Gah! My amp won't turn on!

Discussion in 'Glowing Bottle Tube Amp Forum' started by Wallaby, Jul 4, 2020.

  1. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    It was last working last night, when I turned it off before I went to bed.

    Is there a checklist of things.. to check?

    It's a Carr Skylark.

    I have another amp plugged into the same outlet and there is power.

    Dang.
     
  2. Javier668

    Javier668 Tele-Meister

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    Fuse.
    Tubes.
    If are ok open and pictures.
     
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  3. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    Thanks Javier.

    I'm also searching around - with no pilot light and no power to the amp - like you say - fuse, cord, power tubes.

    I'll do some swapping and see what I can find.

    This is TRAGIC people!

    :D
     
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  4. Javier668

    Javier668 Tele-Meister

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    The good thing is tube amps always can be repaired.
     
  5. dan40

    dan40 Tele-Afflicted

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    A fuse most likely popped when you tried to power up. In some rare cases a fuse may simply pop due to old age and replacing it with a new one will get you going again. In most cases though, the fuse blew for a reason. Old filter caps are one reason but the most likely culprit is a bad power tube.
     
  6. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I am REALLY appreciating the guidance with this - THANK YOU!

    I have a collection of tubes - I think swapping the 6v6 tubes ( there are 2 ) one at a time is a starting point.

    This amp doesn't use a tube rectifier.
     
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  7. rickthescot

    rickthescot Tele-Holic

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    First thing I try is calling it names and swearing at it. Doesn't usually work but it makes me feel much better.
     
  8. MuddyWolf

    MuddyWolf Tele-Meister

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    Have tried telling your amp its sexy. That turns my amp on.
    Were talking about amps, right?
     
  9. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I think I need a blue pill and 27 minutes before I'm ready :)
     
  10. dogmeat

    dogmeat Tele-Afflicted

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    no point in foolin with the tubes if the pilot light isn't on. so yea..... cord, switch, and fuse first, then a check of the wires to the power transformer.
     
  11. Paul G.

    Paul G. Friend of Leo's

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    You have no pilot light, so first find out why.

    1. Check the mains fuse. If it's ok, replace it and unplug the amp from the wall. Turn on the power switch and connect an ohmmeter between the hot and return legs of the plug (what goes in the outlet). You should get some resistance, but not an open circuit. If you get a reading then your PT primaries, switch and fuse are fine. If not, check the switch. Connect your ohmmeter across the switch terminals. You should read open with the switch off, and continuity with the switch on. If not, your switch is cooked. Replace it.

    If it's not the switch or the fuse, some serious diagnosis is required. If you're not comfortable, it's tech time.
     
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  12. Burning Fingers

    Burning Fingers TDPRI Member

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    Start with the fuse.

    Just because the pilot light is not lit doesn't mean that there is no voltage ...I have seen many dead pilot lights over the years so be careful...if the tube heaters come on then you have a HT voltage problem and maybe a dead pilot light.

    From the owners manual:

    "In the unlikely event that a tube fails, the Skylark is protected by a 1.5 Amp slow
    blow fuse for 120v and 100v (North America and Japan) models or a 0.75 Amp slow blow
    fuse for 220v and 240v (Europe and Asia) models."

    When replacing power tubes use a matched pair for best performance...no bias adjustment is required as it is a cathode biased amp.
     
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  13. Wally

    Wally Telefied Ad Free Member

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    Check the fuse. If it is blown, replace it but pull the tubes before firing the amp up. If you get a lighted pilot lamp, shut the amp down and install the tubes stage by stage starting at the input...one 12A-7 at a time. Fire the amp up with the installation of each tube with the power tubes installed last. If the fuse blows at any point, you have found a problem area....it could be a bad tube and/or failed component attached to that tube.
    Imho, it is likely tech time. Nice amp....don’t cheap out on the service. I advise knowing the voltages and bias numbers even if tube replacement gets the amp running. That means one has o go into a live circuit to take those measurements.
     
  14. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I removed the fuse and inspected it visually

    - there are no burns, scorches, stray wires, just a uniform-looking tight coil inside the glass
    - tested it for continuity at 2kohms with my meter, it tests good
    - both power tubes are seated, not scorched or messed up visually

    I didn't open the amp chassis to look for anything burned or melted or sniff for bad odors.

    I reinserted the fuse and put the amp on standby, and the power tubes glowed. I left it on standby for about a minute, and then moved the switch to the audible position and tap-tested it with an instrument cable ( and my fingers ) and it made the noise I expected to hear.

    I'm starting to think it's just the jewel lamp.

    Is there any reason I shouldn't plug in a guitar and test that all the knobs and switches do what they're supposed to do? I already know the volume works.
     
  15. Wally

    Wally Telefied Ad Free Member

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    If the power tubes are not redplating, play away. D8d you pull the pilot lamp bulb to see if it was burned out?
     
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  16. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I have to figure out how to get the lamp lens off to get at the bulb.

    I'll turn it back on and watch the power tubes and see how they look.

    If the bulb really is the problem - I feel like I'm pretty darn lucky!


     
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  17. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    Here is a photo of the bulb, I have never looked at one of these bulbs before and don't know what normal is. I tested it with my meter, it reads .48 with the meter set to 200 ohms.

    The sleeve of the bulb has "CM47" stamped on it.


    upload_2020-7-5_9-20-6.png
     
  18. tubegeek

    tubegeek Friend of Leo's

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    Blown bulb or perhaps just needs to be re-seated.
     
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  19. Wallaby

    Wallaby Tele-Afflicted Silver Supporter

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    I have a question about fuses.

    I'm able to find 1.5 amp slo-blo fuses, but notice they are rated for 250VAC. Is that suitable for my 120V amp? I assume that 250VAC is the maximum rating of the fuse, but thought I'd ask.
     
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  20. tubegeek

    tubegeek Friend of Leo's

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    Exactly. It's so they can suit 240V equipment or 120V, it's a maximum.
     
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