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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

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,

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

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

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

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,

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

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

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:

Tom and JacquesYou are overlooking an alternative, that nothing is actually wrong.? AFAIK. the radio works well but there is a noticeable hum.? Hum is subjective, if you have listened to solid state

Let’s resume the case : Tom pulled the 6SC7 and the “hum” remained. He shorted the two 6V6 grids to GND and the hum disappeared. No hum when the “bass” switch is in the IN position (both

Gents, dunno about all that, but why the no hum in the In position? And when base is boosted? _,_

RichardI was a bit clumsily in my previous attempt so I will try again.?? All aluminum electrolytic capacitors are self resonate.? ?There is a frequency where the capacitor becomes an inductor.?