Vintage tube gear care

Discussion in 'Tube Audio' started by Thatch_Ear, Jul 26, 2002.

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  1. Thatch_Ear

    Thatch_Ear Addicted Member

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    If there is an interest I would be happy to provide ways to warm up with a variac, clean potentiometers and generally go about the cleaning and caretaking of a vintage amp to get it up to speed. This is not by any means a cure all but just a guideline for getting old tube amps up and making sweet sounds. If you follow these basic rules then it makes it easier for a tech to find large problems if they exist. So it is a win win situation. Often the way a piece of gear sounds after a propere warming up can tell you not only if something is wrong but what it is. I am far from being an expert at fixing gear but have gotten very good at avoiding problems through improper warm ups. If you want to play with vintage tube gear there is definatly a method to getting things to work right unless they are broke. Don't go through the method and you do stand chances of creating 60 cycle hums and other bad things that High Voltage gear does not hold in common with Low Voltage Solid State gear.
    Thatch
     
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  2. Thatch_Ear

    Thatch_Ear Addicted Member

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    Here it goes.

    First of all if you run across one of those great finds hope that no one plugged it in to see if the tubes lit. Chances are they did, but maybe for not very long.
    The first thing to do with an old piece of gear is to check the tubes. That might be the reason it was taken out of service to begin with. The second thing is to make sure you get all working tubes back in their original places so before you do the first thing mark the tubes so you know where they were placed.
    Usually a bit of cleaning is in order and a large soft bristled paint brush is a great dusting tool to start with. Get rid of much dust as you can.
    Bake the piece. I know it sounds strange but remove the bottom cover, check for strange deposits of wax or capasitor oil and if none is present then pop it in to the oven upside down. If you can set at at 175 that will be good. The upside down is to allow any moisture inside the transformers to escape. Do it right side up and steam can get trapped and later short out your transformer. The reason for this is that carbon resisters will slowly get moisture ridden and go out of tolerance. This is to get them back in so a couple of hours will take care of that.
    Needless to say, carefully look power cords and replace if need be. Check the fuse, you want it to be original ,ie, old.
    Now you are ready for the variac and if you are warming up a preamp or tuner you are set to go if everything is ok at that point. Power amps you need to remove the power tubes. I am not real clear on why you don't want power going to all the circuits but at this point you are worried only about the power supply and especially the large filter caps in it. If you have a doubt about the caps abiltity to take a charge you can remove all but the rectifier tube and leave it plugged into the variac at 30 volts for 12 hours or more and put a volt meter on it and watch to see if the voltage falls quicky or slowly when the amp is turned off. Slowly is what you want.
    Start your warm up at 40 volts. You can hike the voltage 10 volts at intervals of at least an hour. If you take days to this it is better than rushing it. Also with the power tubes out of any amp you don't have to worry about having a load on it.
    10 volts at at least one hour intervals till you get to 90 volts. At that point walk off and leave it for 12 to 24 hours. After that you can hook your preamp and tuner into a system and proceed with the 10 volts per hour. For an amp or reciever that has an amp in it you need to hook it up to some speakers (power off please) and put your power tubes back in, let it go for an hour and then finish at 10 volts per hour till done.
    Now that your gear is fired up and you can hear it you listen for hums and pops. No hums mean that your caps are ok at this point. Pops can mean a short, bad solder connection or a bad potiometer. You can check out the pots by moving and wiggling the knobs. Pots and cleaners next time.
     
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  3. JonTee

    JonTee Well-Known Member

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    Thatch,

    Do you recommend a soft start on a vintage amp that has been out of rotation for a while? I recently started up one of my tube amps by incrementally turning up the voltage (via a variac) over a 10 minute period. The amp hadn't been used in 3 month's. Is this approach valid or even necessary?

    Jon Tee
     
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  4. Thatch_Ear

    Thatch_Ear Addicted Member

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    I don't know that it is needed but did the same myself spending about 1/2 hour with the power tubes out.
     
  5. Andyman

    Andyman Scroungus Stereophilus Subscriber

    Hi Thatch.

    I've been bringing my Heathkit W-5M up as you describe and just finished with it going all night at 90 volts w/ the power tubes out. I need some clarification on what to do now.

    It seems from you post that I should turn it off, add a preamp, tuner and speaker, replace the power tubes and turn it back on. At that point you say to do the 10 volts per hour thing. But what do I start from? Go back to the 90 volts and go from there? Or go back to 40?
    Also, do I play it; i.e. turn up the volume on the preamp for this final stage.

    TIA, this is a great thread!
     
  6. Thatch_Ear

    Thatch_Ear Addicted Member

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    Start at 90V with the power tubes in.
     
  7. Thatch_Ear

    Thatch_Ear Addicted Member

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    Sticking it in an oven that is lower than operating temp of the trans and tubes won't melt the cord or anything. 125*F (52*C) for a couple of hours with it upside down and you have no moisture problem and if the old carbons have drfted because of damp they just might go back into specs.
    Some people seem to have a big problem with this idea, but I do it all the time and so far it hasn't hurt anything on any piece. Everything is rated to 80 to 85*C. Just as long as you stay well under that your fine. Heck even running it upside down is better than letting a bit of moisture turn to steam up in the coils get a short while you have your hand on it, you better hope your not the best ground going at the moment!
     
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  8. NOSValves

    NOSValves AK Subscriber Subscriber

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    Thatch,

    I like the oven Idea sounds reasonable to me. Great advise !
     
  9. Thatch_Ear

    Thatch_Ear Addicted Member

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  10. Kegger

    Kegger Anything can be S "MODed" Super Mod Subscriber

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    This is still a very good post..

    I would like to add after getting the piece up and running if you follow this method
    to see what kinda shape the piece is in, to still replace "all" of the electrolytic caps
    plus any coupling caps in a unit you are planning on using.
     
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