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RE: GZ34: getting too much voltage drop

Posted by sideliner (A) on February 11, 2017 at 12:20:38

In Reply to: GZ34: getting too much voltage drop posted by banpuku on February 11, 2017 at 06:13:55:

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UPDATE: Resolved by vetmedrobert@gmail.com.

You have 670 volts into a choke. the formula is VAC*0.45, or 670*0.45= 302.5 volts. This for a full wave rectifier as you have in your schematic. Then you must allow for the rectifier voltage drop which depends upon your circuit's current draw.

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I disagree.

At the output of the filter: VDC=0.9*Vrms(trans. sec.) for choke input

At the output of the filter: VDC=1.41*Vrms(trans. sec.) for capacitor input

At the INPUT of the filter: Vrms(rectified) = Vrms(trans. sec.) - Vdrop of the rectifier.

In this case the potential at the rectifier's cathode should be 335V-15V or about 320V (GZ34 Vdrop = 16V at a draw of 200mA) and not 290V. Perhaps it's just a bad tube as in a low emission/transconductance specimen or the transformer has an issue. Did you verify that the no-load-voltage across both half's of the trans secondary is as specified?

Edits: 02/11/17

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