My VTA ST-120 is on the way .....and other loose ramblings of an old fart

Not wasting any time ^^     That jig looks véry useful -  got some more pics of it handy Cletus?

Roy wrote:Not wasting any time ^^     That jig looks véry useful  -  got some more pics of it handy Cletus?

Sure thing   ....here yuh go:

Got up early, had my morning brew (coffee that is ...LOL!) and started mounting some hardware and sorting some wires   ....with the output transformers mounted, there's not much chassis real estate at the sides to hold it in the jig.  

Nice - thank you! Our own 120 kit is slated for next month.. Still waiting on my new Hakko 888 and busy building a little soldering fume extractor using some cooking hood carbon filters and car interior hepa filters so my kid can enjoy helping dad during the construction with no worries - this jig will do nicely also

Roy wrote:Nice - thank you!   Our own 120 kit is slated for next month.. Still waiting on my new Hakko 888  and busy building a little soldering fume extractor using some cooking hood carbon filters and car interior hepa filters so my kid can enjoy helping dad during the construction with no worries - this jig will do nicely also

Great when the kids get involved. Growing up, my kids could not care less, except for my daughter who at 6-years old actually helped dad build the VOTT's ...LOL!

Decided to do the "yellow sheet mod" from the get-go.

https://dynacotubeaudio.forumotion.com/t1006-tube-rectifier-diode-mod

CletusB wrote:

Roy wrote:Nice - thank you!   Our own 120 kit is slated for next month.. Still waiting on my new Hakko 888  and busy building a little soldering fume extractor using some cooking hood carbon filters and car interior hepa filters so my kid can enjoy helping dad during the construction with no worries - this jig will do nicely also

Great when the kids get involved. Growing up, my kids could not care less, except for my daughter who at 6-years old actually helped dad build the VOTT's ...LOL!

Well keep in mind   kids take for granted what is   and they  only become aware of what was very gradually over the years..
My dad he was an engineer - very hands on and direct. His hands were like coal shovels in my mind. He did not have a lot of experience with parents - his he lost in WWII.  He  fought his way through life and did pretty darn good for himself and us but yes   we took that for granted.. Things are what they are..  
Lost him nearly 20 years ago, my mother last year - no grandparents for our little one on my wife's side either. Our son is 5 now and he really wants to do everything his dad can do so bad..You want to protect him from stuff and the enthusiasm and vigor is  hard to channel lol - trying to keep him from hurting himself while not scaring him from things keeping him from exploring is a  very fine balancing act I find.
Thinking back now it is hard to find fault with how he approached things. Father and son wise there is an element of competition I realize now. And I think speaking for myself a lot of things I could not share with my father I went out of the way of so as to not háve to compete - dont know if that makes much sense the way I write it sorry

Looking for a guinea pig to test Roy's new auto bias board ... any volunteers? (nudge nudge)  



One thing I'm not seeing that might be handy is connections for a remote pot to fine tune the auto bias point. Some tubes perform better at different settings. Fer instance, I run my TAD KT88str's at 55 and my KT120's at 60. That can also vary based on typical average wall voltage.

PS - one other accessory you should definitely plan on getting ... maybe the best $20 you'll ever spend.



TRC 90033 Shockshield White Portable GFCI Plug with Surge Protection

Ignore the GFCI part - this type of adapter requires a manual reset on any power blips, and can save yer bacon, preventing multiple inrush loads on the more sensitive bits.

sKiZo wrote:Looking for a guinea pig to test Roy's new auto bias board ... any volunteers? (nudge nudge)  



One thing I'm not seeing that might be handy is connections for a remote pot to fine tune the auto bias point. Some tubes perform better at different settings. Fer instance, I run my TAD KT88str's at 55 and my KT120's at 60.

Let's plug it in and see the color of the "magic Smoke"

VTA Driver Board completed ......time out for a beer!

sKiZo wrote:Looking for a guinea pig to test Roy's new auto bias board ... any volunteers? (nudge nudge)  



One thing I'm not seeing that might be handy is connections for a remote pot to fine tune the auto bias point. Some tubes perform better at different settings. Fer instance, I run my TAD KT88str's at 55 and my KT120's at 60.

