Tube Integrated Power up Question

Discussion in 'Tube Audio' started by newoldguy, Oct 1, 2005.

  1. newoldguy

    newoldguy Member

    Messages:
    95
    Location:
    St. Catharines, Ontario,Canada
    Hello All

    I have a vintage tube integrated amp (garage sale find).I am powering the unit up using the tips in previous threads.I have gone thru 10v steps from 25v to 90v over a 24hr period with the amp presently running at 90v with the power tubes out,4 EL34'S.No problems so far,no shorts,fire, explosions,etc.The rectifier tube is glowing away.
    My questions are, now what next?Do I reinstall the power tubes and continue up to 120v?Do I connect some speakers to it?With or without a source?Listen for noices thru the speakers,hiss etc?Do I need to connect speakers at this stage or just put in tubes and continue to raise voltage?Should I connect some crappy speakers first (old car speakers) or the ones I intend to use (celestion dl8's)?
    This is my first foray into tubes as I have been a solid state guy for awhile.(Mcintosh)Your help will be very much appreciated.

    Regards
    Mike

    PS- My wife will be happy when all the glowing amp stuff is off her kitchen table!!Thanks
     

     

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  2. ldatlof

    ldatlof We are all steak Subscriber

    Messages:
    2,932
    Location:
    Las Vegas
    I am a tube newbie too and have done this only a couple of times. Read the Vintage Tube Gear Care thread (sticky) by Thatch Ear in this forum. At this point, turn off the unit, install the power tubes, a source and a pair of speakers. I am not sure about using car speakers. I would use a pair of the crappiest home speakers that you have. Turn the unit back on at 90V and go up 10V per hour. At 120V turn on the source and listen for excessive hum, popping or crackling. Good luck.
     
  3. Russellc

    Russellc AK Subscriber Subscriber

    Messages:
    5,783
    Location:
    KC MO
    And when you power up, be measuring your bias to see if it is stabilizing or going crazy. I find a unit with a needle dial shows this more clearly, with increasingly wide swings. this indicates ocillation, be ready to shut down before the tubes are damaged. If you have speakers instead of resistors attached, they will be making strange noises for sure! if no ocillation occurs set bias and watch it for 20 min or so, reset and try some sound.

    russellc
     
  4. newoldguy

    newoldguy Member

    Messages:
    95
    Location:
    St. Catharines, Ontario,Canada
    Thanks for the tips guys.

    Russell - How does one go about setting and adjusting "bias".I understand the concept but do not see any place that adjustment could be done.Do I measure this at the outputs on the speaker connections.I have a variety of voa meters and I also prefer an anolog when trouble shooting.I am mostly familiar with auto and marine electrical as that is what I do for a living but am learning electronics as I go.

    Regards
    Mike
     
  5. Russellc

    Russellc AK Subscriber Subscriber

    Messages:
    5,783
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    KC MO
    Does your unit have adjustable bias? Look for some kind of little knobs. On a ST 70 Set your multimeter to dc, black to ground, the other to where the 15.6 ohm resistor connects to the socket, which is connected to the octal socket on the front of the ST70 for a handier measure point. some amplifiers ( like the mcintosh mc225) are not user adjustable, and you dont need to concern yourself with it. What amp are you working with there? When I built my P-P 6550 amp, upon initial power up the meters began to slightly sway back and forth, faster and larger sweeps until I shutdown! I also was shown a neat trick where bya 100 watt light bulb is put in th path of the power cord since I had no variac. Normally the light bulb glows at power on, but then dies down as things stabilize. When the oscillations began, it just glowed brighter and brighter. turned out the schematic I preparrred reversed the leads to the output transformers, once switched and hooked back up, it was stable. If you have some kind of speaker attached, I use an old "project" a 1/2 cu ft box with some kind of polypropelene cone for such occasions. Any oscillation will be accompanied by bizzare sounds as well. Best to have one with a scope look at it, sometimes very high frequency oscillation can be difficult to chase down otherwise. Low frequency motor boating is a little more obvious. Just like swiming, best learning is from diving in and paddling around. After bouncing it off someone who knows what to warn you about. I was fortunate to bump into a guy that did the Mcintosh repair for a large old school stereo store in my area. I came in asking if someone could set the balance on my phase splitters for the least distortion( required signal generator, distortion analyzer, and oscillioscope which I didnt own) and he, liking tube stuff, took a shine to my project and rewired my whole amp! For not a lot of money, I learned a ton about tube P-P power amps and wiring/layout. This was in 1995, and I still use the amp daily, I can't afford anything that comes close to its performance. While it is built on a grey hammond box and looks could only be described as "early industrial frankenstein laboratory" it sounds great and is very reliable.

