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Old 18th October 2007, 03:44 AM   #301
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I actually already have the chassis set up with an octal socket to accomodate a valve rectifier. I also have plenty of fine 5AR4's.

I have to admit though, I am kind of nervous about running the rectifier's heaters from the same 5V tap as the bias circuit. It's rated for 4A, which is plenty. Any pointers on this?

Adam
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Old 18th October 2007, 03:56 AM   #302
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Adam,
Derive the -ve rail from a SS diode from the 50V Tap on the HV Winding rather than using the 5V winding. That leaves the 5V winding to just handle the Rectifier Heater.

A quick look at PSUD2 suggests to me that with the 372JX and a 5AR4 the high voltage will be around +370V. You may be able to get this down enough by just adding a say 47R to 100R 2W resistor in each HV AC lead between the transformer and the rectifier tube anodes.

Cheers,
Ian
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Old 18th October 2007, 04:30 AM   #303
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I'm starting to work with PSUD at the moment.

In my previous setup with the 372JX, I was getting 350V at pin 8 of the 5AR4 with only a 110mA load, so that figure should be manageably closer to the 320 mark under a 200mA load.

The "resistors on each phase of the AC" idea is an interesting one. Will that not affect AC integrity (not contradicting you here, I'm just curious).

"Derive the -ve rail from a SS diode from the 50V Tap on the HV Winding rather than using the 5V winding."

I appreciate your help and hate to be the dunce, but I'm not completely following you here. I'll look into it before I riddle you with more questions. There's also the option of buying a dedicated 5V@1A PT for around $10 if I wimp out.
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Old 18th October 2007, 04:39 AM   #304
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BTW - I was refering to the CCS circuit, not the bias circuit, which was probably obvious.
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Old 29th October 2007, 07:12 PM   #305
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This is a power supply I can build from parts-on-hand. I'll use apropriate resistors in the AC secondaries to get the needed voltage.

Please critique this supply for use with the Baby Huey.

Thanks,

Adam
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Old 29th October 2007, 07:53 PM   #306
anatech is offline anatech  Canada
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Hi Adam,
Try to add a capacitor after the choke. 47uF should do it. Your 23 uF ish input capacitance is good. You won't damage the rectifier tube. You would be safe up to around 30 uF without looking at a data sheet. Possibly up to 40 uF as a design maximum. The tube data would give you the maximum capacitance allowed.

-Chris
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Old 31st October 2007, 04:48 AM   #307
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Thanks for chiming in, Anatech.

You recommended adding a cap after the choke. Would this be in addition to the 100uf cap that's already in line before the output stage?
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Old 31st October 2007, 06:56 PM   #308
anatech is offline anatech  Canada
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Hi Adam,
Quote:
You recommended adding a cap after the choke. Would this be in addition to the 100uf cap that's already in line before the output stage?
No, not if there is one there already. Normally, any filter caps are shown in the supply section and I forgot about the earlier posts and diagrams. I was going on your PS diagram alone when I made my comment.

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Old 2nd November 2007, 03:18 AM   #309
chrish is offline chrish  Australia
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Hello,

I am thinking of building the "Baby Huey" as my next project.

A few quick questions. I am located in Australia, so sourcing parts is not always easy. Particularly the power and output transformers. Additionally, postage is a killer for these items, so I must choose wisely before ordering. I would like to make a tube rectified version if possible, simply because I have a few spare 5U4Gs lying around that look rather cool. Guessing I need around 275 VAC secondary (for recommended 300-330 B+). Any recommendations for power and output transformers? I have used the small Edcor transformers on my SimpleSE project and have been happy. Maybe these? http://www.edcorusa.com/products/tra...25-8-7_6k.html

I am travelling to Beijing at the end of the month with work, so may be able to look out for power transformer and choke there, not sure if I am willing to risk buying output transformer there though.

Any suggestions and help appreciated,

Thanks,

Chris
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Old 3rd November 2007, 02:13 AM   #310
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Default Removing global feedback

Ian -

If the global feedback loop is removed, to what shall the second triode grid (pin 7) be attahed?

What differences did you observe with the global loop removed and the shunt increased to 33K?

Is the current arrangement suitable for 8 ohm output?

Thank you,

Adam
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