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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.?

Yes, wiring is as shown on schematic Yes bass "in" boost the bass response.

Tom, move some stuff and things change… no cold solder joints around there? Sent: Monday, February 17, 2025 8:59 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A Hum

Please confirm: 1, the wiring is actually as shown on the diagram. 2, the bass boost is present with the switch in the IN position. If so I am thoroughly puzzled. If the hum is 60Hz I wonder if

Time to re-evaluate where I’m at and what I’ve tried, yes the hum is still there……. Tried three different 6SC7’s no noticeable difference between each one. Confirmed the wiring of the switch

Richard and Jim, I got caught on the top paragraphs, and did not go thru it all.. but…!!! As I have seen it, at 10mfd, C44 is hopefully holding the “reduced B+” steady for both parts of the

Emanuele, very good that you did all this, you can let your brain cool off now nor a bit. First, do you have any idea if this is an early run, or a later one?. See what is in red first! Richard

Greetings to the group: I see I will have to go back and duplicate Emanuele's measurement setup exactly; I can do that but it will take a while. In the mean time, I have taken some more pictures with

Sweep of MIX tanks: Setup is the same as ANT but the injection point is V1pin8 and the probing point is V2pin8. The signal in band 1 is very low (effect of lack of coupling between V1 and v2). I had

I suppose I have to reply to each comment. The plate load is the impedance in the plate circuit between supply voltage and plate, that develops the signal output. In the half of the 6SC7 that the bass

Jacques, yes, but it just makes things harder to understand. I was originally focused on when and how each L3 coil shorts to ground or doesn't, and quickly decided them must be using the mutual

RichardComments inserted in the text below.Regards,JimLogic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

Oops, I overlooked the price. Sounds great. Tom

Hi Dwight, I have an observatory in Pie Town, New Mexico and plan a trip there as soon as it warms up a bit. I’m now sure exactly where you live but I would like to buy your receiver. What are you

Last night I was able to find another 4hy choke. I knew I had one around just couldn't put my finger on it. It was salvaged from an old R390A AF module.?Dawned on me last night at 8:30 to go check

Could be....? One other tid bit, whenever I switch between in/out there is a loud thump in the speaker - annoying to say the least.

Another coincidence - I just happen to have that book at the office! I quickly looked it up and there it is. Hopefully today is a slow day and I can spend some time reading. Also saw in the index a