Re: [Amateur-repairs] Creating a LSB and USB Test Signal!!

Thanks folks for the feedback.. I documented some tips and tricks for MYSELF several years back on what to do if things become strange, complicated or you want to bang your head on the wall… One was to go back and start everything over again troubleshooting from the beginning double checking what you think you just did! Since it has been a while I decided that I should start by checking all the tubes again.

 

When I first did this I only had a B&K 747 tube checker, but last year I visited an estate sale and picked up 3 nice tube checkers…

A Heathkit TT-1, A Triplet 3444A and a Hickok 539C.. Good be the first on site at 6:30am so I could get the pick of the litter.. Also grabbed all the Tubes, probably around 850 or so..

 

I think I will start with the 539C checker first and if anything seems strange  I will check it on a different checker.. The TT-1 was calibrated by me, and it was very close, the 3444 and 539C tracked very close to the calibrated TT-1.. I did replace all the old capacitor in the Hickok and Triplet and a few in the Heathkit..

 

The Heathkit TT-1 has a built in " I think" a 5 KHz oscillator that they modulate on the grid of the tube.. ???? Maybe I should use that instead of the 539C, may reveal something with a questionable tube.. We will see how all that goes,, Let The FUN BEGIN, after all it is Ham Radio!!! J

 

I am in the middle of finishing up a sensitivity issue on 2 bands only on my recently acquired Eddystone 880/2, all 90 lbs. worth,, and at age 75 my son needs to help me move it! BTW, the Hammarlund HRO-500 seen in the video had a PLL issue as expected, and replacing all 18 capacitors restored it to full operation.

 

I think the hardest part is changing the dial lamps.. What were those engineers thinking, unlike the Eddystone where everything is designed to fix stuff…

 

Robert  WA6PHN

From: Amateur-repairs@groups.io [mailto:Amateur-repairs@groups.io] On Behalf Of James Amos
Sent: Friday, January 19, 2024 5:02 AM
To: Amateur-repairs@groups.io
Subject: Re: [Amateur-repairs] Creating a LSB and USB Test Signal!!

 

Hi Robert, 

I listened to your Youtube video, thanks for sharing that.  Also, great to hear that you've already checked the components that are particular to the SSB/CW demodulation.   What I think I hear in your video is that the SSB signals are not being correctly placed in the filter passband.   I would check the frequency of the BFO if you can.   Any offset in the BFO frequency  can be heard directly in the audio.  I also hear the noise Gary is hearing and agree with his power supply comments.  I would also suspect the BFO power supply, tube, or biasing components.    

Given that the radio is otherwise working, I'd swap the tube out first.  The manual I downloaded also has a voltage and resistance chart starting on page 4-2.   I would do a quick check against that.   One nice thing about tubes is that they are high impedance powered down, so the resistance values are based solely on the passive components.   But, this is also an old radio, so we also need to worry about aged components. 

Keep us up to date on your progress!
73's Jim N8CAH