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    One piece of test equipment you should/must have on your bench

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    Sal

    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    One piece of test equipment you should/must have on your bench

    Post by Sal on Mon May 28, 2012 11:26 am

    There is one piece of test equipment you should have on your bench when building or repairing a tube amp. It is a AC ammeter. I use it religiously whenever I first power up a tube amp for repair or when I build a tube amp like. Let me give you some examples. A stock ST-70 properly biased will pull about 1.7 amps with a 5AR4 tube and a ST-120 biased at 55ma per tube will pull 2 amps. Once you power up your amp, you can monitor the AC ammeter and if the current rises or drops, you can quickly see there is a possible problem. I just tested a amp with a 5AR4 tube, biased it and I noticed the AC amps kept dropping, I rebiased the tubes and the same thing happened. I checked the B+ and sure enough it was slowly dropping. The new 5AR4 tube was bad.

    I have a metered Variac on my bench to monitor the amp and I also have a Kill A Watt plug in digital "meter" that will measure current, watts, volts and killowatt hours. They sell on ebay for about $21 and is well worth it. Here is a seller on ebay that has them for $20.49 with free shipping at http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=360458834329

    Note: I am not affiliated with the seller at all, I just wanted to pass this along.

    Regards,
    Sal

    GP49

    Posts : 735
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: One piece of test equipment you should/must have on your bench

    Post by GP49 on Mon May 28, 2012 1:31 pm

    Agreed. I have a NON-metered variac, and those feedthrough meters work just fine with it.

    Blitzen

    Posts : 47
    Join date : 2009-07-10

    Re: One piece of test equipment you should/must have on your bench

    Post by Blitzen on Mon May 28, 2012 2:44 pm

    Kill-a-watts are even cheaper on Amazon. In any case, a bargain! I've got one on my ST-70 main amp pretty much just for the heck of it- though it's nice to see numbers NOT changing much!

    ruffian

    Posts : 43
    Join date : 2010-02-26

    Re: One piece of test equipment you should/must have on your bench

    Post by ruffian on Mon May 28, 2012 3:54 pm

    The Kill-a-watt is a good all around tool for having around the house. Besides for troubleshooting on the bench, the watthours is great for figuring out how much your appliances cost to run. Like that old extra fridge in the garage with a 6 pack in it, how much is it costing?


    (Best of all, mine came free from some vendor selling computer room power management equipment.)

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