(206) 949-5683, Top Rated Plumber, Seattle
Page 3 of 3 FirstFirst 123
Results 31 to 42 of 42

Thread: Trying to rig a variac switch to slowing raise the voltage on an old tube amp

  1. #31
    DIY Senior Member BobL43's Avatar
    Join Date
    Mar 2011
    Location
    Long Island, NY
    Posts
    1,772

    Default

    Quote Originally Posted by DonL View Post
    I was cheap and bought a compression tool from China.

    I could not see paying 3 times more for one, used at home on occasion.

    Now connectors, I buy the good ones. I like BNC over F, but the new F type are not to bad.


    Enjoy
    Ming was made in China too. Paid 22 bucks in the Amazon Jungle for it. I got the F59 connectors because the lightning supressors I bought have F connections on them. The tool came with dies for BNC and RCA compression fittings too. Its not the best, but once adjusted properly, is does the job correctly. I wrote a review on it in the jungle place.
    I am definitely not a pro plumber, but I am a pro crastinator

  2. #32
    DIY Senior Member CanOfWorms's Avatar
    Join Date
    Feb 2013
    Location
    New Jersey
    Posts
    157

    Default

    Hey guys. Thanks for the input. I actually did this about 5 mintues after I posted this but without the dimmer switch.

    Either way, I blame Bob for the green light.

    I don't know if the fixture was made to daisy-chain or not. It was a builder's basic from the supply house.

    I know that if I put speakers in parallel is cuts the resistence (ohm) in half. But I don't know how that would affect this situation.

    Everything worked out fine regardless.

    Rocket scientist, Thanks for the insult. I noticed you have a hard time with some parts of speach. Maybe that means you should stop typing or possibly even stop speaking English. If you don't know what I mean you should read through your posts. Wait... you wouldn't notice it since you typed it that way in the first place.

    Either way it works and I thought Bob wanted an update. Here is a video I posted when I got it working properly.
    Figuring out how to wire the speakers was a real b--ch. Not only did it require jumpers and dowloading an owner's manual, but also a photo enhancer... don't ask.
    Here's a video. I know I suck. You can make fun of me some more if you want. I don't mind if you don't mind my reaction.


  3. #33
    DIY scratch-pad engineer leejosepho's Avatar
    Join Date
    Nov 2006
    Location
    200 miles south of Little Rock
    Posts
    2,474

    Default

    Quote Originally Posted by CanOfWorms View Post
    I know that if I put speakers in parallel is cuts the resistence (ohm) in half. But I don't know how that would affect this situation.
    Me neither, or at least not for sure, but I believe that might be different since the amp output is determined beforehand where the typical AC lighting circuit is more of an as-needed or "on-demand" system. In other words, the amp circuit needs/wants/expects the load to match the supply where a lighting circuit does not care about the size of the load as long as the demand is not greater than it can handle...but I might be wrong about all of that!

    My Fender Bassman in the '60s was electronic, but other guys I knew would only ever play through tubes. Congrats on getting yours going.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  4. #34
    DIY Senior Member BobL43's Avatar
    Join Date
    Mar 2011
    Location
    Long Island, NY
    Posts
    1,772

    Default

    Oh man Can, you insulted my pal Don; now I won''t even kid around with you anymore here. I'm out. But Don and I DO understand how all this stuff works. By the way, your music video is fabulous and very professional. lol
    I am definitely not a pro plumber, but I am a pro crastinator

  5. #35
    DIY Senior Member CanOfWorms's Avatar
    Join Date
    Feb 2013
    Location
    New Jersey
    Posts
    157

    Default

    I did it just for you Bob.
    I'm sure what's his name is crying in his beer somewhere.

  6. #36
    Jack of all trades DonL's Avatar
    Join Date
    Mar 2011
    Location
    Houston, TX
    Posts
    3,648

    Default

    Quote Originally Posted by CanOfWorms View Post
    Either way, I blame Bob for the green light.

    I don't know if the fixture was made to daisy-chain or not. It was a builder's basic from the supply house.

    I know that if I put speakers in parallel is cuts the resistence (ohm) in half. But I don't know how that would affect this situation.

    Everything worked out fine regardless.

    Rocket scientist, Thanks for the insult. I noticed you have a hard time with some parts of speach. Maybe that means you should stop typing or possibly even stop speaking English. If you don't know what I mean you should read through your posts. Wait... you wouldn't notice it since you typed it that way in the first place.

    Great that you have it working.


    A Insult was not intended, But if the shoe fits then wear it.

    You may have been worried about nothing. The Caps can blow later if they need replaced. Just make sure your amp is fused properly.

    I stand by my Rule, "If you don't know the difference between Series and Parallel electricity, Then You should not be playing with electricity".

    Check out ohms law. The thing that Speakers and AC Line wiring have in common is that they are both AC, Just different output frequencies. And the AC line has a lot more power that can hurt you, If played with incorrectly.


    Thanks for pointing out my English downfalls. I wish I was as good as You. Can you play the French Horn ?

    I am French, and I majored in Electronics, Not English.


