Power, but no sound

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Phil M, Oct 13, 2005.


  1. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    I posted this at another forum, but I expect it will get a lot more traffic here.

    I'll start by saying I've had at least 10 tube amps over the years, some vintage-y, some new-y. I guess you could say I'm somewhat familiar with replacing tubes and fuses but that's it.

    I got a Tophat Club Royale yesterday, installed the tubes (2xEL84, 3x12AX7), hit the power, and let her chill for awhile. The jewel light was on, the speaker jack was plugged in, and the fuse appeared to be intact too. When I hit the standby, no sound. It made me nervous so I turned it off, waited, made sure the tubes were seated and went through the process a couple more times. No sound. There were also no burning smells, buzzes or anything weird. Everything seemed to be in order, but what might I be doing wrong?

    I intend to get new tubes soon, but I assumed that since these were lighting up fine, I should at least be able to get sound out of it.

    Thanks.
     
  2. Reeek

    Reeek Member

    Messages:
    1,208
    Joined:
    Feb 1, 2005
    Location:
    Reno, NV
    Are the speaker leads connected properly?
     
  3. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    Yes, it's a 2x12 and both speakers have all the connectors fitted.

    What do you think about the possibility of a preamp tube going bad (even though it's lighting up)? Could just one cause a complete lack of sound? I'm thinking of starting with swapping all three preamp tubes when I get home.

    Thanks.
     
  4. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    Does it have an internal HT (high tension, B+) fuse?

    If it has just been shipped to you there's a possibility that something either in the amp, or one of the power tubes, has been damaged, which would blow this fuse immediately on switching the standby to on.

    For some reason some amps seem to have the power fuse on the outside but the HT one on the inside... although it's the one that more commonly blows, if the amp has one.

    If it's not that it sounds like a broken connection in the HT circuit, or possibly the standby switch itself. It could also be a preamp tube but it's less likely actually.
     
  5. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    Thanks, John.

    I don't know if there's another fuse on the inside, but it's a Vox style combo amp with the controls on top. I think I can just pop off the back panel.

    If there is an internal fuse, would it be near the "on" switch?

    If I see a fuse inside there, is there any danger in trying to replace it?

    Also, if there is a blown fuse, I'm surprised that the light would come on and the tubes would start to heat.
     
  6. AL30

    AL30 Member

    Messages:
    2,971
    Joined:
    Jul 20, 2005
  7. Erik

    Erik Member

    Messages:
    1,683
    Joined:
    Oct 14, 2003
    Location:
    Late, great, state of NY
    If there's an internal HT fuse, that's exactly what would happen. Not all amps have more than one fuse, but quite a few of them do. My buddy's 5150 has one fuse on the back of the amp which is visible, and there's another fuse inside the head...your amp might be like that.

    Hey Phil, did you tap on the tubes to see if they were all making sounds? Sometimes fuses and tubes can appear to be working just fine, but no juice is going through them. I kind of doubt a tube is blown...but you never know until you rule everything out. How well do you know the seller...could you depend on him or her telling you the truth on the history of the amp?

    When one of my preamp tubes was blown, it still lit up...but no sound came from it. (It was in the V1 position.)

    It could also be a bad solder joint that got damaged during shipping.

    BTW, that's a really cool link that AL30 provided.
     
  8. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    Howdy, Erik. I didn't get home until 1AM and was in to work by 7AM. I really only messed with it yesterday afternoon when I ran home.

    I don't know the seller at all, but he seemed like an OK guy and is visible on other forums. I guess you never know, but I'm giving him the benefit of the doubt. Of the 4 or 5 amp transactions I've done (as both buyer and seller), only ONCE was there not a tube problem so I've had it on both ends. Shipping amps SUCKS.

    That sounds promising actually, and I hope it is that simple. One of the preamp tubes did look more questionable than the other two, but it still lit up. Still, I always figured it would just sound bad, not be totally inaudible. Never seen this particular issue.

    I agree, AL30, cool link.
     
  9. AL30

    AL30 Member

    Messages:
    2,971
    Joined:
    Jul 20, 2005
    I hope the link helps. I use it a lot.

