Single Ended Hum

[35L6]

Make it a head ?

[leadfootdriver]

So this is a newb question:
I finally got the new PT wired in the Chassis.. I did a Full Bridge Rectifier and powered on for a voltage of around 315vdc.
I put a 100uf Cap on with 2-100k 2W R's in Series as a Bleeder for a new voltage of 480vdc!
I suspect adding the rest of the Filtering won't change this voltage or will it?
Should I calculate a Dropping Resistor right after the Rectifier before the 1st Cap based on the 480vdc?

269BX.pdf

[Tom Phillips]

A bridge rectifier used with the transformer you showed and the voltages you listed are perplexing. Could you post a schematic showing how you have everything connected?

[leadfootdriver]

There's nothing drawing current yet. All I've done so far is built the Rectifier and put a Cap to ground after it.
Center Tap is not connected to anything.

[Tom Phillips]

There's nothing drawing current yet. All I've done so far is built the Rectifier and put a Cap to ground after it.
Center Tap is not connected to anything.

I wanted to see how you connected to which taps on the secondary and the primary.

[Helmholtz]

A bridge rectifier used with the transformer you showed and the voltages you listed are perplexing.

I think the voltages make sense.
Unsmoothed average DCV voltage after the bridge must be 10% below PT secondary RMS voltage..

I assume the new PT to have a secondary voltage around 340V. So with reservoir cap the DCV will be around 480V.
This might drop by 10% to 20% with load connected.

Would like to see the PT specs.

To design in a new PT I strongly recommend to use PSUD2.

[leadfootdriver]

There's a PDF Link in my post #63

[Helmholtz]

There's a PDF Link in my post #63

Ok, spec says no load secondary voltage is 338V which confirms your measurements.

[Tom Phillips]

... confirms your measurements.

So I suppose that a bridge rectifier circuit isn't actually being used as stated in the post that started this section of the discussion.

[Helmholtz]

So I suppose that a bridge rectifier circuit isn't actually being used as stated in the post that started this section of the discussion.

How that?
It all makes sense with a bridge.

[Tom Phillips]

How that? It all makes sense with a bridge.

Sorry for my confusion. I mis-read the transformer spec sheet posted. I was thinking that it had a 300V-0-300V secondary but I now understand that it is a 300V center tapped secondary. (150V-0-150V).
Cheers,
Tom

[leadfootdriver]

That was with the 115v Mains.. I think I'll switch it to the 125v..

[leadfootdriver]

SO, I'd like to take advantage of this voltage..
I've searched the topic, but maybe hindsight will give a different answer.
Any problems running a Fixed Bias, SE EL84 at 400vdc? I have a nice little 5H Choke for the Screens. I read that keeping the Screen Voltage under 300 would be safe. Does this sound the best, or does a closer Plate to Screen Voltage ratio sound best?? Any truth in any of this??

[Chuck H]

Any problems running a Fixed Bias, SE EL84 at 400vdc? I have a nice little 5H Choke for the Screens. I read that keeping the Screen Voltage under 300 would be safe.

Safe? Yes. But you won't be able to take advantage of that voltage anyway. That is, you won't get more output clean and with clipping any increased output just amounts to greater asymmetry. I'm not expert in this but that is my own experience. I vote to stay with the lower voltage option.

Maybe Helmholtz will have better news on the matter.

[leadfootdriver]

I was playing around a bit.. I switched the Mains to 125v. I put an 18k 2-watt after the Rectifier into the 100uf with the 2-100k in series Bleeder across it for 348vdc.
The Bleeders are an easy way to bleed off voltage.