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Old 15th March 2009, 01:57 AM   #1
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Default Which power supply would you use?

Hi all. I am just about to the point where I can buy the remaining parts for a parafeed 396A preamp I am building. I have the option of using this supply: http://glass-ware.stores.yahoo.net/ps1kit.html

or using the one that I designed (with a bunch of help) below. Which would you use for the preamp? If I use the regulated supply, which I am leaning towards doing, is there anything to be gained by still using a choke?
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Old 15th March 2009, 03:15 AM   #2
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either should be fine im sure..

the main reason for cheapo regulators is to avoid pricy iron.
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Old 15th March 2009, 03:21 AM   #3
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Quote:
Originally posted by Colt45
either should be fine im sure..

the main reason for cheapo regulators is to avoid pricy iron.
Actually I was thinking of using a choke along with the cheapo regulators. The biggest advantage I can see is a nice smooth filament supply. But I can use my original PSU and also install a DC filament supply. What I'm looking for is a guess, or opinion, of which will sound better. Mr Broskie is not known for designing things that aren't solid performers so I am torn.
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Old 15th March 2009, 03:23 AM   #4
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Here is the circuit it will be powering:
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Old 15th March 2009, 03:29 AM   #5
mach1 is offline mach1  Australia
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Use a WE407A (396A with a 20v filament) instead and save yourself a bundle. Prices are about 5:1.
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Old 15th March 2009, 12:00 PM   #6
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I'm surprised nobody has pointed out that your power supply will not work as drawn. You have the rectifier valve back-to-front. The 150Vs should be connected to the anodes, there should be a separate 6.3V supply connected to the heaters and the rectified voltage should be taken from the cathode.
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Old 15th March 2009, 01:48 PM   #7
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Quote:
Originally posted by barretter
I'm surprised nobody has pointed out that your power supply will not work as drawn. You have the rectifier valve back-to-front. The 150Vs should be connected to the anodes, there should be a separate 6.3V supply connected to the heaters and the rectified voltage should be taken from the cathode.
I noticed that last night. If you look long enough you will also discover that the pin numbers are incorrect. I don't have a model for a EZ81 with the software I use to draw schematics. Here is a semi correct version:
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Old 15th March 2009, 03:38 PM   #8
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Well the new diagram is wrong too. The EZ81's anodes are on pins 1 & 7, the heaters on 4 & 5, and the separate cathode is on 3. You can join the cathode to the heaters if you want but they are physically separate within the valve.
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Old 15th March 2009, 09:02 PM   #9
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Quote:
Originally posted by barretter
Well the new diagram is wrong too. The EZ81's anodes are on pins 1 & 7, the heaters on 4 & 5, and the separate cathode is on 3. You can join the cathode to the heaters if you want but they are physically separate within the valve.
Did you even read my last post. I KNOW it is wrong. I can't change the damn pin numbers or I would have and I'm sure that everyone gets the idea. All I am asking for is some opinions on the two options that I have. Not to have the diagram nitpicked.
To anyone who wants to consider building the CLCRCRC supply it is designed for a 10mA load and it should perform well. The pinout for the EZ81 is INCORRECT because I don't have that symbol in the software that I use to draw diagrams. The symbol itself is also wrong as a EZ81 is a indirectly heated rectifier. Please take note of this.
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Old 16th March 2009, 03:59 PM   #10
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Default Use a tube regulated PS!

If your preamp is tube then use a tube regulated power supply. In addition to the errors already noted, you might look at a 6BY7GT damper diode as a rectifier if you have more than one 6 volt heater winding in your transformer or even a 6X5GT if you want to downsize. The first capacitor before the choke is small in my estimation. I'd use at least 4 uf and make it an oil cap. Then I would add a tube series regulator after the second capacitor with a pass tube like a 6EM7 or 6AQ5 or a 6BQ5 and an error amp like a 12ax7a (this can be a pull as it's not critical as long as it tests ok), and an OA2 gas diode. You could get by with one 6EM7 and a OA2 as a regulator section. There is a circuit in the RCA tube manual on their 50 watt power amp.It powers the screens in the output stage. Then your power supply would be line and load regulated. But of the two I would go with the one you designed with help. Ray
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