    Enjoy.
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  7. #37
    DIY Senior Member BobL43's Avatar
    Join Date
    Mar 2011
    Location
    Long Island, NY
    Posts
    1,772

    Default

    Quote Originally Posted by DonL View Post
    Great that you have it working.


    A Insult was not intended, But if the shoe fits then wear it.

    You may have been worried about nothing. The Caps can blow later if they need replaced. Just make sure your amp is fused properly.

    I stand by my Rule, "If you don't know the difference between Series and Parallel electricity, Then You should not be playing with electricity".

    Check out ohms law. The thing that Speakers and AC Line wiring have in common is that they are both AC, Just different output frequencies. And the AC line has a lot more power that can hurt you, If played with incorrectly.


    Thanks for pointing out my English downfalls. I wish I was as good as You. Can you play the French Horn ?

    I am French, and I majored in Electronics, Not English.


    Enjoy.
    ah, ................................never mind; I did say I was out.
    I am definitely not a pro plumber, but I am a pro crastinator

  8. #38
    Jack of all trades DonL's Avatar
    Join Date
    Mar 2011
    Location
    Houston, TX
    Posts
    3,648

    Default

    Quote Originally Posted by BobL43 View Post
    ah, ................................never mind; I did say I was out.

    You did ?

    But You did not say "Over and Out".


    I must be in the wrong QSO.
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  9. #39
    DIY Senior Member CanOfWorms's Avatar
    Join Date
    Feb 2013
    Location
    New Jersey
    Posts
    157

    Default

    Yeah I overreacted. That's kind of my deal.

    Everyone I talk to that is in the know says this is a very easy recap job. It would certainly be cheaper and easier than replacing the transformers.

    I can't play the french horn, but I can play the didgereedoo.

  10. #40
    DIY Junior Member John in herndon's Avatar
    Join Date
    May 2007
    Location
    VA
    Posts
    25

    Default Using a Variac® to gradually raise the voltage in a tube amp

    I used to be in the audio repair business and used this technique all the time on both tube and solid state amps. It prevents doing a lot of damage if you didn't find all the blown components.

    That said, you have to use a VARIAC® or variable autoformer to do this because this preserves the sine wave of the AC power. Solid state dimmers do not do this. They use SCRs and TRIACs to vary the voltage by delaying the turn on point of each individual cycle of the AC waveform. The result is a non sinusoidal waveform which would not work to power an amplifier or other electronic device.

    If it doesn't weigh 10 pounds or more it is not a transformer and won't work.

  11. #41
    Jack of all trades DonL's Avatar
    Join Date
    Mar 2011
    Location
    Houston, TX
    Posts
    3,648

    Default

    Quote Originally Posted by John in herndon View Post
    I used to be in the audio repair business and used this technique all the time on both tube and solid state amps. It prevents doing a lot of damage if you didn't find all the blown components.

    That said, you have to use a VARIAC® or variable autoformer to do this because this preserves the sine wave of the AC power. Solid state dimmers do not do this. They use SCRs and TRIACs to vary the voltage by delaying the turn on point of each individual cycle of the AC waveform. The result is a non sinusoidal waveform which would not work to power an amplifier or other electronic device.

    If it doesn't weigh 10 pounds or more it is not a transformer and won't work.


    You can use a variable high power resistor also, If you do not need isolation from the mains using a transformer.

    I never have seen a DC transformer that lasted very long. They do not like chopped DC, unless they are designed for it.

    I use a light bulb in series with the AC line and it gives a good indication of your situation.


    Have Fun.
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  12. #42
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Location
    Metro NYC
    Posts
    798

    Default

    Besides seconding the "use a genuine variable transformer" advice, there is also a caution for some circuitry, where it can actually be advisable to construct a replacement for a rectifier tube, using solid-state components and a tube-base connector. I don't have more details at my fingertips, but I know the idea behind the temporary replacement was that the initial low voltage applied in a series of several steps was not going to be enough to make a rectifier tube functional, and the solid-state replacement would function with any input voltage applied to the tube device's power transformer.

Similar Threads

  1. Why do I have voltage when switch is off?
    By Randyj in forum Electrical Forum discussion & Blog
    Replies: 19
    Last Post: 04-28-2011, 01:42 PM
  2. Flickering lights on circuit with low voltage and line voltage bulbs
    By davidwie in forum Electrical Forum discussion & Blog
    Replies: 5
    Last Post: 04-18-2011, 07:34 AM
  3. Wall Socket With Voltage AND No Voltage? HELP!
    By jackvogel in forum Electrical Forum discussion & Blog
    Replies: 2
    Last Post: 12-23-2010, 07:41 AM
  4. Running low voltage in high voltage boxes
    By Ian Gills in forum Electrical Forum discussion & Blog
    Replies: 10
    Last Post: 08-22-2009, 07:27 PM
  5. Installed new low voltage recessed lights - now switch hums
    By taysan in forum Electrical Forum discussion & Blog
    Replies: 15
    Last Post: 05-02-2008, 04:39 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •