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    VTA driver board - resistors heat

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    simonfck

    Posts : 15
    Join date : 2013-03-04

    VTA driver board - resistors heat

    Post by simonfck on Tue May 07, 2013 9:08 pm

    Just complete my VTA 70 form bob, sound very good clear than my friend's st70
    but the resistors on the PCB is very hot. R11 ~R13 also R19 ~R22
    is it normal ?


    gz34
    pin 2 448 VDC
    pin 8 448 VDC


    EL34

    pin 1,8 0.4 VDC
    pin 2, 7 3.5 vdc ????
    pin 3 436 VDC
    pin 4 436 VDC
    Pin 5,6 43 VDC
    pin 8 0.4 VDC

    quad cap

    section #1 half circle 439 VDC
    section #2 no symbol 440 VDC
    section #3 triangle 385 VDC
    section #4 half square 449 VDC


    I can not get 6.3VDC on el34 pin 2,7 what should i check ?anyway still play music good.



    Last edited by simonfck on Wed May 08, 2013 12:36 am; edited 1 time in total

    corndog71

    Posts : 454
    Join date : 2013-03-19
    Location : It can get windy here

    Re: VTA driver board - resistors heat

    Post by corndog71 on Tue May 07, 2013 9:54 pm

    I think the 6.3 volts should be AC.

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA driver board - resistors heat

    Post by Bob Latino on Tue May 07, 2013 10:02 pm

    The 6.3 VAC should be ACROSS pins 2 and 7. The 3.5 VAC from either pin 2 or pin 7 to chassis ground equates to about 7 VAC across the two pins. This is a little high - but OK. Your other voltages are pretty much normal.

    Yes - the resistors get pretty warm ... perfectly normal

    Nothing wrong here ... Listen to the music ...

    Bob

    simonfck

    Posts : 15
    Join date : 2013-03-04

    Re: VTA driver board - resistors heat

    Post by simonfck on Tue May 07, 2013 10:07 pm

    Thanks bob and corndog71. i'll check pin2 and pin7 again thanks you guys.

    simonfck

    Posts : 15
    Join date : 2013-03-04

    Re: VTA driver board - resistors heat

    Post by simonfck on Wed May 08, 2013 12:15 am

    EL34

    ACROSS pins 2 and 7 6.71 vac

    gz34
    pin 2 453 VDC
    pin 8 453 VDC
    pin 4 369 VAC
    Pin 6 369 VAC

    btw over all 5 volts high than earl morning
    that's a little high at night. maybe I'll get VOLTAGE REGULATOR.
    how about this one I have Transcendent Grounded Grid Preamp, JoLida CDP, VTA ST70
    is it good enought ?

    http://www.ebay.com/itm/221195867176?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA driver board - resistors heat

    Post by Bob Latino on Wed May 08, 2013 6:52 am

    That voltage regulator (variac) is fine for use with a VTA ST-70.

    Bob

    sKiZo

    Posts : 1313
    Join date : 2013-04-01
    Location : Michigan USA

    Re: VTA driver board - resistors heat

    Post by sKiZo on Wed May 08, 2013 1:50 pm

    Same test voltages on the ST120 board?

    Be nice to have a set of references for the different boxes if and/or when they're needed for troubleshooting. Maybe even a sticky?

    PS ... I got the exact same model variac for bench work a few years back and it's been trouble free. I did a long term test a bit back when it was pointed out that it would make a good step down transformer for a tube amp and found out it does take a while to stabilize. Turn it on with the Kill-A-Watt plugged into the power out, set it to maybe 117vac, and a hour later it had drifted up a couple. Re-adjusted it, and it stayed pretty much on center for the next couple days anyway, with the slight drops you'd expect in a 100 year old farm house when something big like a furnace kicked in. Anyway, I figure just leave it on if you're using it as a voltage regulator driving the amp. Or set it a little higher so you end up with good power that's still in a good operating range.

    Probably a good idea here as my voltage AVERAGES 122+ according to the Kill-A-Watt ... handy tool btw for those who don't already have one.

    Real deal ... what amazes me is they still do free shipping. Those things weigh like a dead horse.

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: VTA driver board - resistors heat

    Post by tubes4hifi on Wed May 08, 2013 4:49 pm

    that's a GREAT price on that variac, and free shipping!
    everybody that doesn't have one, should get one!

    sKiZo

    Posts : 1313
    Join date : 2013-04-01
    Location : Michigan USA

    Re: VTA driver board - resistors heat

    Post by sKiZo on Wed May 08, 2013 6:19 pm

    Maybe two!

    Show us your variacs!!



    (It's in there somewheres) tongue

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