Switching the dual voltage PT taps

All about iron and copper.

Moderator: VelvetGeorge

User avatar
VelvetGeorge
Site Owner
Posts: 7233
Joined: Tue Oct 14, 2003 5:12 pm
Just the numbers in order: 13492
Location: The Murder Mitten
Contact:

Switching the dual voltage PT taps

Post by VelvetGeorge » Wed Oct 25, 2006 8:11 pm

Let's get all the info in a thread for this. I'm getting a lot of emails.

The theory behind this is:

You switch the full high voltage supply lower taps in the secondary wind.
About 40 volts less AC supply to each side of the diode bridge results in about 100 volts less DC.

So (4) wires from the high voltage secondary are switched going into the rectifiers.

When the voltage is dropped, we also need to lower the bias voltage to maintain our intended idle current.
In the diagram I accomplish this by switching an extra resistor into the bias voltage supply from the PT.

The value of this resistor should be adjusted to make your tubes bias at the preferred current in the low voltage setting.


VG
Attachments
VOLTAGE SWITCHING copy.jpg
(101.63 KiB) Downloaded 7741 times
Check out Plexi Replicas for my personal amp builds...
Image

User avatar
5150loveeddie
Senior Member
Posts: 3340
Joined: Mon Apr 12, 2004 8:52 pm
Just the numbers in order: 13492
Location: Montreal, Quebec CANADA

Post by 5150loveeddie » Wed Oct 25, 2006 8:19 pm

Cool info VG, thanks
Glutathione increase specialist

http://www.max.com/science/448523/full/ ... lutathione" onclick="window.open(this.href);return false;

User avatar
5150loveeddie
Senior Member
Posts: 3340
Joined: Mon Apr 12, 2004 8:52 pm
Just the numbers in order: 13492
Location: Montreal, Quebec CANADA

Post by 5150loveeddie » Wed Oct 25, 2006 8:19 pm

Cool info VG, thanks
Glutathione increase specialist

http://www.max.com/science/448523/full/ ... lutathione" onclick="window.open(this.href);return false;

User avatar
VelvetGeorge
Site Owner
Posts: 7233
Joined: Tue Oct 14, 2003 5:12 pm
Just the numbers in order: 13492
Location: The Murder Mitten
Contact:

Post by VelvetGeorge » Wed Oct 25, 2006 8:23 pm

Nice avatar!! Thank you JF!

VG
Check out Plexi Replicas for my personal amp builds...
Image

User avatar
rockstah
Senior Member
Posts: 12481
Joined: Thu Sep 15, 2005 12:28 pm
Just the numbers in order: 7
Location: Austin Texas

Post by rockstah » Wed Oct 25, 2006 8:31 pm

excellent! seems simple enough. thanks George!

Billy Batz
Senior Member
Posts: 8566
Joined: Fri Dec 10, 2004 8:49 pm

Post by Billy Batz » Wed Oct 25, 2006 10:10 pm

The allusive VV switch has finally been made public by the man himself.

User avatar
5150loveeddie
Senior Member
Posts: 3340
Joined: Mon Apr 12, 2004 8:52 pm
Just the numbers in order: 13492
Location: Montreal, Quebec CANADA

Post by 5150loveeddie » Wed Oct 25, 2006 10:30 pm

VelvetGeorge wrote:Nice avatar!! Thank you JF!

VG
Let me know if this is a little to sexy!! I'll change it!!!!
Glutathione increase specialist

http://www.max.com/science/448523/full/ ... lutathione" onclick="window.open(this.href);return false;

User avatar
Guitar Adjuster
Senior Member
Posts: 1560
Joined: Mon Oct 31, 2005 8:34 pm
Location: San Antonio

Post by Guitar Adjuster » Wed Oct 25, 2006 11:05 pm

I think your Boobs look great, leave them alone! :twisted:

User avatar
Flames1950
Senior Member
Posts: 9294
Joined: Sun Feb 08, 2004 1:04 am
Location: Waukee, Iowa

Post by Flames1950 » Wed Oct 25, 2006 11:21 pm

5150loveeddie wrote:
VelvetGeorge wrote:Nice avatar!! Thank you JF!

VG
Let me know if this is a little to sexy!! I'll change it!!!!
She's sure got her party hats out...... :shock:
Image

User avatar
antosimoni
Senior Member
Posts: 498
Joined: Wed Jul 12, 2006 9:45 am
Just the numbers in order: 7
Location: Fl

Post by antosimoni » Thu Oct 26, 2006 5:46 am

George,
sorry but to me its not clear where I've to put that 27K res in my 1959HW, any help will be appreciated, thanks a lot to every1 :D

User avatar
Flames1950
Senior Member
Posts: 9294
Joined: Sun Feb 08, 2004 1:04 am
Location: Waukee, Iowa

Post by Flames1950 » Thu Oct 26, 2006 7:10 am

antosimoni wrote:George,
sorry but to me its not clear where I've to put that 27K res in my 1959HW, any help will be appreciated, thanks a lot to every1 :D
The 27K should already be on the turret board in the 1959HW.........that's part of the bias section which was already there.
Image

User avatar
antosimoni
Senior Member
Posts: 498
Joined: Wed Jul 12, 2006 9:45 am
Just the numbers in order: 7
Location: Fl

Post by antosimoni » Thu Oct 26, 2006 8:40 am

Flames1950 wrote:
antosimoni wrote:George,
sorry but to me its not clear where I've to put that 27K res in my 1959HW, any help will be appreciated, thanks a lot to every1 :D
The 27K should already be on the turret board in the 1959HW.........that's part of the bias section which was already there.
hi this is mine, could you please point me where this 27K res have to be placed??? lots of thanks if you can help me...
Image

Image
thanks a lot for any advice will come in :wink:

User avatar
wdelaney72
Senior Member
Posts: 1619
Joined: Sun Jan 22, 2006 9:04 pm
Location: Chicago Suburbs

Post by wdelaney72 » Thu Oct 26, 2006 9:44 am

But George, according to the Caswell, Bray, and Assclown business model, you are supposed to keep this a big secret. :roll:

Thanks for sharing. I'm about 75% done with my 12xxx, which includes the switchable PT.

robert
Senior Member
Posts: 862
Joined: Wed Jul 19, 2006 4:15 am
Just the numbers in order: 7
Location: Bancrupt Euroland (Germany)

Post by robert » Thu Oct 26, 2006 9:51 am

Hi wdelaney72,

regarding the Assclown-builders: obviously George doesn't like goop as much as Howie did in his 7umble amps...

Regards

Robert

User avatar
wdelaney72
Senior Member
Posts: 1619
Joined: Sun Jan 22, 2006 9:04 pm
Location: Chicago Suburbs

Post by wdelaney72 » Thu Oct 26, 2006 11:51 am

I'm sure George can find a good deal on some black epoxy.

Post Reply