mill in Manchester on Elm Street....... ask for their best tube amp tech......and show him this thread! There’s a lot of great suggestions here!
     
    Last edited: Aug 16, 2019 at 3:57 PM
  14. xtian

    xtian Member

    Messages:
    1,911
    Joined:
    Dec 15, 2010
    Location:
    NorCal
    STANDBY SWITCH!!! I just solved a very similar issue with a Carvin V3M head. The standby switch becomes pitted from arcing, and gives all kinds of intermittent trouble. The big clue is that you hear a lot of odd noises when you flip the standby switch, and/or the problem resolves temporarily when you flip the switch. Easy test: use an alligator clip to bypass the standby switch, and test it out.
     
    Rod and pdf64 like this.
  15. pdf64

    pdf64 Member

    Messages:
    5,721
    Joined:
    Aug 9, 2008
    Location:
    Staffordshire, UK.
    The amp uses a GZ34 / 5AR4 rectifier? If switched in tube rectifier mode, then (once you've fixed it) ignore standby, just let the rectifier tube bring the amp's HT up nice and smoothly.
     
    jthomas666 and Rod like this.
  16. Daanh

    Daanh Member

    Messages:
    99
    Joined:
    Mar 12, 2016
    I'm sorry, but I can't resist.

    Maybe you should trade it for a Good Cat?

    Please continue....
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice