|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
63.246.183.223
In Reply to: RE: current hogging in a 2 tube rectifier ps posted by DAK on July 27, 2014 at 12:46:43
"I have checked out many schematics of 2 tube rectified power supplies"
I always thought this was considered poor practice due to the relatively high values of balancing resistors needed. Would it be possible to post a link or two to the schematics you've found?
--------------------------
Buy Chinese. Bury freedom.
Follow Ups:
I was just looking at the Scott 296 schematic. It has a 33 ohm resistor after the CT from the heater windings. I thought it use was just for voltage dropping. Also the LK 150 has a pair of 10w 80 ohm resistors after the CT of the heater. The Fisher SA300 has 2 15 ohm 20w in series. I thought those resistors was for dropping the voltage. cheers, Dak
"I was just looking at the Scott 296 schematic. It has a 33 ohm resistor after the CT from the heater windings. "
The 33 ohms resistor is part of the CRC filter (C217-R221-C216) that feeds the output stage.
The following resistors and caps are more filtering (and voltage drop) for the other stages in the amplifier.
There would be a lot more ripple filtering if R221 was a choke instead of just a resistor.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I rebuilt a 296 where I used a CLCLC filter with small 1H x 30 ohm and the sound was much improved. cheers, Dak
I looked at the Scott 296; the two rectifier tubes are not wired in parallel. Each tube is 1/2 of the full wave power supply. Is that what you're building, or have you actually wired two rectifier tubes in parallel? The 33 ohm resistor in the Scott is probably intended to limit inrush current when the amplifier is first powered on.
--------------------------
Buy Chinese. Bury freedom.
Edits: 07/28/14
My rectifier circuit is copied from an earlier post which should be a parallel arrangement. Is there any advantage or disadvantage for hooking up the 2 rectifiers in parallel vs the way in the Scott? My PT doesn't have a ct. regards, Dak
"Is there any advantage or disadvantage for hooking up the 2 rectifiers in parallel vs the way in the Scott?"
The rectifiers conduct alternately in the Scott arrangement, so current imbalance isn't an issue. How are you wiring this if your xfmr has no CT? That requires a bridge with four rectifiers.
--------------------------
Buy Chinese. Bury freedom.
The high voltage is ct. The 5v heater is not unlike the scott.
OK, that's not too important. Most of the 5V heater windings I've seen have not been center-tapped. What are you doing with the rectifiers - two parallel tubes on each leg of the HV winding? Maybe you could post a sketch.
--------------------------
Buy Chinese. Bury freedom.
Hi TK, I copied the schematic from the post on July 12, in this section. It is under the title "what is the best way to hook up 2 rectifiers" and under sub section "tom I am not sure what you mean by that".
OK, I see that what you're doing is identical to the Scott, other than the CT for the filament winding and parallel filaments. There's no problem paralleling the anodes within a single envelope. You don't need balancing resistors, they'll just degrade supply dynamics. If it were me, I'd consider copying the Scott schematic in terms of the 30 ohm resistor and first two filter caps. Increasing the second cap to 40uF or so might be beneficial, but only if the power supply sags on extended low-frequency passages.
--------------------------
Buy Chinese. Bury freedom.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: