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Title: Hallicrafters HT-40 problem Post by: VA3AEX on March 29, 2008, 02:47:05 PM Was inspired to get my ticket (licensed only 2 weekends past) and on the air listening in on 3.885 as a SWL.
I purchased a Hallicrafters HT-40 as my first AM transmitter, and while I can get full RF output when in CW mode, moving to AM mode I have no output. I am following the tune-up process per the manual The tubes check out okay via my basic EMC emission-type tube tester, the mic (crystal) has good good output, and switches/tube bases have been cleaned with contact cleaner. Now I'm stumped. Any ideas? Title: Re: Hallicrafters HT-40 problem Post by: AB2EZ on March 29, 2008, 05:39:34 PM Check to make sure that you either A) close the CW key (using a shorting switch if it has one) or B) make sure there is a switched connection (closed when transmitting) from terminal 3 to terminal 4 of the connector on the back (labeled "auxiliary control"). Unless you close the key or short terminal 3 to terminal 4, your HT-40 will not be in transmit mode (i.e., the crystal oscillator, buffer, and final rf stage won't be on, because their cathodes won't be grounded)
Stu Title: Re: Hallicrafters HT-40 problem Post by: AB2EZ on March 30, 2008, 11:03:19 AM Additional clarification
The way Hallicrafters designed the transmit control on the HT-40, a jumper/short across terminals 3 and 4 on the back of the HT-40 will turn the transmitter on only if the key is removed from the key jack. If the key is plugged into the key jack, then the only way to turn the transmitter on (in either AM or CW mode) is to short the key by pressing it or using a shorting switch across the key. Stu Title: Re: Hallicrafters HT-40 problem Post by: VA3AEX on March 31, 2008, 02:11:49 PM Thanks Stu
Feeling like I had a "duh" moment as I now clearly see what you are talking about in the manual. Will try it out in the next couple of days, and see if can get my first QSO under my belt! 73 Alex Title: Re: Hallicrafters HT-40 problem Post by: AB2EZ on March 31, 2008, 06:15:10 PM Alex
Okay... hopefully it is as simple as that. If not, let me know... and we can explore other possibilities. Best regards Stu Title: Re: Hallicrafters HT-40 problem Post by: VA3AEX on April 02, 2008, 05:57:10 PM Success: RF output with appropriate peaks on voice peaks. Thanks Stu for your help.
Alex Title: Re: Hallicrafters HT-40 problem Post by: AB2EZ on April 02, 2008, 06:31:43 PM Alex AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
You are welcome! I hope to hear you with that rig on the air. Best regards Stu |