Tube rectifier - no center tap on PT ???

[Baguette]

Hello,

Is it possible to run a tube rectifier with a PT that has no center tap on its HV winding?
(the HV winding is a 0 - 300VAC made for a bridge rectifier).
I'm wondering whether a trick exists.

Thanks!

[Jack_Hester]

I built a bridge rectifier, using 2 tubes, that works just fine.  I don't remember how much voltage drop there was, but the power supply worked like a champ.  I used 2 6X5's, as the PT that I experimented with had only a 6.3v filament secondary, and no CT on the high voltage secondary.  I have a sketch of it at home.  

Jack

EDIT... Sorry, I hit modify rather than quote. Your message is still original... sluckey

[Geezer]

I'm wondering whether a trick exists.

You'll need to add a 5v (2 or 3A) tranny to do this one (if using a 5v tube). If you use a 6.3v tube, either use one with an isolated heater (so you can use your existing 6.3v supply, provided you have enough extra current available) or add another small 6.3v tranny to power it.

G

[sluckey]

I built a bridge rectifier, using 2 tubes, that works just fine.  I don't remember how much voltage drop there was, but the power supply worked like a champ.  I used 2 6X5's, as the PT that I experimented with had only a 6.3v filament secondary, and no CT on the high voltage secondary.  I have a sketch of it at home. 

Jack

I'd like to see that sketch. The 6X5 has a single cathode. That makes it impossible to use two of them for a bridge. You would need at least three 6X5s to make a full wave bridge. Maybe you simply have a dual (parallel) rectifier???

[Baguette]

I'm wondering whether a trick exists.

If you use a 6.3v tube, either use one with an isolated heater (so you can use your existing 6.3v supply,

Nice trick Geezer.
I was thinking 6X5 or 6X4.
Would any of these work without a separate 6.3V tap?

Thanks!

[sluckey]

Either of those will work. So will EZ80 or EZ81.

[Jack_Hester]

I'd like to see that sketch. The 6X5 has a single cathode. That makes it impossible to use two of them for a bridge. You would need at least three 6X5s to make a full wave bridge. Maybe you simply have a dual (parallel) rectifier???

You are so correct.  I depending on my memory as to what I used.  I'll look it up this evening and see just what I used. 

Jack

[Baguette]

BTW, will Geezer's arrangement provide a correct B+ (around 300-400VDC) with a 0-300VAC HV winding?

[tubeswell]

BTW, will Geezer's arrangement provide a correct B+ (around 300-400VDC) with a 0-300VAC HV winding?

In a hybrid rectifier, the resulting forward voltage drop will be mainly attributable to the tube rectifier part of it (since an SS diode has a forward voltage drop of only about 0.6V), so you just work it out as if you were using a 'conventional' tube rectified B+.

[Baguette]

Thanks for the answers guys, that's mu ch appreciated :)

[Jack_Hester]

I'd like to see that sketch. The 6X5 has a single cathode. That makes it impossible to use two of them for a bridge. You would need at least three 6X5s to make a full wave bridge. Maybe you simply have a dual (parallel) rectifier???

Done some digging in my notes that I keep at work (from the many night shifts last Spring).  6BY5's are what I used.  Sorry for the poor memory.  I try not to quote without notes, these days.  I did, today. 

Jack

[kagliostro]

I think the way Geezer proposed is the better

but if you can also use this schematic, with this version you can also use a tube with only one diode

May be the way to lower B+ and have Sag at the same time in an amp which has a SS rectifier only

Kagliostro

[Ed_Chambley]

I called the techs at Hammond and they fixed me up with a transformer for my application of adding 5v.  They were very helpful.  I ended up adding a GZ-34 to a silverface bassman.  Worked out really cool.  Converted it to AA763 with a tube rectifier.  Run it into a 4.10's and it sounds just like a Super I guess because it is.  $14.00, I wish I could remember the part number and where I ordered it, but the tech at Hammond gave me the part number and the contact where to order it.  They are very prompt, did not have to be put on hold or wait forever.  Nice people at Hammond.