I continue to try and resurrect the HW-32A and am way down the rabbit hole. Small bits of progress but no major breakthrough.
The 20M band was open last night and I could hear stations on the east coast and a couple of South American call signs. That was not good as the volume control was wide open, and you hear no change in atmospheric noise when you dis-connect the antenna.
My gut tells me it is a front-end issue. Often the most fundamental test with a homebrew radio is disconnect/connect the antenna and can you hear any changes. My HW-32A flunks that simple test. I reason that with a strong band opening and a limp front end then you will hear signals but like they are in the mud. In hunting this down I tried the tube swap with known good tubes and have found some really off value components.
But by and large a target would be caps that link the circuit modules. In taking a look from 5000 feet (look at the total schematic) there are but only a few of those as there is lots of transformer coupling between modules and that is compounded by two such elements L2 and L3 which are sealed and cannot be adjusted.
Switching to the transmit side I now can get about 3/4 of a watt out to the antenna and those two same inductors (L2, L3) are in the transmit chain. I also found that the (small) output is not consistent across the 150 kHz range. Tuning L5 which is in the output side of the 6BE6 heterodyne oscillator/mixer stage can peak the portion of the band where you have the greatest output. Typically, that peak is only about 50kHz wide i.e. not broadband. So, this is noteworthy when I add the JF3HZB dial to the mix.
The plan going forward is to continue replacing any module coupling capacitors with modern units and to look at perhaps not so obvious issues. One target is the single 12AT7, a dual triode. One half is the Product Detector, and the other half is the BFO / Carrier Insertion Oscillator. Insufficient injection of the BFO / CIO would impact the received signal as well as the transmitted signal levels.
The output from the BFO/CIO is taken through two separate caps connected to the cathode of one of the Triodes. (Open cap = low injection, and the cap values are 36 and 47pF).
There are other verification tests like the rails that supply the 250 VDC plate / screen voltages. A too low screen voltage dramatically reduces the output on both receive and transmit. There are test pins on the top side of the PCB that would give access to these voltages. A look see at a couple of points would identify a general condition.
So, I am determined to fix the HW-32A and when I get there it will likely be something really simple bit so far, the simplicity has eluded me.
Now to shift the story to bringing back manufacturing to America. I marvel when I hear discussions on 40M from stations in the 5 and 7 call areas that suggest it would take a month and have it all back and up and running. They are simply wrong and here is a link as to why.
The YouTube video narrator wanted to develop a product that is totally Made In America. It is a simple product that is all mechanical, with no moving parts and no electronics involved. The product is an outdoor grill cleaner. The underlying issue is the lack of tool and die making capability. When manufacturing shifted offshore one of the lost critical skills was tool and die making.
Having run a large-scale production line, I personally do know what it takes to build stuff. Most of the brilliant geniuses, "best people" in Washington have no clue what it takes to manufacture products. So, we will just have to suffer through the next 3.5 years, but the fact remains you know who does not have a magic wand at the end of his finger. The other critical fact: tool and die makers are not churned out after a two-week course.
Them that know can build stuff!
73's
Pete N6QW