    Russellc
     
    Last edited: Oct 4, 2005
  6. Russellc

    Russellc AK Subscriber Subscriber

    Messages:
    5,783
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    With this warm up accomplished, I would replace the power tubes, put some large 8 ohm resistors on the outputs, and make and install shorting jacks on the front end, or hookit up to a turned off preamp, and fire it up and take up to normal voltage slowly in a quiet room listening and watching and smelling for anything funny. If all is well, set bias ( if it is the type of amp that allows adjustment here, get manual or state what this thing is), hook up a source and some old cheap speakers. See what comes out! Be ever ready to cut power at a moments notice. Once stable, replace every electrolytic cap in the thing, and maybe the coupling caps. Upgrade power supply, enjoy.

    russellc
     

     

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  7. newoldguy

    newoldguy Member

    Messages:
    95
    Location:
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    Well it appears my amp. A Bell Carillon 6060,does not have easily adjustable bias.I.E. no knobs or screws.I hooked up a pair of old speakers,powered it up over time using my homebuilt lightbulb variac clone,checked for osilation,all seems ok.I will eventually re-cap this unit but that should be a tough one,unit is point to point wired and a bit of a "dogs breakfast".The tubes were checked on a buddies old tube checker and they are all 90%.
    The unit is now running away in my room,hooked to a cheapt cd player and my Celestion Dl8's.The sound is fabulous,very happy and very surprised.Best $5 I ever spent.
    Thanks for all the help,I have learned a lot and am still learning.This unit is my first foray into tubes and I must say I love the sound.May have to think hard of trading in my Mac ss stuf for some Mac tubes,mc275 or a pair of mac40's.

    Regards
    Mike
     
  8. Russellc

    Russellc AK Subscriber Subscriber

    Messages:
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    KC MO
    Great! Sounds like it may be like the mcintosh mc225 I have...its design doesnt require manual adjustment.

    Russellc
     
  9. Russellc

    Russellc AK Subscriber Subscriber

    Messages:
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    Location:
    KC MO
    Have alook at http://www.ece.vill.edu/~cdanjo/bell/bell.html

    Is this your amp?
     
    Last edited: Oct 4, 2005
  10. newoldguy

    newoldguy Member

    Messages:
    95
    Location:
    St. Catharines, Ontario,Canada
    Yup,thats the one.Mine also is in mint shape,not a scratch.Had to replace one bulb.I no little of this amp,got some info. from some folks on here but even a google search only turned up that linc.Thanks for all your help Russell.
    Kinda cool 60's retro look,like a Plymouth Valiant dashboard.

    Regards
    Mike
     
  11. NOSValves

    NOSValves Super Member

    Messages:
    3,344
    What I can't figure out is who or where are people advising powering up a amp without the output tubes? In an amplifier the output tubes are what draws the most current which in turn causes the proper voltage drop in the power supply without them the voltages could easily exceed the rating of the B+ power supply filters. I've even read people advising bringing up a amp with no tubes? IMHO all tubes should be first confirmed to be a good working condition and 2nd they should all be installed in the amplifier for power up with a variac.

    Craig
     

     

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  12. Andyman

    Andyman Scroungus Stereophilus Subscriber

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    Right here.

    Tube sticky

    I wonder if that's why one of the filter caps cooked on my Bogen challenger. It was fine through 90V with the power tubes out, but I lost a cap after I installed the power tubes and moved to 110V from 100V.

    Then again, it could be coincidence too
     
  13. VtgLife

    VtgLife Member

    Messages:
    52
    I hope you still have that amp. $5 mint?! That's a 4 $$$$ figure amp. Jesus

    Edit. - sorry I just realized this post was 14 years old. Lol.
     

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