Tube Recto with no Center Tap?
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Tube Recto with no Center Tap?
Is it possible? I read a link on Torres site that said he had a kit or something but could find no info on it and searches haven't turned up anything. Is this possible?
Re: Tube Recto with no Center Tap?
[img:350:160]http://www.freewebs.com/valvewizard/Bridge3.jpg[/img]
This is a full-wave bridge rectifier using a tube for one half (the common cathode half) and diodes for the other half (the common anode half). Current has to pass through the tube at all times, so you'll retain the typical tube rectifier characteristics.
Ignore the two resistors as you won't need them, but this is the only drawing I remembered seeing of basically how to wire this.
This is a full-wave bridge rectifier using a tube for one half (the common cathode half) and diodes for the other half (the common anode half). Current has to pass through the tube at all times, so you'll retain the typical tube rectifier characteristics.
Ignore the two resistors as you won't need them, but this is the only drawing I remembered seeing of basically how to wire this.
Re: Tube Recto with no Center Tap?
You also get about twice the voltage from a full wave bridge, is this what you want?
Re: Tube Recto with no Center Tap?
Presumably if the transformer doesn't have a centre-tap then it'll be specified something like 0-250 rather 250-0-250, in which case it'll be exactly the same voltage on the DC side.
Re: Tube Recto with no Center Tap?
I was going to try to use a PT I have for a Trex since the Trex uses an EZ81 with 6.3v heater and the PT I have has two 6.3V secondaries. Wanted to retain that tube recto feel since I have only SS rectified amps around.
The PT is 200-0-200 with a CT. If I full wave rectify i end up with 0.9*VAC = 180. The PT is actually more like 215-0-215 and I end up with about 193VDC after full wave. Too low. So If I bridge rectify without the CT I would expect to get about 560V but I actually get about 424V? Not sure why....
I wondered about using a tube rectifier without a center tap since I thought the tube would drop voltage. But from what you've posted I would end up the exact same input voltage on the output in DC? So 400VAC in would give 400VDC out. That is closer but still high.
I'm thinking either way I can throw some zeners on the B+ line to drop some volts.
I just modeled a normal CT PSU in PSUDII with an EZ81 and 200V transformer and it says I'll get about 240V output. Is this accurate? I could live with this I suppose...
The PT is 200-0-200 with a CT. If I full wave rectify i end up with 0.9*VAC = 180. The PT is actually more like 215-0-215 and I end up with about 193VDC after full wave. Too low. So If I bridge rectify without the CT I would expect to get about 560V but I actually get about 424V? Not sure why....
I wondered about using a tube rectifier without a center tap since I thought the tube would drop voltage. But from what you've posted I would end up the exact same input voltage on the output in DC? So 400VAC in would give 400VDC out. That is closer but still high.
I'm thinking either way I can throw some zeners on the B+ line to drop some volts.
I just modeled a normal CT PSU in PSUDII with an EZ81 and 200V transformer and it says I'll get about 240V output. Is this accurate? I could live with this I suppose...
Re: Tube Recto with no Center Tap?
Your peak DC will be sqrt(2) (1.4) times the AC less any rectifier and filtering losses.
You should get 280Vdc or 560Vdc depending on whether you use a bridge or not, less the rectifier losses which will be greater with the tube.
How have you measured the 424V? That seems really low, so suggests either that the transformer doesn't meet its specs, or is very loosely regulated and really bogging down with some load.
You should get 280Vdc or 560Vdc depending on whether you use a bridge or not, less the rectifier losses which will be greater with the tube.
How have you measured the 424V? That seems really low, so suggests either that the transformer doesn't meet its specs, or is very loosely regulated and really bogging down with some load.
Re: Tube Recto with no Center Tap?
Check to see if there is a CT grounded to the frame of the PT. You don't say if this is new or old. Old ones can be like this and you don't want two CT grounds or you will let the smoke out.
Re: Tube Recto with no Center Tap?
200V x 1.13 = 226Vdc with a 5Y3
200V x 1.2 = 240Vdc with 5U4
200V x 1.3 = 260Vdc with GZ34
200V x 1.4 = 280Vdc diode
How much voltage do you need? Will have to use the voltage doubler as suggested.
Mark
200V x 1.2 = 240Vdc with 5U4
200V x 1.3 = 260Vdc with GZ34
200V x 1.4 = 280Vdc diode
How much voltage do you need? Will have to use the voltage doubler as suggested.
Mark
Re: Tube Recto with no Center Tap?
I had this PT in a Champ clone and it worked fine. 193V on the plates. Had another sitting around so replaced this one with a 300-0-300 hammond in the champ.
It has been used and is good, 200-0-200, 400mA. I just wired up a hybrid SS/Tube with a 6X5GT I pulled from an old phono, and it gives me a good 393VDC.
Now, ten minutes ago, I bridge rectified it and I ended up with only 390VDC. This is with 1N4007 diodes. If I measure the PT leads, I get a solid 217VAC - 0 - 217VAC. 436VAC across leads. That should be well into 550V.
Think something might be up with the PT? Center tap isn't connected to frame..
It has been used and is good, 200-0-200, 400mA. I just wired up a hybrid SS/Tube with a 6X5GT I pulled from an old phono, and it gives me a good 393VDC.
Now, ten minutes ago, I bridge rectified it and I ended up with only 390VDC. This is with 1N4007 diodes. If I measure the PT leads, I get a solid 217VAC - 0 - 217VAC. 436VAC across leads. That should be well into 550V.
Think something might be up with the PT? Center tap isn't connected to frame..
Re: Tube Recto with no Center Tap?
Don't mean to hijack the thread but Paulster, I finally wired up this circuit as you suggested in my Angela Super SE amp. Worked great! I am very happy with the results.paulster wrote:[img:350:160]http://www.freewebs.com/valvewizard/Bridge3.jpg[/img]
This is a full-wave bridge rectifier using a tube for one half (the common cathode half) and diodes for the other half (the common anode half). Current has to pass through the tube at all times, so you'll retain the typical tube rectifier characteristics.
Ignore the two resistors as you won't need them, but this is the only dNot to hijack thread but Paulster I finally wired this circuit up in my Angela Super SE amp. Awesome!!! Worked great rawing I remembered seeing of basically how to wire this.