Tick in 811A - Amplifiers Forum at eHam.net

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eHam.net Forum : Amplifiers : Tick in 811A

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Tick in 811A	Reply
by K2TY on October 21, 2009	Mail this to a friend!
I recently acquired an 811A and am quite happy with it. I do have a question though. Running SSTV at no more than 400 watts, a second or two after the relay drops, I hear a slight 'tick'. It reminds me of the sound of old glass coke bottles in a cardboard carrier. What is that?

RE: Tick in 811A	Reply
by K7WLF on October 21, 2009	Mail this to a friend!
That noise is from your tubes cooling off.

RE: Tick in 811A	Reply
by W8JI on October 24, 2009	Mail this to a friend!
There is a second common source of a metallic sounding "ticking" in a situation like you describe. It is an open circuited safety choke. That's the little reddish color multisection choke near the loading control. It should measure around 20-40 ohms. If it shows open, replace it ASAP. Tom

RE: Tick in 811A	Reply
by K2TY on October 24, 2009	Mail this to a friend!
It looks like L3 provides a high impedance path to ground. Why would it tick if open? I'm guessing when I unkey (if it's not the tubes cooling), that the field surrounding L3 begins to collapse and arcs to ground?

RE: Tick in 811A	Reply
by KE3WD on October 24, 2009	Mail this to a friend!
A coil that should measure that high in DC resistance likely has enough turns on it to generate quite the back EMF when the field around it falls. If there is ferrite involved, so much the merrier on that front. Good idea to at least check it with the ohm meter like the man says. Couldn't hurt.

RE: Tick in 811A	Reply
by W8JI on October 24, 2009	Mail this to a friend!
L3 is a safety choke that bypasses the tank to ground for dc. It serves two purposes: 1.) It allows the blocking caps to charge or discharge without making the air variables arc. 2.) It provides operator safety in case a plate blocking cap fails. If L3 is open, you will hear a ticking from the loading capacitor as the charging or leakage current of the blocking caps tries to elevate the tank components to 1800 volts. It has nothing to do with inductance, just with the dc properties of the plate blocking capacitors and that choke. Tom

RE: Tick in 811A	Reply
by W8JI on October 25, 2009	Mail this to a friend!
I'm not saying you don't hear the glass in the tubes tinking, just that you want to be sure it is not the choke making the loading cap tick from an arc.

RE: Tick in 811A	Reply
by K2TY on October 25, 2009	Mail this to a friend!
I understood you and intend to check L3 as you suggested.

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