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arc V70 blue flash in KT90 tubes
arc V70 blue flash in KT90 tubes
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Old 1st September 2009, 03:53 PM   #1
muizel is offline muizel  Netherlands
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Default arc V70 blue flash in KT90 tubes


I have an arc V70 wich is operating flawlesly, but I noticed when I shut down the power in all 8 KT90 tubes I see a small blue flash just like a high voltage spark, is that normal ? I put in 8 new valves and it makes no difference.

I hope someone can help me out on this.

Rehards René.
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Old 7th October 2009, 05:19 PM   #2
richwalters is offline richwalters
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Bit late responding to this. We need a circuit diagram to get further.

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Old 7th October 2009, 09:19 PM   #3
Miles Prower is offline Miles Prower  United States
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Need to have a look at the power supply schemo. That looks like some sort of high voltage pulse that's somehow occurring on power down. Any interruption of current through inductance is going to cause flyback. Don't know why it's happening with that amp.
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Old 7th October 2009, 09:31 PM   #4
rknize is offline rknize  United States
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My guess would be the bias supply is collapsing long before B+. The blue flash are the tubes going into full conduction while B+ discharges.
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