Bottlehead Crack and PT-7

[wabibito]

Hello, we have a bottlehead crack using the PT-3.  I read that we can also wire it to use the PT-7 which is supposed to be more quiet.  the PT-7 doesn't have the 9 terminal.  I wonder if how would I wire the PT-7 in the crack.  I want to do this mainly for the curiosity reason lolz.

 

[Paul Birkeland]

I read that we can also wire it to use the PT-7 which is supposed to be more quiet. 

It is? 

The PT-7 and PT-3 are close to the same, with the PT-7 only having a single HV winding but also IIRC it has a heater center tap.  Swapping one for the other is pretty straightforward.  Personally I would not go through the trouble of taking a working Crack with a PT-3 and installing a PT-7.

 

[wabibito]

Thanks Paul, does this mean i would skip the bridge step between terminal 6/7 and 8/9.  Also how would the 4 rectifiers hook up if that is the case?

Also i am not taking off a working crack.  I am trying to fix a crack with a bent plate due to shipping.  I have completely taken it a part, ordered a new plate before i putting it back i saw an article on from Doc this from 2013.  Which spark my curiosity.  The nerd in me is wanting to try =).

 

[Paul Birkeland]

Thanks Paul, does this mean i would skip the bridge step between terminal 6/7 and 8/9. 

The PT-7 doesn't have two separate windings, so there's nowhere to put those jumpers.

Also how would the 4 rectifiers hook up if that is the case?

Exactly the same way.

 

[wabibito]

Thank you much again Paul.

Going through the old 1.0 manual screenshot below. PT-3 terminal 9 is connecting to terminal 19 and PT-3 terminal 10 is connecting to terminal 18.

Seems like the PT-7 transformers is voltage terminal is reverse for 6 (0V, 150V on PT-3) and 7 (150v, 0V on PT-3).  I am assuming I will connect PT-7 terminal 6 to terminal 18 and PT-7 terminal 7 to terminal 19?

Thank you.

 

[Paul Birkeland]

There are pretty much the same labels on the PT-3 and the PT-10.  Wire like for like.  The phase of the high voltage winding doesn't matter in the Crack.  You can leave the CT disconnected or move the connection to the safety ground from one end of the 6.3V winding to this connection. 

 

[wabibito]

Thanks Paul,

I assumed this step still needed?  Connect PT-7 terminal 6 to terminal 18 and PT-7 terminal 7 to terminal 19 where the rectifiers connected to.

 

[Paul Birkeland]

You do need to connect the high voltage winding to the Crack for the amp to function properly.

 

[wabibito]

Thanks Paul.  Will try to test this out next over the long weekend.