Stray Cat / Hot Cat rectifier question

[3choplex]

I'm building a hot cat clone using the ceriatone layout. There's something on the (GZ34) rectifier that confuses me, though. The ceriatone layout is about like I would expect, except there is a diode between each of the plates and the PT. It seems like the recitifier is getting  half wave rectified power? What are these doing? Is it protecting the tube from the SS rectifier?

The layout is located at http://ceriatone.com/images/layoutPic/matchlessLayout/StrayCat30Ceriatone.jpg

[John]

I believe they are used to protect the PT from flyback voltage in the event of a rect. tube failure.

I've never noticed that little cap across the plates before.

[Willabe]

I believe they are used to protect the PT from flyback voltage in the event of a rect. tube failure.

Or are they to protect the rect. tube?

I've never noticed that little cap across the plates before.

I think that cap is there to kill any SS rect. switching noise. Using ultra fast diodes is said to lesson this noise quite a bit. KOC's TUT books talk about this and it's in Merlin's PSU book also.

This noise/hash not only goes forward/up stream but also go backwards/down stream in the PSU, back into other windings on the PT, like the 6.3 fillament. Merlin has a few scope pic's. in his PSU book showing this noise.         


             Brad      

[John]

Or are they to protect the rect. tube?

Dang, now I gotta look it up again! 

[Boots Deville]

Here's some info, half-way down the page:
http://www.freewebs.com/valvewizard/fullwave.html