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Old 25th August 2015, 08:40 PM   #1
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Default Need Help With Screen Switch

I have an amp I built using a OPT w/ UL tap, and I want to use a switch to switch between UL and Triode mode. However, the first couple switches I used caused horrible noises to come out of the speakers.
I tried again without a switch, with both UL and Triode mode hardwired and there was no noise whatsoever, so I am assuming the noise was created from the switch (maybe it was not insulated well enough from the high voltages).
Is there any switches (either rotary or ON/ON rocker switches) you would recommend that any of you have used with success at voltages of 300VDC and up?
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Old 25th August 2015, 08:50 PM   #2
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DON'T switch it with power on! Problem solved!
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Old 25th August 2015, 08:53 PM   #3
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Quote:
Originally Posted by Tom Bavis View Post
DON'T switch it with power on! Problem solved!
I should have clarified. I have never switched it with the power on, and I built the original switch into the back of the chassis near the OPTs so that no one would do that. I know better than that
Just having the screen run through the switch was causing noise (thumping, etc.), which is why I was asking for switch suggestion (probably ones with better voltage insulation than the one I used, which was a cheap $0.50 switch from china with no real specs)

Last edited by Nailbunny7; 25th August 2015 at 09:22 PM.
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Old 25th August 2015, 09:24 PM   #4
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Switch is wrong.....for 1$?
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Old 25th August 2015, 09:29 PM   #5
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Originally Posted by azazello View Post
Switch is wrong.....for 1$?
Yeah, realized that after. I just used some that I had readily available on hand from a different project. I thought it might be easier to ask what switches people have had success with before a ordered some random rotary switch off eBay.
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Old 25th August 2015, 09:34 PM   #6
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I used some dpdt mains switches (rated for 240Vac @ several amps).
No noises in my PP EL34 amp (360V idle).
Don't remember where I got them.
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Old 25th August 2015, 09:37 PM   #7
TheGimp is offline TheGimp  United States
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I've used C&K miniature toggle switches up to 325V. The switches are rated for 250VAC.
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Old 25th August 2015, 09:55 PM   #8
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Have you Grid-Stoppers in place, both Screen and G1?

Sounds to me the extra wiring is making for sufficient pick-up/radiation to cause oscillations.
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Old 26th August 2015, 03:57 AM   #9
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Originally Posted by Alastair E View Post
Have you Grid-Stoppers in place, both Screen and G1?

Sounds to me the extra wiring is making for sufficient pick-up/radiation to cause oscillations.
I use a 1K grid stopper on G1 and a 20V Zener on the screen
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Old 26th August 2015, 09:31 AM   #10
DF96 is offline DF96  England
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A zener is not a stopper. Put a stopper resistor on the screen.
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