Visible pcb's ?

Why is the VTA input pcb always visible ? I have seen a few custom builds
that haven't done it like that. You might think it's heat related or..... ?

that's the way Dynaco designed the chassis 60 years ago, easy enough to cover it up if you want to . . .  the only heat is in the tubes
check out this OLD post, can also be made in aluminum . . . . https://dynacotubeaudio.forumotion.com/t622-new-product-vta-driver-board-cover-photo?highlight=VTA+cover

Ok, thanks.

It's become part of the charm of these things. And it motivates one to do a tidy job of stuffing and soldering the board.

To me it didnt seem smart to leave high voltage parts open to touch but wanted to preserve the general look of the stock amps.   I fabricated covers from 6mm thick glass with copper risers to make about 2mm gap between top of chassis and bottom of glass to allow ventilation.

vtshopdog wrote:To me it didnt seem smart to leave high voltage parts open to touch but wanted to preserve the general look of the stock amps.   I fabricated covers from 6mm thick glass with copper risers to make about 2mm gap between top of chassis and bottom of glass to allow ventilation.

I'm doing the same but will be using metal (1,5mm copper).

Dahlberg wrote:Why is the VTA input pcb always visible ? I have seen a few custom builds
that haven't done it like that. You might think it's heat related or..... ?

Keep in mind that the original 70 *did not* have a 'visible' PC Board. There was a cage over the whole shebang to protect users from heat, high-voltage and other dangers involved with exposed tubes and circuits.

Only the modern affectation of removing the cage while the unit is in use gives rise to this question. It was certainly not the original intention.

Given that our household is often overrun with grandkids, and the home of two active cats and two active dogs, the cage remains firmly in place on my 70 & 35, and the LK 150 is above reach of all.

to my knowledge, only the factory wired versions of the ST70 had the small cage over the PCB, none of the kits did

Peter W. is referring to the large cage that covers the whole unit, tubes and all. And his point is that originally the Dynaco ST-70 was conceived as a "covered" unit. The custom of "letting it all hang out" was not a "thing" yet, until the groovy 60s and Free Love.

Ga-rooo-vy, bay bee. Shockingly groovy!

I had a friend that solved this with MkIII :

He had 6 MkIII in a clouset , each driving it's speaker ( Base horn, lowter medium and at that time , jbl treble horns) A little later the base horn was built in the cellar with 2 openings in the floor, 4 by 1 meter large( the horns was made in bricks and concrete and went down to 16hz)
The opening had to be covered by a grid since the dog ( an old english sheepdog fell down causing
a lot of noise.
But the circuit boards was covered !

PS /
the dog was named Donovan, later a few amps was given that name in remembrance of the dog
/DS

Can't see mine ... neener neener!



No heat issues. If anything, I expect the board would run cooler as there's a "chimney effect" that sucks air from under the chassis plate up through the gaps around the tubes.

PS ... I've seen a few with additional holes for accessing the bias pots, but I went with remotely mounted full size pots.

I guess I have an unusual perspective. I see this as five extremely hot items that need to be away from accidental exposure to kids, cats, dogs and other assorted sharers-of-space. The older cat (at 20#) is capable of, and does, jumping from the floor to the top of the refrigerator - so anything exposed has to be 6' up or higher. Otherwise, caged against small hands and paws.

The Scott LK-150 (no cage) moved back into the 'radio room' when we discovered Murphy's jumping prowess - until I install a wider high shelf.

well hey, you can always buy the entire cage cover!!
http://www.dynakitparts.com/dynakit-products/covers/DYNAKIT-ST-70-COVER
rarely but occasionally on ebay for about $30. I sold my spare about a year ago.