the dual operations of both AM and FM were due to an early stereo transmission by having one channel on AM and the other on FM. The odd arrangements on the pwr supply diodes is that this is a voltage doubler circuit.
Some early stereo radios were set up for am on one channel for one side FM on the other side this was common in the States but not in other places interesting it worked but had problems
The web page at 18:50 in was telling you to click on the "schematic "side where all the pages are available from the Heath manual! A fellow named John from Cleveland has a great web page ( Radio Boat Anchor) about restoring his dad's old AJ-10. You should look at it Jim. Your close up view of the obviously good diodes show two failing Astron Minimite E- caps! You can clearly see whitish effluse leakage out of the bottom one! Why would you not change them as well as the multi section cap? They are over 60 years old and would get very warm and leak badly after a few hours of powering it on.
I would venture a guess that the AM Fidelity allows the receiver to expand its bandwidth and thereby increase the quality of the reception. This was not uncommon on higher end tube receivers. The drawback to this mode is that you sacrifice selectivity so you'd have less ability to discriminate between two stations close in frequency on the band. Selecting the normal mode would narrow the bandwidth filtering allowing for that finer tuning control.
the dual operations of both AM and FM were due to an early stereo transmission by having one channel on AM and the other on FM. The odd arrangements on the pwr supply diodes is that this is a voltage doubler circuit.
Some early stereo radios were set up for am on one channel for one side FM on the other side this was common in the States but not in other places interesting it worked but had problems
The web page at 18:50 in was telling you to click on the "schematic "side where all the pages are available from the
Heath manual! A fellow named John from Cleveland has a great web page ( Radio Boat Anchor) about restoring his dad's
old AJ-10. You should look at it Jim. Your close up view of the obviously good diodes show two failing Astron Minimite
E- caps! You can clearly see whitish effluse leakage out of the bottom one! Why would you not change them as well as
the multi section cap? They are over 60 years old and would get very warm and leak badly after a few hours of powering
it on.
I would venture a guess that the AM Fidelity allows the receiver to expand its bandwidth and thereby increase the quality of the reception. This was not uncommon on higher end tube receivers. The drawback to this mode is that you sacrifice selectivity so you'd have less ability to discriminate between two stations close in frequency on the band. Selecting the normal mode would narrow the bandwidth filtering allowing for that finer tuning control.