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Title: Viking ll problems Post by: KR4WI on November 18, 2006, 10:21:44 AM Hello Fine Folks: I am having a problem with a hum/distortion sound on my viking ll audio, it sounds ok on cw, Here is what im seeing on the heathkit sb610 scope. In the trapezoid position, the tx in a variac, when I get to 90 volts the vertical line begins to spread out left to right. I have replaced all electrilitics caps in power supply, I measured the oil filled cap for filter it measured ok. I have been using the tx for abt a yr now with no disortion, until now.
I am listining to it on a sp600 rx, and tx intothe dummy load. amplified d104 mic, it sounds like a harsh hashing sound on the audio to me. I hope this information is not to confusing. Thanks for any thoughts. Matthew KR4WI Title: Re: Viking ll problems Post by: w3jn on November 18, 2006, 11:27:15 AM You have a parasitic, probably in the audio. Get in there with a scope and poke around. Could also be RF getting in thru the mike jack or into the audio stage and causing trouble. Yank the audio driver tube to see if it goes away.
Title: Re: Viking ll problems Post by: Steve - WB3HUZ on November 18, 2006, 11:35:20 AM I'd suggest using the scope in the envelope display and not the trapezoid. I think it's much easier to see what's happening, especially when looking for hum or oscillations. The trapezoid pattern is great when you use a sinewave input. You should get a perfect trap or sideways triangle. Any variation means distortion. But with voice input, it's more tricky to my eyes.
Good luck with the Viking II and hope to hear you on 75 meters. Title: Re: Viking ll problems Post by: ve6pg on November 18, 2006, 10:22:28 PM ...MATT...DO YOU HAVE THE RESISTORS IN LINE FROM THE MOD TRANSFORMER, TO THE PLATE CAPS OF THE 807s?...CHECK THEM FOR RESISTANCE, THE VALUE MAY HAVE CHANGED...IF SO, REPLACE OR REMOVE ALL TOGETHER...ANOTHER THING TO TRY, IS REVERSE THE PLATE CAPS...YOU COULD BE OUTTA PHASE...THINK OF THE AUDIO CHAIN FIRST..TRY USING A HI-IMPEDANCE CRYSTAL MIKE AS WELL...THE IMPEDANCE OF A AMPLIFIED D104 IS QUITE LOWER...LET US KNOW HOW IT'S WERKING OUT..TIM....SK..
Title: Re: Viking ll problems Post by: KR4WI on November 19, 2006, 05:57:17 PM Thank You Men: I did not have any resistors on the plate caps from tranny. So I put one on each plate cap to the 807s, I also change the plate caps around, so maybe it was out of phase. I also found an old broken d-104, The element was bad. I put in a crystal element I ordered from Mouser a while back. This one is not amplified. So hope things will be ok now. Matthew KR4WI AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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