Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: RobBozic on July 16, 2015, 01:41:10 am

Title: PT in Tweed super using KT66's
Post by: RobBozic on July 16, 2015, 01:41:10 am

Hi,
 
My tweed super clone currently has 6L6's / JTM45 6.6K OT / GZ34, as opposed to the original set up of 5881's / 5.3K OT / 5U4GB.
I want to install KT66's which we all know require 1.3A each over the 0.9A of the 6L6's, (therefore 0.6A extra).
If I install a Weber Copper Cap WZ34 which doesn't require any filament draw from the PT and emulates a GZ34, and the fact I'm using a 6.6K OT which draws less current than a 5.3K OT, is there going to be any issues with using KT66's with regards to the Power Transformer?
 
Regards
Rob

Title: Re: PT in Tweed super using KT66's
Post by: AZJimC on July 16, 2015, 02:47:02 am

They should run fine, however the 6.3v winding is a point of concern. The GZ34 would be on the 5v winding and unloading it may help a bit, but overloading the 6.3 is possible. Try to find out the capacity of the PT and see if it should carry the load. Each 12a_7 is 300ma so the power tube swap would be like adding two more preamp tubes.

Could try it, since it is .6a increase, measure the 6.3vac before and after, and see how hard it pulls it down, watch for trans heating up.