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Don, no idea about the run of this unit. The serial on paper is almost impossible to read; looking carefully it seems read "serial. 196479". No other info. Here is an info briefing: As arrived, the

Hi Scott, Talk about timing... I have an SR-160 (upgraded to SR-500), an SR-400, and matching P-500 power supply that I would like to find a good home for (all in good working order and

Hi Scott, Talk about timing... I have an SR-160 (upgraded to SR-500), an SR-400, and matching P-500 power supply that I would like to find a good home for (all in good working order and

Thanks Jacques, well that seems to pour cold water on the magnetic coupling theory. If the trace I copied is typical {I don’t know}… ie; assuming that hum is 60 cps with third harmonics at /I n

Thank you. Since its a different choke it doesn't explain why the original was humming. Doesn't matter if the problem is solved but would be interesting to know. Its possible there is a leak

In a SX-28A, the CH2 is as far as it can be from the power transformer: The black “core” at the left is the CH2. You can see the bottom of the power transformer and the filtering choke

Yes, I replaced the original CH2 with another 4hy one I had from an R390A AF module.

Please clarify, do you mean you replaced the original choke and the problem went away? If so it could confirm my idea of filament current somehow coupling through the chassis. -- Richard

Tom, if I recall it was not fastened to the chassis… at least in the same way. If the power transformer is near by the choke, it’s flux can/might use a bit of the chassis and the choke could

Interesting Don........ When I replaced the choke, CH2, this all went away so I don't know how it would be related to the power xfmr? Tom

Tom and/or anybody still tuned in. Still looking for what really failed and how. For anyone wondering about the details and possible source, I copied a bit of your first Video so I could take a

Hi Scott, The Tornado (SR-500) is an excellent tri-bander. It is a single conversion receiver that performs better than a lot of dual conversion rigs. With its 250 to 300 watt output it will punch

Excerpt from?https://www.chavfreezone.me.uk/2023/sx28.html.? Might want to read the entire article. There is also an underlying very low-level hum present which is totally independent of audio

Jim,? You are correct. I had replaced the choke but with 12" leads outside the chassis. There was a reduction in hum but it was still there. This time I installed it in the same location as the

Richard,? The choke is held to the chassis with two screws that have internal tooth lockwashers on both sides - one under the screw head, one under the nut. That is how it was when I removed it and

TomDidn't you report that you replaced the 4H choke on Monday and that there was still hum?? What changed? Looking at your videos, I notice that the frequency readout on the o'scope does not agree

TomDidn't you report that you replaced the 4H choke on Monday and that there was still hum?? What changed? Looking at your videos, I notice that the frequency readout on the o'scope does not agree

I was thinking about magnetic coupling through the air. Also about just electric coupling due to currents in the chassis. Has to be coming from someplace. I had a very puzzling hum problem in an

Hi, Lately I’ve been waxing nostalgic about the old Hallicrafters transceivers. A friend loaned me his SR-160 for several months back in 1971 while I was in Senior in High School and I used it for

I wonder about that. R-38 is shown in all three versions of the handbook I have. In the civilian S-28 and S-28A its shown as a 47K or 50K half or third watt. In both drawings there is a straight