    That's RG Keen's page and it is loaded with very good info - mainly about pedals. If you have time and the interest his "Technology of..." series of papers is fantastic. It breaks down pedals to the roots and goes into detail about how each part effects the overall sound - tube screamer, fuzz face, wah pedals etc. Great reading material.

    Here is the main page http://www.geofex.com/

    Good luck with the amp.

    AL
     
  10. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    Anyone got any other ideas based on my description?

    I talked to the local amp guru, but I won't be able to bring it to him until next week because he's going away for the weekend. I described it to him over the phone and he didn't think it was tubes. Besides, I put some known good ones in there and also tried my own speaker cabinet. He said something about possibly a disconnected wire or maybe a problem with the rectifier/transformer.

    Remind me never to buy or sell an amp online again. These things cost too much for this kind of headache right out of the gate.
     
  11. Reeek

    Reeek Member

    Messages:
    1,208
    Joined:
    Feb 1, 2005
    Location:
    Reno, NV
    I would follow up on what John and Erik said. I had an old Peavey Triumph 60 tube head that had the same type of fuse. The panel lit up but the amp didn't work until the internal fuse was replaced.
     
  12. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    I checked and there is no internal fuse. Just the one on the outside.
     
  13. Erik

    Erik Member

    Messages:
    1,683
    Joined:
    Oct 14, 2003
    Location:
    Late, great, state of NY
    Hey Phil, if the guru your talking about is out of town until next week...try giving John at Main St. Music in Webster a call. I know he does do amp repairs...one of the guitarists in Loopus kept having the exact same problems you describe with his amp and John fixed it. Granted, it wasn't a Top Hat and I'm sure the turnaround time won't be as quick as John Nau usually is, but it might be worth a try. He's a straight up guy, if he doesn't know or if he can't do it...he'll be up front about it.

    If it isn't any of the tubes, and the seller was honest about it working before shipping it out...it is probably just a bad solder joint or contact point. If it was a rectifier/transformer problem, it probably didn't work before the guy shipped it out. (But you already know that.)
     
  14. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    HA! He was the first person I called as that's the closest store to my house and I thought he might have EL84s in stock. He started asking me some questions and then started trouble shooting. He's the one that initially scared me about the tranformer, and after talking to John Nau, he might be right. I didn't know that John from the music store could do amp repairs, but he certainly seemed to know his stuff.
     
  15. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    I gave it another whirl. The preamp tube in V1 didn't look as bright as the other, so I swapped it again. Now, if I crank the volume (preamp) and master all the way up, plug into input 1 and engage the fat boost switch, I can actually hear something very faint. If I sit right next to it, I can hear overdrive and can notice when switching pickups. Again, the amp is cranked and the sound is extremely quiet, but I can hear SOMETHING which is an improvement from the other day.

    Whatcha think? New power tubes?
     
  16. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    OK, I'll finalize this post. The amp is fine for the most part. The problem I THINK was a couple of things. Like I said, when I swapped the preamp tubes around again I could get marginal sound, but still not right. Out of frustration, I started toggling the boost switch on the amp back and forth and BAM! Sound. Very loud sound. It went away later when I moved the amp, but I got it to come back and it hasn't happened since. I also plugged some of the tubes into another amp just to test, and they made weird stuff start happening, especially in V1. One of them were OK, I chucked the other two.

    As for the switch, I've been recommended contact cleaner. At the very worst, I'm not too worried about having that replaced.

    Thanks.
     
  17. Erik

    Erik Member

    Messages:
    1,683
    Joined:
    Oct 14, 2003
    Location:
    Late, great, state of NY
    Cool...so it sounds like the amp probably worked fine...before it got shipped. Looks like a soldering job will fix it just fine.
     
  18. Phil M

    Phil M Supporting Member

    Messages:
    10,355
    Joined:
    Apr 25, 2002
    Location:
    Rochester, NY
    Yep. I need to get some backup tubes too since I used the last of the 12AX7s. The EL84s get really hot too, so I suspect they won't last long.
     

Share This Page