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 Tubes4hifi.com products and all Dynakitparts.com products


    Low PH 10 phono volume in PAS 2

    Share

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Low PH 10 phono volume in PAS 2

    Post by Dingojazz on Fri Jun 05, 2015 9:15 pm

    Hi All

    Just completed VTA Aikido Linestage rebuild of PAS 2.  Very cool sounding.

    Time to add PH 10 phono stage build...

    uh oh... phono  comes on and is audible, but volume is very low.  Not just low gain, but like need to turn volume to "10" and still low, as in "2.5" on volume scale low.

    Before the new board upgrade, phono worked fine.  With new PH 10, no distortion, in fact, sounds pretty good, just no volume...  

    Will pull it down and check layout and connections.  Any experienced help as to where to begin to look for troubleshooting much appreciated.

    Thanks in advance,

    K.

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    No help?

    Post by Dingojazz on Sat Jun 06, 2015 4:45 pm


    Jeez, no ideas? Someone has to have run into this... No?

    K.

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Low PH 10 phono volume in PAS 2

    Post by Bob Latino on Sat Jun 06, 2015 6:38 pm

    Are you sure that the two tubes that you are using (12AY7) on this board are good ? IOW have you eliminated the tubes as a source of the problem with low output ?

    Bob

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Good tubes

    Post by Dingojazz on Sat Jun 06, 2015 9:21 pm


    Hi Bob,

    Yes, first check. Two sets of brand new 12AY7s, both with exactly the same result.

    This may be purely coincidental, but tube #1 looks slightly dimmer than #2 in the board for both brands of 12AYs.

    K

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Allright

    Post by Dingojazz on Sun Jun 07, 2015 10:17 am

    So, I guess what I'm gonna try is to pull some voltages from the schematic and check with VOM.

    It'll be interesting, because I'm not especially adept at reading schematics, but hey, it's a starting place.

    Recommendations accepted for likely locations pin #s, Rs, caps, etc. gladly accepted

    If I find anything that looks wonky, I'll may post back here for ideas / next steps.

    Thanks,

    K

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Ok, it appears that

    Post by Dingojazz on Sun Jun 07, 2015 1:07 pm


    There's only about 200v coming off the power supply B+ out, and the schematic calls for 250-280v depending on which one I'm looking at. There are also corresponding lowered values around the PC 6 board, which I expect may be a result of the upstream issue.

    Seems odd tho, that the same power supply / hookups to the old PC 6 didn't manifest any issues with output...

    Thanks,

    K.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Low PH 10 phono volume in PAS 2

    Post by tubes4hifi on Sun Jun 07, 2015 1:16 pm

    are you using the v14 regulated power supply? stock power supply, standard upgrade power supply, or v13 regulated supply none of them will work,
    you need the higher current rating of v14 (or newest v17) power supply, that's why ALL of your B+ voltages are low, and probably extremely low filament voltage.
    My PAS upgrades are now sold by TubeNirvana, check here. . . . . http://www.tubenirvana.net/pas3-power-supplies.html

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Ok then

    Post by Dingojazz on Sun Jun 07, 2015 1:50 pm

    Yes, although it's not marked, it's probably the "standard" power supply upgrade from a few years back.. thus inadequate.

    I have the v14 PS upgrade already with the "ultimate" upgrade package, I hadn't yet added it as I was replacing the boards singly, hoping thereby to decrease the overall install error potential.  

    The "v17" wasn't even available 2 weeks ago when I ordered the package... Things do change fast around here!

    Okay, good to know.  I'll add the upgraded PS and see what's what.

    Thanks all for the information,

    K.

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Resolved

    Post by Dingojazz on Mon Jun 08, 2015 11:34 am


    Issues resolved by installing the v14 Power Supply. All voltages are up and unit is breaking in.

    Cheers, and thanks to all who chimed in.

    K.

    Sponsored content

    Re: Low PH 10 phono volume in PAS 2

    Post by Sponsored content Today at 3:01 pm


      Current date/time is Mon Sep 26, 2016 3:01 pm