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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 wire

Richard I just replied about that now. Your wording might be better than mine.. well not quite , you propose magnetic coupling thru the air?, I was thinking the steel chassis might couple depending on

Tom, that is good, but that choke is always zipping up and down wrt ground. Is it possible that the mounting to the chassis makes the difference. As in magnetic coupling to the power transformer? At

Hi Mike, then the question becomes which loop? They use/assume the chassis as if it has zero resistance and zero self inductance and zero mutual inductance. We just hope there was some method hidden

Once the choke is removed from the chassis can you investigate if its position makes any difference. I mean is the hum the result of an induced field from something? Also, does it make any difference

Dang ! Could you measure a leakage between the winding of the “original” choke and it’s core ?? Happy that this “mystery” is solved ! 73, Jacques, VE2JFE in Montreal De :

Hi Don, Yeah, there is a misprint in the TM11-874 schematic. The 180M (180K) is the value of R39 (see parts list), but there is another “270M” in excess just below it…. 73, Jacques, VE2JFE in

Hi Tom. Very clean SX-28A specimen ! Better shape than my two samples, actually… And an original SX-42 (R-42) speaker ! I have the radio, but never found the matching speaker… I have a PM-23 one,

Ok folks, I found the culprit – that dog gone choke! I replaced it with a 4hy one from an R390A AF deck and the hum is gone. I laid it in the chassis, insulated from the circuits and wired it in

I received a direct email from a member of this reflector asking what my comments about ground loops in an amplifier chassis had to do with the SX-28 hum discussion. Sorry, I wasn’t specific enough.

Richard, Did you see my response with links to videos of the hum? Tom Sent: Tuesday, February 18, 2025 7:30 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum A couple

A couple of things: Its quite possible the SX-28 has some residual hum. I don't have one and little experience with them. The hum in the original complaint has not been described in level. Is it

With the switch in the “out” position, no bass enhancement, the hum is present. With the bass set to the “in” position, there is bass enhancement but no hum. Tom Sent: Tuesday, February 18,

Years ago, a PA system amplifier that had been donated to us for hamfest use had an annoying hum when we checked it out before its first hamfest use. Nothing I tried would “fix” the hum. Until ---

I recapped my Swan 270B about 21 years ago and its been my most modern HF rig since. When I use a nice old set of headphones, there is no hum. But a modern set of high fidelity phones introduces

Jim Re:: “The Bass IN/OUT thing could be attributed to the change in gain of the 1st audio amp. Figure 11, the audio filter curve, shows that the gain is 100+X higher when the bass switch is in the

Jacques, I “may” guilty of not returning caps to the same ground as original………… I need to look into this. I took lots of before and after pics so I should be able to confirm Tom Sent:

Ok, made a couple videos, excuse the camera work and narrating………. https://drive.google.com/file/d/10rFu1-W59o6I1Ro8Q4Lq0jG9HbNen6Dt/view?usp=sharing

I don’t know Jim, I have several other radios (too many actually…) of this vintage that don’t have this hum. Yes I neglected to address the speaker, sorry. My bench setup uses an older

Jacques, I was going thru your recent post and started turning into a pretzel; adding and then removing a resistor. See my “side-by-each” . 180 “M?” but no squiggle Sent: Tuesday, February