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Old 29th January 2007, 01:03 AM   #1
jkeny is offline jkeny  Ireland
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Can anybody tell me what category PS this is? (voltage doubler?, etc). Is it reasonable - it looks very basic to me? How can I improve it while using existing trafo?

It's from a Rogers cadet III integrated amp. I am rebuilding output stage to Gingertube's baby Huey schema with Sy's LED cathode biasing idea (red light district amp).

I wanted to give a clean, robust PS to this output stage. I was thinkg of using SS soft recovery diodes (any recommendations?) but am worried about inrush current & life of tubes, etc. How can I avoid this?

I looked through Tubes threads but found nothing that gives me this info. Help appreciated.

John
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Old 29th January 2007, 10:07 AM   #2
jkeny is offline jkeny  Ireland
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Sorry, I always seem to forget to post attachment

here it is!
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File Type: gif rogers-cadet-iii.gif (31.8 KB, 261 views)
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Old 29th January 2007, 10:25 AM   #3
Tweeker is offline Tweeker  United States
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Its a voltage doubler. Inrush can be limited by use of an NTC thermistor on the primary. Im sure whatever UF4007 type diodes you could come up with would be fine.
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Old 29th January 2007, 11:19 AM   #4
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You can improve it by using a 10H choke instead of the 470R 1W smoothing resistor. Make sure the choke can handle the current. I would also increase the reservoir cap from 24uF to 220uF.

If you want to stick with the same power trafo, then you're also stuck with the voltage doubler. It should work OK though.
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Old 29th January 2007, 11:33 AM   #5
Tweeker is offline Tweeker  United States
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Rather expensive mod for the screen supply, would rather use regulator tubes if going to the trouble.
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Old 29th January 2007, 11:51 AM   #6
jkeny is offline jkeny  Ireland
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Thanks guys,

So it's a voltage doubler - just didn't seem like other schema I have seen! I can now investigate voltage doublers.

I have changed the smoothing caps from 24uF to 220uF.

Would a starter choke from fluorescent tubes be suitable? (As you can see I want to do it on the cheap - so no tube regulation I'm afraid)

thermistor seems like a good idea. What about using fast soft recovery diodes?

John
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Old 29th January 2007, 12:36 PM   #7
Tweeker is offline Tweeker  United States
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The fluorescent choke may work, I have no idea how much current it will take before saturating though.

I meant a simple 1-2 tube shunt reg using VR tube(s), but its still more money than a resistor or scrap. Im sure whatever fast soft recovery diodes youd like would work (within their ratings.)
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