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Old 5th October 2009, 01:33 AM   #1
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Default PSUD & The JE Labs 2A3

OK!
Started working with Duncan Amps FREE (Thank you!)PSUD II program & I came up with this simple PS. It has a brief short spike at about 300 to 400mS then settles down to my target 300 VDC. Does anyone know how I could drag out the start-up.........a slower ramp-up of B+?
I found a local supplier of a Power transformer (Yipee!) at 220VAC PRI, 375-0-375 @ 300mA, 6.3 VAC@7A. I have E-Mailed out for ordering info...
Another curious thing, the software when I select "Full-wave" it shows two seperate envelopes, as in two seperate rectifyers ..is it really just the two anodes as on a 5AR4?....as I have drawn here?
Further, the JE labs schematic shows two B+s', one at 300 VDC at the OPT and the other at the pentode for 330VDC, but with 11K on the Anode.
Can this schematic be redesigned easily for 300 across the board?....so one doesn't have to come up with two different values?

Thanks!

__________________________________________________ _Rick.....
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Old 5th October 2009, 02:14 AM   #2
tomchr is offline tomchr  United States
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Quote:
Originally Posted by Richard Ellis View Post
OK!
Started working with Duncan Amps FREE (Thank you!)PSUD II program & I came up with this simple PS. It has a brief short spike at about 300 to 400mS then settles down to my target 300 VDC. Does anyone know how I could drag out the start-up.........a slower ramp-up of B+?
I think the cause of the spike will need to be investigated. Without seeing a scope trace, it's a bit tough to make any guesses. It could be caused by the parasitic capacitance of the inductors or it could simply be the transient response of the two LC tanks. You could try to "de-Q" the tanks - add some resistance in parallel with the capacitor for example. You'll need bleeders anyway.

If you want an exact ramp rate, you're probably better off with a regulated supply where you bring up the reference voltage at the desired rate. But that stuff can get a bit tricky. You need to make sure your supply will actually start up every time...

~Tom
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Old 5th October 2009, 02:20 AM   #3
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first question - several options. The first is do nothing and allow the inherent soft start of the tube rectifier do the work for you. Second is to use a thermistor as a soft start in the B+ circuit, but I'm picking they will be hard for you to find. Third there are a variety of electronic methods of soft starting - a short google will get you there.

With what you have you should be able to get the correct voltages - why change the circuit design? Caveat - I haven't calc'ed your actual tube currents, too lazy!

And yes, that is just how the PSUD software shows a 5AR4. Your schematic is correct and matches the PSUD schematic.
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Old 5th October 2009, 03:55 AM   #4
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Default RE...

Forgot my bleeders!!
Yes, down here stuff is VERY hard to find & when you do any imported stuff is multiple times the going price.
I will keep on tweeking to see if I can get it right.
Thank you all!

__________________________________________________ ____________Rick....
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