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#26 pre amp
#26 pre amp
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Old 20th March 2013, 09:42 PM   #2681
merlin el mago is offline merlin el mago
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No I haven't take the center tape to ground. Each one is 125VAC so I wired to get 250VAC: 0-125+0-125 = 0-250
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Old 20th March 2013, 09:43 PM   #2682
stajo is offline stajo  Sweden
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#26 pre amp
Quote:
Originally Posted by merlin el mago View Post

I haven't grounded the cathode resistors, Rod told me his filaments regs must be connected floating never connected to ground.
Normally in a PSU you ground after rectifiers. But in in the PSU for Rods filament thingie you cant do that, because you will have a ground loop if the filaments are also grounded. I guess that is what he ment by that.

So you dont ground PSU for Rod-thingie, just the filaments.
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Old 20th March 2013, 09:44 PM   #2683
ErikdeBest is offline ErikdeBest  Switzerland
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#26 pre amp
Hi Merlin. Rod's filaments should indeed be left floating. Still, one end of the resistors should go to ground. If you omit that there is no way that the current fed from the gyrator or OPTs can return to the ground of the amplifier circuit.

Good luck. Erik
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Old 20th March 2013, 09:46 PM   #2684
merlin el mago is offline merlin el mago
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So have I to connect the - Rod's reg to ground?
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Old 20th March 2013, 09:49 PM   #2685
stajo is offline stajo  Sweden
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#26 pre amp
Yes. See Andys in #2616
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Old 20th March 2013, 09:52 PM   #2686
massimo is offline massimo  Italy
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Check this schem (the one suggested by Stajo I guess)
The filament PS is totally floating, BUT the 10 ohm R is connected to gnd
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Old 20th March 2013, 09:54 PM   #2687
vgeorge is offline vgeorge  Greece
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#26 pre amp
So let' s say you have one transformer 0-250. Where do you connect the ground on your PSU? In your simulation you showed that you have a 229-0-229 transformer.
I' m puzzled.
Also as Erik said, you should ground the point where the 10R resistor and - of Rod' s supply meet.
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Old 20th March 2013, 10:15 PM   #2688
merlin el mago is offline merlin el mago
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That's because psud don't have hybrid graetz rectification.

Both 10R grounded

Bingo, my last psu cap isn't grounded, thanks George.

Last edited by merlin el mago; 20th March 2013 at 10:21 PM.
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Old 20th March 2013, 10:30 PM   #2689
andyjevans is offline andyjevans  United Kingdom
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OK. First get the filament supply right, then look at the PSU. Don't connect up the B+ until the filament supply is working correctly. You should now have about 11v on the top of the cathode resistor, and the bottom is connected to ground. What is the actual voltage you have now on top of the cathode resistor?
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Old 20th March 2013, 10:39 PM   #2690
vgeorge is offline vgeorge  Greece
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#26 pre amp
Quote:
Originally Posted by merlin el mago View Post
That's because psud don't have hybrid graetz rectification.

Both 10R grounded

Bingo, my last psu cap isn't grounded, thanks George.
That' s why no current was flowing!
Do the tests Andy says before applying B+ again.
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