I see a multi-turn pot on there, could that be the bias "fine-tune"?

Made some progress this evening with chassis wiring:

..you're going to have to order another one at this rate ^^ Not going for an iec socket btw?

Roy wrote:..you're going to have to order another one at this rate ^^    Not going for an iec socket btw?

Nope, no IEC. Toyed with the idea of a 3-wire cord and plug though, using the non-functional STEREO/MONO switch as a ground-lift for the earth wire. We'll see, Don't think I need it though as it would probably just create a ground-loop.

From what I have gathered from those that put in an IEC and grounded the chassis hum will not be an issue with the vta's - only issue is fitting one in.. Won't fit right behind the power transformer so the fuse holder's position is a good spot for it..

Started at the crack of dawn this morning and the progress has been good.  Really a nice kit to work with and no need to shout out to Bob as yet. Excellent instructions Bob !  

A nice touch I think, having it autographed and dated by the Grand-master himself

sKiZo wrote:Looking for a guinea pig to test Roy's new auto bias board ... any volunteers? (nudge nudge)  



One thing I'm not seeing that might be handy is connections for a remote pot to fine tune the auto bias point. Some tubes perform better at different settings. Fer instance, I run my TAD KT88str's at 55 and my KT120's at 60. That can also vary based on typical average wall voltage.

PS - one other accessory you should definitely plan on getting ... maybe the best $20 you'll ever spend.



TRC 90033 Shockshield White Portable GFCI Plug with Surge Protection

Ignore the GFCI part - this type of adapter requires a manual reset on any power blips, and can save yer bacon, preventing multiple inrush loads on the more sensitive bits.

Amen to what Skizo said. *Manual reset* GFCI is a life-saver. Or at least a power-supply saver. Best insurance policy on the planet, even if you have to crawl underneath to re-set it. We get plenty of power blips in northern Idaho this time of year as they switch substations when a tree falls on the power lines due to snow loads. It's *almost* instantaneous but enough to send the pwr supply electrons to war when the juice comes right back on.
No experience with Roy's auto-bias option but if it's anything like the one Don Sachs uses, definitely worth the expense. Don's is a tube-saver, too, as it won't let the outputs red-plate. They merely crap out when they're done, no fireworks. Mine are biased at .68/tube, due to lower plate voltages. Lose a little power in the ST-120 as a result of the lower plate dissipation, but if your speaks are 90+ dB efficient you won't notice. It has held rock-steady for a half-year now and just flat rocks.
You can still check the bias tube-by-tube via a selector switch with a Fluke.
I would definitely investigate.

Got one on order already!  ....TRC 90033 Shockshield White Portable GFCI Plug with Surge Protection (bought the yellow one)

pff  goes to show   a fault can hide well.. Before I got to type here had to fix my pc - would not switch on.. Took it all apart and finally having ruled out a whole lot of other things took out the cpu and found a tiny dust bunny connecting one of the 1155 pins under there... Least its all clean now but   puts to mind a question - do you just visually inspect all the connections Cletus or  before switching it on for the first time do you measure all the connections to make sure?

Good question, and very timely indeed, as we're at the moment of truth now.  My standard procedure is to inspect it very closely one section at a time, take a good break, inspect it again and do as much ohmmeter measurements as possible, then bring it up slowly with a variac or a 100w light bulb in series and observe what's happening with the current.  Of course I will also integrate Bob's writings in the instructions with that protocol.

Drum roll please   .....here she is:

CletusB wrote:My standard procedure is to inspect it very closely one section at a time, take a good break, inspect it again and do as much ohmmeter measurements as possible, then bring it up slowly with a variac or a 100w light bulb in series and observe what's happening with the current.

Maybe I should've been more careful and cautious, I built the M125's and just plugged em right in, with an extension cord at a safe distance mind you.

NO BLUE SMOKE!   She fired right up and biased without any issues!  Sounds absolutely AWESOME! I never thought that I could get kind of quality sound at the modest price that Bob has for these kits !

I will post pics of the completed unit tonight.  

Here she is, check out the Ice Hockey Pucks for legs:

my son next to me here is going like oooooh wow thats the one we are gonna build

Looking good Cletus ! Funny, I just finished that book last week same edition even lol