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PostPosted: July 15th, 2016, 6:32 pm 
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Well, I'd say there is no need for a 650 ohm resistor. It is kind of a blunt weapon approach.

Shoot for 10% high B+ and you'll survive. A 300 ohm choke will get you there and add filtering instead of being only a small space heater for your capacitors, which don't need it. A 650 ohm resistor is like 10W dissipation @ 120mA and will be a smokin hot device.


Actually, resim that PSU with the 30 ohm 1H choke between the rectifier and the first filter cap and stick in a 250 ohm 10H choke where the 1H lies. A choke (or resistor) in that input slot will reduce charging impulses at 120hz, and a choke will add a bit of LP and ripple filtering. The series resistance makes the job of the rectifier easier.

A 1H choke is below the "critical inductance" so the power supply will charge up close to the peak value of the AC, i.e. it will still act as a capacitor input filter.

GZ34 is a real good rectifier, especially old production tubes, and I'd strive to keep it in there, personally. For one thing, it is indirectly heated/slow turn-on and, secondly, they sound really good. 5R4s in my experience tend to sound thinner than GZ34 and this may not be what you want/need....but experiment, by all means. Assume every case is different, experiment, and learn.

All bets are off with Russian GZ34s, unless they have gotten a lot better in recent years.


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PostPosted: July 15th, 2016, 6:57 pm 
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Joined: July 15th, 2016, 10:02 am
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FerdinandII wrote:
You can get by with a much smaller resistor between the rectifier and the first capacitor, like <100 ohms in order to get the voltage drop you need.
Now you have an R-C-L-C filter, and the R-C part doesn't charge completely, so you get a lower final output. It's not a strict V=IR relationship in that part of the circuit. Try the Duncan PSUD program; it's easy-peasy to install and run, and you will see how it works.



Whaaaaa..... :o It only takes an 80 ohm resistor! I can get away with like a 3W resistor! This is awesome! I need to understand how this works. Can you explain more?


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PostPosted: July 15th, 2016, 9:03 pm 
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Joined: April 22nd, 2013, 12:58 pm
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I'll let the simulation speak for me.... :pray:
Your current setup:
Image

[/url]Heathkit AA-100 CLC 001 by Butzi Porsche, on Flickr[/img]




justinis wrote:
FerdinandII wrote:
You can get by with a much smaller resistor between the rectifier and the first capacitor, like <100 ohms in order to get the voltage drop you need.
Now you have an R-C-L-C filter, and the R-C part doesn't charge completely, so you get a lower final output. It's not a strict V=IR relationship in that part of the circuit. Try the Duncan PSUD program; it's easy-peasy to install and run, and you will see how it works.



Whaaaaa..... :o It only takes an 80 ohm resistor! I can get away with like a 3W resistor! This is awesome! I need to understand how this works. Can you explain more?


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PostPosted: July 15th, 2016, 9:05 pm 
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Joined: April 22nd, 2013, 12:58 pm
Posts: 155
With a 100 ohm resistor at the output of the rectifier: = 25V lower
ImageHeathkit AA-100 RCLC 001 by Butzi Porsche, on Flickr


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PostPosted: July 15th, 2016, 9:07 pm 
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Joined: April 22nd, 2013, 12:58 pm
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With the 5R4 and RCLC = 60 volts lower with half the resistance, 50 ohm

Image

Heathkit AA-100 RCLC 003 5R4 by Butzi Porsche, on Flickr


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PostPosted: July 16th, 2016, 2:07 pm 
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Joined: July 15th, 2016, 10:02 am
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So cool!


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PostPosted: July 16th, 2016, 3:08 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 155
Am I being dense when I ask why not use solid state silicon rectifiers in the power supply since in these day ones with appropriate ratings exist? It the ideal of being as close to the original as possible. I ask because back in the 1980's I built a Japanese tube amplifier kit (30 W/channel triode mode, 40 W/channel tetrode mode) and it used solid state rectifiers in the power supply. On the front panel of the amplifier was an engraved statement "Made with the perfect knowledge of vacuum state technology."


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PostPosted: July 16th, 2016, 3:11 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 155
I found a link to the kit that I had made (it was pentode mode) -

http://www.thevintageknob.org/luxman-LX33.html


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PostPosted: July 16th, 2016, 3:24 pm 
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Joined: January 14th, 2015, 11:15 pm
Posts: 104
Using solid state rectifiers will result in about 500 volts using the same R, C and L values.

You can do all of this simulating easily yourself and play to your heart's content. Download and install PSUD at

http://www.duncanamps.com/psud2/

There are some tutorials out there, but start off by trying to duplicate the diagrams already shown.

ray


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PostPosted: July 16th, 2016, 3:30 pm 
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Joined: January 14th, 2015, 11:15 pm
Posts: 104
See attached file for the solid state version.

ray


Attachments:
psu test.PNG
psu test.PNG [ 43.48 KiB | Viewed 1211 times ]
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