开云体育

Don, Richard: I do not agree. CH2 is listed as a 4Hy choke in the parts list, and the C43 across is a 5100pF (0.0051?F). Both form a parallel resonant circuit centered at 1114 Hz. So when they are

Hi again Tom, Maybe some will find the following approach brutal, but here is what I will try with that SX-28A. Solder-tack two pieces of wire from the 6V6 pins 5 to GND: connect GND where both C47

Jacques, maybe look at “scope” sweeps in here and some in just after posts I think. I didn’t get far, and misinterpreted scope face info. I have to copy then and add my own marks or I will get

Richard ,agree again Re “I am pretty sure the markings on the schematic are reversed. Agree again It seems to me the Bass switch also changes the gain of the stage by increasing the B+.” perhaps

TomOK, does R35 have any affect on the hum? Can you scope the terminals of CH2 when the Bass switch is in both positions?? You most likely will have to do either a differential measurement using

Yes, hum is present – at the same level – regardless of the AF gain position. It does not change with AF gain adjustment so the issue is after the AF gain pot. CH1 and CH2 are not near each other.

6SC7, sorry. Thanks for the input, yes more poking is needed. Hopefully later tody. Tom Sent: Sunday, February 16, 2025 12:08 AM To: [email protected] Subject: Re: [HallicraftersRadios]

The B+ goes to the plate of the first audio through R-37, when the Bass switch is in the IN position (as shown on the schematic) the choke is bypassed, the B+ to the plate through R-37, when the

Richard, we agree about the switch position labels on the schematic being reversed. Sent: Sunday, February 16, 2025 5:00 AM To: [email protected] Subject: Re: [HallicraftersRadios] SX-28A

I am curious about that switch. I would interpret IN as meaning the bass was boosted but the switch shows it the other way. Also the frequency response chart shows the bass boosted with switch "IN".

TomWhen R33, the audio gain control, is set for minimum volume, do you still hear the 120 cycle hum regardless of S10, the Bass IN / OUT switch position?? If you still hear hum then the source of the

Do you mean the 6SA7 or 6SC7? The 6SC7 is the dual triode that acts as the first audio and phase splitter. Pulling that leaves the 6V6's active. CH-2, the bass boost resonator, connects from the grid

Hi Jacques, last reply tonight Ok Ill try. I guess I must be getting cranky! I followed this case more or less since Emanuele posted it, so be kind if I misunderstood anything about. I remember that

Bob, Some of us are not bean counters, but want to know now things work and don’t work, and give them some love too. You can go back to Stephah Gray in about 1750 who found out electric fluid moves

Hi Don, I followed this case more or less since Emanuele posted it, so be kind if I misunderstood anything about. I remember that Emanuele complained about a complete loss of sensitivity in the lower

Oops! In my note number 2 I should have said "... except for C62." Thanks for catching that, Don. 73, Maynard W6PAP

Tom, as you are able to measure it, what is the ripple across C48 and across C44 when the bass switch is “IN” ? What is not normal is to have more “hum” when the bass switch is “OUT”

I rebuilt my SX-28a about 10 years ago including pulling the RF deck out etc. I have never experienced a hum with the bass switch in either position. [email protected]> wrote:

It seems that the way to look at this switch is that in one position the plate load is provided by the choke while in the other the load is switched to R37, and as an aside the choke gets shorted ?

I feel that the guy that had the original post many moons ago was correct. Get rid of it. The job of any good bench technician is to be able to recognize a dog and move on, not beat a $40 radio to