B+ ramping up before CCS filament - danger? - diyAudio
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Old 27th February 2011, 04:04 PM   #1
phrarod is offline phrarod  United States
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Default B+ ramping up before CCS filament - danger?

This is my first time with CCS filament supply. The problem is the good part of CCS - slow ramp up - is so slow that even my slow start 5AR4 rectifiers hit the tube with voltage that begins to climb to almost 100VDC over the final stabilized voltage once the heaters come up to full voltage.

Is this a potential problem that could cause cathode stripping?

The only way to further slow the B+ would be to use a thermistor but I don't know if that would have sonic implications.
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Old 27th February 2011, 04:07 PM   #2
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... delay the filament voltage for the 5AR4 until the other filaments are up.

Greetings,
Andreas
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Old 27th February 2011, 04:14 PM   #3
phrarod is offline phrarod  United States
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With a thermistor? I would need about a 15 second delay
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Old 27th February 2011, 04:18 PM   #4
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Depends on the question if you find a thermistor capable of 1,9A filament current for the 5AR4 and reasonably low hot resistance...

On my amp project, I will do the delay "manually" via a rotary switch: Pos1 - tube heaters current limited, Pos2 - tube heaters on, Pos3 - tube heaters, rectifier heaters and HV on...

Greetings,
Andreas

EDIT: Not the most practical solution, but I decided to do completely without semiconductors. Using them, you can built beautiful delay circuits instead...
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Old 27th February 2011, 04:26 PM   #5
phrarod is offline phrarod  United States
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Thanks Andreas. I think I would like a built-in auto solution that is 'wife friendly'.

I promised she could actually use the new preamp and not be afraid of it. lol
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Old 28th February 2011, 12:36 PM   #6
Arnulf is offline Arnulf  Europe
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Time relay ?
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mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."
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Old 28th February 2011, 03:13 PM   #7
phrarod is offline phrarod  United States
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Yes, as mentioned I need around a 15 second time delay.Tell me how Arnulf?
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Old 28th February 2011, 04:53 PM   #8
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What about this!

http://www.sophiaelectric.com/pages/...tion_board.htm
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Thanx!
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Old 28th February 2011, 05:15 PM   #9
phrarod is offline phrarod  United States
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That is AWESOME. Unfortunately I don't have a 6.3v tap for it and no room for another transformer. I'll call them though and see if there's any alternatives.
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Old 28th February 2011, 05:53 PM   #10
phrarod is offline phrarod  United States
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I just spoke with Sophia and an issue would be getting power to the module. I would have to tap off my 12.6V ac tap that is going to my filament supply. He said to put it on the filament of the 5AR4. With this in mind wouldn't a thermistor be an easier solution?
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