The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all products and all products

    Newbie - 1st post



    Posts : 298
    Join date : 2010-11-10

    Newbie - 1st post

    Post by mantha3 on Wed Nov 10, 2010 2:15 pm

    I own a Pocked Digital Multi meeter (22 Range, Voltage, Current, Resistance, Full Auto Range, Diode test) Will this work for setting Bias?

    PS I am new to this and have not yet even built the amp.

    I purchased an ST-120 about 4 weeks ago. I got the unassembled kit, upgraded caps, stepped attenuator.

    I also purchased the KT88 Gold Lions (new issue), Mullard 12AT7 (one for center), Phillips 12AT7 (Left and Right), Sovtek 5AR4 and a Webber Copper Cap WZ68.

    I recently moved to a new home… Wife and kids keep me busy. I'm planning to use some vacation time from work to dedicate to the build. I put some money into the Amp and Tubes so I want to have the home clear of wife and kids for the build… do it right. So I'm getting all the things In need in place.

    I have -
    AMP ST120
    Weller 45 Watt Soldering iron and electronics solder
    Meeter I mention above.
    Tool kit

    Bob Latino

    Posts : 2382
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Newbie - 1st post

    Post by Bob Latino on Wed Nov 10, 2010 2:45 pm

    Hi Mantha3, and welcome to the Dynaco Tube Audio Forum,

    The multimeter you have will work just fine for checking and setting the bias on your ST-120. Some mulitmeter's are "auto ranging" where you just place the black probe on the chassis (ground) and the red probe at the bias measuring point. That tube's bias will read out on your meter. If your meter is not autoranging then set the meter on the DC SCALE to 0-2 volts when you measure bias.

    The bias pots on your amp will work in reverse of a volume control. When you want to turn the bias DOWN, turn the bias pot in a CLOCKWISE direction. When you want to turn the bias UP, turn the bias control in a COUNTERCLOCKWISE direction.



    Posts : 23
    Join date : 2010-09-15

    Re: Newbie - 1st post

    Post by bigmm79 on Wed Nov 10, 2010 2:52 pm

    I recently built an ST-70 and it was my first electronics kit experience.
    Sounds like you have what you need to get started. I would also recommend plenty of space to lay out the parts and working copies of the parts lists and instructions that you can mark up. In my kit most of the resistors were unsorted and unmarked as to value. This may be because I got the low gain version and the resistors came from Roy instead of directly from Bob. I wished I had sat down in advance and sorted the resistors, checking them against the parts list and labeling them, prior to starting any building - so you may want to do that if your resistors are not sorted/labeled.

    Oh also, if your kind of inexperienced, as I was, you will want something to de-solder with. I found copper braid to work much better than the plastic vacuum pumps they sell at radio shack.

    Have fun, its a blast to build these things.


    Posts : 298
    Join date : 2010-11-10

    Re: Newbie - 1st post

    Post by mantha3 on Wed Nov 10, 2010 3:21 pm


    Thanks for the quick posts. I got a new home and a nice work space in the basement with a nice big work bench light overhead. Nice big old table. I can lay things out and then keep the kids out.

    I'll get the copper braid. I'd like to just have the things I need on hand... Then reserve a 3 day or so time frame to work on this. If I don't get this fully done I will hoepfully be close and I'll work a weekend as I have time. I can't wait but I think I'd be better off waiting to have nice long days off VS working an hour here and there after work (with the wife and kids in the mix).

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