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Re: [Amps] Apparent Arcing

To: "Roger Parsons" <>, "Amps" <>
Subject: Re: [Amps] Apparent Arcing
From: "Jim W7RY" <>
Date: Mon, 4 Sep 2017 20:09:11 -0500
List-post: <>

Are you using solid state relays for the step start and the primary of the transformer?

Jim W7RY

-----Original Message----- From: Roger Parsons via Amps
Sent: Monday, September 04, 2017 3:25 PM
To: Amps
Subject: [Amps] Apparent Arcing

I recently 'completed' a new amplifier. Everything seemed fine and I was quite happy. But I was only checking the transmit functions.

However: I now find that when I power on the HV I get rf noise in the receiver - sounds and spectrum are just like power line arcing. But it's not.

Obviously the first suspect was the high voltage circuitry. I disconnected the wiring to the tube, followed by the capacitor bank and bleeder resistors, followed by the rectifier diodes. No difference.

So it seemed I was left with the power transformer. With AC power on the primary and nothing on the secondary I get the noise. I tried an RFI filter in series and it fixed it completely. However, I am not very keen on leaving that in circuit because it seems to be covering the real fault. I then tried connecting the power transformer primary directly to the circuit breaker (no secondary load). No noise. I then connected the power transformer directly to the circuit breaker (again no secondary load), but reconnected the soft start, etc (That wiring going nowhere). No noise. (I can't connect the primary of the HV transformer directly to the circuit breaker with a secondary load as I need the soft start in that condition.)

(The HV transformer is new and very well impregnated. It does not get hot or let smoke out. I find it difficult to believe that there is something like a shorted turn causing the noise, but I suppose it is possible.)

OK, I thought. Perhaps it's a bad contact in the soft start relay or the HV relay. Cleaned the contacts up (they actually looked fine before anyway) and no difference to the noise. Bypassed everything I could find. No difference.

Last thing. The noise only happens when the transformer has AC power. Once the power is off, the noise disappers even before the capacitor bank has discharged.

Obviously I'm missing something! Any ideas what?


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