Bewitched Bothered and Bewildered. Have I forgotten how to read a schematic? Did someone forget to send an important page in my kit? I received a pre assembled board so I'm assuming it's wired correctly. The NFB leads have me baffeled. In the instructions and the schematic and the wiring diagram on the website show one lead from each channel going to the output strip. My board came with a twisted pair from each channel. I've wracked my poor old brain and can not figgure out how to wire them. HELP
3 posters
Tubes4hifi VTA70 v12-ccs driver board HELP!
charlief64- Posts : 13
Join date : 2012-12-21
Bob Latino- Admin
- Posts : 3276
Join date : 2008-11-26
Location : Massachusetts
Charlie,
On a stock ST-70 amp conversion to the VTA driver board > On both channels the 16 ohm tap on the terminal stip has a yellow wire from the transformer connected to that 16 ohm tap. There should also be another wire going from the 16 ohm tap to each of the two "NFB" eyelets on the STOCK ST-70 driver board which are eyelets 12 (left channel) and 13 (right channel). You just extend these two wires that once connected to eyelets 12 and 13 on the stock board to the two NFB eyelets on the VTA driver board.
Bob
On a stock ST-70 amp conversion to the VTA driver board > On both channels the 16 ohm tap on the terminal stip has a yellow wire from the transformer connected to that 16 ohm tap. There should also be another wire going from the 16 ohm tap to each of the two "NFB" eyelets on the STOCK ST-70 driver board which are eyelets 12 (left channel) and 13 (right channel). You just extend these two wires that once connected to eyelets 12 and 13 on the stock board to the two NFB eyelets on the VTA driver board.
Bob
charlief64- Posts : 13
Join date : 2012-12-21
Thank you. Each pair that came soldered to the board has a green and a white wire. It looks like the white wire is a ground. Is that correct?
Thanx again
charlie
Thanx again
charlie
Bob Latino- Admin
- Posts : 3276
Join date : 2008-11-26
Location : Massachusetts
Charlie,
Post a photo of the board with the wires - BUT - It is pretty simple for the NFB eyelets > A wire goes from each NFB eyelet to the 16 ohm tap on the two speaker terminal strips.
Bob
Post a photo of the board with the wires - BUT - It is pretty simple for the NFB eyelets > A wire goes from each NFB eyelet to the 16 ohm tap on the two speaker terminal strips.
Bob
charlief64- Posts : 13
Join date : 2012-12-21
The green wire in the pair go to the NFB eyelet. The white wire goes to the boards ground. So with the green wire to the 16 ohm post I think I'm good. 
Cant get the picture to be larger sorry
Cant get the picture to be larger sorry
Roy Mottram- Admin
- Posts : 1838
Join date : 2008-11-30
Hi Charlie,
yes, the green wire is NFB and the white wire is ground.
BTW, do you have the ground wire of the speaker outputs grounded to chassis?
It won't work correctly if you don't.
You don't really need to connect the other end of the white wires, as it's already grounded on the PCB, it's just their as a "shield".
Connecting them would actually form a couple of ground loops . . .
yes, the green wire is NFB and the white wire is ground.
BTW, do you have the ground wire of the speaker outputs grounded to chassis?
It won't work correctly if you don't.
You don't really need to connect the other end of the white wires, as it's already grounded on the PCB, it's just their as a "shield".
Connecting them would actually form a couple of ground loops . . .
charlief64- Posts : 13
Join date : 2012-12-21
Yes. the speaker ground is grounded to the chassis. I thought the white wire might act as a shield. It is not connected to any thing. Thank you for your help
Charlie
Charlie